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Re: Survey Results - Yagi Beam Combo



Hello, 
I didn't see the first posting so I didn't have a chance to add my 2
cents. I have some additional comments and suggestions.

>hheidt@erols.com wrote:
 
> ******* Comments *******
> 
> >>>>>>>>>>>>>>>>> KLM Antennas:
> 
> --------
> The 435-18C mounting plate came with wrong holes drilled.
> After 5 years at 15 Km from beach I see corrosion on the KLM 2M-14C
> balun.

All of the circular KLMs have a mounting plate set-up that was 
engineered without taking into consideration of the weight misbalance
caused by the addition of feed line or pre-amp to the antenna.  I have
had to move or redrill the mount set-up on each of the KLMs I have
owned.

> --------
> After 5 years I am having difficulties to copy Oscar 10. But not sure
> if this is really due to antenna degradation. Terrestrial operation
> seems to be good.
> --------

The KLM 2M-22C and 2M-14C use a PC board that is exposed to the
elements.
When I installed my 2M-22C, I fitted a small plastic cover over the PC
board.  I'm sure this helped protect the relay and DC polarity input
jack from some corrosion, however, because the plastic was not UV 
protected it has since desinegrated.  I would suggest to KLM to devise
some sort of cover for the PC board.  Better yet, a box like used on the 
435-40CX.  The person that sent the above comment could be having
another
trouble I had with my 2 meter circular KLMs.  The SO-239 connector
jack is mounted in a plastic cap that fits over a piece of PVC tube. 
Inside the tube is where the two pieces of coaxal balun are soldered to 
the connector.  Considerable stress is placed on this assembly as this
is where your coaxal feed is connected to the antenna.  Mine pulled 
apart here.  One side of the ground became disconnected and SWR was
always bad when it rained.  I have since constructed a replacement 
assembly which uses a water tight metal box and now has a "N" connector.

> --------
> ...the only comment I would make to the manufacturer is that the use
> of the stainless steel 'keeper' rings is a poor choice for those of us
> who disassemble the antennas a number of times in the course of the
> antenna's life...
> --------

This is a problem, some of us like to use our KLMs at field day.  One
solution I can think of is to use small pieces of rubber hose that would
fit snuggly next to the blue plastic keepers.  This would only be good 
for a year, maybe two, because of the UV deterioration problem.  The 
up-side of the steel keepers is they are available cheap from KLM. I
just snip them off and use new.

The most important difference between the KLMs and M2 antennas is the
KLMs have switchable polarity.  I work the "FO" birds and the extra
3dB or so, gain makes a big difference at times.  If the M2 antennas
had switchable polarity, they would be the obvious superiour antenna
because of their rugged mechanical design.
 
> >>>>>>>>>>>>>>>>> M2 Antennas
 
The 2 meter mobile SQLoop and the 2 meter Egg-Beater are the only M2
antenna I have owned.  I can attest they are very well built and have
worked fine.
 
> >>>>>>>>>>>>>>>>> Other Antennas:

I built the 435 MHz crossed yagi featured in the July 1991 AMSAT 
Journal.  This was a great antenna.  Entire parts list; 10 foot
piece of 3/4 inch copper plumbing pipe, brass welding rods, an
"N" connector and 22 inches of UT-141. Only draw back is non-switchable
polarity.  Worked great, and with this "bullet-proof" design it looked
as good as new after two years of service.

73 from n8ocx@amsat.org
Brook Smith


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