Simple low cost test equipment

There was an interesting post in the last day on the GQRP Yahoo group asking about portable workbenches that led on to talk about test equipment. This got me thinking about simple pieces of test equipment and what one needs to do basic QRP design work.

In my own case the most useful pieces of kit are (1) a signal generator, (2) an inductance/capacitance meter, (3) an oscilloscope,(4) a basic power meter, (5) a wide coverage all mode RX, (6) a multimeter. I keep thinking about building a dead basic spectrum analyser too. Test probes too of course. Also a good lot of cables with BNC plugs one end and croc clips on the other.

Just wondering what other people use? Certainly for HF QRP work only very basic test gear is needed, which is why I enjoy it so much.

In a way it is a little surprising that no-one sells a low cost "all in one" test box for amateurs with many of the above in one unit. A bit like a CB test box?

Not the best of weeks

Well, apart from the excitement over the ferrite rod on TX, this has not been a too brilliant week.

As you saw in the last post, my website domain name provider seems to have messed up web forwarding thereby screwing up the G3XBM website, for now at least. This is annoying as it has also caused issues on the www.cambschoral.org.uk website that I set up and maintain for the Cambridgeshire Choral Society.  And then there is 137kHz where a week of trying has netted me spots from just 4 unique reporters. Even the effort to get WSPR15 working was all but scuppered by the 4Hz drift over 15 minutes in the FT817.

In the grand scheme of things none of this much matters. Perhaps next week will be more fruitful, HI. In the meantime, I'm watching TV and having a whisky!

Website woes

In the last few days I've done a major overhaul of my main website www.g3xbm.co.uk . All was working fine, but for some reason the web forwarding is not working correctly. Landing on the www.g3xbm.co.uk site you should automatically be forwarded to https://sites.google.com/site/g3xbmqrp3/ which is where the site is now located on Google Sites. So far so good, and this happens, although the address bar, which should change to the new site address based on how I've got my forwarding set up does not. Not only that, but clicking any images does NOT bring up larger, clearer images as it should although this works fine when you start with https://sites.google.com/site/g3xbmqrp3/ . So, I think it is a problem with the web forwarding, which I will try to fix.

In the meantime, you may want to go directly to https://sites.google.com/site/g3xbmqrp3/ if you want to explore the revised site.

First WSPR15 transmission decoded successfully

After a LOT of effort, G8HUH managed to decode my WSPR15 transmission on 137.607kHz at 1815 this evening. Even with a very low (1.7MHz) LO, the drift was still 4Hz in the 15 minute TX period, mainly due to the FT817 I think. At only -32dB S/N decode this was actually not as good a result as with WSPR2 over the 250km path. Short of force cooling the FT817 or using a rig with a TCXO reference, there is nothing more I can do.

My WSPR15 transmissions were also copied and decoded by G4FFC and G4FEV.

CONCLUSION: WSPR15 is a much more tricky mode to use successfully unless the transmission is very stable. This is the screenshot Tom G8HUH sent me.

30uW ERP 137.607kHz WSPR15 signal received by G8HUH 

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.