73 Magazine back-issues on-line

http://mikeyancey.com/73mag/listauthor.php? is a searchable list of articles from the old 73 Magazine. I was pointed to it by Leon Heller for an article by Richard Q Marris, G2BZQ about ferrite rod transmitting antennas. Mike Yancey's site has some other useful stuff too, so worth a more general look.

Requests to share xbmqrp website

Friends, PLEASE, bookmark my main website correctly. Don't bookmark my pages where they are actually located (Google Sites) as these may change, as they did yesterday when I did a major site update.

So to access my main website go to, and bookmark:

www.g3xbm.co.uk

Dry eyes and RF?

Testing the ferrite rod antenna on TX this evening (with lots of RF within a metre of me) I'm noticing something I used to get when testing VHF RF PAs years ago in my design days: dry eyes. I assume this is an effect of RF on the body.  Apart from being madder than ever (!) I cannot say RF exposure has done me any noticable harm, but wonder if others have noticed this dry eyes effect?

Although the evidence in general is not strong, there was strong correlation back in my Pye Telecom days between those working on the design of high powered HF/VHF/UHF PA devices and those fathering girls. Maybe there was some subtle damage to sperm with exposure to high RF that made girl pregnancies more likely to succeed? Co-incidence?

A lot more controlled tests are needed, but with the widespread exposure to Wi-Fi and mobile phones it won't be too long before we find out more. So far the evidence is not at all conclusive but you do wonder whether, like smoking, we'll look back in 50 years time and say, did they really all use mobile phones and Wi-fi devices?

More Ferrite Rod TX DXing

This evening I fired up the FT817 and the small 15mm diameter ferrite rod tuned with a 365pF air-spaced variable and have been spotted on WSPR even further away. This time a couple of spots from Norway, the best being LA9JO 2096km away. As someone pointed out, I may be coupling into local wiring and this might help, but the ferrite rod behaves just like a loop with good directivity and matching just as you would expect i.e. a very low impedance tap point is needed for a good match and tuning is extremely sharp. Personally I believe the radiation is all coming from the ferrite rod and nowhere else.

WSPR reports with a ferrite rod TX antenna on 40m (5W into rod)

TXing with a ferrite rod antenna on 7MHz

Just for fun this morning I tried WSPRing on 7MHz using JUST a ferrite rod wound coil and a 365pF tuning capacitor as a tiny loop antenna sitting on the desk. All other antennas and grounds were disconnected fully. I used one of the low tap positions to find a 1:1 SWR position and put the FT817 on 2.5W (3 blobs). The rod did not get warm. The wire used is around 0.5mm enamelled copper with around 60 turns, tapped at every few turns at the cold end.

The ERP was very small, although I have not yet measured it. To my total amazement, I got an immediate -24dB S/N WSPR report from OZ7IT in Denmark at 853km. Just proves how incredible WSPR is and what a powerful tool it is for simple experiments like this.

Ferrite rod TX antenna on 7MHz WSPR - it worked!

OFCOM licence exemption

Martin G8JNJ has brought to my attention a little known, to me at least, OFCOM concession that appears to allow licence exempt operation under certain conditions in many, if not all, parts of the radio spectrum for research and development purposes.

Although OFCOM will grant Non Operational Licences (these were once known as Test and Development Licences) and charge you £50 a year for the privilege (!)  to test new equipment or carry out specific research, they do NOT require a licence if emissions measured at a specified distance are below certain levels (supressed radiation conditions). See http://licensing.ofcom.org.uk/binaries/spectrum/non-operational-tech-licence/ofw357nonopguide.pdf for some guidance notes on this.

My own interest is to research earth-electrode antennas in the frequency range between 8.97kHz (where I already have done some tests) and 137kHz (where I have also tested this antenna structure). Using WSPR and other weak signal techniques, quite a lot of useful work can be done with low uW EIRP levels. It would be interesting to see how such an antenna structure behaves at say, ~40kHz and 73kHz. It may just be possible to do tests at moderate ranges (in the far field) without a licence. Now wouldn't that be interesting?

Lack of WSPR2 activity on 137kHz

Having run WSPR2 now for a couple of days on 137.5kHz, I have still only received reports from 2 different stations, although I have had LOTS of their reports, suggesting my signal is consistently reaching 250km. My signal is clearly visible to at least this distance, but without people looking I cannot be sure how much further can be expected with the earth-electrode antenna and 30uW ERP.

Although I will box up the new 137kHz transverter and tick the "finished" box I am disappointed that there is not more activity. Most LF/MF people are exploring the new 472kHz band, so interest in Europe for 137kHz is not high apart from DK7FC who is putting out a massive signal that is being copied in both North and South America.

