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Although I don’t enter the contests as such, I always enjoy taking a few moments to try and make some contacts in the RSGB Christmas VHF/UHF Cumulatives. I particularly enjoy the multi-band element – where you work someone on one band and then try and work them on the other bands that they have available.

This year, I had 144 and 432MHz available as per normal, but I thought I would try on 70MHz FM as well. In theory, I have 70MHz CW/SSB, but as you will remember, the FT847 has such a poor receiver for weak signals, it’s not really worth using in a ‘tropo’ context. I missed most of the first session, but was intrigued to hear 2E0NEY from near Bath on 70MHz FM, on the Wouxun handheld, as I was coming back from a walk. Naturally, I called him, but alas, I still haven’t made a QSO on the handheld!

Some of the notable QSOs from the two sessions; ON4WY was worked on 144MHz in two sessions, GW8IZR from Anglesey, (IO73) was a very welcome one on 144Mhz. It’s not that far, but the antenna isn’t that good to the north as there are some local obstructions. It was good working Dave, G4ASR on both 144 and 432MHz. I even heard him a couple of times on 70MHz FM but didn’t manage to attract his attention! Stewart, G0LGS from Cheltenham was loud on both 144 and 432MHz which I thought was good going, considering the path over the Cotswolds. Similarly, Brian, G6HIE in Worthing, under the South Downs was doing well and it was fun to make it on both 144 and 432MHz with him. I should really have tried on 70MHz FM – could be an interesting path!

Chris, G4CCC was the best DX on 70MHz FM at 42km, only just further than Colin, G3TA at 41km! Lots of fun trying a bit more 70MHz FM and I’m confident the gear is working reasonably well now.

No great DX in the sessions, but an enjoyable mix of contacts on different bands during the sessions

I finally solved the problem with the cable I was trying to make to interface my VX-8GR with the computer, as described in my last post. As I had begun to suspect, the trouble was caused by the 2.5mm jack plug not fitting properly in the VX-8GR data port socket.

As suggested by one of my readers, I tried the cable in the COM port of the TH-D72. Although I couldn’t figure out how to make data appear on this port, I did see some output when turning the TNC on and off which suggested my cable did work.

I then tried it back on the VX-8GR and used my oscilloscope to look for anything digital. I didn’t see anything. I then tried another 2.5mm jack with the sleeve off so I could get the ‘scope probe on the solder tags and with a firm press it went in with a click. I now saw -5.6 V on the TX pin – clearly an RS-232 signal level.

The jack I originally used had a plastic sleeve or cover and the diameter of the base was just a bit too much to allow it to go all the way in. One with a metal sleeve had a slightly smaller diameter base. The metal sleeve itself interfered with inserting the jack, but I could put the plastic sleeve on that jack and it would still go in. So that, finally, is what I did, and I now have a VX-8GR PC cable that works. It also works with the COM port of the TH-D72 should I find a use for that.

As a ham and electronics enthusiast I don’t believe in buying things I can make myself, but sometimes making it yourself can turn out to be more trouble than it is worth!

Series Three Episode Twenty-Seven of the ICQ Amateur / Ham Radio Podcast. Our end of year episode discusses Amateur Radio Ethics and a Ham Radio website review.

Screenshot of QSO with KG6ASY

Last night was a good night with the Warbler, with five contacts made using PSK31 on 80m. The locations of the contacts were varied; Ontario, Illinois, Kentucky, New Jersey and also Nevada.  This last one was a real surprise as checking the distance between myself and KG6ASY in Washoe, NV, revealed it was a little over 2,200 miles.  As the power out from the Warbler is 3W, it has not yet reached 1000 miles per watt but it is getting close. Tim, KG6ASY gave me a 549 report and his signal was 579 for me.

There is some DX coming in too on 80m  as I saw a French and a Spanish station on the waterfall last night.

The Warbler is proving to be a fun transceiver to use during the night on 80m.

