29 Nov 2012

Small Wonder Lab Kits

Dave Benson K1SWL has produced some wonderful Small Wonder Lab kits over the years including the famous RockMite transceivers, but he has decided to slow down a bit and get back to enjoying the hobby as a hobby. I think we don't realise just how much work is involved in a small ham radio company producing and supporting a range of kits. Dave's point about technical support and repairs rings bells with me: I get around 5-10 questions a week from people interested in my website projects and I am not even selling kits!

This was the notice on his website last week:


I took a ‘leap of faith’ in 1996, leaving the corporate world to undertake ‘Small Wonder Labs’ as a full-time venture.  Since then, it’s been a great experience.  I have to face facts, though: I’m getting older. The shortcomings in vision can be overcome with close-up glasses. More troublesome, though, are the muscular issues from spending hours a day at the computer, or with my head down, sorting parts into bowls.

Over the years, I’ve assisted countless customers with no-questions-asked replacement parts and troubleshooting advice. The issue of repairs has been problematic, though.  While no one really objects to paying $50/hour to have a $1000 rig repaired, that’s not true of a $50-100 kit. I’ve had some good people doing repair work for me, but it’s just not economically viable. Neither can I do the work in a timely manner. Therefore, and effectively immediately, I will not be accepting returns for troubleshooting/repair.

It’s not clear to me at this point if I’ll release any additional product offerings. Although I love the creative process involved in a new design, everything that follows is now just ‘work’.   Along the way, I lost the ‘hobby’ aspect of ham radio. I have not been on the air in almost 5 years. I want my hobby back!

I’ve finished our home here in the woods of New Hampshire, and it’s time for me to move on to other interests.  I’ve still got a garage/barn to build, a garden that grows larger each year, and a wealth of outdoor activities I can’t seem to find the time for. Retirement is clearly not for the faint-of-heart!

I’ll continue to sell RockMites forever, apparently.  Demand is still brisk, with more than 8000 of them out there so far. Ongoing activity for the RockMite as well as support for ‘legacy’ kits occupies me for 2-3 hours each day.  At this stage of my life, that’s ‘enough’.

73- Dave Benson, K1SWL
19 November 2012"

ARRL 10m contest (48hrs Dec 8-9th)

A reminder that the ARRL 10m contest is on next weekend (not this) over the full 48 hours Dec 8th and 9th. As conditions on 10m are pretty good right now this will be a good chance to work a fair number of US, Canadian and Mexican states and provinces, even with QRP levels in CW or SSB. I'm away on the Saturday but hope to be on for the Sunday.

26 Nov 2012

Cutting big pieces of copper laminate

When I was working I had access to a guillotine to snap out large pieces of copper laminate to convenient sizes for project breadboards. Being retired I no longer have this method to hand. SO, I asked a question on the GQRP Yahoo group this evening to find out what other people did. Several suggestions but the favourite is "scoring and snapping", summarised by the post from Duncan G4DFV which I have reproduced below.
"My method of cutting large pieces of copper laminate:-
  • Place a steel rule along a previously drawn line on the board where you require to cut.
  • Pressing down firmly on the rule, using a stanley or other utility knife, score along the line.
  • Repeat the scoring in the same cut for perhaps 10 times, then
  • looking at the edges of the board, you will see each point where the
  • scoring starts and finishes. 
  • Carefully mark these points over on to the other side of the board and  
  • place the rule exactly along a line between these points and score as before.
  • After about 10 scorings, place the board on a flat surface such that the
  • scored line is on a straight edge.
  • Holding the board down with one hand, press down over the straight edge with the other.
  • The board should break cleanly along the scored line.
  • Any uneven/rough edge can be smoothed with sandpaper.
Duncan G4DFV"

Tenbox TX progress

Good progress today with the transmit side of my Tenbox 10m AM transceiver.

The series  modulator was breadboarded a few days ago, so today I built the 3rd overtone oscillator, the buffer and the modulated PA stage. Results were as expected with around 50-60mW of clean well modulated AM available at the output. With a single linear amplifier with around 10-13dB gain (easy at 29MHz) this will take me into the 500mW-1W carrier level, which is my design aim. As I did not have a suitable 29.05MHz crystal (anyone know where these can be obtained cheaply?) I used a 28.500MHz one on a dummy load. With this frequency, any range tests will have to be done at night to avoid QRM to SSB stations.

When the linear is added , maybe even before then, I'll do a local "drive around" test with the TX on "speech beaconing" mode (using an MP3 file on the PC) and with the RX attached to a mag-mount antenna on the car. This will establish the useable local coverage.  Assuming this power level is OK, I'll then complete the full design on a tidy breadboard and publish the initial schematics on my blog and website. After that, a PCB may be in order and a neat enclosure.

This project is great fun: a simple, straightforward and easily reproducible design and a project that will be useful at the end. Much more fun than working DX with 400W and a 5 el beam in a contest with a £5k commercial HF transceiver.  Honestly, I'm having a real ball with this.

25 Nov 2012

10/20W versions of popular transceivers

In the Japanese home market, several of the transceivers available in the USA and Europe are available in lower power versions too. For example, the IC7000 is available as a 50W version and a 20W version. Prices aren't always lower though. For example on the www.icom.jp site, the IC7000S (20W) is available at 168000 yen, the same price as the 100W radio.

The reason these lower power radios are not available outside of Japan is clear: lack of sales volumes and lack of the necessary approvals. It is a pity that the major dealers like W&S and Martin Lynch don't offer to import these on request though if they met EMC specs as I can imagine a reasonable market with QRPers with a bit of advertising: they have enough space in RadCom and PW after all!

How to avoid expensive calls to 0870 numbers

The website http://www.saynoto0870.com/ is a useful resource in the UK if you are looking for a lower cost, or even free, way to contact companies such as Virgin Media or Dell where an expensive 0870 call make be needed.  I get infuriated when big companies keep me waiting on an expensive call saying things like, "your call is important to us" then waste the next several minutes with drivel.

Most of these alternative numbers get in "via the back door" and work on the assumption that you will be transferred internally to the correct department. It may not always work, but if you want to save a few pounds it is worth a go.

CQWW CW - guess who forgot!

Julian G4ILO has posted a piece on his excellent blog about the CQWW DX CW contest this weekend. Well, yesterday was my wife's birthday and we had family here and today I did my tax return. In the process I managed to miss this contest completely! For some reason I thought it was NEXT weekend. Never mind, there will be other occasions to work the DX.

