Richard Clark wrote:

On Sun, 10 Apr 2005 18:17:42 -0500, Tom Ring
wrote:

Hi Tom,

The number of variables in the description of your (Mark's) method is
rather considerable, so I will remark by the parts you offer:


The range has a source yagi for each band, that yagi has a low power AM
modulated signal on it (as I remeber, might be wrong on this).


So far, fine.


The other end has a reference yagi off to the side from the test position.


Commendable.


A yagi with "known gain" is run against the reference yagi, and the
relative signal strength is measured.


I might slyly point out how do you know the gain? It visits the age
old logical knot offered:
In a town of clean shaven men,
there is a barber who shaves everybody who does not shave himself;
who shaves the barber?



As I state later, the absolute gain number is suspect. And I quoted
"known gain". That's a clue to it really being a variable to a certain
extent.

And, as you well know, having been in the business since day minus one,
it is possible to build standard gain antennas for UHF and microwave
that will pretty much dead on every time. They are available in many
texts you already probably own.

OK, the method is good and robust, but your sudden departure from
expected results are on the scale of 5 to 6 times the range of your
typical error.

snip

I would offer that if the elements oxidized, so did the connectors (or
connections). Simple, repeated connector matings (like swapping in
and out for the range test) were sufficient to break bad contacts and
make the difference which was attributed to scrubbing the elements.
In the normal course of my calibration of various items with
connectors, I always inspected and cleaned them first. N connectors
have erosion problems that will give rise to variations outside of
0.1dB - comes from those threads. The "standard gain" antenna should
be suffering from this erosion by now, but you don't report it.


The corrosion was on an antenna that had not been in the barn, it had
been used for 4 years in an EME array, and was fairly well corroded. We
tested it to see how it would compare to the protected identical
prototypes, and then we cleaned it for a second test run. And the
connectors are always N connectors. 'nuff said.

The standard gain antennas are also not left out in the rain, and do not
live in a city.

This raises suspicions for me - you have too much fulfillment of
expectations which is truly extraordinary. I have made thousands of
calibrations of isolators, pads, couplers, meters and so on that have
shown a gaussian distribution of results for premium equipment. Your
range experience shows very little variation - much too little when we
are talking about being within 0.1dB.


I can't address that; maybe he has been lucky, extraordinarily careful,
or there aren't enough points graphed yet.



73's
Richard Clark, KB7QHC

Thanks for getting me to call him and review how it was done. I spent
an hour and 3 quarters getting up to date. And he is about to get 500
watts at the feed point on 2304 going. That is a fairly impressive
amount of juice homebrewed on that band. Only 4 transsitors to do it.
Ain't technology wonderful? And he has a 32 foot homebrew dish.

tom
K0TAR