SOTA Activation Ditchling Beacon G/SE-006

On Saturday 26 July I activated SOTA summit Ditchling Beacon (G/SE-006). Although there is a bus from Brighton to Ditchling, I enjoy walking so I took an early train to Lewis followed by a 10km walk along the South Downs Way.  My plans went slightly awry when the Southern train broke down at Haywards Heath, but after a 30-minute delay we arrived at Lewis.  This section of the South Downs Way is well signposted and so I did not get lost this time. My pack was a little heavier than usual. It was a very hot day so I carried extra water, not knowing that there would be an Ice Cream van, also selling water (but two quid a small bottle!), at the Ditchling car park. The walk took around 2 ½ hours, including a short sandwich stop.

M0BGR/P at Ditchling Beacon, G/SE-006. July 2014

 

I have never suffered a catastrophic failure on one of these expeditions but today was the exception. I use a small plug box (in the foreground of the photo) so I can quickly connect several items to my  lead-acid 7.2Ah battery. I wired up the FT-817 and switched it on while I set up the Super Stick HF antenna. After about 5 minutes there was a bang from the vicinity of the plug box and the 817 reverted to internal batteries. I quickly disconnected the lead-acid battery and began to investigate, thinking something had shorted. All the external wiring seemed OK so the problem had to be in the plug box.

I carry a small tool kit but I had omitted to include a small Posidrive screwdriver, required to open the plug box, and a multi-meter which would have been helpful when fault finding. I could have carried on by either using the FT-817 internal batteries, which would have lasted about an hour, or directly connecting the 817 to the battery – a little inconvenient as I could only power one item at a time. I decided to investigate and was able to open the plug box, carefully, with the tip of my pen knife blade.  The inside was a complete mess! It used to have an electrolytic capacitor but this had blown itself apart. As this was not required for battery operation I surgically removed it, cleaned out the wreckage, put the box back together again and re-connected everything (carefully!).

The 817 was still not receiving power but checking fuses without a multi-meter is difficult and none had obviously blown. I am a bit fanatical about fusing everything and there were three fuses in the 817 circuit. Fortunately I carry spares, taped to their respective leads so I opted to replace them all even though only one should have blown. I had been some time since this plug box had been used. I powered it up before leaving home, but only for a few seconds, so I guess this was not enough to reveal a weak electrolytic capacitor even though this was adequately rated for the job (100 uF, 25V).

 Next time – check tool kit, test everything properly, before leaving home, and carry a multi-meter!

Finally, I was on the air and firing on all cylinders. This was the day of the IOTA contest so I spent most of my time on the WARC bands, with occasional calls on 2m and 4m FM. This was the first real outing for my new Wouxun KG-UV6D – it performed well.  Band conditions were not great but I quickly worked the four stations I needed for a valid activation, thanks to Mike, G6TUH, who I worked on several bands and also spotted me on the clusters. I was on the air for three hours and worked 14 stations, including 5B4KH in Cyprus (Asia-004 in the IOTA contest). During the afternoon lots of people stopped to ask what I was doing. Although this interrupts operating time, I always take the opportunity to explain amateur radio and why it is relevant today.

I packed up in time to catch the last bus to Brighton, but it was such a lovely afternoon I decided to walk back to Lewis, after pausing for an Ice Cream! The walk back was uneventful, apart from getting a painful blister on my right foot with about a mile to go which I had to stop and sort out (I always carry a basic First Aid kit). On the walk back I was passed by lots of Ghurkha soldiers who were doing a 100km run along the South Downs Way that very hot day, which rather puts my 10km walk into perspective, but they weren’t carrying an amateur radio station!  

Software Defined Radio (SDR) - First Steps

I have often seen adverts in the amateur radio press for Software Defined Radios (SDR) and wondered why they are so expensive. During a discussion at my radio club (Cray Valley - www.cvrs.org), I learned that a TV/Radio Dongle receiver can provide the hardware for SDR. I found a suitable dongle (RTL2832 plus either R820 or E4000 chip set) on Ebay; ten UK Pounds from Hong Kong so, being the last of the big spenders, I went ahead and ordered. While I was waiting for it to arrive, I downloaded a copy of SDR Sharp  (SDR#) and the installation instructions (http://www.sdrsharp.com ).
 

