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Re: [TowerTalk] Measuring sma relays at UHF

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Measuring sma relays at UHF
From: jimlux <jimlux@earthlink.net>
Date: Mon, 13 Aug 2018 18:11:29 -0700
List-post: <mailto:towertalk@contesting.com>
On 8/13/18 5:58 PM, Norm n3ykf wrote:
Hi all!

Playing with my toys.

Using an Anritsu S113b which does not have direct voltmeter readout.
These numbers were calculated by making a return loss measurement and
converting it to relative phase with their Line sweep tools software.

I went through this whole process (took about 5 times longer) prior to
my trip to 5J0 and realized that mistakes had been made. Took a pair
of crossed linear 10 element diddled by a Tohtsu spdt 12v instead
Worked like a charm from AOS to 5-7 degrees above the horizon so that
I could switch polarities. What a blast. Used my homebrew rotator.

https://www.youtube.com/watch?v=1sDP6lAiWGw

Please ignore my 2yo little monsters. They can and do make s9+ noise.

Trying to get the coax for a cp antenna correct this time. Waste no more coax..

I have two Transco SMA 24V relays and an SMA jumper, consisting of two
elbows and a straight piece.

First order of business was to calibrate all the test gear. Note how
long the adapters attached to the N connector were as well as noting
the length of the test cable.

Got some interesting results:

RYA NC: 232.2 degrees

RYA NO 231.8 """"""

RYB NC 231.3""""""""""

RYB NO 231.0 """"""""""


SMA jumper to connect Common->NC to NC->common 281.3 degrees.

Does this look correct? How does such a small package contain such a
lengthy RF path?


wavelength is about 70cm, so 1 cm is 360/70 about 5 degrees in free space. More like 7-8 degrees in coax.

what was the reference plane for the calibration of the analyzer? The spread among paths is <1 degree which is plausible for a small relay. I'd expect the path length to be a few cm. You might compare the measurement you get with a barrel connecting the two test cables and the relay connecting the two test cables (e.g. COM-NC).

a couple feet of coax would add about 200-250 degrees of phase.


Norm n3ykf
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