The hazards of LF operating

On the LF reflector there was a salutary message from Mike G3XDV today.  Doing some 136kHz tests overnight his loading coil caught fire melting his flat roof extension!

LF amateur radio can be very dangerous as extremely high voltages and/or high currents can be generated with even quite modest powers because of the electrically short antennas. This is one reason why I stick to QRP(ish) powers on 136 and 500kHz.

See Mike's post:
Damage to the G3XDV loading coil ....and roof! See http://g3xdv.blogspot.com
"I am currently off the air following my loading coil catching fire and damaging the house. I have had to take my mast down to allow access to the builders who are repairing the damage. Fortunately I was insured.

Hopefully I will be able to receive before Christmas and transmit again some time in January.

Details and pictures are on my blog at:

Mike, G3XDV"
This picture (linked from Mike's blog) shows the damage.It begs the question of how readily will an insurance company pay up when an amateur installation fails?

More 10m (28MHz) Projects

With the Tenbox coming along just fine - I should have a completed breadboard version on-air this week - I am beginning to think that I could spend nearly all my free time designing different ideas for this, my favourite, band!

Here is just a brief list of some of my 10m ideas (all do-able with some time):
  • 10m QRP AM transceiver (Tenbox)
  • 10m QRP DSB transceiver
  • 10m pocket SSB/CW "holiday" receiver
  • 10m mixer-VFO controlled CW transceiver
  • 10m compact portable antennas for mobile and hand-portable
  • 10m VXO controlled QRP TX
  • 10m phasing SSB transceiver (10W)
  • 10m beacon RX
  • 10m test box (power meter, ATU, SWR bridge, FS/mod meter)
  • Modules for 10m rigs (VXO, mixer-VFO, LPF, TX strip, DC RX, AM modulator, audio power amp etc)
Now, as I like to do so many different things in this exciting hobby - including on-air operating some times! - it is unlikely all these will get done anytime soon.

What occurs to me, if I had the time, is that a mini-series in a magazine like PW or RadCom entitled "Ten Projects for Ten Metres" would be a nice idea. 10m is one of the best bands for homebrewing as layout is not too critical, as long as sensible RF rules are followed, antennas are small, superb DX is possible in the better years and Es DX possible for 4-5 months every year, local ranges are useful for nattering across town. All in all, this band has SO much to offer.

A 2m AM calling frequency

At the recent RSGB Spectrum Forum Meeting (Nov 3rd 2012) the ongoing matter of an AM calling/working frequency was raised. At issue is why our national society, which is there to help and support ordinary experimenters like you or I, seems to be totally against putting a 2m AM frequency properly in the UK band plan. 144.55MHz is the frequency of choice.

This is what appeared in the minutes:
"7.7 G-QRP
Report accepted

Listing of an AM centre of activity frequency in the Band Plans
It was noted that this has been raised previously with no success. It was suggested that a “custom and practice” approach would be the only way of moving forward i.e. identify a frequency, use it and make it known."
Excuse me dear Spectrum Forum members, but this is stupid!  You have centre frequencies for all manner of other modes, but not AM. So, why not just print these words in the bandplan? :-

144.55MHz   AM calling frequency and centre of AM activity

I am not one to get easily irritated, but the RSGB stance on 2m AM is beyond belief.

Taxing times

Today I'd planned to finish the breadboard TX of the Tenbox 10m AM transceiver and do some range tests locally. The plan was to put the TX on at home with a PC voice recording and drive around with the FT817 and the Tenbox super-regen to see what sort of range was reliably possible.

Instead, I started to do my annual HM Revenue and Customs tax return, a task I hate doing as so much form filling is needed and lots of bits of paper have to be found in order to fill it all in. I do mine online, so the deadline is the end of Jan 2013. Starting at about 10am it took me until 4pm to complete, not because of the complexity of my affairs particularly, but because I couldn't find all the bits of data I needed. On their website they have a nice picture of a guy smiling away whilst filling in his form online. I spent about 6 hours pulling what little hair I have left out!  A reminder that the deadline for online self-assessment tax returns in the UK is Jan 31st 2013, or you get a fine.

Anyway, job done. Yet again I owe money - why do they never owe me money? - and will pay up in the next few weeks. So, a boring, tedious, annual task done and this week I can return to the interesting amateur radio project stuff.

24 Nov 2012

Simple TRF based AM radio ICs

Many years ago when my sons were little I made them a couple of Medium Wave AM radios using just a ZN414 3-pin TRF receiver IC. It worked very well considering how simple the circuit was using just a small ferrite rod antenna and a crystal earpiece. This IC is no longer available but there are other similar parts available such as the MK484. Although I have not tried one of these as an IF stage I have no doubt they could be useful in simple rigs like the Tenbox currently under development. The advantages over a super-regen would be selectivity. These devices have input impedances of around 4Mohm so if a ceramic filter was to be used ahead of the IC a step-up transformer would be needed to minimise loss. As they only work to around 3-4MHz they would only be suitable as an IF in the Tenbox 10m AM transceiver.

A useful page I've just found on how to get the best from these simple ICs is http://theradioboard.com/best-of-the-best/mcgillis-mk484.htm.  The datasheet for the MK484 is available here.

A page showing the use of the MK484 as an IF stage in a simple 160m RX is  http://www.vk6fh.com/vk6fh/mk484radios.htm . See also http://www.youtube.com/watch?v=qdlXVKOITe4. I am told that a similar design appears in 'Radio Projects for the Amateur' Volume 4 by Drew Diamond VK3XU. 

I'm still likely to stick with a very simple super-regen RX in the Tenbox - they ARE the best in the intended application - but I may make it in a modular form so that different TX strips and RX strips can be used and compared.  I can see a whole series of simple AM designs in the pipeline, HI.

More big wheels and turnstiles

When looking around for possible homebrew designs I saw an article that appeared in QST back in 2008.  Looking at this approach I am not convinced it is easier than the conventional big wheel design though. See http://radio-amador.net/pipermail/cluster/attachments/20100107/a2f81f3e/AntenaHPOD.pdf

A design for a 70cm big wheel, designed to be used with a beacon, is available at http://www.qsl.net/dl4mea/antennas/bigw.htm .

