13 May 2012

Universal QRP Projects Box?

This is really a follow-on from the previous post. As a "mechanically challenged" QRPer I really do hate the stage of putting a completed project into a tidy box. Some people love drilling holes but many do not, so I wonder if there is a market for a "universal" QRP projects box with pre-drilled holes at the front and back? Perhaps a variation of the GQRP Limerick project box could be made available for wider project use?

Most QRP transceivers need a power connector, a coax socket and a key on the back. They need a VFO(or VXO) control knob, a gain control and a socket for phones. Maybe another control and a couple of front panel switches.

So, I wonder why no-one (as far as I know) produces a pre-drilled box that could be used for a range of projects. Surely there is a market for this. A set of water transfer control legends could also be supplied with the box (remember the Radio Constructor sets?).

Just my thoughts having spent an afternoon engineering a 481THz transceiver mechanics and drilling an aluminium box.

How I hate drilling boxes

This afternoon I have been "engineering" my dual lens optical transceiver mechanics. This consists of 2 34cm long 110mm drain pipes (with 100mm lenses at one end) fixed together on a tripod mount with a sighting scope attached to one tube and an end piece at the focal points which will support the aluminum box housing the detector, the TX LED and the electronics. I had to work out how to support the two tubes in close alignment and how to fix these and the electronics to the tripod mount. This has involved a fair bit of mechanical engineering, which is the part of the hobby I absolutely detest. By this evening I think everything is ready and fixed together OK. The electronics box has all the holes drilled for switches and sockets. Now all that remains is to build tidy versions of my sensitive detector and AM transmitter.

When everything is finished - the end is in sight now - I will ask Bernie G4HJW for a sked over a fairly short (2-3km) line-of-sight path to check alignment and that everything is OK. Assuming this goes well then it will be time to try a 481THz QSO over a reasonably DX path.

12 May 2012

Light beam RX improvements

This afternoon I played around with my light beam RX trying to squeeze a few more dB of sensitivity from it. Well I think I have managed it by further optimisation of the electronics and by optimising the focal length. Now, in the dark, a barely lit LED in the ceiling of my lab is detectable on the bench without optics. With the 100mm lens I can detect a 1kHz subcarrier on the 481THz optical signal when there is no sign at all of the LED being illuminated. Some tests using an LED as a detector were less successful, so my plan is to make a dual optics AM transceiver with 2 drainpipes and 2 100mm lenses. With this I should be able to work the local nanowave stations over line-of-sight paths.

JT6m 6m QSO

This evening was a slightly historic occasion: my first ever QSO using JT6m mode on 50.230MHz. I have used JT65HF on HF but this was the first time with JT6m. Now you may be expecting me to say I worked some exotic DX by MS but this first contact was with M1BXF who was only about 20km away! Listening (more accurately looking) on 50.230MHz has resulted in seeing European DX on 6m under flat band conditions using JT6m. It can be quite entertaining to just leave the RX and PC running to see what DX turns up. You'd be surprised.

11 May 2012

QRP Auto-ATUs

For some years now I have owned an Elecraft T1 auto-ATU which works very well with the FT817, especially with the FT817 interface cable which automatically retunes the ATU when changing bands on the rig if the settings have previously been used. Just recently I started to have problems with this ATU when sometimes it simply refused to work. I contacted Elecraft for help and they replied to my email overnight, which was pretty good customer service. In the end it looks like the problem is just battery contact pressure: I managed to snap the plastic that ensures good pressure on the battery contacts and, by chance this evening, I found that pressing the battery hard brought the unit back to life. I may replace the 9v battery contacts with a snap connector. 

On the subject of QRP auto-ATUs, has anyone experience of the LDG Z-817? This is a bit bigger than the diminutive T1 but in some ways is a better arrangement for home use. This has to be retuned every time bands are changed but the method of interfacing to the FT817 control (to change mode and power during tuning and then switching back automatically when done) is good. The memories also store previous tunes so retuning when changing bands takes just a second or two I believe. I also like the way the Z-817 sits on top of the FT817. The T1 is fine for portable use but I never quite know where to put it when used on the desk at home!

