All posts by Tom

RADARC on Discord

Hope you are all keeping safe and also well hydrated in this heat!

Some members may not know that RADARC is now running a Discord server. Discord is an internet-based chat tool that runs quietly in the background, and is great for those times between meetings that you just remember something you want to discuss, either to someone specific at the club, or as an open discussion. It’s much more lightweight and quick turnaround than email is.

It’s available for Windows, Macs, iPhones and Android phones, is free, and pretty easy to use once you’re up and running. There’s been lots of interesting chat already on lots of different topics, and you can mute what you’re not interested in. The only thing missing is you!

If you’re interested, ping someone on the committee directly for an invite, or email committee @

GB7PY Repeater Stolen

Some unfortunate news from our friends over at Cambridge Repeater Group:

[DMR Repeater] GB7PY has been stolen from Madingley, Cambridge, on 23rd December at approx 2115hrs.
Repeater info:
Motorola SLR5500 UHF:
Tanapa : PMUE4392AA
Serial: 478IRW1189
Also stolen was a Teltonika RUT950 4G router:
IMEI on the Router ends with 6502, which has been network blocked and will therefore not work on any network now.
Any information, please pass to Cambridgeshire Police quoting crime reference number 35/92597/19.

Obviously this is a significant loss for the group. Can members please be on the lookout for this equipment through the various channels, and should anything come to light please do the right thing and pass on any details as requested, however insignificant it may seem.

Portable ex-military HF at Reading Rugby Club

A few quick snaps taken of our members Michael M0MPM, Harry G3NGX and Jim G0LHZ enjoying a play with some man-portable vintage ex-military gear. With one of the radios dating back to WWII, and with the split frequency operating figured out, at least one legitimate QSO was had, with good reports both ways. With the solar cycle in full swing a new DX record was set, with a mighty 0.2km achieved across the front of the rugby club.

With thanks to our members for supplying the pictures.

Michael M0MPM/P

Harry G3NGX/P


Operating on QO-100

Heard of QO-100? Also known as Es’hail 2, the first geostationary satellite carrying amateur radio transponders launched from Kennedy Space Center at 20:46 GMT on Thursday, November 15, 2018 and is now in a geostationary orbit at 25.9° East. These are the first amateur radio transponders to be put into geostationary orbit and the satellite footprint covers an area from Brazil to Thailand. The transponders are very wideband indeed, and have been designed to be relatively straightforward to access. Being a wide linear transponder, there’s plenty of room, but also plenty of activity, and the activity is in all sorts of modes, including digital ATV, digital voice, CW and SSB. The downlink is 10GHz and the uplink is 2.4GHz. These frequencies are no coincidence…

Receiving QO-100 is a matter of connecting an inexpensive commercial LNB, like you’d find on the arm of any Sky dish, to a suitable power supply via a bias-T, to an inexpensive SDR connected to your PC, including the RTL USB dongles, or indeed to any wideband multi-mode receiver that covers 7-800MHz. An unused Sky installation could be used pretty much as-is, by simply tweaking the dish to point to a very slightly different point in the sky – 25.9°. Indeed there are reports of QO-100 being heard via Sky dishes while the dish is still aligned on the Sky constellation at 28.2°E. PLL-equipped LNBs are better, but not essential.

Once you have a receiving setup sorted, it’s time to turn your attention to the transmitting side. The uplink is in the 13cm amateur allocation, adjacent to 2.4GHz Wi-Fi. There is a lot of room for creativity here, and lots of options. OE5HSR has pulled together an excellent PDF, which is pretty much a must-read for this topic. You can find this here.

I’m sure that some of our members will be having a go at working this unique satellite, and if you’re one of them, we’d absolutely love to hear from you at one of our show-and-tell evenings, or even better a live demo!

72000km+ SSB QSOs using a couple of watts and some recycled gear? Yes please!

Credit: AMSAT-UK for orbital and footprint information

Mentoring meeting update

From member Min G0JMS:

Following the large number of helpers and stations on last Thursday’s Mentoring Meeting evening and the club net, which was very popular, we are planning to run this evening event again in a simpler format with very local stations or anybody with a mobile HF rig. Reduce the QRM by using different rooms.

