Category Archives: HF

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 6.25W 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!

Can we talk?

After 6 years away from the radio what is different? Everything and nothing. Still the same camaraderie and immense kindness in the hobby. That has not changed. The difference is there seems to be a growing reluctance to actually talk to each other on the air.

What has become apparent is the reliance of the internet. I saw a message on the net recently from a VHF op who said he had spent a long time calling CQ with no response. The reply was that he needed a ‘spot’ on the ON4KST site and then people would know he was there. I assume from that nobody turns on the radio and tunes around anymore.

Then there is ‘the HF bands are dead’ mantra usually followed by it’s not worth turning on the radio as there is nothing much on the DX cluster. Again, it looks as if ops are sitting in front of their computers waiting for to see something happen instead of using their radios.

And the automated digital QSOs, jt8? And digital propagation checking where you don’t even need to contact another human being to know how far you signal has travelled.

Is that what it is all about now? Only operate when there is DX around? Never call CQ because nobody is listening?  But what gets me most is never ‘talk’ (voice or CW) to another human being? Have radio amateurs lost the ability/desire to speak to each other?

Don’t get me wrong, I am all for using the latest technology and moving with the times but if we insist on removing the human element or reducing it to the shortest possible exchange for the points or to bag another country then we lose the very basis of the hobby. There must still be a place to rag chew on 160m or 80m or 2m, I want to talk to another human being and not a computer.

Using SMD – part 1

Why do I like using SMD? Let me explain, I began making radios using valves, it was all there was at the time. When I started work in the industry the first training courses were on valves and how they worked. Then the transistor came, then integrated circuits followed by surface mount devices, SMD. I guess I have followed the technology.

It is easy to be overwhelmed by progress and stick with what you know but there are many advantages to using SMD:

  • individual components, resistors and capacitors, are very cheap
  • many older devices are no longer available as wire ended e.g. the SA612
  • PCBs are smaller due to high packing density
  • high frequency boards are easier and cheaper
SI5351 board

An SMD VFO module

Above is an SI5351 board (ready made apart from soldering the SMA connectors) it is just 30mm wide and can used with an Arduino to make VFO with 3 programmable sine wave outputs. Current cost is less than £5 on ebay plus the Arduino.

You might need some new tools like a magnifier, fine tipped soldering iron and good quality tweezers. There are more including heated tweezers and a hot air gun for component removal but they can wait for a while.

So, my advice is do not be put off and have a go. Find a simple kit to practice with and then progress to more complex circuits. It helps if you know something about how SMD components are sized. Srat with the larger sizes and work down.

1206 and 0805 are popular SMD sizes

This is another good one to print out.

Over the coming month I will add to this series of posts and share some of the projects I am working on which include: a remote tuner, vector network analyser (VNA), wide range VFO/signal generator, a switched attenuator.

The antenna

The antenna is back up after 6 years! Nothing fancy just an inverted L at about 11m (~35ft) and around 38M (125ft) long. Still need to put in a counterpoise in the lawn but the ground is rock hard after weeks of drought, so it will have to wait.

Also need a remote tuner and plan on making one based on an Arduino.
https://hamprojects.wordpress.com/2016/12/31/hf-automatic-tuner/

I have a nice waterproof box that housed a commercial tuner to house it and will probably make it solar powered to avoid have to DC up the coax. Hope to get the coax in this week, it is something like a 40M run of RG-213. So, work to do before winter!

A scratch build Wilderness radio SW-20

This is an amazing build of a favourite of mine, the Wilderness radio SW-20. It shows just how neat and effective ‘ugly’ construction can be. In my opinion it is far from ugly!

I would love another but they are no longer available. Maybe this is what I should do over the winter – build one!

It is interesting that he started with the case and cut the copper clad board to size. It seems like a very ordered way of working.

A Scratch-Build of N6KR and Wilderness Radio’s SST for 20M

I had one of these radios a few years back and made many contacts on it. I did some mods but cannot remember what the function of the extra knob on the left side.

Amateur Radio Transponders on Planned Chinese Satellites to Include HF

From: The ARRL Letter” 24 May 2018

China’s Amateur Radio Satellite organization, CAMSAT, has released some details of three new Amateur Radio satellites that could be launched as early as September. Two of the satellites, CAS-5A and CAS-6, will carry transponders; one will have HF capability.

CAS-5A, a 6U CubeSat, will have an HF/HF (21/29 MHz) mode linear transponder; an HF/UHF (21/435 MHz) mode linear transponder; an HF CW telemetry beacon; VHF/UHF mode linear transponder; a VHF/UHF mode FM transponder; a UHF CW telemetry beacon, and UHF AX.25 4,800/9,600-baud GMSK Telemetry. Transponders will have 30 kHz passbands, except for the H/U unit, which will be 15 kHz.

The tiny CAS-5B, weighing 1/2 kilogram, will be deployed from CAS-5A in orbit. It will carry a UHF CW beacon on an Amateur Radio frequency. It will be placed into a 539 × 533 kilometer, 97.5° orbit.

CAS-6, a 50-kilogram microsat, will include a VHF CW telemetry beacon; a U/V mode 20 kHz linear transponder, and AX.25 4,800-baud GMSK telemetry downlink. It will also carry an atmospheric wind detector and other systems that will operate on non-amateur frequencies.

A launch at sea is planned for CAS-6, which will be placed into a 579 × 579 kilometer, 45° orbit.

CAMSAT has applied to the IARU to coordinate frequencies for all three spacecraft. — Thanks to AMSAT News Service via AMSAT-UK