Sunday 29 March 2015

CTARC Report on March Meeting - 29 Mar '15

On Saturday 28 March, the Cape Town Amateur Radio Centre held it's monthly members' meeting at the CTARC clubhouse in Rondebosch.

Our chairman, Rob / ZS1SA started off by welcoming us all, and announced some administrative notices and decisions made at the Committee Meeting held on the previous Monday. Then he introduced us to OM Colin / ZS1RS, who was there to give us a talk and demonstration on Fox-Hunting.

Colin has had extensive experience in this particular aspect of our hobby. Locating radio transmitters by way of direction-finding techniques, using directional antennas to locate the source, has many practical applications in addition to the sport aspect. For example, a burglar alarm company in Gauteng enlisted the radio hams to succesfully locate an alarm transmitter that had gone off-frequency. And, of course, the location of illegal transmitters that cause interference on amateur radio frequencies is required from time to time.

One message Colin gave us is "Learn to trust your equipment". By this he meant, once you have tested your DF antenna and are familiar with its quirks, it usually gives consistent readings. He showed us some relatively simple equipment anyone can build to use effectively in DF hunts. The sky is the limit, though, in terms of complexity and cost for those who really get involved in depth.

Simple techniques were shown, such as using your body as a shield (and therefore a direction indicator), and using a cardboard cylinder wrapped in tinfoil to "hide" the receiver in to attenuate the signal appropriately.

The aspect of Attenuation was also discussed. The important thing here is that, at the appropriate level, the directionality of a signal can be clearly indicated: Too high a signal level and the antenna shows no directionality. Too low a signal and the squelch doesn't break open. At just the right level of attenuation, the direction of the transmitter is relatively apparent as the signal breaks through the squelch when the antenna is pointed in the right direction. When closing in on the "fox", attenuation becomes critical.

The sport aspect of fox-hunting is mostly carried out on the two-metre band frequencies. RF signals are sufficiently directional at this wavelength, the antennas are manageable at this size and most hams have 2m rigs. Colin showed us a variety of antennas and other equipment used to locate the direction of  transmitters.

After demonstrating these items in the clubhouse, Colin went outside to hide the "fox", and some of us went out to try and locate it. Things were made easy for the "hunters" - the transmitter was located in a relatively open area and so not difficult to find.

Truly diabolical techniques used in more competitive situations include...

Placing the "fox" next to a long fence, which becomes part of the radiating setup...
Placing vertical dipole antennas of resonant length in trees to mis-direct the hunters...
Operating the "fox" via your vehicle's own antenna, in a car park full of other vehicle antennae...
Moving the location of the fox (though this is considered to be unsporting)..
A variety of disguises (limited only by the imagination) for the fox and its operator!

This was a particularly interesting club meeting, and we hope to hold a proper fox hunt event soon. Thanks to Colin for stimulating all of our interest!

Rob / ZS1SA opens the meeting

Colin / ZS1RS shows an easily-built 2m DF dipole and attenuator

The Active Attenuator (the silver box) is an RF diode mixer

Colin shows us a home-brew planar loop antenna with signal strength meter

The simplest attenuator (and highly effective) ! A cardboard tube with tinfoil tape.
The handie slides into the centre of the tube to attenuate the signal

Colin demonstrates using the body as a directional RF shield

A simple switched attenuator box that goes between antenna and rig

A more complex doppler DF indicator, used in mobile DF hunts

The back of the DF planar-loop antenna, with signal-strength meter.

A home-brew doppler-shift DF antenna. A change in audio pitch indicates direction

The members go outside to try to locate the fox

Rob / ZS1SA finds that a signal null indicates direction more accurately than a peak

Judicious use of the attenuator is critical as one gets closer to the fox

Two young guys showed great interest! The fox antenna is poking up just to the left of the kid sitting on the concrete

This commercial "fox" is a milliWatt CW transmitter. Its frequency and CW message can be programmed by computer

Further discussions inside. Colin regaled us all with some amazing fox-hunting stories!

Monday 23 March 2015

CTARC Forthcoming Meeting - 28 Mar '15

The Cape Town Amateur Radio Centre will hold it's regular members' meeting (in addition to the Ham Fleamarket on 7 March) on the usual fourth Saturday of the month, which in March will be Saturday 28 March 2015, at 14h00.

