31 Jul 2013

20m WSPR with 0.5 to 2W

As I wind down activity from this QTH before my move, I have been allowing my WSPR beacon to run on 20m using an indifferent wire antenna strung to a low tree at the bottom of the garden. At its lowest point is is only about 2m above ground. Power out has been 500mW or 2W. The results below speak for themselves: WSPR spots from across the planet.
20m WSPR unique spots in last day or so
These are just some of the unique spots: the actual list goes on and on down the page. I am a real fan of WSPR for checking rigs, antennas and propagation. It is also a way to still enjoy the hobby whilst packing up books, CDs, DVDs and other household rubbish in preparation for a house move!

26 Jul 2013

Reflex Receivers

In the days when semiconductors were very expensive parts, the reflex receiver was a very popular design for AM broadcast and simple amateur AM receivers. The basic idea is to use a single transistor is several different ways: as an RF amplifier, possibly a detector and then finally as an audio amplifier by clever feeding of the RF and AF signal back around the transistor. Even today they are fun circuits to try. For example, see the schematic at http://www.ke3ij.com/reflex.htm . Rick has a number of novel circuits on his site.

In Rick's circuit, Q1 first acts as an RF amplifier. The 1N4148 rectifies the signal which is again applied to the base of Q1, which is now used as an AF amplifier stage. Although adaquate level is available on the collector of Q1 to drive a high impedance earpiece, Rick added another low cost stage to drive an 8 ohm speaker.

Another example of a reflex circuit is at http://www.sm0vpo.com/rx/reflex_rx.htm . Perhaps the most famous reflex circuits came from Sir Douglas Hall in a series of circuits in Radio Constructor back in the 1960s and early 1970s. Some of these are collected at http://www.spontaflex.free-online.co.uk/ . Sir Douglas was a UK overseas diplomat and a very nice gentleman. One of my old school friends lived in the same Devon village and visited him to try some of his prototypes.

24 Jul 2013

Speech processors

Earlier today someone asked me to forward them some links I had on speech processors. This reminded me of a VERY effective speech clipper I built many years ago for a 2m AM QRP transmitter. The audio pre-amp had 2 stages of 6dB/octave pre-emphasis followed by very hard clipping and an active low pass filter to keep >2.5kHz audio levels to very low levels. The signal sounded remarkably punchy and allowed this little 100mW AM transmitter to punch well above its weight. It sounded like a rig running several watts. At some point, after we move, I'd like to replicate the design and give it a go again. It was based around the audio stages I used in the Pye PF8 PMR handheld but with value changes to increase the gain and add the second pre-emphasis stage. Double pre-emphasis meant that there was less clipping at lower audio frequencies and more at the higher end. Compressors are meant to be better, but honestly this little circuit took some beating.

Satellite tracking app (free)

The always interesting Southgate ARS News page has a link to a free app by Tom W9KE for iPhones, iPads and iPod Touch devices to allow tracking in real time of satellite passes. The app has a nice user interface and looks to be extremely useful if you enjoy tracking satellites and the ISS as well as want to work through some of the amateur radio satellites up there.  The App is available from https://itunes.apple.com/us/app/satellite-explorer-pro/id669039200. The only thing the app seems to miss is a list of the amateur satellite frequencies (up/down) and their modes of operation. I guess one has to look this up somewhere else. 

23 Jul 2013

Thunderstorms and Es

Sporadic-E (Es) is an exciting propagation mechanism that allows contacts on the HF and VHF bands out to around 2000km regularly (with multi-hop Es MUCH greater ranges can be covered) in the April-Sept period in the Northern Hemisphere. There is another smaller peak around Dec/Jan too and propagation by Es can occur at others times of year, but much less frequently. Exactly what creates good Es conditions is open to debate still but some believe thunderstorm activity in the troposphere can impact it.
A way of checking on thunderstorm activity is to look at the map at http://www.blitzortung.org/Webpages/index.php?lang=en .  Right now there are plenty of thunderstorms over northern Europe with lots over the UK earlier, spreading northwards. Looking at the map one might expect good conditions towards Italy and Greece on Es if whatever rises from the tropo region reaches the E layer mid-path.