Now, of course, if the FT817 replacement ever happens (Dayton in a few weeks maybe?) we will expect to see an ATU inside the rig, as for the Elecraft KX3.

10 May 2012

Radio Nederland and shortwave broadcasts

One of my favorite shortwave broadcast stations back in the 1960s was Radio Netherlands . I still have my QSL card from them somewhere. When testing my shortwave crystal set today I noticed a strong transmission of the Dutch language service today in the 31m band. Little did I realise (until tonight) that this is the very last day ever of transmissions in their worldwide Dutch language service.

The HF broadcast scene is quite a lot different from when I last seriously listened some years ago: there are far fewer English language services to be heard. I guess these days people who want to find out about different countries listen to broadcasts on the internet.

Also, the CW maritime services, which could be perfectly copied sometimes on a crystal set as a result of cross-modulation (the CW sounded like a raspy hiss keyed) are long gone. One of my interests some years ago was seeing how many HF marine coast radio stations I could positively ID on a simple crystal set: the answer was quite a few around western Europe.

In fact SWLing on HF is rather a dying scene I think, although devotees will no doubt disagree.

9 May 2012

Crystal set sensitivity experiments

This afternoon I had a little play with a simple crystal set to see what sort of minimum discernible signal (MDS) was possible. My previous experiments with single germanium detectors had yielded an MDS of around -55 to -57dBm in the 5-30MHz range with a high impedance crystal earpiece.

Today I tried the same test with both germanium diodes and a hot carrier diode (HP2835) with and without some bias applied to the diode(s). Best results were with the HP2835 and with about 0.11V forward bias applied. Only a few uA are needed so battery drain is next to nothing. MDS was around -62dBm for a well modulated AM signal. For the tuned circuit I used a T50-6 toroid with around 20 turns with an antenna link winding adjusted for best sensitivity/selectivity and a 365pF variable capacitor .

Incidentally, forward bias for the diode could be obtained by rectifying other signals available on the antenna such as MW/LW broadcasters using a separate tuned circuit, rectifier and reservoir capacitor. I must give this a try sometime. Several hundreds of mV DC should be possible.

Then I tried switching the diode with a second signal generator at a power of between 1-10mW to see what sort of sensitivity could be obtained on a CW signal. MDS improved by around 25dB to around -86dBm i.e. I could just hear down to around 10uV. This would be a just usable level as a basic HF SSB/CW receiver.

I also tried the same tests with a pair of high sensitivity ST-3 headphones that Michael AA1TJ kindly managed to find for me. These are much lower impedance than the crystal earpiece so I experimented with antenna match and the match of the diode to the tuned circuit, expecting a better performance at the best settings. Disappointingly, the results were several dB worse than with the crystal earpiece.

Now, the results with the crystal earpiece are very close to those (without bias) that I obtained some years ago, so I don't think my hearing (at 63 years old) has changed much for the worse. So, Michael must have incredibly sensitive ears as there is no way I was able to hear down to the levels he could with his passive receivers.

At the moment I am playing with the AM crystal set with -62dBm sensitivity listening to shortwave broadcasters. Fun.

Six continents on 10m WSPR

This afternoon I exchanged WSPR reports with RI1ANF in the South Shetland Is in Antarctica on 10m. This now means I've had reports this year from every continent on the 10m band using 5W or less with the wire halo antenna.

PA1B's power attenuator calculator (see link below)
As this is all getting rather too easy (!) maybe I need to follow Bert PA1B's advice and build a switchable attenuator so I can repeat the challenge with much lower powers. See his power attenuator design page for details of how to make suitable RF attenuators to reduce QRP rig output powers to milliwatts.

8 May 2012

50MHz, 432MHz and 481THz this evening

Well, this was an interesting evening. Just after teatime I noticed 50MHz was open with some strong Es signals from Europe. A few stations were worked on QRP SSB using the newly erected halo antenna (S52NR, S53OQ and OE5FIN). Heard, but not worked, on 50MHz were CT8/K0RUI in HM68 (Azores Is) and 4X4DK in KM72. Both DX stations were good solid signals on the halo.

