Category Archives: HF

20m End fed half wave

I used a 20M EFHW and few years back with varying degrees of success. It was about the time when ‘squid poles’ became a popular antenna supports. The single core wire element was wrapped round the pole but the problem was that most poles then were made of a carbon fibre material which made them conductive. The antenna did not work so well.

This week I tried out a new, 10M fibreglass pole and, like before, wrapped the wire round to the pole. First indications are good with low SWR using a commercial 49:1 balun. This was much better than using the small EFHW tuner I made some years back.

Another idea is to use an off centre loading coil to make it a multiband antenna. More to come, watch this space.

 

Building an HF Transciever

Over the years I have built a lot of gear from simple test equipment to an eight band CW transceiver using reclaimed parts. Technology moves on and I now have three commercial SDR rigs. The performance of modern transceivers is amazing but I feel something has been lost; it’s all done in software which feels a bit cold, clinical even.

A few years back I followed a series of articles in RadCom written by Eamon Skelton, EI9GQ, where he described how he built a transceiver mainly from discrete components. I bought the book a couple of years ago and now feel I want to make my version of his project.

Why now? It is mainly the availability of cheap test equipment like spectrum analysers, VNAs, GPS locked frequency meters and wide band noise sources which work well with SDR receivers like the RSP1A.

Not long ago all we had were grid dip oscillators, drifting sig gens and frequency counters with dubious accuracy.

I have made a start and almost fallen at the first hurdle! Instead of making a 9Mhz, 2.4Khz wide SSB filter I have bought one from Spectrum Communications. That will save buying lots of 9Mhz crystals and spending hours matching them to get a good shape.

I have already built a VFO based on a synthesiser chip. There are some things it is not worth trying to replicate and a drifting VFO is top of the list. I did build a free running 8 Mhz VFO in the early 1970s that was multiplied by 18 to drive an old Pye valve TX on 2M. It took hours to sort out the drift but eventually it was rock solid. The key was an Oxley Tempatrimmer. The fixed vanes of the capacitor were fixed to a bimetalic strip so as as the temperature varied the capacitance changed. They are impossible to find these days.

Watch this space as I will post progress reports as each stage is completed. The first thing to do is tidy up the workshop, I may be some time…

Hi-Fi SSB?

A few years back it was fashionable to use ‘HiFi SSB’. The idea was to transmit a much wider AF frequency range with the emphasis on getting more bass response. I remember hearing a station who was proud of his studio mic and loads of processing gear. His signal had lots of bass and extend higher frequencies. His bandwidth was nearer 8Khz than the usual 2.4Khz. He said he did not care because he had spent a lot of money getting ‘better’ audio.

Years back I was taught that the frequency range for intelligible speach was 300hz – 3.4Khz.  I find that lots of bass makes signals harder to copy, especially when they are weak. Which is exactly why the military and aviation communications limit the bass response.

Why spend lots of money on expensive ‘studio’ microphones and other fancy audio stuff when all it does is make your signal less readable? Is it the just the dealers making money again? Is it the desire to be different/better that other ops? Or is it a lack of understanding of what radio communication is about?

Home construction, QRP, solar power 8 months on

When I came back to amateur radio in March 2018, I set myself some aims, more aspirations really.  I said that I wanted the station to be QRP, all homebrew and solar powered.

I have always enjoyed making stuff and now I have finally retired I have a lot of time to do just that. Second, I have previously thrown money at the hobby, got on the air and become bored.

QRP? Life is too short say the kilowatt cynics. Over the years I have enjoyed using a lot of small, home made radios with spectacular results. It takes more effort to winkle a signal out of the noise, but the rewards are bigger. Like many things in life it takes effort and patience to get results but the reward are higher.

uBITX

As the solar power I am trying to reduce my carbon footprint as I fear we are on the brink of a climate catastrophe.  You may not agree but I would urge you to read the evidence, from climate scientists, not newspaper articles, who agree that there is a big problem. Besides saving energy in the home saves money!

80w folding solar panels

So, 8 months on I am back on the air with a uBITX with the mods to reduce spurious emission and harmonics. Next is the AGC board. Using a LiPo battery I can get near 20W output but that is trimmed down to 5W. I also have a 20M QSX and am eagerly awaiting the launch of the multiband QSX.

20m QCX

The auto antenna tuner is nearly finished but in the mean time I have a 9:1 balun at the bottom of the antenna and an L match at the radio end. I can get below 1.5:1 from 106m to 10m which is fine for now.

The only thing to sort out now is a more permanent solar panel battery charging facility. I have the gear from ‘the van’ but want something more permanent.

80M DX on the uBITX

This is a recording of W1MBB on 3.798Mhz at 0754 this morning. My antenna is a long wire strung between two trees with a homemade tuner. I also heard a ZL this morning.

 

So, what does this prove? That the uBITX receiver works well although I must add the AGC board! That there is DX out there if you know where to look. That amateur radio need not cost a lot. And, most of all, there is nothing to beat the kick of building a radio and using it on the air.

I know I could never work him on the uBITX but I also know that using higher bands it is perfectly possible to work across the pond on 2W of CW.

Why home construction?

I am often asked why I bother with home construction. Why make stuff when it is so easy to go out and buy it? The questioners sometimes go as far as asking why I waste my time.

There are lots of reasons; it is something I have always done, it saves a lot of money, you know your gear well so can repair it and most of all I learn something, sometimes the hard way!

All of that is summed up in this quote I found today:

“The excitement of learning separates youth from old age. As long as you are learning you’re not old” Rosalyn Sussman

First test of the remote ATU. The control box is the next job.

I am now eight months in to my aim to build a totally homebrew station. I am at the point of having some working transceivers, power supplies, an antenna analyser and a long wire antenna. The remote tuner is almost done but is proving troublesome. By the end of the year it will all be sorted!

More DX on 80m

Another listen at the top end of 80m this morning produced more DX –  ZF2ZB. He was calling CQ or QRZ and was eventually answered by a Canadian station which I could only just hear. Still amazed at the performance of the RSP1A SDR RX fed by the untuned long wire.

When I first heard him at 0755 he was 5-7/8 but I had problems with a faulty memory card in the recorder. On this recording he was 5-5/6 but it was 0805 by then. At 0830 he was still just there in the noise but I heard KC4GL call him.

The history of Rugby radio station

This is a fascinating book about the history of Rugby radio station. It was a huge TX site, part of the HF point to point system and with the well-known LF, MSF transmitters. Now the site has been flattened ready for a housing estate. Why have we not preserved at least some of the HF comms system?

Bearley RX station was paired with Rugby although I never got to visit when it was operational. I vaguely remember the author of the book, he would have been at the Leafield training school at the same time.

Order the book here  (I have no connection with the book or its publishers.)

HF radio communication is not dead!

It seems that the US have tested HF radio as a means of long-distance communication of speech and data. Maybe they have realised that satellites and fibre optic cables are not as safe as they thought.

Satellites are easy to take out as the Chinese demonstrated a while back. There was also a report in the UK press recently about the vulnerability of underwater fibre optic cables.

It is interesting how things go around in circles. It is only ~30 years since the UK closed its point-to-point HF radio system. Now we are looking at HF again for strategic communications. It will be interesting to see what happens.

See the full article here