Sunday, 20 March 2016

CTARC Report Back on Work Party - 20 Mar '16

Yesterday, Saturday 19 March 2016, starting at around 10h00, the CTARC ran a long overdue antenna work party at the clubhouse. Our rotatable HF beam antenna had been giving intermittent and high SWR readings for several months now.

Some ten radio hams pitched up to assist. Danny / ZS1BL managed the activities. Fred / ZS1FZ was there with his trusty MFJ antenna analyser and his insights contributed greatly to our eventual isolation of the antenna's faults to where they were found and fixed. Richard / ZS1RIC (so central to the design and manufacture of the tower's hardware) was there too. Jean / ZS1JPB and his brother were both particularly helpful throughout. Grateful thanks to Tony / ZS1TK, for providing cool drinks and snacks for the work party. And to all the other stalwarts, both new and existing, who pitched up to assist and without who's help we would not have been able even to lower or raise the mast in the first place!

Also present was a roving photojournalist from a commercial magazine who was there to take photos and ask us questions about our club and the hobby in general. We look forward to seeing his published article when it appears.

We began by slowly lowering the rotatable mast with its winch and resting the beam end of the mast on a ladder. As the antenna was winched slowly down, roped-in teams on either side of the lowering mast, guided by Rob / ZS1SA, held the mast true to it's required plane of movement until it was resting safely on a ladder with the back of the beam reflector just above ground level.

Fred then did some tests on the feed line coax cables. A physical inspection revealed one cable (to the upper beam) had deteriorated sufficiently to require complete replacement. The coax braid to one element of the dipole had snapped, probably due to buffeting by the wind. The lower beam and it's cable were still in good physical and RF (i.e. SWR) condition.

So a new cable (with a new "ugly balun" at the top end) was cut to length and prepared  for the upper beam. While it was being mounted on the pole, further tests were done on the feed-in patch box on the wall of the clubhouse. Further problems were discovered there in the form of corrosion of the connector sockets there.

Eventually the outside cables were fixed to a supportive stainless steel cable which in turn was fastened to the mast. Because the entire mast rotates at the base of the tower, the cables can be fixed to the mast without fear of preventing one complete 360 degree circle. Then the mast was winched up again. Danny / ZS1BL and Nick / ZS1ZD will have awoken this morning with protesting muscles they never new existed in their right arms!

All of the above sounds relatively simple, but it was robust physical work at times and managed to consume the morning and afternoon for most of us. We packed up at around 5 p.m. However, the benefits of being there were many and are discussed further on.

The job isn't entirely complete yet. We will need to fine-tune at least one of the beams, better secure the feedline cables running from tower to clubhouse and complete work on the incoming patch box. But the main problems have been identified and repaired and the end goal is in sight.

Some thoughts on the philosophy of a work party [here]

Above: "Hmmm. Now how shall we take it down...?"

Above: Very slowly the tower is lowered on its hinge. Rob / ZS1SA ensures that
the left- and right-hand guy ropes keep the tower in the middle as it lowers.

Above: Richard / ZS1RIC and Hylton / ZR1HPC (in front) were the
support stays on the RHS as the antenna was lowered.

Above: Almost down... The tower is winched down very slowly to avoid instabilities.

Above: And down! Danny / ZS1BL adds the finishing adjustments to the wooden support
ladder, which assumed the proportions of a trapeziod but nevertheless held fast.

Above: Close up view of the "Ugly" balun. We decided to replace it with new coax.

Above: Jean works on opening up and cleaning connectors in the feedline

Fred / ZS1FZ checks SWR readings (and checks again) on the
MFJ antenna analyser

Above: The patch-box leading into the shack was, we discovered, the source of a
lot of the problems. Bad corrosion has taken place here.

Above: Richard / ZS1RIC

Above: Meet "Rolene". She's quite an impressive lady.
The CTARC has acquired her on temporary loan from CCC Sports & Rec Dept
to assist with the extraction of overdue Club subscriptions...