Stations worked on 432MHz this evening (5W/4el)
Later I went out portable with my FT817 (5W) and my small "coat hanger" 4 element yagi for the RSGB 432MHz activity contest and worked 14 stations in just over an hour before closing as it was dark and I could not see the logbook very well. Best DX 155km although I did hear, but not work, F8BRK in IN99.

Finally, for the very first time, I have detected GB3CAM on 481THz (red light beacon) at a distance of 32km from the Nine Mile Hill site where I was active in the UHF contest. Signal was weak with lots of scintillation, no doubt caused by the rain that started up just as I began listening with my 100mm optical receiver (KA7OEI/K3PGP hybrid). If I can find another 6dB sensitivity I think the signal will be solid in low haze/clear conditions over this LOS path. GB3CAM is a very low power light source, so copying it is a big challenge.


7 May 2012

Monday nights at 8pm on 144.575MHz FM

Every Monday evening a number of East Cambridgeshire locals get together on 144.575MHz FM for an hour between 8-9pm clock time. The usual stations on the net are G6ALB, G3KKD, G4NUA, M3YPZ and G3XBM.

Originally this started as a regular session between G6ALB and G3XBM on 144.55MHz AM. We managed to engage in some sort of QRP related experiment most weeks. We've worked each other on all bands from 1.8-432MHz with extreme QRP and had 1-way contacts on 8.97kHz, 136kHz and 500kHz QRP too. We are 3km apart, which is an ideal distance to try all sorts of things from listening to each other on crystal sets to trying to see how weak a signal can be copied on each band: you may be surprised how little signal can be copied at this range: it is no wonder we suffer from so much interference on HF these days as nanowatts go a long way.

These days the net conversations cover all manner of subjects but, sadly, Andrew G6ALB and I don't get to do experiments so often: this is a drawback of a larger net. At some point I think Andrew and I will find another spot to do experiments on another evening whilst letting the Monday net continue as it is. It is fun to simply chat.

Let me share a pearl from this evening:  Alex M3YPZ, who has a truly fascinating background going back to working on radar in WW2 and research in Cambridge University, mentioned he had a book on how to improve his memory.  He lent it to someone   ....but could not remember who.  The joys of getting a bit older!

If you are the area feel free to call in to the net.

10m across the pond

Late this afternoon I was very surprised when my 5W to the halo was spotted on 10m WSPR by K9AN 6505km west of me. It is unusual, I think, to get 10m transatlantic propagation at this time of the year by F2, so wonder if this was Es propagation? There were quite strong PY stations coming through earlier, so it could be F2 back-scatter. Incidentally, 4X1RF and I seem to have a pipe between us on 10m: we WSPR spot each other most days and I often copy him when his beacon is running 50mW.

Further to my earlier post, WSPR allows one to do "gentleman's DXing": you can see how far your signal is reaching whilst running QRP and a simple antenna and still do other things in the shack at the same time. Perfect.



DX Chasing (no thanks)

Chasing DX is just not my thing any more. For example, on 10m CW this afternoon there was one heck of a pileup of stations trying to work 7O6T in Yemen. This is a rare country but those who get through tend to be the stations with the BIG beams, high power and who call and call. Occasionally, a QRP station with good skills can manage it. On rare occasions I have found DX before the pileups or the DX cluster shows it's there and then a QSO is possible.

But basically I am past this stage in the hobby now. I prefer to explore new things, experiment and have fun. I know that if I had 400W+  and a big beam up high I could work the world if I was patient, but having amassed well over 100 countries worked with 5W SSB/CW it matters not to me that I don't work that rare DX.

On VHF and UHF it can still be fun though, and counting squares is still my answer to train spotting, HI.

6 May 2012

AM lightbeaming down the street

With my wife manning the TX this afternoon and pointing it out of the landing window we managed a daylight speech test today with 100mm optics at both ends at 0.3km using the v.simple AM lightbeam TX described in the previous post. The LED was run with an 80mA standing current. Biggest problem was aligning the TX beam and the lack of talkback, but I managed to get 59+ copy of my wife saying, "I'm bored with this. Come home and have some tea" when I was aligned on the TX beam.