The turnstile design on the EA4EOZ website
Another simple approach to a VHF or UHF omni-directional horizontally polarised antenna is the simple turnstile (a pair of phased cross dipoles that produce an almost 360 degree clean radiation pattern with about 0.9dBd loss only). These can be stacked to produce gain, as with the big wheel.

Overall, the conventional big wheel design is my favoured approach for 2m and 70cm. Whether I make my own or buy a Wimo version remains to be seen.

Another ham radio company bites the dust

Via an email from Steve G1KQH I've just heard that Snowdonia Radio Company has ceased trading completely and closed its business. If I understand correctly they closed down last year but had one last try again this year. You may recall that this company produced antennas such as the X80 HF vertical antenna which appears on an earlier blog entry last year I believe. I erected and used one and it worked very well.

This is sad news as it was a small UK company making good products for the amateur market. Clearly the market is not big enough to support the volume of trade they had and all their commercial overheads. One wonders how many other small companies can make a success in our market unless they get major publicity in the big magazines or have a good website that attracts a world-wide audience of potential and actual buyers. I cannot recall SRC advertising too widely: maybe this was their problem - getting a critical mass of customers who told others and came back for more themselves.

This was the message on their website today: 
Due to an ongoing decline in trade Snowdonia Radio Company has stopped trading.
All contact avenues have stopped.
This has been a hard decision as we only reopened in January 2012, but ongoing high costs and a rapid decline in trade have forced our family business to close permanently.

Thank you for the business over the years from Simon and Liz, and we hope to speak to you on air.
Please note that there are some poor quality non SRC antennas available, These antennas look like SRC products but are not. SRC do not make antennas for anyone else......

73,   _._

23 Nov 2012

Big wheel antennas?

www.wimo.com big wheel
When I move to my new (higher) QTH on top of our local East Anglian "hill" next year I'll have to give some thought to what VHF/UHF antennas to erect for horizontal SSB/CW/digital DXing. I could go for a decent set of beams and a rotator or I could go for an alternative approach and erect a stack of big wheel antennas for 2m and 70cm. A single big wheel has a horizontal gain of around 2-3dB over a dipole but a couple will give almost 5dBd, which is similar to an HB9CV beam but without the hassle of a rotator and with almost 360 degree coverage.

For my sort of (occasional) 2m and 70cm DXing the big wheel may be a suitable solution. I have around 6 months to sort this out, so no rush, but I'd value inputs from people on this. Have you used big wheels? How effective were they?

Incidentally, even from my old QTH I've worked all sorts of decent VHF DX with just a halo and a few watts QRP in contests, so a lot depends on how prepared one is to wait for lifts or big contest stations to work. Clearly if the aim is to work 600-700km under flat band conditions then 100W and a largish beam are almost essential. I'm not entirely ruling such a station out of the question, but it would be a big change from my usual QRP, so pretty unlikely.

A photo in QRP Basics (2nd edition)

My wife has bought me a copy of QRP Basics (2nd edition) by G3RJV for Christmas. It came this week so we opened the pack to check all was well, before putting it away for a month.

Imagine our surprise when we spotted a photo in it of me with grandson Lucien (when he was very young) at my operating table.  Lucien is the little lad (now 5) who was tapping out CW on one of my YouTube videos and playing with my audio kit on another. As I never did manage to get either of my two sons interested in ham radio, I'll be lucky to get any of my grandchildren interested, but I shall try.  Regarding the rest of the book, I'll let you know on Christmas day after reading it with a minced pie in hand. As it is written by Rev George Dobbs, I am sure it will be another excellent book about QRP.

20 Nov 2012

10m local range?

With the 10m AM Tenbox design coming along nicely I'm reminded of the fun we had in the early 1980s with 10m FM using converted CB rigs here in the UK. Using a converted CB radio with 4W FM into a vertical half wave antenna I was usually able to make contact with similarly equipped stations up to around 25-30 miles away pretty regularly. Certainly within a 5 mile radius signals were fully quietened, even to mobiles.

So, I am wondering how I'll get on with 0.5W of 29MHz AM? My expectation is that with a similar antenna (1/2 wave vertical - I currently use a horizontal halo) I should be able to cover 3-5 miles without too much problem. I'm wondering what sort of ranges people achieve with AM CB radios (WITHOUT add-on PAs!) where this mode is legal?  Running a few dB more power is no problem if required of the Tenbox design.

When 10m is wide open it is possible to work thousands of miles on FM but I always found that the competition was too great and therefore the mode is not well suited to DXing. The aim of the 29MHz AM Tenbox is just for very local communications and definitely not for DX working. In my mind I see the Tenbox being a modern version of the old Heath HW19 (the Tener) rig - see the image and data on the Rigpix page

WISPY 10m WSPR beacon video

A few people have requested a video of WISPY, my QRP WSPR beacon for 28.1246MHz. This video shows the TX beacon only. I have a companion RX breadboard that works well and at some point these will be combined into a small 10m WSPR transceiver.

Tenbox 10m AM RX video

It is hard to contain my enthusiasm for simple transceivers and super-regen receivers! This video shows just how well the RX breadboard for the little Tenbox 10m AM transceiver works. 1uV (-107dBm) is a very good signal and it will still detect a well modulated AM signal at -120dBm. Selectivity is not good with this type of receiver, which is the main drawback. However for its intended application - a simple transceiver for local nattering across town - it should be fine. Some people use super-regens as the IF stage of AM receivers. If a filter is added ahead of the super-regen IF this overcomes the selectivity issue but makes the RX design more complicated.

19 Nov 2012

Tenbox 10m AM rig - a bit more

Although I had little time today, I experimented with adding varicap tuning to the Tenbox AM transceiver's RX section. Only problem was I had no varicaps, so tried using a few different diodes and a transistor as a varicap. 1N4148 and a Germanium diode reverse biased hardly produced any change in capacitance going from 2-12V. I know a 1N4007 works quite well but could not find one. Then I used a 2N3904's base-collector junction and got a few pF of change. In the end I just did as I did in the Sixbox and used a fixed capacitor in series with a 365pF polyvaricon tuning capacitor. This moves the RX frequency as much as I need at around 2MHz maximum.

2 countries worked on 500kHz with JT9-1 mode

Well, the JT9-1 test QSO with G3ZJO was a total success and completed in around 10 minutes this evening. Later, I called CQ on JT9-1 and got a reply from OR7T in Belgium who is 334km away. We worked, exchanging reports and 73s but I am not quite "all with it" with the sequencing of reports, R, RRR etc in JT mode exchanges.I am learning, HI.

