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Chelmsford Amateur Radio Society
G0MWT, GX0MWT, GB5HF, GB5SM, GB2TAM, M2T, GB100MWT, G100RSGB & GB5RVA

CARS Meetings January - March 2016

 Award for All

15th Mar 2016

 Added March Antenna talk

January Meeting
Tuesday 5th January 2016, 7:30-10pm
Oaklands Museum, Moulsham Street		 Meteor Detection using 2m Amateur Radio
Peter Meadows M0ZBU

The January talk described how to detect meteors using a homebrew 2m antenna and a Software Defined Radio, by exploiting the GRAVES transmitter near Dijon, France. GRAVES transmits a powerful CW Radar signal on 143.050 MHz for space object/debris tracking, making it a great source for scattering from ionised meteors trails, using a simple receiving antenna and SDR.

Peter's talk included descriptions of the equipment, how it has been set up, and what software is required to record the meteor radio reflections.


The GRAVES Radar Transmitter near Dijon is on 143.05 MHz

 
Initial testing used the FUNcube-1 satellite - using a homemade 2m antenna and a SDR Dongle

 
Recent Meteor detections from Peters equipment

 
Peters heated timelapse Optical Camera - and a Meteor it caught


Peter M0ZBU being presented his CARS Mug by Chris G0IPU - with the homemade 2m Receive antenna behind

Useful Links:-

February Meeting
Tue 2-Feb-2016, 7.30-10pm
Oaklands Museum, Moulsham Street		 "Satellites"
By Steve Hedgecock M0SHQ

The February meeting featured Steve M0SHQ on 'Getting started in Amateur Radio satellites'. Steve has been a regular supporter of Skills Nights, and his talk was pitched as a beginners guide. Steve brought with him his 2m/70cm antennas that lets him work FM Satellites and APRS /SSTV from the ISS. These operate in Low Earth Orbit (LEO) so can give quite strong signals - but do pass over within minutes so software/apps that give the orbital times/positions are a key aid. This was a timely talk coinciding with Tim Peake's mission on the Space Station and over forty people and visitors attended.

 
Steve M0SHQ receiving Satellites at Shoebury - and introducing his talk with a Cubesat model

 
Explaining orbits and a home made dual band 2m/70cm antenna

 
Doppler can be an issue. SO-50 split frequencies and CTCSS tones


Steve after his interesting talk

The talk prompted plenty of questions on antennas, satellite operating, power limits particular satellites and peoples experiences of receiving Tim Peake on the ISS.

The teabreak was held downstairs in the main museum area due to a special exhibition - but David and Myra coped well and it was a good opportunity to see the exhibits. Afterwards the famous CARS raffle was ran by Chris G0IPU and Andy G7TKK, with Steve helping.

 
David/Myra with the teas - and the raffle after the break


March Meeting
Tue 1-Mar-2016, 7.30-10pm
Oaklands Museum, Moulsham Street		 "Novel Antennas"
By Andy Chapman G7TKK

The March talk featured the work carried out by Andy Chapman G7TKK since Summer 2015, on developing a selection of novel compact, portable, foldable antennas - as recently seen at some Skills Nights and other events. Three wide bands were considered - HF, VHF, and UHF. Practical, pragmatic aerials were presented by Andy, whose aim was being effective, rapidly deployable, and lightweight.


Andy G7TKK introducing his talk

HF wavelengths are often greater than the practical sizes achievable. This results in sub-optimal radiation efficiency. However, for real life applications, this limitation can be accommodated by tuning circuits and adjusting the Quality factor, Q, of the aerial. Optimisation of these parameters, along with judicious selection of aerial type, can result in a satisfactory compromise for amateur radio use.

Modeling using 4NEC2 was shown - rf engineers may recognise the Smith Chart.

 
A Tetrahedral model and a Smith Chart of antenna impedance

After the break, CARS had its famous raffle and another well known CARS antenna guru, Tony Gilbey G4YTG, joined the discussion and also showed some of his material on how the Post Office tower was built

 
Tony and David Bolwell, G3JCM seated looking at the comstruction of the Post Office Tower

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