There is no doubt the simple circuit can be refined to improve audio quality when clipping, but it works. The RX is far more sensitive at night too.  I am now finding a way of replacing the XYL for these tests by using another source of speech such as a radio receiver or MP3 player. She is good at cooking and other things, but not at doing optical tests!

Later this week I'll begin experiments with a simple single LED AM 481THz transceiver.

481THz AM transmitter

This morning I took a step further towards making a complete 481THz lightbeam transceiver by breadboarding and testing a simple AM transmitter for use with a high brightness red LED. The circuit could hardly be simpler but works very well. The bias on TR2 is adjusted to give around mid-rail so the LED has a standing bias before audio is applied. Listening (without optics) on my modified KA7OEI receiver head and looking on a scope, the modulation looks good with around 150mA current into the LED.

4 May 2012

Dual band 10m/6m halo erected

10m and 6m nested wire halos on the mast
The Homebase-10 halo is now a Homebase-10/6 with a second dipole within the first covering the lower part of 50MHz. After just minor adjustment both bands have a near unity VSWR over the parts of the bands where there is CW/DATA/SSB activity.

Since making the changes I have exchanged 5W WSPR reports with FR1GZ  on 10m, and got -19dB S/N on 10m WSPR from CX2ABP (11127km), so that is still working as before. I have yet to work something on 6m to be able to judge the omni-directivity of the 6m halo.

Dimensions for the inner 6m dipole were simply scaled down from the values at 10m: the outer sections are 564mm long and the folded dipole inner section 873mm long (these are the dimensions each side of the feed point). A single 50 ohm RG58 coax feeds both 10m and 6m sections.

Details of the original Homebase-10 were in my Practical Wireless article a few years ago and also on my webpage at https://sites.google.com/site/g3xbmqrp/Home/homebase10 .

3 May 2012

Optical DXing and refraction

Although my own experiments at 481THz have so far been limited to around 9km non line-of-sight, the amateur experts around the world have been achieving remarkable ranges both line-of-sight (LOS) and over the horizon (NLOS). In the UK several groups are looking for longer line-of-sight paths up to around 147km.

Some interesting information is coming to light (no pun intended) about the refractive index of the lower atmosphere at optical frequencies. At radio frequencies the refractive index (K) is around 1.33 and I had always assumed that for lightwaves it was just over 1. But tests suggest this is NOT the case at lower levels such as over the near line-of-sight paths now being attempted. A recent paper by Barry Chambers G8ACN on the UKNanowaves Yahoo group suggests a much higher figure may be more appropriate for a lot of the time meaning that what may appear to be a non line-of-sight path actually is one. He cites some observations by G8CYW and others of distant factory chimneys and cooling towers that should not be visible over the distant horizon but frequently are clearly visible.

Many are familiar with optical mirages, but the fact that the optical refractive index is frequently in the 1.1-1.33 range surprises me. It suggests many more distant optical paths may be workable with suitable equipment than was previously thought possible without having to resort to clear air scattering or cloudbounce. With 481THz cloudbounce and clear air scattering the additional path loss (compared with a LOS path) can be in the 30-50dB range, so equipment for NLOS paths is much more demanding than for a quasi line-of-sight path.

May Projects

All being well I have a window of a few weeks before visiting grandchildren and the like, so I have a couple of new aims:

(1) Convert the 10m halo to a dual band 10m/6m halo
This should be a fairly easy task as I already have dimensions for the 6m halo and I've air tested it in the loft. All that should be necessary is to take down the 10m halo and change the feed and support arrangements so both the 10m and 6m halos are fed from the same coax. The pair of halos well clear in the air should prove an effective QRP antenna system for my 2 favourite bands.

(2) Complete my first optical speech transceiver
Strange though this is, I have made several quite sensitive optical receivers and a couple of reasonable power QRSS3 and CW optical beacons, but I've still not got around to making a complete optical speech transceiver. Locals hereabouts use baseband audio for TX, so this is what I should do if I want to work people like Bernie G4HJW. It would be good to get a few line-of-sight short range (up to around 10-15km) 481THz QSOs in the log-book soon. Based on my optical work so far this is not a difficult task, just one I need to crack on with.