G3ZJO in QSO with G3XBM this evening on 500kHz
The WSJT digital mode JT9-x is certainly an interesting mode. There are a few bugs in the code still, and more bugs in the operator using it (me!) but I am sure to use this mode more in future on 472kHz and 136kHz.

500kHz JT9-1 test this evening

G3ZJO and I have reported each other's 500kHz WSPR signals and each managed to get reports from close on 1800km away but, despite being only 50km or so apart we have yet to work each other on MF. This evening we are going to attempt a WSJT mode QSO using JT9-1 mode with 1 minute TX periods. I'll report back later how we get on!

More Chromebooks

The new Acer C7 Chromebook on the
www.cnet.com site
A few weeks ago I mentioned the Samsung Series 3 Chromebook which is available in the UK for £229. Now I see there is a new entry, the Acer C7 Chromebook which retails for just £199 here and $199 in the USA. This sports a 320GB hard drive and, like the Samsung, a high resolution 11.6 inch display.

The main drawback (or is it an advantage?) of a Chromebook is that it uses the Chrome OS and depends a lot on cloud based applications, although quite a lot of applications work off-line too these days.

Certainly for a second PC at home and on the move it has to be a good bet.

18 Nov 2012

472kHz WSPR this evening

After the CW QSO and 500kHz WSPR TXing this evening I switched over to 474.2kHz USB dial WSPR receiving, whilst I watched "Homeland" on TV (BTW, this is a truly excellent US drama series - I don't usually like US dramas). Good signals coming through from the usual suspects, HI. The weaker signal at the bottom of the image is DF2JP.
474.2kHz WSPR this evening
It sounds like the first UK access to the 472-479kHz band will be for old 500kHz NoV holders, which includes me, on Jan 1st 2013. It is NOT likely the band will be generally available in the UK at that time, but some time later. Even the 500kHz NoV holder access to the new band is not yet certain on Jan 1st 2013. Watch this space!

CW QSO with M0FMT on 500kHz this evening

After the usual reports from all over the place on my 50mW ERP 500kHz WSPR I took a listen around for some CW stations this evening. G3XIZ was calling CQ and listening on 80m crossband, but then I heard Pete M0FMT not too far away in Hitchin calling CQ. He heard my reply and gave me 529 report. He was about 549 with me deep in the noise that remains on the band. A few days ago this QSO would have been impossible because of the local noise here. The offending noise source (central heating controller SMPSU) is switched off!

Barbados on 10m QRP

8P6BX in Barbados
Whilst looking for QSOs with Lesser Chirpy on 28.060MHz this afternoon I heard Ron 8P6BX in Barbados calling CQ. No go with 70mW so I turned on the FT817 and worked him with 5W getting a 569 report. He was running 3W and was peaking 589 with me. It was a nice, solid 2-way QRP QSO on CW.

17 Nov 2012

Autumn projects - an update

Well, I don't seem to be getting on too well with my autumn project list! The 472kHz transverter got finished, as did the WSPR beacon rig for 10m. I also managed some VLF earth-mode work. However, I've still to get back to the 481THz (lightbeam) over-the-horizon tests using the new higher power Phlatlight 5W LEDs. Neither have I rebuilt my 10m halo or erected a proper RX antenna for LF and MF. Mind you, I've added a new project, the Tenbox 10m AM transceiver, which is progressing quite well so far.  In the end it doesn't matter what gets done and when as long as I'm enjoying the hobby and experimenting with simple ideas.
Burwell Steven's Mill © Copyright Rodney Burton and licensed for reuse under this Creative Commons Licence.
Around the middle of 2013, if things go to plan, we are moving home to a bungalow in the same village which is located on the "hill" (this is a relative term in East Anglia!) next to Burwell windmill and museum. The windmill has just received a National Lottery grant and should be fully restored to full working order with 4 sails. This will be about 20m from our front door! I'll expect to be asked to do a "windmills on the air" weekend, HI. Burwell Museum is really something quite special and well worth a visit.

With what will be a much better VHF and UHF take-off I will be tempted to get much more active DXing on 2m, 70cm and 23cm from the new QTH. This is likely to bring a whole new set of challenges.

Lesser Chirpy spans the Atlantic (10m QRP)

My 28.060MHz ultra-simple QRP transceiver was copied in the USA this afternoon. K3MM (Maryland) reported me on the Reverse Beacon Network as 7dB S/N at 15wpm on 28.060MHz. K3MM is in FM19JH which is 5886km away.
Initially I was unable to hear any stateside stations to call for a QSO. Still, the rig has now been copied across that big ocean! Power out into the halo is around 70mW.
VE2TH was coming through OK with 5W and might have been workable but the band faded out.

Testing the Tenbox on 10m AM today

Today I wanted check how good the Tenbox 10m AM receiver (part of the intended transceiver) was in real use as opposed to measuring it on a signal generator.

So, I set up my FT817 on 10m AM TX on the lowest power setting, which is around 150mW carrier, and fed this into a makeshift vertical tuned with the T1 ATU. Using my PC, I made a short message "G3XBM testing on 10m AM" that I played in auto-repeat.
I then went for a drive locally with the little super-regen RX in the car being fed from a vertical mag-mount antenna on the car roof. The only antenna I had was an ATX15 base loaded whip for 15m, so I pushed a few sections in to make it resonate on 29MHz.

Results were encouraging. Out in the car my 150mW AM TX beacon message could be copied out to about 2 miles away, although this was limited by QRM from W2VW (!) and VE3OWV (!) who were coming through with 59 signals on the RX on 29MHz AM. When they dropped carriers copy was fine. It's fascinating to think my 150mW AM signal was having QRM from 5000km away!
A super-regen is not really suitable for use when 10m is wide open, like it was this afternoon. Nonetheless I was able to copy stateside stations on 10m AM on a short base loaded mag-mount pretty well. For its intended purpose as a local across town natter box, I think the Tenbox is going to be fun. With 6dB more power out (my aim for it) it should be certainly possible to work G6ALB 3km away in the next village.

The next stage is now to build the TX part and test this.