The guest speaker will be OM Colin, ZS1RS, who will give us a very interesting talk and demonstration on the topic of Fox Hunting and Direction Finding.

As part of the event a fox will be hidden nearby the club house and members who bring their 2 metre hand-helds will be instructed on how to locate the fox. No special antennas or other equipment will be required for this exercise.

We look forward to seeing you there. This sounds like it will be a fun club event !

Sunday 22 March 2015

CTARC New Members - 22 Mar '15

The Cape Town Amateur Radio Centre welcomes the following new members to our club:

ZS1AX / Ettienne Vosloo has just sent in his membership application and proof of payment to join the club.

ZS1AG / Alex Bauer, and his good lady, Natalia Bauer. They currently live in Austria but will be moving to South Africa at the end of April.

We heartily welcome all these new members and trust their membership of our club will be a long and happy one!

Saturday 21 March 2015

CTARC Committee Meeting - 23 Mar '15

Committee members of the Cape Town Amateur Radio Centre are reminded that there will be a committee meeting at the clubhouse on Monday 23 March 2015 at 19h00.

Do please make every effort to attend.

Monday 9 March 2015

CTARC Nigel / G3TXF visits CTARC - 7 Mar '15

Here are some photos of Nigel / G3TXF, who accompanied Paul / ZS1S on his recent DX-Pedition to Tristan da Cunha. As those who will have worked him will testify. Nigel is a highly accomplished CW operator!

Sunday 8 March 2015

CTARC Flea Market Photos - Batch 3 of 7 Mar '15

Report on Fleamarket * Batch 1 * Batch 2 * Batch 3

Matt / ZS1MTF, Andre / ZS1AN, Ettienne / ZS1AX and ZS1ROM approach the food stall

Dave / ZS1DFR and Hugo / ZS1HSF

The magnificent catering ladies, deserving of great acknowledgement for their kind contribution!

Sometime during the afternoon, Patrick / ZS1PDY grew an extra arm!

Left to Right: Hugo / ZS1HSF, Barry / ZS1FJ, Mike / ZS1TAF and Frank / ZS1CM

John / ZS1AGH and Matt / ZS1MJJ

Left: A home-brew oscilloscope and (right) a PSU, were among the items for sale

Paul / ZS1PXK

Dave / ZS1DFR and Danny / ZS1BL

Geoff / ZR1GFT, Pierre / ZU1DX and Eldred / ZS1DJ

Yet again, Geoff / ZR1GFT was spotted with the most original hat of all who attended the flea market!
We really ought to have a trophy for this!

CTARC Flea Market Photos - Batch 2 of 7 Mar '15

Report on Fleamarket * Batch 1 * Batch 2 * Batch 3

Tony / ZS1TK casts a proprietorial eye over his items for sale. Rassie / ZS1YT looks on.
Dirk / ZS1VDP and Pierre / ZU1DX

Adri, Rassie / ZS1YT, Dirk / ZS1X, Andre / ZS1AN, Paul / ZS1PXK and Mike / ZS1MDJ

Fred /  ZS1FK and Alfie / ZS1HX

Our chairman, Rob / ZS1SA and Hylton / ZR1HPC

This is the essence of the Ham Flea Market - The serendipitous discovery of Good Stuff!

Louis / ZS1LVH

As always, the annual CTARC flea market is well attended
Mike / ZS1FP kindly brought along and set up his PA system
to assist with announcements

Amidst the extraneous noise and discussion,
perfection is discovered, hiding in a box
Dave / ZS1DFR and Tony / ZS1APB. Both are
founder members of the Eccentric Hat Club

Pierre / ZU1DX, mobile again and looking good

The Secret Weapon to accumulation of Club Funds...
The ubiquitous Boerewors Roll

Patrick / ZS1PDY and Paul / ZS1S both fall victim to the Lure of the Boerie Roll!

Bob Commerford-Smith decides that perhaps hamburgers will hit the spot.
Glynnis in attendance on RHS

May the Wors be with you! Tony / ZS1TM lifts the lid on food operations