Target for both projects is within 2 weeks i.e. by May 17th. We'll see.

New Granddaughter

Our granddaughter - just a few hours old
Not much amateur radio here these last few days as we've been to stay in Kent welcoming our newest grandchild into the world. She is our fourth grandchild. Mother and baby doing well. Not sure if I'll manage to get her interested in our hobby, but her brother is very keen on batteries and screwdrivers at the age of 3, so there is some hope there.

29 Apr 2012

More 10m DX and some Es

500mW 10m WSPR results - ZS6BIM best DX
Today I ran my 10m WSPR beacon at 500mW into the wire halo antenna. Conditions were quite reasonable with some good DX reports. Later there was a first sign of sporadic-E propagation around Europe - a sign of things to come for the next few months. I did try beaconing at 50mW for a little while but propagation had deteriorated so no reports were received this time.

28 Apr 2012

Amateur radio history DVD?

The ARRL has produced a DVD recently on the history of amateur radio in the USA over the last 50-60 years. See http://www.arrl.org/shop/The-ARRL-Film-Collection/ .  I wonder how much material exists on old film and video in the UK/Europe and whether there would be enough to make a DVD on the history of amateur radio on this side of the pond?

As I mentioned a few years ago, there was (once) a 78rpm sound disc made by G5UM of the last night of UK operation on the old 56MHz band back in the 1940s, but this appears to have been lost. Although there have been several books on the early history it would be wonderful to find and collate old film material on amateur radio in Europe.

Win XP PC - a full restore?

My main Windows XP laptop PC is now around 6 years old. It has a small 32GB hard drive and my own files occupy around 8GB of this, yet the PC says the C drive has only 3.8GB spare. There is a small back-up partition (about 3GB) and the rest must be program files and Microsoft bloat accumulated over the years. I've already done defrags several times and deleted all the files I know are safe to delete. CCleaner is also regularly run to sort out registry issues and I have compressed files where possible. McAfree anti-virus seems to do a decent job of keeping out the malware.

Although I hope to invest in a new PC soon, I'm considering doing a full system restore back to original factory settings in the hope of recovering all the lost/wasted space.  A full restore will need a few days of work to reload updates (SP2/3 etc) but there must be a lot of unnecessary rubbish there which would be cleared by a full restore.

My plan is to use this "old" PC to run WSPR and some VLF programmes and use a new PC for everyday tasks.

Apart from the usual back-up of any photos and data that are important, does anyone have any advice before I go ahead?

Better 10m conditions


Today I put my 5W 10m WSPR beacon on for a few hours during the day and was rewarded with reports from CX, PY, 5Z4, 4X, LB and G stations. Conditions appeared better than I have noticed in some while and this is proved by a look at recent sunspot activity. See http://www.solen.info/solar/ .

26 Apr 2012

Google Drive (bye bye Dropbox issues)

With the introduction of Google Drive, an online storage facility, I can at last overcome my issues with Dropbox and my VLF grabber. With Google Drive one can store up to 5GB free and more for a fixed price. With the PC or Mac add-on, the drive appears as a file(s) on the computer into which documents can be saved in the normal way. These then appear/sync on any PCs when you sign in to Google Drive.

The bonus is that you can make any file public and get a URL that others can go to. This means that a saved .jpg screen shot of a VLF grabber can be saved to a unique filename on the PC which then is visible to the world if they know the URL. From a webpage I can point people to the URL and they can see the screen grab as it is updated regularly.

I could do all this with Dropbox until about 4 months ago when it started playing silly and refused to sync on my WinXP PC complaining of a registry issue. Despite trying all sorts of recommended fixes none worked and I gave up on Dropbox.

In the coming weeks I will be mounting a more permanent E-field probe which will be connected to the PC whenever it is running and the VLF spectrum view(s) will be available on my sub-9kHz website.

25 Apr 2012

Email questions

As my blogsites and websites attract quite a few visitors, I get a good number of emails from people asking me questions about my projects/thoughts. Whenever possible I try to respond to these right away but occasionally, for example when I am on holiday or have filed the email in the wrong place before answering, I don't reply. Please accept my apologies and write again if after a week or so you've not had an answer.