16 Nov 2012

After the noise: 160m CW QSO

Following my small successes last night battling my local man-made noise sources, this evening I managed nearly a full QSO with GW0IRW on 160m CW when running 5W to my vertical coax to the 10m halo. The noise level is now low enough to sensibly copy stations on 160m, which I've not been able to do for months at night.

I am now monitoring 474.2kHz WSPR hoping to improve on my reports now the local noise floor is much lower. SM6BHZ is already coming in at a respectable -14dB S/N. He is usually pretty strong so it will be interesting to see how many others come through this evening.

15 Nov 2012

Winning the noise battle a step at a time

This evening I've been trying to track down various noise sources that have been making reception on MF and the lower HF bands all but impossible in recent weeks. I'm pleased to report a couple of successes.

My first "trap" was the 12V Netgear AD6612 AC-DC adaptor that feeds my Virgin Media internet superhub. This little terror was producing an S6-8 noise floor on many of the lower ham bands. I tried ferrite chokes in the leads but to no avail. Fortunately I had an old Linksys 12V supply with the same sort of rating and 12V plug. Swapping the PSUs over and, guess what, the lower HF bands were much quieter once again.

At 470-500kHz though I still had an S8 noise floor, so there was another candidate noise generator around. Switching everything off in the house the noise floor dropped, so it was in the house. In the end I tracked this down to a Salus mains powered controller that receives wireless signals from the central heating roomstat. Turning this off and, guess what, 470-500kHz goes much quieter too! This unit is quite close to my antenna wire and must have a noisy SMPSU inside. Luckily we tend not to have the central heating on in the evening so all I have to do is turn off the Salus wall unit controlling the central heating boiler and I can, I think, go back to better reception on the MF bands in the evenings.

In 30 minutes I've reduced the noise floor in my home considerably from LF to at least 10MHz. This goes to prove that with a little bit of detective work we can do a lot to overcome many of the noise issues plaguing us these days. Both the Virgin Media superhub and the Salus unit are new (less than 6 months old) so this also explains why the noise issue was not such a problem last autumn and winter.

If you have a noise problem then I recommend you do some detective work and very good luck.

Coils for projects

Many of the old TOKO range of coils are hard to find these days but an alternative source for many of these is now available from Spectrum Communications in the UK. See http://www.spectrumcomms.co.uk/Components.htm for more details. If you are a member of the GQRP Club, many of these are available through its excellent club sales. An example, the 45uH coil specified in my 472kHz transverter is available from the above suppliers.

Spectrum also sell a useful range of crystals as well as some of the harder to find, once common, MOSFETs.

14 Nov 2012

SHAMateur radio

Today the December 2012 RadCom dropped on my doormat.  P16-17 contains a review of the Acom 1500 1500W linear amplifier for HF and 6m. Now, I am sure this is a very well engineered piece of kit, but at £2750 including VAT surely this is not for real amateur radio?

Anyone buying this has probably spent a few thousand on a big Yaecom black box multi-mode HF rig, another £400-500 on a beefy rotator, another few hundred on a mast and another few hundred on an HF beam to put on the top. Total bill for all this approaching £5000 if not more! They may be able to work some DX slightly more easily than me with a 5W or less radio and a small wire antenna strung up in the tree, but I bet they have less fun.

I have no objection per se to people spending the money they earn as they choose, but what I object to is this sort of expensive kit being projected as a necessity to enjoy our hobby.

To my mind this is SHAMateur radio, not amateur radio. It is a cheque book hobby far far removed from the hobby I wish to be associated with.

I wish our national magazine would publish more articles about REAL amateur radio, the sort that young kids and people on tight budgets can afford and enjoy. If the RSGB is short of material then it should ask the GQRP club for some ideas and circuits! Amateur radio is a very varied hobby and I do not want to be a killjoy, but anyone picking up RadCom would believe you need a very deep wallet to be able to enter the hobby. This simply is NOT the case. OK there is some good beginners content (for example the excellent series by Eamon Skilton) but not nearly enough.

One thing that IS good in this month's RadCom is the review of QRP Basics by G3RJV on p39. The first edition of this was a very good book that showed what amateur radio is really all about. I expect the new second edition will be even better. I commend it to you!

Are you a radio amateur or a radio shamateur?

13 Nov 2012

Dell Inspiron 1545 power socket repair

My wife's laptop is a 3 year old Dell Inspiron 1545. Although otherwise a nice PC, this has a stupid design weakness: the power connector socket. This is on the side of the PC (back left) and it is almost impossible to use the machine and not snag the cord and socket regularly.

Consequently, over time, the SMA connector inside the PC has gone intermittent. The PC is covered by a 4 year hardware warranty and I hope that Dell will just fix this and not argue "wear and tear". I have had other PCs where the power socket is strain relieved within the housing and not had a problem.

One has just to look at the number of videos telling you how to fix this very issue to see it is a very common one. I like this video showing the repair in 3 minutes, although in reality it would take about 1 hour. In the limit I could do it myself, but let's see if Dell are in a good mood and are helpful first!

I do get really annoyed when a consumer product goes to market with such an elementary design weakness: this is the sort of rubbish that should have been spotted early in the design phase by design reviews looking for possible failure mechanisms. Dell should know better.

Tenbox progress (10m QRP AM transceiver)

Tenbox breadboard RX -115dBm MDS
Today I breadboarded a simple, but sensitive receiver for 10m AM in the Fredbox tradition. The standard Fredbox and Sixbox circuit was simply scaled down to 29MHz with great results using the breadboard with the Marconi 2022 generator. MDS for a well modulated AM signal is better than -115dBm (around about 0.5uV) which is actually better than I was achieving on 6m and 2m. Not bad for just 2 MPF102 FETs and 1 2N3904. For the tuned circuits (RF amp output and detector) I used a couple of T37-6 (yellow) toroids tuned with 15pF trimmers. There is a 10pF coupling capactor between them.  Of course this is a super-regen with a grounded gate RF amp to isolate the detector from the antenna.

The intended use of the Tenbox is local "across town" nattering when the band is quiet. The selectivity would NOT be suitable for DX use, although I'm sure it would pick up stateside 10m AM stations OK.  I am always amazed by how well a simple super-regen RX works: they just fly for me and are always incredibly sensitive and non-critical. People who have not played with these do not know what they are missing. I highly recommend the RX in the Fredbox

Next stage is to breadboard up a simple AM modulator and TX strip. Again, I shall copy the basic Sixbox design but this time add a linear amp (a few 2N3904s in parallel as in the WISPY beacon) to get the carrier power to a useful level.

