Low cost frequency standard

I have been looking for a low cost frequency standard for a while to replace one I once had about 10 years ago. The only way to do it then was to build a GPS locked oscillator. I chose the extreme overkill route and locked a doubtful rubidium standard to GPS. It worked for a while and then the rubidium kit stopped working.

The next solution was to lock a temperature-controlled 10Mhz crystal oscillator. It worked well enough as along as it was left on all the time. Recently I have been looking for a cheaper and less complex way of providing a 10Mhz standard signal for test equipment and radios.

Things have moved on and the GPS modules that used to be relatively cheaply available on ebay are no longer there. Ditto oven-controlled oscillators. Then I found the ideal solution on the QRP Labs web site; a “ProgRock – triple GPS-disciplined programmable crystal” which is basically a Si5351A chip programmed for a single frequency. It can be GPS locked via a 1PPs signal from a GPS receiver, the “QLG1 GPS Receiver kit.” An order was placed.

The kits arrived, and I spent a few hours yesterday building them. As usual with QRP Labs kits they all worked first time. The first check was my £17 ebay counter, a Racal-Dana 9918. It was 5.2Hz low at 10Mhz! I could try adjusting the internal 10Mhz oscillator but it might take a while to get it to read 10,000,000!

The better option is to complete the project by building a small distribution amplifier which will give 3, 10Mhz sine wave outputs from the ProgRock and use one of them as an external timebase for the counter.

The PrgRock with scope probe attached

GPS board with patch antenna.

The kits, parts for the distribution amp and a case will cost around £35 in total. That is probably about one tenth the cost of the previous project!

Is this all overkill? Well yes and no. Modern transceivers are accurate but when you build your own you never know. Also, the move to VHF, UHF and microwave for satellites means I want to be sure that the frequencies are correct. This crucial when multiplying up free running crystal oscillators as any error will also be multiplied.

The usual disclaimer, I have no connection with QRP Labs other than being a satisfied customer. This review/article was not solicited by them and they had no knowledge I was doing it.

 

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.

Slow scan TV from the ISS

At the third attempt I managed to copy an SSTV image from the ISS. It is noisy as it was orbit 1924 which showed a minimum distance of 1038km and maximum elevation of 19.15 degrees.

I used the dual band antenna I made last week with a Baofeng GT-3 and a Zoom H5 audio recorder. It all worked well enough but a bit more gain at 2m would have helped. I am thinking of making crossed yagis for both 2m and 70cms. As the wind chill was somewhere around -3C today the new antennas will be motor driven!

Contest time again

Having and SDR receiver makes it very easy to look at band activity. Today is the start of the two days of mayhem that is called the CQ WW Contest. What is interesting is the number of stations on the air when the bands are supposed to be dead!

A quick look at 20m at 1104 UTC showed wall to wall phone stations. The antenna is still a mismatched long wire so I guess I was missing the weaker signals.

There were a few stations on 17m but more on 15m. That was surprising and a quick listen found that they were all in eastern Europe and Russia. Good steady sigs with no QSB.

What interests me most is that the bands were not ‘dead’, there were people using them. There may not be the exotic DX out there but even that is still possible at times.

So, the only time we speak to each other now is to scream CQ CONTEST followed by 59 QSL. I bet that could be automated with voice talkers and some nifty software, if it has not been done already.

Update 29/10/2018 I dropped in on a mate working /P from the top of a local hill during the contest. He had modest antennas, a doublet and a 20m vertical both quite low. True he had a bit of power but barely 400W PEP. He had worked all over the world including VP8 on Sunday morning. His comments were the same as mine – who says the bands are dead! Don’t wait for a contest get on the air!

 

 

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

 

Last transmission from KPH/KPS/KSM

Just love this video on Youtube. It is the last transmission from KPH/KPS/KSM

UA1OM decoded the Morse:
CQ CQ CQ DE KPH/KFS/KSM NW PLEASE JOIN US FOR THE TRADITIONAL CLOSING MESSAGE # DEAR GODDESS THE MEMBERS OF THE MARITIME RADIO HISTORICAL SOCIETY ARE YOUR HUMBLE SERVANTS AND WE THANK YOU FOR PROTECTING US THIS PAST YEAR AS WE CONTINUED OUR STEWARDSHIP OF THE STATIONS KPH AND KSM THE MUSIC OF MORSE HAS GLADDENED THE HEARTS OF MANY AS WE HAVE CROSSED THE BARRIERS OF TIME AND SPACE WE ASK YOUR AND GUIDANCE IN OUR DECISIONS AND ACTIONS DURING THE COMING YEAR THAT WE MAY BE WORTHY OF THE EQUIPMENT AND TRADITION THAT HAS BEEN ENTRUSTED INTO OUR HUMBLE HANDS BLESS ALSO THE EARS AROUND THE WORLD THAT SHARE THE FRUITS OF OUR LABOURS Z UT 73 / 88 DA DE KPH/KFS/KSM CL AR”

Es’hail-2 satellite ground station

I am looking to put together a station for the Es’hail-2 geosynchronous satellite that is about to be launched. Amsat say:  “Qatar’s Es’hail-2 satellite will provide:  “… the first amateur radio geostationary communications that could link amateurs from Brazil to Thailand.”  It will have a narrow band linear transponder with a 2400.050 – 2400.300 MHz uplink and 10489.550 – 10489.800 MHz downlink plus a wideband digital transponder which I will not be using.

At the Microwave group stand at the RSGB convention last weekend I saw a domestic satellite LNB connected to an SDR RX running at 613Mhz. I have the RSP1A and want to try it with an LNB and a 100cm dish for the 10Ghz downlink. The uplink is a bit more complex and I can only think of making a 13cm transverters. There are some kits around, but they are not cheap, and I do not need the RX portion.

The ideal would be conversion of suitable commercial gear. I like to hear about any ideas, suggestions you have especially if you doing something similar. Use email ‘m5fra’ at this site address if you can help. Thanks.

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.