My standard answer when people ask advice about my circuits is that they are never guaranteed and some experimentation will be needed in any particular implementation layout. The circuits worked for me and should for you if you are prepared to "tweak" values a little.

24 Apr 2012

50MHz UK Activity Contest

This evening I have been listening (and having a few 5W QRP QSOs) in the RSGB 50MHz Activity Contest. This is a good opportunity to find out how effective my wire halo in the loft is. Well, I have worked the locals (G6UW, G3PYE/P and G4BWP) and managed a "QRZ the CW" from G3MEH about 50 miles away. I suspect the results would be several dB better with the halo further up in the air co-located within my 10m halo on the external mast.

Elecraft KX3 production ramp up

Elecraft KX3 units are starting to make their way into customers' hands now, although the initial product rate has been quite low. On the KX3 Yahoo Group there have been a few reports of initial huccups although this is to be expected in any new production run and, as always, Elecraft has handled these very well. According to Wayne Burdick, production is soon expected to ramp up now these initial problems are being ironed out. Wayne writes:
"Off the top of my head....  We had one unit with a dead MCU clock crystal (extremely rare). One radio wouldn't turn off because a mic wire was touching another component (we're looking at heat shrink for that). Two had problems with EEPROM due to a firmware bug I found and fixed at 1:30 AM on Monday morning. This firmware is already in beta test. 

Mostly just new-product syndrome. We really are on the verge of serious shipping increases."
 I have still to decide if/when to order one. The initial reviews on www.eham.net have been excellent.

18 Apr 2012

Low cost rotator

In my search for a low cost rotator for small and lightweight VHF/UHF yagis I see that Conrad Electronics UK sells an "external TV rotator" for £52.99, plus postage from Germany with a free 2 year warranty.

3 core cable, 70 secs 360 deg rotation, 45kg load, 300Nm bending moment, 21.6Nm torque.  See eBay item 180832166179.

Does anyone have any experience of this rotator?

16 Apr 2012

Rotators or big wheels

There was a time when a small rotator capable of turning a modest 2m yagi could be bought for around £40 but there appears to be little available now below £300. The low cost Yaesu rotator (G250?) appears to be unavailable now.  I was thinking about erecting small beams for 6m, 2m and 70cm and was wondering about suitable rotators, but am rather put off by the costs.

A better alternative may be a big wheel antenna with around 3dBd gain omnidirectional, or more if two are stacked. 5dBd is at least as much gain as an HB9CV without the worry of a rotator.

Elecraft KX3 leadtimes

As a potential buyer (still thinking about it), I asked the sales desk at Elecraft what sort of leadtime I could expect if I placed an order for a fully loaded , ready assembled KX3 in the next couple of weeks. This was the reply:
Roger,

Thank you for your inquiry and interest in the KX3 Transceiver.  Orders placed now will ship in 90-120 days. We are working hard to make it less than that, but right now that is my best estimate.


Thank you,

Lisa
So, 3-4 months wait currently.

Homebase-6 (50MHz halo)

Homebase-6 50MHz halo prototype indoors ready for tests
This afternoon I had a go at scaling my Homebase-10 (28MHz wire halo) down to work on 50MHz. I simply scaled the dimensions by 28.3/50.1 (the ratio of the centre frequencies) and performance was almost spot on with a low VSWR in the DX part of 6m. So far I have only tried it in the shack holding the antenna in the air by hand and keying the TX to measure SWR. Next stage of tests will be to erect it in the loft space before erecting a more permanent version within the 10m halo on the top of the mast at the back of the house at a decent height. Still, a promising start. In the end I may opt for a small 6m beam like a Moxon or HB9CV though.

UPDATE 1600z : I have now erected this horizontally in my loftspace although it is more triangular than square. Match is good so I'll see how it performs locally next.

UPDATE 2100z: I am surprised that I'm unable to copy the more distant UK 6m beacons such as GB3BUX and GB3RAL which use horizontally polarised antennas. I need to monitor for longer to see if they appear by MS or tropo.