So, what next?  My mind is beginning to think of my new QTH in the village, which we expect to move to in the summer.  What antennas can I put up without upsetting the neighbours? What will the noise floor be like? How much better will VHF/UHF coverage be from the top of our little "hill"?

Main G3XBM website facelift

Revised G3XBM main website

This week I have been doing some housekeeping on my main website www.g3xbm.co.uk .  At the moment the content is much the same as before, although some old pages have not been recreated.  Hopefully the new site layout will be easier to navigate using the sidebar menu. Please let me have any feedback or errors that you spot with links or content. Over the coming weeks I hope to add further new content.

If you bookmark the site please bookmark www.g3xbm.co.uk and NOT the page it automatically redirects too. You will no longer be able to reach the old site and I do not propose to grant individual access permission to the archived old site. Already I have had several requests for access to the old pages.

My new WSPR DX record on 137.5kHz

Having run the 137.5kHz transverter with WSPR-15 (15 minute on periods) overnight - around 30uW from the earth-electrode antenna - I wasn't too hopeful about my chances with WSPR-2 this morning. WSPR-15 failed because of the thermal drift in the 15 minute on period I think.

Anyway I put the TX on WSPR-2 on 137.5khz this morning and let it run. After a couple of hours with no success I was VERY pleased to see I had been spotted several times by G8HUH at 250km. My previous record a year or so ago was just 148km (G3YXM) so this is considerably further and entirely in line with my predictions based on the QRSS3 beacon results.

WSPRing again on 137.5kHz

Today I built a breadboard version of my transverter for 137kHz and now I have it running WSPR-2 for the evening.

RF power from the IRF640 transverter PA is around 30-40W (depending on the PA voltage) and the ERP should be around 25-30uW using the earth-electrode antenna.  At present, the transverter is only on 20% duty cycle TX and I have still to add the RX preamp and switching.

My recent 137.766kHz QRSS3 tests using a measured just 6.6uW ERP from the earth-electrode antenna have now concluded.  Best reports were G3WCB (101km), G3XDV (61km) and G4FEV (56.7km).

G3XBM just detectable on G3WCB's trace at 101km

Stronger signal with G3XDV at 61km

Similar signal at G4FEV at 56.7km

Judging by the QRSS3 results with 6dB lower ERP than my WSPR signal, I think reports out to >100km should certainly be possible as long as people are looking.  WSPR2 is able to detect at about the same level as QRSS10, so overall I have around 11dB more "system gain" (5dB QRSS3 to WSPR, 6dB ERP improvement).

Oscar 6 and 7 satellites

Way back in the 1970s I took my first steps into amateur space communications by listening to the SSB and CW signals coming down from the new (then!) Oscar 6 and Oscar 7 satellites as they passed over. Equipment was an HB9CV antenna in the loft, a 2m-80m homebrew converter feeding a Codar T28 receiver. It was crude, but it worked fine. The same set-up worked well for monitoring 2m CW and SSB terrestrial activity as well.

Using my "osculator" - a map with the satellite paths and an overlay showing when the satellite would be in range on the various paths I could predict when signals would first appear from the south and disappear in the north.

Best passes were ones over the mid Atlantic when , for around 10-15 minutes, sometimes less, US and Canadian stations would appear at the top of the 2m band. It was very exciting at the time. If I recall correctly HB9HB was a beacon near the top of the band and that could be copied too via the satellites.

Although I had one satellite QSO years later with a 10m-15m transponder on one of the later Oscars, I never did get into it on TX.  In the Southgate News today I read that Oscar 7 is still good for DX QSOs even though it is now 37 years old. Whatever happened to the Phase III satellites in geosynchronous orbit like Oscar 40? Did that fail to work?

You can see where the satellite is now at various websites allowing tracking. For example http://www.n2yo.com/?s=7530 .

137.766kHz ERP - now measured at 6.6uW

So, today I repeated my field measurements to establish the ERP of my 8W 137.766kHz beacon feeding my earth-electrode antenna. This time I did the measurement correctly. Here's how.