Finished Warbler in box

I have spent a frustrating couple of hours trying to make a PC cable to communicate with the VX-8GR. In the VX-8 Yahoo group it was stated that the cable is the same as for the Kenwood TH-D7AG a diagram of which is given in YO3HJV’s blog. It was also pointed out to me that there is a diagram in the back of the manual – the one place I never thought to look!

It is easy enough to make up. No level shifting components needed. Just a 2.5mm stereo jack for the radio end and a 9-pin D plug for the PC end. But the damn thing refuses to work.

I have tried a Prolific USB to serial adapter and an FTDI one. I’ve tried the FTBVX8G software and I’ve tried a terminal program to see if I can detect any data. Nothing. Nada. Incommunicado. I know the cable is OK because if I short between tip and ring of the jack plug I can type in the terminal program and see the text I typed echoed back over the connection.

The only thing I can think of is that the standard 2.5mm stereo plugs I have here are a bit too short. It seems to me that the  plug isn’t locking firmly into place, more that the radio is trying to push it back out again. It’s as if the tip needs to be a bit longer to get past the spring loaded contact in the socket. I measure 7/16in from the base of the plug to the tip of it. I had a similar problem trying to make a cable to send audio from my FoxTrak APRS tracker into my Motorola GP300. Then I had a plug from a speaker mic to compare it with and I could see that it needed to be longer.

Perhaps someone who has a VX-8G PC cable that works could measure the plug on theirs. Or perhaps someone will spot the stupid wiring mistake I’ve made from the photo I’ve posted.

Santa was, as usual, very generous in his, er, deposits here. There were no specific amateur radio themed gifts this year, as I am well provisioned in that department! I did, however, have a couple of things for my astronomical telescope.

One of these was a Pentaflex ‘Mobile Power Station’. This looks like a giant torch, but is in fact, a great big rechargeable battery. The idea was to use this for my telescope which otherwise uses a gazillion AA batteries to guide the tube onto the correct target and it can go through them pretty quickly! I’ve got more crafty and thrifty about moving the telescope around, but I realised that the PSU for the scope would be a good idea.

Of course, the unit will not just power a telescope! It will be absolutely ideal for powering an FT817 or similar on holiday. It’s relatively portable, though quite heavy – so I don’t think it’s the answer to carting up a mountain for SOTA or similar activities – but definitely a great answer to having plenty of 12v readily available.

Over the last couple of days, I’ve had the 70MHz FM set on when I’ve been in the shack. I’ve probably said, but the set is an converted Philips FM1000 series set.

A few days ago, I called CQ and Dave, G4AQK from Swindon called me and asked if I knew there was a lot of hum on my transmission. I didn’t but, switching on the monitor receivers confirmed the issue. I soon found that if I touched the case, the problem went away. I tried various earthing points without any success. Caught up with Rob, G4XUT a bit later and he suggested that it might have been an RF feedback issue.

Bearing in mind Rob’s suggestion (which I was quietly a little sceptical about, as the issue seemed to be independent of power level) I grabbed a ferrite ring and put it on the power lead, close to the rig. That solved the problem – so I forgot about it.

A few days ago, I called CQ on 70.45MHz FM again and thought I’d check the transmission. Despite the ferrite ring, the hum was back! Tried another ferrite on the microphone lead, but that didn’t do any good! Then the penny droppped!

The outside temperature was around -12C (unseasonally cold in these parts). I think there was ice on the antenna (probably in it too!) and this was affecting the SWR. This morning, outside temperatures had risen and thawed a lot of the snow and ice. The hum has gone! So I’m sure that’s what causes the problem.

Meanwhile, this morning, I heard Chris, G4CCC from near Reading calling CQ on 70.450MHz. Called him back and was surprised to hear him say that three people had come back to his CQ! Two of the others were in Surrey and barely audible up here in the frozen wastes of Oxfordshire – but it’s great to hear more activity on 70Mhz.

Got a 70MHz FM set? Why not hook it up and try and make a contact or two?