Winter projects review

Back on Jan 4th this year I put a list of projects that were on my "to do" list on the blog. As winter is now over it is time to review progress (or rather lack of it):
Lightbeam RX. The aim is to detect the GB3CAM 481THz optical beacon at a distance of 32km from my nearest highspot.
Well, the RX has been improved considerably and is now very sensitive and is capable of NLOS reception, but I have still to make a successful reception of this beacon.

Light beam transceiver. Following on from (1), this will either be a transceive head with a transverter or an FM transceiver that I can duplicate so I can talk to others who can borrow the second unit.
This has not progressed at all. It is still my intention to do this.

Rebuilt VLF earth mode beacon transmitter. In a few weeks time I will be able to put out a stable signal on 8.97kHz  (the usual VLF test frequency) rather than 8.76kHz. My intention is to rebuild the whole beacon TX so I can run 10wpm CW, QRSS3, 30 and 60 modes as well as WSPR.
 I have recrystalled and tested the existing beacon for 8.970kHz but the full rebuild has not happened.

Improved LF loop and E-field probe antennas. I want to erect a more permanent external antenna for VLF and LF grabber work and mount these away from the house.
Improved E-field probes have been tested but I have not erected these externally.

Case up the 137kHz transverter. This has been a rat's nest on a piece of copper laminate for too long!
Still to be done.Not started.

28MHz WSPR transceiver based on a 14.060MHz crystal doubled in a DSB direct conversion transceiver circuit.
Not started and now unlikely to be done.

In my defence, I  have done a few other projects including some 160m transmitter and 160m loft antenna work and quite a bit of experimentation on the 481THz kit although few products at the end of this. I want to do one more thing very shortly and that is to erect a 50MHz (Homebase-10 style) wire halo either in the loft space or on the mast outside in time for the Es season.

In summary, I think one can say I am what my mother-in-law called a "fireside fusilier": I'm always gunner (going to) do this and gunner do that!


My old 2m AM rig

This morning, whilst clearing out some paperwork I came across this old B&W photo showing my 2m AM transceiver from the mid 1970s. It had a tunable RX covering 144-146MHz using a free-running VHF VFO (perfectly fine for AM use) and a crystal controlled transmitter; if I recall correctly, it had a few crystals that could be switched. The TX put out around 500mW of AM and was based on the PF2AM transmitter by Pye Telecom, a project I was involved with at the time. It was built in an aluminium box covered in wood effect Fablon.

The rig was also used for CW, goodness knows how, by having an external BFO held near the rig to demodulate a CW signal. Drift was a major issue on CW as you can imagine! Using this Heath Robinson arrangement I had a weekly sked with G5UM some 80km away every Monday night for several months and regularly received 559 using an HB9CV antenna in the loft.

The rig worked some useful AM DX across the UK with the best DX from home being a station in northern France one evening but it was really used as a local natter box in the Cambridge area.

When the ubiquitous Liner-2 2m SSB rig appeared I managed to buy a second hand one and this homemade AM rig was abandoned. I cannot remember what happened to it. It is nowhere to be found, so was probably taken apart for bits, which was a pity. Today I still use 2m AM from time to time and it remains a perfectly acceptable mode for local contacts with very simple kit.

15 Apr 2012

KX3 reviews on eHam.net

There are now 4 reviews on www.eham.net for the new Elecraft KX3 QRP transceiver and the rating is 5 for every one so far. See http://www.eham.net/reviews/detail/10271. Although it is a lot of money it certainly looks one fantastic little radio. I am tempted!

There is a video walkthrough too by K2UM which is worth a look.

The Titanic Radio Page

Lots of interesting information and photos about the Titanic radio room at http://www.hf.ro/.

The photo shown is from the above site (I could not link it) and shows the only known photo of Titanic's radio room. It was taken by a passenger who disembarked in Ireland.

14 Apr 2012

Lynton and Barnstaple Railway


On our holiday in north Devon last week we enjoyed a ride on the steam hauled Lynton and Barnstaple Railway. This is a delightful narrow gauge line that runs through a small piece of Exmoor countryside. When the line was originally build and opened in 1898 this 1ft 11.5inch gauge line ran all the way from the market town of Barnstaple to Lynton on the north coast winding its way around the hills. It included some long 1 in 50 inclines. The narrow gauge was chosen to minimise the costs and to allow tight curves on the line. It closed in 1935. Today the line is run as a trust and only over a very short length although, funds permitting, it is eventually hoped that the whole length can be reinstated as few obstructions prevent this. If you are in this part of the west country I can recommend a visit to this fascinating little line.