In summary, an interesting and productive hour or so after tea.

Weak signalling comparisons

Over the last few days I've been trying out my Lesser Chirpy 10m 80mW CW rig putting out CQ calls on 28.060 periodically and listening for replies and RBN reports. In three days I've only managed 2 RBN reports at around 3000km with it. So, this morning I fired up the hombrew WISPY WSPR beacon on 10m to see what happened. This runs about 6dB more power at around 200-250mW pep effective on the WSPR band. On the first transmission I got 3 reports immediately at 2200-3500km. With WSPR it is SO much easier.

Conclusions? Well if you just want to know what propagation is like then a small homebrew WSPR beacon is all you need. If you want the fun of the chase and the chance of a few QRP CW contacts with a human then the Lesser Chirpy rig is up for the challenge.

Life is too short to sit there endlessly calling CQ with the key though. So, I think Lesser Chirpy will be brought out when  conditions and activity are good. Otherwise WISPY will whisper away quietly in the shack whilst I get on with designing interesting new little projects, HI.

UPDATE: After a few hours of 10m WSPR at 200mW I had a page of reports out to around 6500km. Back on 10m CW I tried a brief call with the FT817 at 5W and got a couple of USA spots on the RBN. A further 30 minutes of calling CQ with the 80mW transceiver and no reports or QSOs. Think I'll have to come back to 10m QRPp another day!

AM broadcasts on Medium Wave

The BBC recently switched off some of its MW local radio AM outlets for some weeks to see if anyone was listening. Results suggest few people listen to their radios in the UK on Medium Wave any more. I know I am one of them, preferring to use Band 2 FM. We also have a DAB radio but it is pretty useless in the kitchen where FM is perfect. I think it is a signal strength issue.

So, will the BBC switch off all its MW output? Will anyone care? It may soon be that AM will be a dying mode unless we radio amateurs use it and show its strengths.

See www.theregister.co.uk/2012/11/08/dab_am_bbc/.

12 Nov 2012

Microsoft Essentials virus protection

On our regular local Monday night 2m net on 144.575MHz (in the all mode section) - anyone is welcome to join us in the East Cambridgeshire area - the subject of PC virus protection came up tonight. Some months back someone told me about Microsoft Essentials which is a free virus protection package. I still use McAfee here and have another year to run on it, but wonder what people think about the free Microsoft package? Does it work well?

More DX on Lesser Chirpy

Another report via the Reverse Beacon Network from 5B4AGN in Cyprus this morning, but no QSOs and no further RBN spots. A brief outing this afternoon in which I'd hoped to get across the Atlantic proved to be a disappointment. There is always tomorrow....

The Argonaut VI is coming soon....

Just received this reply from Stan WD0BGS at Ten-Tec regarding the progress with the Argonaut VI. It sounds like they are now very close to releasing it.
"Hi Roger,

The Argonaut VI model 539 is in beta testing as we speak.  Our first production has gone into the hands of many users to determine any slight improvements before the second production run begins next month.  Our web site will be turned on and ready to place orders when all final numbers have been established and any firmware changes have finalized.

The price of the Argo VI will be $995 and available around December/January time frame +/-  The Argo VI will not be a kit and it will be a small 1-10 watt output multi-mode QRP transceiver.  It will not contain 60 meters or 12 meters due to the design and size restrictions.  Watch our web pages in December for release notes and a page about the Argonaut VI.

Stan Brock, WD0BGS"
Now, I have not done the sums yet, but $995 does not sound like a very competitive price for a radio that misses 2 HF bands out. The Argonaut has to be a seriously good radio when put next to the Elecraft KX3, but then Ten-Tec know this only too well. They must have decided this price is right and it will sell.

The UK price tends to be close to the US price but in pounds. If importing from the USA directly we have to add Royal Mail handling charges (£8) and VAT at 20%. I gather import duty is not payable though. Against a 10 year old FT817 this looks like a lot of money.

Another 472/500kHz transverter built stateside

Just got this nice email from John WA3ETD/WG2XKA who has successfully built another copy of my 472/500kHz transverter.

"Hi Roger,

I completed your design XVTR Saturday here, on the air on WSPR last evening had eight uniques and flawless operation.

I slightly modified the PA by adding the gate resistor and diode, as well as driving the FET via a cap. I only had surface mount IRF-510, that is the raised, floating copper heatsink that sits on two tiny standoffs at drain potential.

Thanks again for publishing your design!  PIX attached.


WG2XKA's version on my 472/500kHz transverter

11 Nov 2012

Rotatable dipole or HF halo?

DES Rotating Dipole
A new antenna is being advertised by InnovAntennas: a compact rotatable 15, 10 and 6m dipole with droopy ends so that the overall length is no greater than a single 10m dipole. It is called the DES-Rotating Dipole. The image on the right (from the InnovAntenna website)  shows the neat arrangement which can be fed directly from 50ohms. Without lossy traps the power rating is at least 5kW, rather more than I would ever need.

Now, neat though this is, I question whether it is really worth the expense. At this stage I have no idea of price but I would expect somewhere between £50-100? My simple Homebase-10 wire halo is MUCH smaller because the 10m dipole is arranged in a square. A 6m halo can be nested inside very easily and fed with the same coax. To add a 15m halo would only increase the size by 50%. Unlike the Cobweb antenna, my simple design could be assembled as a 3 band version for less than £15 with all new parts.

Homebase-10 10m halo
How much down is the halo compared with the nested dipole?  In most directions, apart from a tiny segment in the direction where the ends of the halo meet, less than 2dB. What is that in S-points? Hardly noticeable at all at about 1/3 of 1 S-point.

A dipole, if rotated, does have the advantage of being able to null out interference but I am not sure this is such a benefit. For me, it is either something like a horizontal halo which tends to be a "quiet" antenna picking up little local (vertically polarised) man-made interference or a small beam which would have some gain and directivity. However, the latter will only add about 0.5-1 S-point in signal level and, time you buy a decent rotator and the beam, you will have paid 10-15 times more for the privilege. A beam does add directivity and interference rejection, but is much larger. For me it is a "no brainer".  My simple little halo has allowed me to get QRP reports on SSB, CW and WSPR from all over the world. It is simple and works well.