It’s reported the local RD repeater was very busy with some newly licensed operators joining in.

Members at the RRFC answered many questions from new operators and the evening was a success with club members helping to put up and strip down the stations. We operated on HF and VHF.

Offers of help would they please contact Min G0JMS

Apollo Experience Report – Lunar Module Communications System

A fascinating document from the Apollo programme was recently unearthed on the NASA website by a local amateur, Jim M0YOJ. It goes into loads of detail about the development and use of RF systems on board the various vehicles involved the lunar programme. For some light bedtime reading, the full document is here. Thanks Jim (and John!) for highlighting this.

The development of the lunar module communications system is traced from ‘the initial concept to the operational system used on manned lunar missions. Included are the problems encountered during the development, the corrective actions taken, and recommendations for similar equipment in future programs. The system was designed to provide communications between the lunar module and the Manned Space Flight Network, between the lunar module and the command and service module, and between the lunar module and the extravehicular crewmen. The system provided the equipment necessary for voice, telemetry, and television communications; ranging information; and various communications links.

Exercise Blue Ham – this weekend

As happens every so often, this weekend the Royal Air Force Air Cadets will be organising and running a military style national radio exercise named ‘Exercise Blue Ham’. The Cadets invite all amateur radio operators to take part, making this the biggest radio exercise that the Cadets are involved in.

The exercise will take place on the MOD 5MHz (60 Metre) band and a significant part of the exercise will be on the section of the band that amateurs are authorised to use.

Locally, at least Woodley Air Cadets are taking part and will be active 9.30am to 2pm Sunday- I know they would appreciate good strong local signals since they live under a blanket of S9 noise.

Some important notes if you’re interested:

This exercise does not give amateur stations permission to operate outside of their normal licensing conditions.

– the allocation is not continuous- refer to for full details if necessary

– the allocation is for full licencees only

– maximum PEP 100W and 200W EIRP

– max antenna height 20m AGL

– secondary allocation, no interference to MoD stations

A summary of suggested spot frequencies in the 60m amateur allocation follows:

5278.5kHz USB

5298.5kHz USB

5301kHz USB

5304kHz USB

5317kHz AM

5320kHz USB

5335kHz USB

5354kHz USB

5363kHz USB

5379kHz USB

5395kHz USB

5398.5kHz USB

5403.5kHz USB

Note upper side band, against convention.

Selecting a USB frequency from the list above will ensure compliance and is largely compatible with allocations in other countries. Please do not transmit USB on 5330.5kHz, 5357kHz, or 5360kHz.

Various Cadet stations will be operating on each of the days, mainly from 08:00 to 20:00, but could also be outside these times, and will be on various frequencies within the band. Where possible stations will advertise which frequency they are listening on live on this website as the exercise is in progress and amateurs are welcome to check this page and call in on the advertised frequencies.

Cadet stations will call ‘Alpha Charlie’ which is the equivalent of CQ, and amateur stations are welcome to reply. Exercise Callsigns will all be in the range MRE01 up to MRE98 although other MR, MF and MA prefixed callsigns may be taking part.

The information exchange to score the contact will be

Your Callsign,

Signal Report,

Antenna Type,

Transmitter Power

Your Location. 6 Digit Maidenhead. Need not be precise.

As Cadet stations change frequency contacting them again on a different frequency will score as an additional contact, as these frequency changes they will be reported on the exercise website where possible.

The contacts will be plotted almost live on the exercise web server.

The ACO will issue certificates for amateur stations that contact 10 or more Cadet stations during the period of operation using your callsign contact details on Contact with the same station on different days count as separate contacts. Email your callsign and contact details to claim a PDF Certificate to:

The ACO looks forward to operating as many amateurs as they can during the period of the exercise and it will give their young operators an ideal opportunity to utilise their radio operating training on HF equipment to a different audience.

Once a contact is logged into the system it shows up onto a map which can be accessed at

Thank you in advance from the Cadets for taking part and giving the operators plenty of ‘Air time’ which cements their radio training that they have received.