Broadcast - 31 March 2024
Last technical night saw an excellent variation and improvement on a particular type of portable antenna mast. Colin VK7ZCF brought in his newest creation to awe the members present. Allegedly it was still in the prototype stage, but it was quite obvious a lot of time and constructional care had already gone into it.
Every item with the exception of the rotator came from Colin’s junk box or the “Recycal” shop, see that’s why we keep the stuff, just in case one day we need it.
The unit is basically three sections that can be assembled or disassembled at will or as transport and storage space dictates. It is made up of a hinged base unit, a four section telescopic aluminium pole and the antenna mounting section with rotator.
The hinged base is made of two different steel box section profiles and fits comfortably into a standard 50mm “Hayman Reece” towing hitch and is secured with the normal locking pin. The other end of the inserted base incorporates a hinged mast socket that allows the mast to be tilted over onto the ground for antenna fitting or adjustment. The mast clamping, tilt lock, flanges and nuts are all steel and Tig welded to a high standard that I reckon even Ross VK7ALH would be impressed with. Final adjustments and clamping is accomplished with stainless steel threaded hex bolts.
The actual mast is a four section telescopic aluminium pole extending to 5 metres. It must have been the find of the decade at the local “Recycal” agent. For a ridiculously low price of $10….. you know, the price you can’t pass up for what it is, especially if is a nice and sturdy commercial 5 metre telescopic pole!
The telescopic sections are locked together with metal press in buttons that pop into a hole when each section is fully extended. None of those plastic “twist to tighten” ring versions that eventually seem to lose their enthusiasm for holding anything vertical. The sections start off about 63mm and step down to about 30mm at the top.
The antenna section clamps onto the top of the pole and consists of two aluminium tubes. One slides easily within the other and rotates freely.
Now for the only purchased “new” part of the build, a relatively small cylindrical 12 Volt motor and gearbox from e-bay. This is mounted within the larger diameter of the two tubes.
Colin had lathed up an aluminium coupling adaptor that sits between and attaches to the gearbox output shaft and the final vertical used for antenna mounting. At a full 12 Volts DC the final mast section rotates about one revolutions in thirty seconds. Even though it was a relatively small motor and gearbox it certainly produced a very usable torque.
The next part of the project is a Pulse Width Controller to vary the rotation speed and a three position switch for clockwise, stop and anti-clockwise rotation.
With the exception of the motor and gearbox purchase everything else was salvaged, re purposed or came from the junk box. It certainly created a lot of interest and discussion for the night.
If you were wondering….. yes Colin can still fully open his rear hatch with the mast in use, so this was either good engineering or good luck, hihi.
As always, pictures will soon be available on the NTARC Web site under “Blogs” for this broadcast.
UPCOMING EVENTS
TestNet and TechNet session - Every Wednesday, TestNet/CW course on 3.580MHz from 7pm till 7.30pm…. and a TechNet on 3.567MHz from 7.30pm till about 8.30pm. Your host for the evening will be Nic VK7WW.
Coffee Morning - held every Friday in the NTARC Club rooms. Time is from 10am to noon and we look forward to seeing you all there. So why not pop in and join us for a cuppa, there is endless tea and coffee along with biscuits available for a donation.
Club Room - gathering to watch the REAST presentation on “Universal Time”. Wednesday the 3rd of April, doors will be open by 7:00 pm.
Finally - A reminder to all members that if you have any items of news you would like added to our weekly roundup, no matter how trivial, then please email them to the Secretary at the following address news@ntarc.net all items to be received no later than 5pm on the Friday prior to the Broadcast.
That’s all folks,
73, Stefan VK7ZSB, Secretary NTARC Inc.