1. Travel 2km from the home QTH with E-field probe, FT817 and PC running Spectran.
2. Choose a location in the best direction for the "loop in the ground" so the measured signal strength is close to the maximum possible i.e. not off the sides of the loop.
3. Set up FT817 so the RF gain is adjustable and turned well back and the AGC is inactive.
4. Tune in my LF beacon and adjust the RF gain to the lowest possible detection level.
5. Measure the S/N of my signal with Spectran and note reading.
6. Retune to DCF39 (138.830kHz) and, without adjusting the RF gain at all, measure the S/N with Spectran.
7. Repeat these measurements 5 times.
8. Calculate the difference in dB between my signal and DCF39 (in my case 41.3dB)
9. Using the assumption that DCF39 has a field strength of 1mV/m, work out my own field strength (in my case 9uV/m)
10. Using the formula ERP = (E^2 * d^2)/49 work out the ERP.

Answer? My measured ERP on 137.766kHz is 6.6uW

Caveats:

1. If DCF39 is not approx 1mV/m then the ERP needs to be adjusted up or down proportionally.
2. Measurement error is +/- 2dB.
3. The ERP is the figure measured in close to the best direction. Off the sides of the loop the ERP will be much lower.

Conclusions:

1. Stations able to detect the QRSS3 signal at any distance are doing well as the signal is very weak indeed.
2. Using my proposed WSPR transverter at 32W, for example as a reasonable target output, would give me 6dB more ERP at around 25uW.
3. Based on results with QRSS3, I should be able to be copied using WSPR-2 at up to 100km on ground wave. At night with sky wave, considerably further is possible. 
4. Using WSPR-15 and 32W my ground wave range should be up to around 200km, possibly a little more. 

The QRSS3 beacon is still running over the weekend and more reports would be welcomed

SMA version of the G3XBM 472kHz transverter

In an email,  John G4BAO tells me he has built an SMA version of my 472kHz transverter. At present, he is getting 5W RF out using standard SMA parts and a different FET.  If you wish to enquire about this version please contact John and NOT me!

G4BAO's SMA version of the G3XBM 472kHz transverter

Amateur activity on VLF in the last few days

Several amateurs in Europe have reported strong signals on 8970.022Hz VLF, a frequency used in the past by DJ8WX near Hamburg. It is some months since there has been any amateur "dreamers band" activity, so this is very welcome. This is the signal as seem in the Czech Republic on the OK2BVG grabber. Note the timescale on the grabber picture. It is necessary to watch the signal for very many hours to see the signal appear. Hence, very stable transmissions are needed, and a receiving system that is able to hold to a few uHz for hours and hours on end. Just listening on VLF and you will have ZERO chance of detecting such signals.
Amateur VLF reception is usually a "whole new ballgame" compared with listening for the strong MSF signals sending to submarines which are very strong.

VLF amateur signal, believed to be DJ8WX yesterday seen on Lubos, OK2BVG's grabber

My ERP on 137.766kHz is.......

Thanks to G4FEV, I've just realised that I made a fundamental mistake measuring my field strength, forgetting to turn off the AGC when taking the measurements of my signal relative to DCF39. Whereas my initial measurements indicated the ERP was in the low mW region, in reality my signal is much, much weaker. For example, G4FEV reckons my signal is some 70-80dB weaker than DCF39 where he is, if not more! So, tomorrow I shall have to try the test again and see if I can get a sensible figure with AGC turned OFF.

G3XDV's screenshot of my QRSS3 LF signal this afternoon.

Mike G3XDV (61km) has just sent me a very comprehensive report with 178 screenshots of my QRPp signal over the last 30 hours. Copy was remarkably good considering everything. Again, I am amazed how well this works.

G4FEV reports my QRSS3 LF signal at 56.7km

Path between G4FEV and G3XBM

This afternoon I was out and about with my E-field probe checking signal levels of my little 137.766kHz QRPp QRSS3 beacon at various locations around the Cambridge area. The furthermost point I tried was near Comberton, 21.5km WSW of the home QTH in Burwell. I have taken a lot of measurements, including the level of DCF39 at the same locations so that later I can work out my field strength and thence ERP.

G4FEV's screen shot of my QRPp QRSS3 137.766kHz beacon at 56.7km

When I arrived home I had an email from Dave G4FEV 56.7km due west of me to say he had copied my signal and had sent a good clear screenshot. Signals with Dave looked quite good, suggesting the signal due west may be stronger than signals in the Cambridge direction (SW - WSW). The earth-electrode antenna has directivity but, aside from a zero copy at one location orthogonal to the "loop" I have still to work out exactly which directions have the strongest signals. Based on the above I think it is close to W-E.

Disappointment on 137.766kHz

Despite running my QRP LF beacon for over 2 days continuously I have received no successful reports. A couple of people looked without success, but at least they tried. I am leaving it running QRSS3 today as I want to do some further reception tests this afternoon and measure my ERP by taking actual field strength measurements out to about 15km from home. Let's hope I get a few positive reports as the signal should be detectable out to at least 60km.

