137.5kHz WSPR15 tests

Using a very stable external signal generator as my 10.0000MHz LO 5dBm injection, I'm now in a position to try WSPR15 with a stable signal. After a quick frequency check with WSPR2 I propose to switch to WSPR15 with its greatly improved weak signal capability for this evening and overnight. WSPR15 activity takes place in the 25Hz slot just above the WSPR2 activity.

Please let me have any reports.

The first WSPR15 transmission will occur at 1600gmt.

Update: Tom G8HUH reported an upward drift of 5Hz during the 15 minute TX burst, so I've moved the LO to 1.7000MHz and the FT817 to 1.836kHz. Drift (all due to the FT817) is now 1Hz. Awaiting decodes. 

137.5kHz ...it's getting repetitive

Well, I've had the 137.5kHz WSPR2 beacon running for about 18 hours now, almost continuously on a 25% TX cycle. I've tried to drum up reporters by posting on the WSPRnet chat page, RSGB LF Yahoo Group and the LF Blacksheep reflector, plus a few direct emails to stations likely to copy my signal.

Consistent 137.5kHz WSPR spots from G8HUH at 250km, but no others!

All I've managed are the very consistent reports from good old G8HUH at 250km. The signal is obviously spanning this distance without any issues so why no others reporting?

Later I am going to replace the 10MHz LO in my transverter with the stable source from my synthesised signal generator and have a go tonight at WSPR15 (15 minutes TX periods) and see if that gets me a few more reports. It should be several dB more sensitive. If that fails to get anywhere, then I am calling it a day on 137kHz. In terms of returns for effort, this is not good value.

Internet Time Servers

For WSPR, and probably quite a few other programmes, it is important to have your PC's clock accurate to within a second or so. With WSPR, if you are more than a few seconds out the software will be unable to correctly decode signals. There are several internet time servers around which sync the PC clock to very accurate time standards around the word.

The one I use is http://www.worldtimeserver.com/atomic-clock/ . This allows you to download a program called atomic.exe which syncs your PC clock at an interval you choose to an internet time server. It is a great help to keep an old PC in time for WSPR. Without this my old Dell Inspiron would be all over the place with time. Once installed there is nothing to do as long as you have an internet connection.

Going QRT on 137kHz

Another evening on 137.5kHz WSPR and reports again from G8HUH at 250km,  BUT FROM NO-ONE ELSE. I really don't want to run higher power or erect a big antenna. To be honest it is not worth the effort continuing on this mode on this band as there are too few monitoring stations. At the moment I am not inclined to box and finish the transverter. Instead, I think I'll try something else. Not sure what but the potential and unfinished project list is huge.

Ferrite Rod TX on 10MHz WSPR

This morning I tried the ferrite rod antenna on 10MHz WSPR TX for an hour. As before, I mounted the ferrite rod VERTICALLY on the wooden desk with all other antennas disconnected -  the only other antennas are a VHF colinear and a 10m halo, and both of these are around 10m away from the shack. Quite a respectable number of spots we obtained with 2.5W from the FT817.

So far I have not managed to get the ferrite rod antenna to match on 14MHz. It may be the losses in the ferrite are starting to impact performance?

I am still unclear how this tiny TX antenna is working: the assumption is a combination of a small amount of radiation off the H-field (ferrite rod coil) loop and some E-field radiation off the coiled vertical section above the tuned part. Then there is still the possibility that it is just acting as an efficient coupler into the house wiring that is doing the real radiation. Whatever, it puts a signal around Europe and occupies a volume with the tuning cap of just 15cm x 10cm x 5cm on the wooden shack table.

More Ferrite Rod TX experiments

Vertical orientation today - good results on 40m WSPR TX

This morning I tried to get a few more WSPR reports on 7MHz using my small ferrite rod antenna. I managed a few only, then after about 20 minutes I decided to try again with the ferrite VERTICAL on the desk. Don't ask me why I did this, but then I started getting a large number of spots!

Now, all other antennas were disconnected and I tried this arrangement in several places around the room and ALL got decent spots. Maybe what I have here is a bit of a hybrid. If you look at the diagram there are about 80turns on the rod beyond the parallel tuned circuit that I assumed was the magnetic loop doing the radiating. Then again you can consider the parallel tuned circuit as a base loading for the 80t short vertical above it. Tuning C1 will bring the whole system to resonance and a low SWR can be found by adjusting the tap point, which turned out to be best very close to the bottom, about 1 turn up. There is no earth connection. I make no claims as to how this works. Some suggest it is just an elaborate coupler into the house wiring, but the very sharp tuning makes me think this is not likely. Also, if this was the case then surely moving it around in the room would make a big difference? Below are the spots for a few hours on 40m.

WSPR spots with the antenna above on 40m today

However it works, it manages to do pretty well. Now I do not believe in "snake oil" antennas, and make no claims for this one: a small ferrite rod will radiate something (H-field). Add a ferrite loaded vertical as well (an E-field antenna) and that will radiate too. What happens in the far field goodness only knows!

When the weather is better I will take the whole kit into the back garden well away from the house and repeat. If it is working without coupling into the house wires (as I think is the case) then results should be comparable. If spots disappear then it will have turned out to be a very good random wire coupler, HI.

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)