Category Archives: HF

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…

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.)

The SDRPlay RSP1A-a momentary lapse

At the RSGB Convention last week I broke my pledge to have a 100% homebrew station. There was a demonstration of an SDRPlay RSP1A right next to the Martin Lynch stand with a small pile of boxes on sale! Not only is it a wide band receiver there is also spectrum analyser software available and all this for just less than £90.

The justification was simple; I build transmitters and need to be able to check the harmonics and other spurious signals to conform to licence regulations. It does not have to be an absolute measurement just the level of the spurious emissions compared to the carrier. And spectrum analysers are expensive.

Then there is the imminent launch of Es’hail, so I need a 10Ghz receiver to listen to it. The conscience clincher was a demo by the microwave group of a modern satellite TV LNA connected to an SDR receiver. Simple. Another reason to get the RSP1A.

And then there is 630m. You get the message, justification for the temptation and I must confess I had a moment of weakness and succumbed. I am trying to atone by finishing the remote tuner.

Not had much time to play but what I have seen is impressive. SDR receivers are incredible, amazing etc. This morning I listened at the top end of 80m for the transatlantic DX spot, 3.798Mhz and was astonished to hear AA8KB at 5-7 on the meter. This is on an untuned inverted L sloper with the high end at about 10m and low end at 6m.

This is a short recording of AA8KB holding the recorder close the the PC speaker.

I can only confess to this lapse and argue that this was a one-off purchase of an extremely useful piece of kit!

The usual disclaimer, no connection with the company and these are my own views.

Update a half hour later. Just gone back to the SDRPlay and found the RF gain was almost turned to minimum.

Life is too short….

Last week I heard a QSO on 80M SSB where each op was using 400W and each gave the other 5-9+20db One op said ” I always use QRO, life is too short for QRP”. Reducing their power to ~6w would have resulted in report of 5-9+2db. Why waste so much power?

Interestingly I found this today on the North American QRP CW club web site; “According to Rich Arland, K7YHA (now K7SZ), in World Radio magazine (Feb. 1990, year 19, issue 89, pp. 46-47) the long-distance low power record is held by KL7YU and W7BVV using one micro-watt over a distance of 1,650 mile 10-meter path between Alaska and Oregon in 1970. This is the equivalent of 1.6 billion miles per watt.”

That is why I use CW with a 5W power output limit and often use much less. It takes more effort to work some stations and more skill and patience but the rewards are well worth it especially when using homebrew gear.

SW20

160m – Topband – best for solar mimimum

I was digging around on the net today looking for simple deigns for Topband,  160M gear.  I found this article saying that it was best for solar minimum:  “The 160-Meter Band: An Enigma Shrouded in Mystery” which first published in CQ magazine in 1998. Here is some of what it says:

“Topband is one of the last frontiers for radio propagation enthusiasts.”

“The correlation between sunspot numbers and signal strength is only about 5% as strong as the correlation on higher frequencies.

”There are several important components that can improve your chances of successfully working DX on Topband. […] The trick here is to wait for sustained intervals of quiet conditions over the high latitude regions.”

It used to be the band for local rag chewing and I get the feeling it is either classed as just that or seen as the preserve of DX chasers with huge antennas farms. It can be both, but we can all have fun on Topband over the coming years without the constant depression of low or non-existent sunspots. I have a 38m long inverted L and had reasonable results on 160M a few years back so please do not dismiss the band without giving it a try.

It also appeals to me because it was my first intro to amateur radio. I used to look out of my bedroom window across the road to an aerial pole in the back garden of the next street. It belonged to G3LIO, Jim Gibbs. He was the first licensed amateur that I knew, and he and his father were very generous in helping me to start short wave listening back in the mid-1960s.

I have a few projects to complete to get back on the air but over the coming months I will make some Topband gear and give it a try. It will be low(ish) power AM to begin with. I also like the idea of working /P with long wire antennas supported by tall trees. It is time to modify the catapult launcher!