Lesser Chirpy reaches Cyprus

No QSOs this morning yet but a RBN report from 5B4AGN in Cyprus with the 80mW lesser Chirpy 10m CW transceiver to the Homebase-10 halo. This is the first time I've looked for RBN reports with this tiny transceiver.
Reverse Beacon Network report for 80mW Lesser Chirpy
When I got back from my grandson's birthday party in London in the late afternoon I put out about 10 CQs on 28.060MHz with the rig, but no QSOs or RBN reports. I shall try again during the week.

10 Nov 2012

Ten-Tec Argonaut VI - has it died?

The Ten-Tec website still has no information whatsoever (that I could find) about the Argonaut VI which was supposed to be ready to order by now. I'm wondering if, despite talk of pilot runs and the like, Ten-Tec has had second thoughts and decided not to release it after all.  I've just written to Ten-Tec to find out what the news is. I've asked when it will be available and at what price. We'll see what comes back from the sales team.

Solar prediction update

NASA has slightly modified its predictions for the current sunspot peak showing the peak month as May 2013 with a 95% prediction of just over 100. The smoothed number will peak later.  Although conditions will gradually deteriorate after the peak, the monthly sunspot number is still expected to be over 60 right until mid 2016. See http://solarscience.msfc.nasa.gov/images/ssn_predict.txt . The evidence in the short- term looks somewhat less good, but things can change rapidly.

So, get on the air, especially on the higher HF bands and enjoy the good times!
Date/Month 95%   50%     5%
2012  11  96.1  68.7  41.4
2012  12  97.2  69.7  42.1
2013   1  98.2  70.5  42.8
2013   2  99.1  71.2  43.4
2013   3  99.8  71.8  43.9
2013   4 100.4  72.4  44.3
2013   5 100.9  72.8  44.6
2013   6 101.3  73.1  44.9
2013   7 101.6  73.4  45.1
2013   8 101.8  73.5  45.2
2013   9 101.8  73.5  45.2
2013  10 101.8  73.5  45.2
2013  11 101.6  73.3  45.1
2013  12 101.3  73.1  44.9
2014   1 100.9  72.8  44.6
2014   2 100.4  72.4  44.3 

Delay getting 472-479kHz released in the UK?

On the GQRP Yahoo group today Colin, G8FRA/M5FRA, posted this message regarding the release of the new 472-479kHz band in the UK. If his information is correct, there could be some delay in the bulk of UK amateurs gaining access to the new MF band. This would be a great pity.

From what I learned by talking to a couple of people at Newark (RSGB and OFCOM) we will not get the new allocation in Jan 2013. Those with existing SRPs will have them changed to remove 500kHz and add 472-479kHz. I asked when applications would reopen and there was no date for that. Evidently OFCOM have to consult before there can be any changes to the license schedule and have been too busy with the Olympics to make any progress on that. I did suggest that the RSGB should come clean as anybody who has spent time and money on new equipment might just be a bit disappointed.

Colin - G8FRA/M5FRA

If this information is correct, then why is our national society, the RSGB, not making this public? I have written to OFCOM and the RSGB asking for more concrete information.

10m Lesser Chirpy in a new box

Lesser Chirpy (should be No Chirpy!) 10m transceiver
At last I've got around to putting my Lesser Chirpy ultra simple 28MHz CW transceiver in a case. I've added an extra switch so I can listen on another RX if conditions are such that the internal RX struggles, although even with my 64 year old ears I can clearly hear better than -100dBm signals on Lesser Chirpy. Offset is set at about 700Hz between RX and TX. The FSK keying is a bit odd - there is only around 100Hz shift between carrier on and pseudo off (i.e. shifted) but there is zero chirp. This is now a seriously useful transceiver, albeit very very simple. Power out on this sample is around 80mW, so I believe this is certain to span the Atlantic in the next few days, if only to be spotted on the Reverse Beacon Network.
Lesser Chirpy cased
I have not got an internal low pass filter on this model. One should be added between the rig and the antenna to ensure low 2nd and 3rd harmonic levels.

9 Nov 2012

Ferrite Rod RX antenna for 472kHz

 In an attempt to overcome my high LF noise level, today I made a small ferrite rod antenna and preamp for 472kHz which I've been trying out on RX. The ferrite rod was just a small 10mm diameter 60mm long rod (i.e. it is a small ferrite rod) tuned with a 365p variable capacitor and fed into an MPF102 gate at high impedance with the output fed to the FT817 via an emitter follower. At the moment the rod is sitting on the bed in the shack. Despite this, it is picking up WSPR from DK7FC.
I shall have to try a larger ferrite rod next and try placing this remotely in the garden away from noise sources. For a first attempt this is encouraging.
The prototype used to receive DK7FC and G3ZJO

UPDATE: later I tried the 60mm ferrite rod and preamp on 500kHz and copied G3ZJO on several occasions. 

8 Nov 2012

MF "swish, swish, swish" interference

In recent months I've been suffering from man-made noise on MF which was not there before. I've a constant S8 noise floor now (it was around S1-2 before) and as I tune from 300-500kHz I get a rapid  "swish swish swish" every few hundred Hertz. I think there are frequencies where it is stronger but the new 472-479kHz is BAD, although I still manage WSPR decodes from DK and SM. For CW it would be just about impossible.

Now, I haven't yet tried to systematically work out what this is yet and nor have I tried a small external loop on RX or an E-field probe down the garden.

Before I start to investigate, does anyone have a clear idea what this rapid "swish swish swish" QRM is likely to be? I don't think the source is in my own house and on one side the neighbour's house is currently unoccupied. I have tried the obvious (turning off lights and SMPSUs in my own place) with no success.

Any knowledgeable help would be much appreciated.

Man-made interference at MF and LF is a critical consideration for newcomers. I hope that a new version of the RSGB book "LF-Today" (if one is planned) will give some information on how to search out such sources and some strategies for how they might be mitigated.

Building requests

In the last 24 hours I've had a couple of requests from people asking me if I'd build some of my projects for them. One person asked if I'd build them a Pipit 15m transceiver and another a 472kHz transverter. Regretfully I had to say sorry that I could not.

It is not that I don't want to. Rather, it is because I don't have enough spare time! I've so many projects on the go currently, and a stack more in my head waiting to get started, as well as trying to live a normal family life doing the usual chores. Then we have the grandchildren who take time, not that we mind this at all.  So, please do not ask if I can build projects for you. I always try to help with advice and suggestions when asked - I try to respond within 24 hours unless I am away -  but I do not want to do building.