22 Jul 2013

My internet saga continues - positive outcome on cable at new QTH

Yesterday I reported that at the new QTH our new home was the only one on the close that was unable to get fibre optic broadband, phone and TV services from the provider I currently have used for over 12 years: Virgin Media.

Well, today their field engineer surveyed the road and has confirmed that we WILL be able to get cable services at our new place after all. They were very quick checking this - I only asked yesterday - and it looks like everything will be ready for when we move mid-August.

21 Jul 2013

KX3 purchase?

For the last 6 months I have been saving the pennies in my amateur radio kitty towards the purchase of a new transceiver for general use at the new QTH. I am still very tempted to splash out on a new KX3 from Elecraft, despite the high UK cost when fully loaded with auto-ATU, narrow roofing filter, battery pack, charger and mic. As I tend to hang on to gear for a LONG time, this may be a good investment. All the www.eHam.com reviews are very good and it does appear to be a first class radio. What bothers me though is that for the same price I could buy 2 FT817 transceivers and still have change! My main interest is e weak signal mode experimentation and I am not sure that the KX3 is an ideal radio for use as a base rig for this application: there seems to be a need for lots of cables to connect to a PC, whereas the FT817 is easy using a Signalink USB interface.

As was the case when pocket calculators came on the market in the 1970s, the default position here is to "wait and see", which means I buy nothing and hope that a clear winner becomes obvious in the months ahead. In the 1970s I ended up not buying a scientific calculator at all, HI.

Ending operations at this QTH

Nearly the end of an era (37 years) at this QTH. I will resist taking down the antennas until the last moment in a few weeks from now, but already my mind is turning to the new QTH.

Would you believe it, but every house in Mill Close, Burwell is able to get Virgin Media apart from ours! Even next door they have it.  I contacted Virgin Media who have agreed to send out a field engineer to check why this is. The CATV box on the pavement is about 4m from our drive. It is not the end of the world: I can revert to Sky (or BT) phones, TV and broadband and get over 10M download speeds but I will wait until the VM engineer feeds back his findings as it would be preferable to stick with our current provider. Virgin's broadband is VERY reliable and fast.

I now have a firm plan on where to erect the VHF/UHF antennas. The earth electrode antenna for VLF/LF/MF will be installed in the next few weeks. I have still to decide on the location of HF wire antennas in a way that is "sleuth" i.e. low profile and not obvious. Our new patio is right outside my new shack, so operating in the garden should be very easy and fun.

18 Jul 2013

Going batty

We are spending a few days with our son and family near Canterbury where he lives in an 18th century cottage not far from the school where he teaches. In the last few months their home has become an hotel for a colony of tiny pipistrelle bats who have taken up residence under the centuries old tiles on the side of the cottage. A bat expert estimated there are at least 300 living there.

This evening, as the light faded, we watched as they  flew out from what appeared like impossibly small gaps in the tiles. Bats are a protected species, so they are not allowed to get rid of them, but apart from their tiny droppings they are not a nuisance. It was quite amazing watching them fly off for food this evening.

IC-7100 UK price: £1249.99 from Martin Lynch

The IC-7100 multi-mode multi-band 100W radio is now available for £1249.99 including VAT from Martin Lynch. Although not yet in stock this is the price advertised, which is some £500 less than I was expecting. Considering it includes all the HF bands, 6, 4, 2 and 70cms this is not bad value. I just hope the touch screen is not tacky and unreliable. See http://www.hamradio.co.uk/amateur-radio-main-equipment-mobile-radio-icom-mobile-radio/icom/icom-ic-7100-pd-5020.php .

New VLF tests from Germany

News from Germany of an upcoming VLF test at 8.970kHz using earth electrodes as the TX antenna with an ultra-stable Spectrum Lab derived signal.

Hello Group,
We are planning some VLF-activity at 8970Hz during a meeting of  electronic hobbyists nearby  Kassel / Germany (JO40vr) on this weekend.  The plan is to run a VLF-PA between some ground electrodes. Due to other activities we have no exact time plan, when to start. Depending on internet access i will inform you about the details. 
Thanks for looking for our signal in advance.

14 Jul 2013

HF activity - the weakest maximum in 100 years?

Space.com reports that the peak of cycle 24 is likely to be the weakest for 100 years with the next one likely to be even worse. See http://www.space.com/21937-sun-solar-weather-peak-is-weak.html .