Checking my 137.766kHz ERP by measuring field strength

Well, today has been a bit of a disappointment: my QRP QRSS3 beacon has been running for over a day on 137.766kHz and, apart from my own highly successful reception tests out to around 8km (as far as I went in the best direction) not a single station has reported seeing it  ....yet.

Tomorrow, I am going to do one more experiment using the QRSS beacon: knowing the field strength of DCF39 on 138.830kHz, a commercial station in Germany, is around 1mV/m here in the south of the UK in daytime, I want to measure the S/N of this station about 5km from home using the mag-mounted E-field probe. Then, at the very same spot, I will measure the S/N of my beacon with the same bandwidth settings and RX kit.

Based on these two measurements, I should be able to work out the ERP of my beacon to an order of magnitude and probably to within +/-3dB. The field strength of my own signal can be worked out just by comparing the S/N with that of DCF39.  Knowing the field strength and the distance from the home QTH, I can work out the ERP needed to produce this.

Any guesses what ERP I am using? I'll tell you the answer tomorrow!

New 137kHz Transverter thoughts

IRF640 FET

This evening, I've ordered a reasonable sized heatsink to use with the new 137kHz transverter. I am aiming for a power from the transverter of at least 30W and want to be sure that with mismatch the PA is able to survive quite hard abuse. The IRF640 looks a good choice for the PA, maybe a pair, as it is rated at a high voltage (200V) and high current (18A) so I can run the PA from a 30V (or even 50V) supply to get more out. Even with 30W RF, the ERP will still be in very low milliwatts.

As I want to ensure the 10MHz LO signal is very stable so I can use it with WSPR-15 and QRSS30 modes, I may put this in a separate insulated enclosure and pipe the injection signal in via coax.

What I am most concerned about is the lack of activity on the 137kHz band: the last time I gave it a go with WSPR the biggest issue was the very few people actually monitoring WSPR on the band. At the moment, the new 472kHz band is very much the focus of attention with up to 50 WSPR users monitoring and/or TXing on any evening. On 137kHz however the number of WSPR users is often just 3 in the world with no-one on in Europe at all.

Still, I am convinced that with WSPR-15 I should be able to reach near Europe even with my 20m earth-electrode antenna if I can get the power up to around 30W from the transverter. It may even be possible, just, with WSPR-2.This is worth a go, before getting back onto other projects ...like finishing off the Tenbox transceiver!

Lightning across Europe

Lightning map of Europe http://www.blitzortung.org/Webpages/index.php?lang=en

Sometimes it is useful to know where there are lightning strikes taking place across Europe: for example, there are some theories linking sporadic-E propagation to a secondary effect of lightning, although I forgot where I read this. Also, it is useful to know how noisy the VLF and LF bands are likely to be as a result of sferics from such strikes.

Well, http://www.blitzortung.org/Webpages/index.php?lang=en gives a map showing this data.

Homebrew RF Circuit Design Ideas website

HA5KHC's useful website

Wandering around looking for 50W PA designs for 137kHz this afternoon,  I chanced on a website that I don't remember seeing before by HA5KHC. It consists of a HUGE list of very useful links to other websites arranged by design topic (transceivers, receivers,  etc).   It is a massive list of useful links that I could spend days trawling through for ideas and inspiration.  It was quite flattering to see a couple of my designs linked.

Unfortunately there is nowhere on the page with a contact address for the website owner, although I expect HA5KHC's details will be on QRZ.com.

UPDATE:  Adrian YO5PBG said:

"I believe it is a mirror of the original site... of Iiulian - YO3DAC/VA3IUL - http://www.qsl.net/va3iul/Homebrew_RF_Circuit_Design_Ideas/Homebrew_RF_Circuit_Design_Ideas.htm" 

New frequency for LF QRSS3 beacon : 137.766kHz

Using the strong German commercial station DCF39 on 138.830kHz (it is S9+ with me) as an accurate frequency reference, I have checked the frequency of my QRSS3 QRP beacon and it is running higher up the band than I thought due to the way the crystal is loaded. 

Frequency to look is 137.766kHz   +/- . It should be within 1Hz of this frequency. 

Reports and screenshots (looking now in the right place) would be very much appreciated. I shall leave the beacon running all today at QRSS3 speed.

