Category Archives: Satellite

ARISS SSTV award

Got my ARISS SSTV award today from a download last weekend. I used the homebrew antenna, a Baofeng and a portable recorder to record the audio which was uploaded to MMSSTV. It was a low pass of the ISS, never more than 19 degrees above the horizon and around a minimum of 1200km. I reckon I picked up the sig when they were over the mid-Atlantic and lost it when they were over Chad. So, I am pleased to get the award considering the basic equipment used. Now on to bigger things, a tracking rotator and 2M plus 70cms crossed yagis for circular polarisation. All homebrew.

 

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.

 

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!

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.

A lost age – marine HF radio

My first job was as an apprentice at a Post Office HF radio station, Bearley near Stratford-upon-Avon. It was part of the HF point-to-point system that provided worldwide telecommunications. It was state of the art in 1967 and scrapped in 1980.

The station had 50 of the first professional, transistorised communications receivers,  Plessey PVR800s. The early versions had some germanium transistors which proved to be unreliable. They were replaced by the ultra modern silicon types!

They were used for telephony, 4 voice channels on double side band reduced carrier. The audio was inverted so that short wave listeners could not eaves drop.

There were also 50 Marconi HR11, valve telegraphy receivers. Each had the capability running 48 telex services on one radio channel using time division multiplex.

As services were transferred to satellites the station took over the maintenance of UK coast stations used for marine communications. They also suffered the same fate. Eventually all HF communications was taken over by satellites and the point-to-point and coast station were closed down. This Post Office film from 1979 shows something of what HF coastal communications in the “good old days”.

It was then end of an era and still saddens me to think that all the old skills have been lost, particularly commercial Morse.

If you want to read more about the HF point-to-point HF radio network, then see this book by Paul Hawkins who worked at the Dorchester TX station. (click the image >)

Remember, radio amateurs still use Morse!

Also see the Radio Officers Association

Tracking electrical storms

When a thunder storm is forecast I always disconnect and earth the antenna. Yesterday the UK Met Office  issued storm warnings for central and southern UK. A good way of tracking storms is to use an EU weather radar that gives a real time 3 hour forecast. You can pin your location making it easy to see if you are in the path of approaching weather. The storms missed this QTH, the northern edge being about 80 miles south of here.

The site is also a useful resource for predicting short term weather for portable operation. Like any weather forecasting it is not infallible!

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