Although I venture onto the HF bands every few days usually, I've not found the level of activity, excitement or interest that I had in previous solar cycle peaks. On 10m back in the 1979 peak the band was filled with stations at any time in the day, even outside of contests. There just doesn't seem to be the same level of activity these days? Perhaps it is because having worked over 100 countries with just a few watts, many on SSB, there is, for me, less interest in chasing DX now. Also, I tend to enjoy more creative parts of the hobby whether on VLF, lightbeams, etc. and don't have the time (as much) for HF operating where the competition is often from ill-mannered, QRO stations more interested in their egos than the ham radio spirit.

Crystal Set DX log from 1991

As I clear out my stuff ready for our move, I've discovered my Crystal Set DX Log from 1991, which was 2 sunspot cycle peaks ago. Looking through the entries in the log (all received with a VERY simple shortwave crystal set using a toroid, a germanium diode, a resistor and a crystal earpiece and a longwire antenna about 15-20m long) it is quite astounding how the HF world has changed.
Shortwave Crystal Set DX log - from 1991
For a start, many of the coast radio stations used to transmit in CW on HF and these could often be read due to the cross-modulation from other stations. This was the technique used to detect those shown in the log above.

Also, the shortwave bands were still filled with English language broadcasts. In the few days covered by this log I managed to receive broadcast stations from Cuba, UAE, India and Australia directly (not via relays) as well as plenty of Europeans. Before this date I had no idea that worldwide reception on a crystal set would be possible.

There is no doubt that conditions were very good back in 1991 and I am not so sure that it would be possible to repeat this in 2013, but I would be delighted to hear of success by others with crystal set DXing on HF in more recent times.

I still enjoy crystal sets: they are simple and fun to make yet there is still something unbelievably good about using the electricity from the TXing station to hear them, not my own, especially when the signal comes from very far away.

12 Jul 2013

IC-7100 UK launch July 17th at Martin Lynch

A few hours after I commented on the price in the US of the IC-7100, I had an email from Martin Lynch and Sons announcing the UK launch on July 17th.

There is still no information that I've seen that gives the likely UK price although I doubt one will be in my new shack.

The IC-7100 is bound to cause a lot of excitement as it is one of the first commercial multi-modes to include 4m (70MHz). The press release seems to indicate that D-star will be supported in the standard product i.e. my understanding is this is NOT an optional add-on, but you get it with the basic product you buy.

The pdf leaflet on the IC-7100 is now available.

11 Jul 2013

Weather boots for coax plugs?

I'm looking for what I believe are called "weather boots" to slide over the end of PL259 and BNC coax plugs to help protect them up the mast from water ingress. I guess it is still necessary to add a smear of silicone grease. There are such items for Sky dish F connectors (see eBay item 251296277220) but I have not yet found a source for the common 50 ohm plugs.

Anyone know where such rubber/PVC boots can be obtained please?

2m big wheel antennas on 70cms?

Just wondering if anyone has checked what a horizontally polarised 2m big-wheel antenna looks like (gain, match, directivity, polarisation) on 70cms?

At the new QTH, the most likely antenna on the apex of the bungalow will be a 2m big-wheel (for 2m datamodes, SSB, CW) with a V2000 fitted above it (for 6m Es, 2m and 70cm FM) with suitable spacing between them (>1.3m). It would be useful if the big-wheel behaved well as a half decent horizontal omni on 70cms too so it could be used in UKAC contests.

IC7100 prices

Image at http://www.hamradio.com/images_manuf/H0-011766A.jpg
The new multiband, multimode mobile/base radio from Icom is now available in the USA for $1,824.90 from Ham Radio Outlet store with a 2 year warranty. It is available for $1,664.95 without the extended warranty. See http://www.hamradio.com/detail.cfm?pid=H0-011766.  If importing from the USA don't forget VAT and import duty.

The usual UK price is about the same in pounds as it is in the USA in dollars, so I guess around £1800-1900 is likely to be the going price, although I don't think the UK dealers have them yet.