137kHz E-field probe mag-mount

Tiny E-field probe on the car roof on mag-mount

This is the schematic of my simple mag-mount based E-field probe for 137kHz reception in the car. I use a low cost MPF102 FET and a low cost 2N3904 transistor. Performance seems to be totally adequate, detecting my very low ERP QRSS3 beacon as I drive around the local area up to around 10km (yet to test at greater range) from home. The whole unit is attached at the base of a 15cm whip on a mag-mount stuck on the centre of the car roof. The coax from the EFP connects into an FT817 with the IPO button ON - this makes the sensitivity better on 137kHz, a tip worth knowing.

QRSS3 tests with QRP on 137.685kHz.

This afternoon I started my tests on the 137kHz band again. With my 8W (RF out from the unit - ERP will be uW level) crystal controlled beacon sending QRSS3 feeding the 20m spaced earth electrodes, currently under 8cm of snow, I ventured forth in the car complete with an E-field probe built into the bottom of a mag-mount antenna on the car roof. The E-field probe whip is about 12-15cm long only. It looks like a small UHF quarter wave, rather than an antenna for 2200m! The TX frequency is currently around 137.685kHz and this QRSS3 beacon will remain on overnight. I am hoping that stations out to around 100km will take a look for it.

QRP earth-electrode antenna signal at 8.2km on 137kHz band

Well, results have been spectacular with some excellent signals around 8.2km away in the line of the earth-electrodes. Orthogonally, the signal was not copyable at all at a similar range. This is classic loop directionality again.

/M RX signal at 6km orthogonal to TX antenna.

The receiver consists of the 10-15cm long E-field probe feeding the FT817 with IPO button pressed (improves sensitivity when ON at 137kHz) feeding the PC running Spectran at 0.34Hz resolution.

I do find it unbelievable that such a TX "antenna" buried under the snow with NOTHING in the air at all and with earth rods just 20m apart can put out such a decent signal on the 2200m band.

New ERP calculations on 472kHz with earth-electrode antenna in 8cm snow

With several repeatable ground wave reports on 472kHz WSPR using the earth-electrode antenna, it is time for a recalculation of my ERP based on a formula (for 500kHz) supplied some years ago by M0BMU.  The assumption (from M0BMU, that I am not at all sure is right) is that the noise floor is around 3uV/m in a 2500Hz (WSPR) bandwidth. So, based on the WSPR S/N ratio the field strength when using the earth-electrodes can be calculated.

• G3ZJO at 79km gets me at around -19dB giving my field strength around 355nV/m. 
• G3XDV at 61km he gets me around -12dB S/N giving my field strength around 810nV/m.  
• M0BMU at 69km he gets me around -30dB S/N giving a field strength around 100nV/m

ERP Calculations

• ERP using G3ZJO's results = (E*d)^2 / 49; with E = 355nV, d = 79km   ERP = 16uW
• ERP using G3XDV's results = (E*d)^2 / 49; with E = 810nV, d = 61km  ERP  = 49uW
• ERP using M0BMU's results =  (E*d)^2 / 49; with E =100nV, d = 69km  ERP = 1uW

Now, to me these figures seem far too low, so perhaps the noise level is much higher than 3uV/m. Certainly that is the case here where I have an S4- S8 noise floor due to SMPSUs and other noise sources. I think these numbers can be doubled based on ground wave losses but, even so, the figures appear to be extremely low.  My Marconi antenna is some 8dB (average) better than the earth-electrode antenna and I am sure the ERP is well above 1mW using this antenna.

Conclusions

I am totally puzzled: measuring antenna current on the Marconi I get ERPs that are an order of magnitude higher yet measured results with the earth-electrode antenna average just 8dB down on the Marconi. This suggests ERPs for the earth-electrode antenna in the low mW region, which I find much more believable.

Any thoughts please?

Is this Chinese HF radio a wind up one?

As the person who started the FT818 hare running a year or so back (my thoughts and ideas for an FT817 replacement - thanks to a little Photoshop editing!) , I'm wondering if the attached is real or also a spoof?

It purports to be a new Chinese HF radio retailing for £299. It looks very much like an IC718 with some stickers on. It was brought to my attention by Steve G1KQH who found it at
http://s3.zetaboards.com/copythat/topic/7467118/1/ but the date on this is 2011. Surely if true the radio would be on sale now? Somehow I am of the opinion this is (also) a bit of wishful thinking, but I would be delighted to be proved wrong.

A real Chinese HF radio at this sort of price is not totally out of the question: labour costs are low and there are already some very nice Chinese VHF/UHF handhelds on the market that under-cut Yaesu and Icom by around 100%. It is surely just a matter of time before an FT817 or an IC718 look-alike radio is available from one of the Chinese makers.