There are some hardware things that I needed to do while waiting for the dongle. The dongle has a tiny MCX antenna plug. Fortunately Maplin sells an adaptor cable to standard TV socket (part N59LN) and I had already made a TV-BNC cable for another project, so this was not a problem. These dongles are very vulnerable to high levels of RF, so if you transmit while receiving on the dongle it will fry. The solution is to solder a couple of reversed diodes into the adaptor cable to limit the maximum input voltage.

The dongle arrived. The package also contained a remote control (only useful if you want to use the dongle for its intended purpose, but being radio amateurs we don’t do that do we?), a whip antenna (which works surprisingly well) and a software disk. Do not install this software as this will conflict with SDR#. The only tricky bit was changing the dongle driver from the Windows default to RTL 2832. To do this, you need a piece of software called Zadig (link on the SDR# site) and I also had to temporarily disable Heuristic protection in Norton which took violent exception to what I was trying to do.

All set, and Norton back to full protection, I plugged in the dongle and fired up the software. Operation was quite intuitive, but I started with the FM broadcast band – all was well and all the expected stations showed up on the display any gave me some strong, predictable signals to set up and learn how to use the software.

 

 

The dongle, with the E4000 tuner, covers from about 24MHz up to 1.7GHz, so it is a broadband device covering all the amateur bands from 12m up to 23cm. That’s the good news; the bad news is that there is no front-end filtering. Also these dongles mix the RF signal down to a few tens of kilohertz, to input to computer sound cards, so spurious signals are a real problem, particularly on the lower bands. For example I get a strong ‘Classic FM’ signal in the middle of the 10m band. It is possible to manage these phantom signals by carefully choosing the ‘Centre’ frequency and adjusting the RF gain, which can be accessed through the ‘Configuration’ menu, but my next move will be to build some filters to clean up the input signals.

I have also experimented with receiving  some digital modes using this SDR receiver. It is possible to patch the microphone socket to the speaker socket on most PCs so the digital modes can be decoded with standard software. There are a couple of drawbacks: you can’t hear the audio signal and the signal gets converted from digital to audio then back to digital again. There is a better solution – a piece of software called Virtual Audio Cable (  http://software.muzychenko.net/eng/vac.htm ), which does what the name suggests, but without the Digital/Audio conversions. With VAC, it is possible to ‘split’ the system so the audio output can be heard, recorded or shared with other programmes. I have successfully decoded RTTY, PSK-31 etc.

My Dongle SDR has several advantages: it is very small and everything is controlled from the keyboard so easy to configure. For example, filter bandwidth can be adjusted very precisely and easily.  The waterfall display, which can be adjusted, allows large segments of a band to be viewed at once and you can see when stations come and go then click on the ones you want to listen to. Combining the SDR with the VAC software provides a very flexible setup. For example, I can operate digi-modes while listening to my favourite music on the same computer. 

This SDR radio will never be as good as a full communications receiver, but it was definitely worth a tenner and I hope its performance will be even better with some front-end filtering. It has opened lots of opportunities for experimentation that were not available to me before and after this initial experiment, I may be tempted to invest in an SDR transceiver, but that is for another day.

I have frequently lamented to poor HF band conditions on here, and now the 2008 solar report is out. This shows that in 2008 there were 266 days with NO sunspots (source: Spaceweather.com and NASA). This has not happened since 1913, which had 311 spotless days.

The good news is that cycle 24 now appears to be established and we should see improving conditions over the next few years. That said, I just really struggled to work EA7ES on 20m CW. We had very deep QSB so he was fading from S5 to 'no copy' for several minutes at a time - thanks for persisting Manol. Apparently this was due to a minor disturbance on the sun, which will wipe out and feeble ionisation that we do have.

I have never done much on 80m as I only have a small garden and so short antennas, but I have been trying this band late in the evenings during the long winter nights. I have not yet worked any spectacular DX, but I have had some very satisfying European contacts.

Dave

http://www.howardcommunications.ltd.uk