At the time of writing there are only a couple of reviews of the IC7100 at www.eham.net

Antennas start to come down and wi-fi range tests

Today marked the beginning of the end for amateur radio at the present QTH. We've lived very happily here for 37 years, bringing up our 2 boys and welcoming our 4 grandchildren. Now we are just a few weeks away from our move to the bungalow 300m away up on our local "hill" next to the windmill, the latter currently undergoing a £417k refubishment courtesy of a National Lottery grant. The new home is a nice place and we are looking forward to the move, but it won't be without a few sad moments: closing a chapter in our lives but also opening a new one. The last time we moved, the removal van cost just £11 - it was a LONG time ago, HI.

Today I removed the first part of the antenna system: my 20m spaced earth-electrode wire running in the back garden. Next to come down will be the coax feed from my workshop to the upstairs shack where I operate. The V2000 vertical and the Par 10/20/40 end fed will come down in a few weeks time. I also de-cluttered the bedroom shack to some extent, clearing out all manner of the "I may need this some day" rubbish that fills drawers and cupboards. It is just unbelievable how many SMPSU wall blocks I have that belonged to equipment like routers and scanners long gone. The worst is always the stuff you've kept because, "I may need this one day".  I am trying to be ruthless and give it to a local charity store, recycle centre or the dump if it has not been used, read, looked at for several years. For certain something that goes will be needed next week.

I did a test at the new bungalow tonight on the internet wi-fi coverage: I took my Virgin Media wireless super-hub and set it up (locally, no internet connection) and walked around the new home with my iPod Touch 4g to see how strong the signal was in the shack, bedrooms and garden. Results were promising: I think I may get away without a range extender.

10 Jul 2013

WonderLoop antenna

If you have just bought a copy of the August 2013 copy of Practical Wireless you may have noticed that in the next edition (September) I'm doing a review of the WonderLoop antenna, although the editors managed to give me a new callsign by mistake in the "Coming next month" column on p77, HI.

Confidentiality prevents me saying anything yet until the edition is published, but I much enjoyed carrying out my tests.  I have absolutely no affiliation with the manufacturer or supplier. As a keen blogger I find it hard not to blog about something radio related that I have played with!

The Wonderwand page is at http://www.wonder-wand.co.uk/WonderWand/WW_Homepage.html .

If you are interested in reading my review, please buy the Sept 2013 copy of PW on sale August 8th.

Birdlip in the Cotswolds

The distant Malvern Hills from near Birdlip
There have been no posts for a few days as my wife and I have been away from home staying a couple of nights on the western edge of the Cotswolds at Birdlip. The occasion was a gathering with cousins I'd not seen for around 50 years. The gathering was excellent. We stayed at the Royal George Hotel (3 star rating) which was superbly located right next to the Cotswold Way path with good rooms, large gardens and excellent value meals.  I am please to report that everyone had a great time and got along fine!

This part of the Cotswolds would make an excellent VHF-microwave location with the Cotswold escarpment meaning the ground falls away dramatically towards Wales and the west. I didn't take any radio gear, but will do so if I stay there again. The hotel was a good find.

6 Jul 2013

472kHz in Canada - getting closer

From Joe VO1NA:
Dear Group,
Last week, Industry Canada published its Proposed Revisions to the Canadian Table of Frequency Allocations. It includes the 630m band for the amateur service.  So we wait with much anticipation...


VHF/UHF QRP DXing with weak signal digital modes?

When there is a decent contest with some portable stations with decent antennas about, it is surprising how far can be covered with QRP kit on 2m and 70cm. This makes me wonder just what sort of ranges could be covered with QRP and modest antennas on these bands using WSJT digital modes.

Going from SSB to one of the more effective weak signal modes is like gaining another 30dB, i.e. far more that the antenna gain of a big contest station, suggesting that ranges of 200-300km should be ALWAYS possible on 70cms with quite modest QRP stations with small yagis or colinear vertical antennas in flat band conditions.

I am speculating what sort of ranges should be possible under flat conditions (no lifts) with 5W and a small omni or broad beam yagi such as a Moxon or HB9CV.  When I move to the new QTH I think some 70cm skeds are called for with stations out to 300-400km using WSJT modes using 5W or less.

70cm VHF NFD with a simple QRP station

4 ele 70cm yagi on car
Just for a little fun in the sunshine I took my FT817 and "coathanger" 4 el yagi onto a local high spot (actually nothing is high here in East Anglia!) to try just over an hour of operating on 70cm SSB during VHF NFD. Conditions were average, but I heard EI, F, GM and PA and worked 12 stations in just 70 minutes of casual operation with the best DX 262km.  Power output was either 2.5W or 5W.