Quite a few of my projects would benefit from a small PCB. This is also something that I rarely get around to because I've already moved on to something else. There is probably a small business possible, if I was inclined, designing projects, making a PCB and selling kits. This is unlikely ever to make me rich though and I'd prefer to be a source of ideas instead.

Norway on 4m

The Norwegian authorities have granted further access to parts of the 4m band (70.1875 - 70.2625MHz), with some regional limitations. This is great news for 4m where more and more countries are now gaining access. The following chart on the Four Metres Website (I've linked to it here) shows the countries with 4m allocations currently.

6 Nov 2012

Norway gets 472-479kHz right away

Norway has been granted immediate access to the new MF band with CW and all digital modes permitted. See  https://www.nrrl.no/318-news/latest-news/492-lb1g .  I hope some LA stations come on to WSPR in the new band this evening.

More 474.2kHz WSPR

This evening I am copying 3 stations, so far, on 474.2kHz USB dial WSPR: SM6BHZ and DK7FC are both good signals with QSB but I've also copied DL3ZID at -27dB S/N. QSB is slow and it takes about 12 minutes for DK7FC's signal to go from -27dB S/N to -12dB S/N.

Lesser Chirpy 10m transceiver

You may recall that some months back I did a tiny transceiver for 10m CW ....that chirped. Well, this is the latest version that does NOT chirp! Instead of keying the oscillator current, I now key the capacitor that sets the oscillator frequency instead i.e. FSK keying. The latest version is shown here. Have a go: 10m is is good shape and you may get a few QSOs.
If the going gets tough (the RX audio level is low!) try adding an extra antenna change-over switch so you can receive on an external receiver instead. or add a 100n from TR2 collector and feed the signal into a sound card and SDR so you can use the PC's audio gain to help with copy and tune either side a few kHz.

472kHz transverter (rev K)

Several people have now built versions of my 472/500kHz transverter. The latest version is shown below which includes provision for an additional low pass filter when using a fairly long (less sharply tuned) antenna. Although some capacitors could be combined to reduce the component count, I've shown it using readily available high voltage capacitors. The 16uH inductors are 43turns of 0.71mm wire on 22mm white PVC pipe.
In the last few minutes I've been looking on 472kHz WSPR and see that SM6BHZ and DK7FC are coming through OK despite my S8 noise floor.
SM6BHZ and DK7FC this afternoon on 472kHz WSPR

5 Nov 2012

December's Practical Wireless

The December 2012 edition of "Practical Wireless" has my article about the 2m AM Fredbox and the 6m AM Sixbox transceivers that are described in more detail on my website. These simple QRP VHF transceivers proved to me that you don't need to spend lots of money to make simple transceivers that work. Both have produce interesting QSOs: the 2m Fredbox had several 90km QSOs with one at 160km, despite being only 10mW output and using just a whip antenna!

Today there is not that much AM activity on the bands but I think this is a great pity as the mode has a lot to offer. I do hope the RSGB can be (eventually) persuaded to add 144.55MHz as the AM calling/working frequency in the band plan. It is mentioned (almost lost) in the foot notes, but it needs to be properly shown. For some reason the RSGB seems to have a problem with 2m AM.

I hope others will build simple AM gear for 144.55MHz or crystal up some ex-commercial PMR radios and again enjoy the fun of 2m AM. Second hand AM gear for 4m and 2m can often be obtained for just a few pounds as no-one wants it.

GPS Route Logger

Last week I bought a Ventus G730 GPS Route Logger from Martin Lynch for £34.95. Today I tried it out for the first time on a walk in the bright autumn sunshine at Ickworth park, near Bury St Edmunds. I am totally delighted with it.

The map below shows the route taken as plotted on Google Earth. The data that comes out of the logger shows route taken, speed (average and instantaneous) , distance traveled, and altitude up and down. If linked to a digital camera file it can be used to geotag photos on a walk. I am very impressed that something this small shoved in your pocket can produce such fun results. I now need to find a use for this in my amateur radio experiments.
Google Earth plot of a walk today using data from the Ventus GPS logger

4 Nov 2012

500kHz WSPR tonight

My last post with this title got corrupted when I tried to edit it, so this is a shortened revised version. 500kHz WSPR this evening has been very good. In the last couple of hours I've been getting 8-9 reports with each transmission slot when running less than 50mW ERP. Best DX 707km to DG3LV.
500kHz WSPR reports this evening
I've downloaded the latest version of JT9 software and hope to try this for 2-way QSOs later this week on 500kHz. My current problem is the S8 noise floor which I hope to reduce by using a better sited E-field probe or loop antenna (for RX only) further away from the house.

There are still plenty of CW stations on 500kHz. One evening last week I had a very enjoyable CW QSO on the band with G3XIZ. Semi-locally there are around 3-4 stations on a regular Sunday morning 500kHz CW net.

1 Nov 2012

Projects pause

This week I am having a bit of a rest from amateur radio. We have two of our little grandchildren staying with us until Sunday and they take top priority. Anyway, one sleeps in my bedroom shack!  So it is off to ride on toy tractors, eating some cakes in a cafe and help Grampy deliver poppies.

With the XYL and grandchildren
There are some geomagnetic storms around so HF conditions are unlikely to be very good for operating.

Next week should see me back in action. My first task is to make some changes to the 472/500kHz transverter - adding an additional filter as shown in the Rev H schematic on my website so that it meets FCC requirements before an article on the small transverter appears in QST magazine next year all being well. It has been accepted. I've also got to update the schematic and parts list.

Next on the list is probably to get my 10m halo down for its rebuild that didn't get done last week. Then I am in to several possibilities including getting "Lesser Chirpy" going on air (the chirp free version of Chirpy) and casing it up. Also, there is the 481THz NLOS beacon with those BIG powerful LEDs I bought a month or so ago. There is also a new 136kHz transverter (like the 472kHz design but for 136kHz instead). And then there are all sorts of other ideas floating around in my head which probably won't get done for another year. These include a simple Fredbox version for 10m AM, an ultra-stable GPS locked frequency source to use on VLF and maybe microwaves later,  my permanent E-field probe and grabber for VLF/LF/MF,  an improved 136kHz stand-alone receiver, etc, etc. Hey ho!