UPDATE 1755z: maybe this IS real. See http://www.tradekey.com/product-view/1538868-518398/Hf-Transceiver-ft-808-.html

Back on the earth-electrode antenna on 472kHz

The red dots show where the wire to my far earth rod goes - under the snow!

This afternoon I've installed a coax cable from my operating shack down to the back of the garage where I do my radio building and where I can connect to the earth-electrode antenna running down the back garden. Now I have my 472kHz transverter in the garage too so it can connect directly into the earth-electrode antenna without any matching. Even with 8cm of snow on the ground and nothing of the antenna visible above the snow line (!) this antenna is still radiating a decent signal with reports already this afternoon from G3ZJO (-22dB S/N) and G3XDV (-12dB S/N) at good range. I find it truly amazing this system works at all.

I am signing G3XBM/1 on the WSPR database to distinguish my signal from that transmitted using a Marconi where I use G3XBM.  I hope no-one minds me using this suffix for a short period, but it is very much in the interests of good research. The signal level with G3XDV at 61km is about 8dB weaker on the earth-electrode antenna than on the vertical Marconi.

ILER-40 and ILER-20 QRP SSB transceiver kits

The ILER-40 and ILER-20 are low cost, simple 4-5W QRP SSB transceivers for 40m and 20m from Spain, designed by Javier EA3GCY.  They are designed around NE602 ICs working bi-directionally to save parts.

Built on a 12 x 10cm PCB, they look easy to build.  Details are available at http://www.qsl.net/ea3gcy/ . The price is a snip at just 67.50 euros plus 10 euros shipping. It looks a very well engineered kit.

ILER-40 (and ILER-20) QRP SSB kit from EA3GCY

See http://www.eham.net/reviews/detail/10700 for a number of (very good) reviews of this kit which looks like a neat introduction to QRP SSB operation. Kits now being supplied include a small AGC sub-board. The kit does not include a microphone or case.

IC7100 price

Whilst checking the trade-in value of my Elecraft K1 transceiver with Martin Lynch yesterday (in my case for another FT817), I asked when the IC7100 was likely to be available in the UK and its likely price.  Indications are that the IC7100 is going to be here in the spring with a price tag of around £1700. This does not include the D-star option. Clearly these dates and prices are not certain. It will be considerably more expensive than the IC7000 though. That much is certain.

An IC7100 at that price is rather more than I would want to pay, but if it was to last 12 years like my current FT817 already has, it might be worth it, especially with 4m,  2m and 70cm coverage. On the other hand, a second (additional) FT817 would do all I really need at under a third of the price!

E-field probe mag-mount now built

This morning I decided that it would be better to build the E-field probe for 137kHz RX at the base of the whip directly on the mag-mount base rather than inside the vehicle and having to tune out the cable capacitance. This way,  the cable capacitance is no longer an issue. I built the E-field probe into a small plastic box and arranged it so the whole unit attaches to the mag-mount using a PL259 plug in the bottom of the unit. Radio 4 on 198kHz is an S9+ signal with the mag-mount sitting on the bedroom window-sill with around 10 inches of whip. It appears to be working well.

The present design is a poor man's PA0RDT probe but using an MPF102 and a 2N3904 rather than the better devices used in Rodolph's high IP2/3 design. I may put a tuned circuit in the FET drain to increase the gain at 137kHz and reduce the gain outside the band. I will experiment with this before going out in the car.

Currently it is snowing continuously here, so road testing the EFP and checking coverage of my QRP 137kHz CW and QRSS3/30 beacon will now have to wait until later in the week.

UPDATE: I have modified the EFP so that the FET output comes from the drain with a drain tuned circuit tuned to 137kHz. I have the source resistor not decoupled initially but will consider adding this if I need a little more overall gain as the barefoot FT817 is very deaf on 137kHz.

A mag-mount as an E-field probe for 137kHz

Next week, assuming the snow has gone, I want to drive around the local area to plot the polar pattern of my earth-electrode antenna working on 137kHz.  My 7-8W beacon transmitter can send a range of QRSS and CW messages, so I want a way of driving to different places using my FT817 fed via a preamp and measuring the S/N using Spectran whilst remaining inside the car.

Portable RX loops are fine, but these are directional and need to be set up each time a measurement is taken outside of the car.  Ideally I need an omni-directional RX antenna like an E-field probe. So, I'm looking for a way to drive to a spot, take a quick measurement from inside the car, then move on; a loop works, but when it is -2 deg C outside and the ground is icy, it is not ideal.