This is a video on YouTube showing the line as it was in 1935.

QRP FM pedestrian portable

Today I got back from a week in north Devon where my wife and I had a holiday cottage. The weather was pretty good for the time of the year allowing us to get up onto the hugher parts of Exmoor on several occasions. With my trusty VX2 handportable I managed to work plenty of stations through various repeaters in South Wales but my best DX was a simplex QSO on 145.525MHz with G4TRA in Gloucestershire at 101km. Despite just using the VX2 and a quarter wave whip he gave me a report of 59+20dB when I held the rig horizontal. To quote Steve, "you sound like you are in the next garden". Following this contact I worked MW0ZAP simplex. Time (and batteries) prevented me trying for more QSOs but I'd forgotten how well FM simplex works when you are on top of a moorland hill with a 360 degree takeoff.

4 Apr 2012

FT817 in short supply?

I am hearing repeated stories of the FT817ND being in short supply from various dealers in the UK. One rumour is this is due to component supply shortages so units are not arriving from Japan in the numbers needed.

Of course there could be another explanation: the rig is about to be replaced at long last.  It is not unusual for dealers to be told to run down stocks of the older models which will be harder to shift once a newer model becomes available, except with significant discounting (think of the iPad3).  Once a new model arrives sales will go sky high.

Now, I have no information at all, so don't write to ask me, but I would dearly love to know the truth.

2m/70cm DXing

See http://www.f9ft.com/ antennas
On a few occasions in the last year I've operated /P in the RSGB's UK Activity Contests (UKAC) on Tuesday evenings and thoroughly enjoyed them. Even with just a small halo on 2m and a 4 el yagi on 70cms I was surprised how much could be worked and the high levels of activity.

It is some years since I've used 2m and 70cms from home with a horizontal yagi and I am tempted to erect something to give it a go. I know that outside of contests activity these days is low, but it still seems like worth doing. Whether I erect a rotatable yagi or a stacked turnstyle remains to be seen. It is a long time since 2m was filled with G8 stations using FT290s, 30W linears and Tonna 9el yagis!

Right now I have other antennas erected on the 2 small masts attached to the house and it may be some months before I make changes, but maybe I will get something in the air and see what happens. As well as SSB/CW DX there is so much more to explore these days with digital modes.

1 Apr 2012

Gmail Tap


OK it is April 1st but this is actually not such a daft idea http://mail.google.com/mail/help/promos/tap/index.html

Trying to see the light (very dimly)

As other nanowave enthusiasts have told me, it is very useful when experimenting with light beams at 481THz to have some sort of lab test range that allows repeatable sensitivity measurements. So, today I rigged one up.

Up on the ceiling of my "lab" I've semi-permanently fixed a standard brightness LED fed via a 1K resistor with a 1kHz tone from my 0-1MHz audio/LF generator. I can now adjust the output until the LED is only just visible to the naked eye, with difficulty,  when the room is totally dark. I then place my optical heads (without lenses) on the same spot on the workbench aiming upwards to the very very dim light. The spacing is about 1.5m. I had to check that the signal being picked up was optical and not inductive coupling from the wiring. With this setup, my most sensitive detector can detect the beam at around S2 in a pair of headphones.

I've been experimenting with the drain current of the detector FET and with optimisation of the post cascode stages of my KA7EOI head and may have made 1-2dB S/N improvement. With this test setup I can make very repeatable sensitivity measurements. However, as the tests require TOTAL darkness I have to judge the S/N by ear. My laptop could be set up outside the room with a long screened audio lead allowing Spectran to be used to measure quantitatively the S/N but I'd have to ensure the darkness of the room is preserved.  For an example of this see http://reast.asn.au/optical/Light_Preamp_Performance_Comparisons_20071119.pdf .

At least now I can do lots of initial tests at home and only venture into the field when I have good confidence in the system performance.