The 4 el yagi is mounted on a 22mm PVC pipe mast that is simply wedged in the car rear window and manually rotated. The whole set-up can be erected and taken down in about 2 minutes: I don't take contests THAT seriously you see :-)  The map shows the stations worked before going back home for tea.
70cms QSOs in 70 minutes with 5W to a 4el yagi

After tea I parked the car outside my new QTH and erected the 4 el as shown in the photo. Signal strengths from DX stations (PA0 and a station in SW England) were very similar to those on my local /P site, suggesting the new QTH, on a local bump, is promising for VHF/UHF/microwaves.

70cm is a great band and sadly under-used these days on SSB. It is also sad that there are so few 70cms beacons on the air in the UK now. I believe the Bristol 70cms beacon - it was a good conditions indicator here in East Anglia - has recently gone QRT too?

4 Jul 2013

30 line TV

It is a long time since the Baird 30 line TV system was replaced by 405 line and then 625 line TV here in the UK. However, there are still enthusiasts building mechanical 30 line TV systems and getting respectable results. At one time I joined the NBTV group (does it still exist?) who promote(d) hobby activity with 30 line TVs, particularly mechanical versions with scanning discs etc. Bandwidths needed for such systems are very narrow (audio) so the signal can be transmitted using a standard voice transmitter. These days it is possible to produce 30 line TV using a PC, but this not quite the idea: one can after all communicate worldwide by Skype video or FaceTime.
 This video (linked from its original location on You Tube) gives some idea of what is possible.

Wellbrook LF RX Loop

A Wellbrook ALA1530 loop antenna for VLF-HF reception is now in my plans for the new QTH. This is not a low cost antenna - currently around £200 in the UK - but its performance is excellent judging by reports from people I know and reviews. It looks like the very best choice of RX antennas for the 136kHz and 472kHz bands where local noise can be a real issue. It does not need to be mounted high, just about 5m from the house. The photo above (linked from the Wellbrook site) shows the antenna mounted on a fence.

The technical specification speaks for itself: truly excellent OIP2 (+90dBm) and OIP3 (+49dBm) figures and a 1dB compression point of +28dBm in the Medium Wave band. It can stand a local field strength as high as 400V/m. As a loop, this antenna has a figure of eight pattern, so local noise sources can be nulled in many cases. It covers from 20kHz to 30MHz.

This looks like a good investment before the LF DX season.

VLF kit at PA3CPM

Henny PA3CPM has been continuing his 8.270kHz VLF transmissions, on and off, for some weeks now and is getting reports from several stations in western Europe despite his modest antenna. Paul Nicholson in Todmorden and Eddie G3ZJO regularly receive his signals using integration over several hours and extremely narrow bandwidths to dig the signal out of the VLF noise.

8.270kHz VLF loading coil at PA3CPM
This is a photo of Henny's huge loading coil used to bring his 40m sloper to resonance on 8.270kHz. The loading coil uses a LOT of wire (several kms) and building such a VLF loading coil is not for the faint hearted! I suspect that a large wire loop may be an easier TX solution?
PA3CPM's VLF PA unit
Henny is using a 200W PA and this is shown here. Note the fans to cool the unit.

To radiate an amateur signal at VLF requires special dedication, yet Henny has shown that even a modest 40m antenna can get a signal hundreds of km on VLF with quite modest powers. It is indeed a new and exciting area of the hobby.

3 Jul 2013

Analysis of the PA0RDT E-field probe RX antenna

Image of miniwhip on VK1OD's website

VK1OD has done an interesting analysis of the PA0RDT E-field probe miniwhip receiving antenna. This is very popular as an effective antenna from 8.9kHz right through to the HF bands. I have used my own versions on the VLF, LF and MF bands with great success, but I commend the PA0RDT design to you. His design uses readily available semiconductors to give excellent IP2 and IP3 figures. You may be surprised how something this tiny and simple can work so well if mounted away from the house on a small pole. Remember, you do NOT need big antennas to receive on the lower bands: it is S/N that matters not very low noise figures. VK1OD's analysis is somewhat harsh: in my view it works as a true E-field probe should, even at VLF.