Either I put the electronics for an E-field probe right at the base of the mag-mount (mechanically not ideal) or I have the electronics in the car and somehow tune out the coax cable capacitance.  At the moment I am still experimenting to find an arrangement that works with good sensitivity by checking the strong Greek commercial signal just outside the 137kHz band.

Based on 472kHz results, the earth-electrode antenna behaves like a loop with loop-like directionality. I 'd expect to see the same pattern on 137kHz.

K7AGE video of his KX3 build

Randy K7AGE has done a wonderfully amusing video of him building his Elecraft KX3. I won't spoil the fun, but recommend you watch it and see how it is done.

Square trade eBay Warranties - any good?

Just looked on eBay for various amateur radio items and noticed the Albrecht AE2990 10,11,12m handheld on sale from various UK suppliers from around £150. Now also shown was an optional 3 year warranty - see http://pages.ebay.co.uk/safetycentre/buyingwithconfidence/warranties/index.html which cover failures to the device outside the manufacturer's warranty period. So, for less than £200 you can have a multimode HF handheld complete with 3 yr warranty.

Peace of mind 3yr warranty for £27 - too good to be true?

My question is this. Has anyone here bought an eBay item with one of these warranties - they seem to be widely offered - and had to make a claim?  It sounds almost too good to be true. These warranties are also available on low cost VHF/UHF handhelds as well where the warranty cost is only around £8-9, which looks remarkable value if the product fails. This is as long as the warranty is a decent one that is honoured and the small print doesn't render it worthless. They also offer a 5 day repair or replacement service.

Mixed results with WSPR-X and WSPR-15

The new version of WSPR works well with plenty of reports given and received on 472kHz with it over the last 12 hours using the 2 minute version (as before but now with a waterfall and better interface), but mixed results on the slower 15 minute slot WSPR-15 which can detect much weaker signals.

My problem is TX drift over a long 15 minute transmission. My small 10W transverter is in a tiny plastic box. When using a 2 minute transmission the PA barely gets warm so there is little heat transferred to the crystal oscillator. With the much longer TX burst the PA warms more and the crystal warms up several degrees, moving the oscillator frequency by some 10s of Hz. So, although I was able to copy signals in WSPR-15, I was not able to be detected by others overnight. There are also far fewer stations monitoring yet on WSPR-15.

The solution is to rebuild the transverter into a bigger (metal) box with (a) better heatsinking so the heat rise with a mismatch is lower, (b) a slightly more efficient PA - problem here is with weather changes the antenna match goes off optimum sometimes and the heat rises as it the PA becomes less class E, and (c) put the conversion frequency oscillator physically further away from the PA, currently it is less than 10cm.

If I fix these issues and am sure that I transmit a more stable signal in the narrower (25Hz wide) WSPR-15 slot then I have a better chance of succeeding with the more sensitive version.  With another 7-9dB S/N detection improvement, my signal could reach some of the more distant stations like TF3HZ.

Iceland get the new MF band

Icelandic radio amateurs have been granted access to 472-479 kHz and temporary permits for 1850-1900kHz, 5.260-5.410 MHz 70.000-70.200 MHz have been extended.

WSPR-X and WSPR-15

A note from Joe Taylor K1JT informing us about a new version of WSPR.

WSPR-X and WSPR-15

Wed Jan 16, 2013 8:23 pm

Some of you may be interested in trying WSPR-X, a new version of WSPR that includes the slow mode WSPR-15. WSPR-15 uses 15-minute T/R sequences, rather than the standard 2-minute sequences; at MF and LF it is 9 dB more sensitive than WSPR-2, decoding signals as weak as -37 dB in the standard 2500 Hz reference bandwidth. WSPR-15 is not recommended for use at HF: the tone spacing is only 0.183 Hz, less than the Doppler spreading typical of many HF paths. The main intended application for WSPR-15 is for very difficult paths at 137 kHz and the new 472 kHz band. It may be interesting to try on 160 meters, as well. Note that the recommended WSPR-15 sub-band is a 25 Hz slice just above the 200-Hz WSPR-2 sub-band, i.e., 1600-1625 Hz above the standard "dial Frequency". This will be handled automatically if you set up WSPR-X in the normal way.

A brief online User's Guide for WSPR-X is posted at
http://www.physics.princeton.edu/pulsar/K1JT/WSPR-X_Users_Guide.pdf ,

and the Windows installation file is posted at
http://physics.princeton.edu/pulsar/K1JT/WSPRX_07r2948.exe .

At present, WSPR-X does not support I/Q audio (for use with direct conversion receivers and transceivers) and does not do “band hopping”. Otherwise most familiar WSPR features are present and working well.