More loops

HF TX loop in the bedroom
Small TX magnetic loop performance continues to astound me. This evening I erected my little loop antenna made with 6mm diameter copper pipe and tuned with a standard 365pF air-spaced variable as used in my regen receivers. The loop has a diameter of just 65cm (about 2m circumference) and is mounted on a piece of PVC pipe as a support. The 365pF is attached to the hi-Z part of the coil with a couple of crock-clips. Matching is with a coupling loop about 1/5th the diameter of the main loop.
The simple tuning unit - a 365pF airspaced variable
Without any effort, apart from the tuning sharpness,  it tunes from 10-28MHz and got loads of spots on WSPR. I then tried with 2W CW on 14MHz and received several European reports via the reverse beacon network. The loop is just resting against a wall in the shack. Overnight on 20m WSPR the best report was from 8338km with 2W indoors. On 10m this morning (July 4th) it is already exchanging WSPR spots with CN8LI despite being orthogonal to him i.e. in the worst orientation, 2W and indoors.

According to my loop calculator the efficiency should be around 12% or 9.3dB down on a "proper" dipole antenna on 14MHz. This is less than 2 S-points difference. Results bear this out. On 28MHz the efficiency is better.

Purists will point out that the crocodile clip connections will have a few milliohms resistance and this will reduce loop performance. At 2W there is no sign of arcing across the plates. The point is with QRP one can get away with simple circuits that would not be possible running 100W.

My 1990s station ...and clearing out

Whilst sorting through my collection of SPRAT magazines to give to a local amateur G4NUA - I recently bought the SPRATbook and have most on DVD - I came across this photo inside one of them. It must have been taken around 1992 I think and shows the amateur radio station I had then. What is interesting  is that I actually had a 100W radio (FT747) at that time, although it was hardly ever used at that power because of the problems with RF feedback into the rig. The shack then consisted of a table by the window in our main bedroom. My wife must have been very tolerant!

The 10m Lincoln President, derived from a CB radio, was actually a very nice radio: I recall working mobile with it and having a solid SSB QSO with a station in India early one evening around the 1990 solar maximum whilst driving near Cambridge. It was sold long ago though. The little Mizuho MX2 (I still have one) was used to drive a 10m transverter and I worked plenty of 10m DX with it and around 1W pep to a vertical CB halfwave. The Standard handheld rigs came from my workplace: at one time we were considering OEM-in of PMR radios from Standard (before they joined with Yaesu)  and one of my colleagues got a pile of samples on a trip to Japan. Guess who got some of them after they had been "evaluated"? In the end we got some portable PMR radios from a source in South Korea and that was a disaster.

Today I have far fewer transceivers - all QRP - but get just as much fun. There are no homebrew rigs in this 1990s picture although I did have some. Today quite a lot of my kit is home made, although not all rigs remain in their cases for too long as I tend to note the schematic and take a few photos, then reuse parts and enclosures.

1 Jul 2013

Google Mars and Google Moon

Having played a bit more with Google Earth, I see that you can also view Mars and the Moon too. Quite fun to fly over the Martian and lunar landscapes.

When looking around the Moon tonight I noticed some quite strange markings in one area. Does anyone know what these are?

Again, I have attached a screenshot (Google copyright acknowledged - will remove if told to do so, but Google you are getting yet more FREE publicity for this tool).

Path profiles using Google Earth

My thanks go to Richard G3TFX for showing me this Google Earth feature, which may be of interest to VHF/UHF/SHF, microwave, nanowave and SOTA enthusiasts. I had no idea you could do this.

Using the ruler tool (in the menu at the top) in Google Earth click between two places. A line appears together with a distance measurement. Save this as a temporary file in Google Earth. Right click on this file in Google Earth and choose "show elevation profile" and a path profile between the 2 spots appears.
Google Earth path profile

The image above (screenshot from Google Earth - Google copyright acknowledged - will remove if a problem, but you are getting free publicity!) shows the non line-of-sight path between Burwell and the village of Stow-cum-Quy that I managed to span recently with my 481THz QRSS3 beacon using 100mm optics and a TX power of around 0.5W.

This does not appear to take any account of the Earth's curvature, so is probably only useful for relatively short distances. Does anyone know how to factor in this?

Looks a useful facility to me for seeing how close to line-of-sight a moderate length path is.

Roger G3XBM