For software enthusiasts: Unlike older versions of WSPR, the user interface of WSPR-X is written in C++ and the Qt programming framework. My expectation is that this shift will make for easier development and program maintenance in the future. At present a click-to-install package is available only for Windows. Source code for WSPR-X is available from the open-source SVN repository at berlios.de. Anonymous checkout of the full WSPR-X source code can be accomplished with the command svn co svn://svn.berlios.de/wsjt/branches/wsprx

User comments, suggestions, and bug reports will be very welcome!

-- 73, Joe, K1JT

Band Plans and AM - Feb 2013 RadCom

In the new February RadCom that just dropped on my mat at lunchtime there is a copy of the band plans for all bands from 136kHz to 134GHz.  What I fail to understand is why does the RSGB appear so anti-AM?

For many years now there has been a clear choice for an AM centre of activity on 144.55MHz. The RSGB has been made aware of this on many occasions and yet still we have a (begrudging) footnote, just about visible if you look hard, saying this is where to look. Even this comment ends with, "although this frequency is not officially recognised within the 2m band plan". Why not? We have a FAX calling frequency listed and goodness knows how many DV Internet Voice Gateway frequencies listed, yet we cannot be allowed an official AM centre of activity properly listed! AM is not a common mode these days, but those who enjoy the mode need to know where to meet on the band. The RSGB is giving no help at all here.

I also get frustrated with the 10m band plan where AM is again almost treated as a disease. Most AM activity has been in the 29.0-29.1MHz segment for years now: this is THE part of the band where AM users congregate, yet the all-mode section with up to 6kHz bandwidth does not start until 29.1MHz upwards! Does no-one who creates these band plans actually listen to see what actually goes on? In the last 30 years I have had many AM contacts on 10m and not one outside 29.0 - 29.1MHz.

So, next time you consider the band plans, please:

(a) Add an AM "centre of activity" frequency into the 2m band plan - it is 144.550MHz in case you don't know.
(b) Show 29-29.1MHz as the AM sub-band in the 10m band plan.

Back on 137kHz TX

QRSS and CW beacon TX for 137.685 kHz

Today I went into the shack with the intention of making a new transverter for 137kHz based on my recent design for 472kHz.

Instead, I ended up building a new CW, QRSS3 and QRSS30 8W beacon transmitter using an IRF640 PA device. This evening and overnight the beacon will run QRSS3 on approximately 137.685kHz and I have requested reports and screenshots.

The antenna being used is my 20m spaced earth-electrode pair set-up used very successfully on 472kHz last weekend. On 137kHz signals are much weaker than on 472kHz, so I await reports with interest.

The whole unit runs quite cool when housed in a plastic box. Switches on the front of the boxed unit allow up to 7 pre-programmed messages to be beaconed at varying speeds. As normal, I use the K1EL beacon chip for the beacon message generation. The signal source is a 3.579MHz crystal in a divide by 26 circuit implemented in a PIC like device and kindly supplied to me by a French amateur Francis F6HSI a few years ago.

eQSL cards

Brazilian QSL card received via www.eqsl.net

To be honest I'm not very good at QSLing.  In years past I would regularly write out QSL cards and send them out to the bureau and look forward to the next batch of cards. These days I do send out some paper cards, but not that many. Instead I tend to use eQSL cards instead, but I was way behind with reviewing incoming QSLs so this evening I spent an hour or so getting up to date. I rejected a few cards - one for a WSPR "QSO" where what had really happened was an exchange of reports via the WSPRnet database, and the other for a voice-over-internet QSL with a JA station.

Checking my totals I see that I have 55 countries confirmed by eQSL cards. All these will be with 2.5W or less on all modes, mostly SSB on 10m and 6m. Many of my DXCC countries pre-date the eQSL era and I have not been that active in DXing as such in recent years, apart from the occasional contest like CQWW SSB, which I enjoy with QRP.  As you know, I prefer to carry out crazy experiments somewhat on the edge of sanity on strange bands with odd antennas instead!

More IC7100 photos

http://www.universal-radio.com/catalog/hamhf/3071.jpg

Universal Radio staff in the USA had the new IC7100 multi-band multimode transceiver demonstrated to them in early December and they have posted a few informal photos on their website.  At this time there are no indications of price, but my guess is somewhere in the £1400-1800 bracket here in the UK.  A lot of money, but also a lot of radio, including for the first time full 70MHz transceive facilities and, if this floats your boat, D-star built in. It also has a touch screen interface. I'd like to see a QRP version of this although I doubt the price would be much less. The receiver also covers a wide band 30kHz-200MHz and 400-470MHz.