On Wed,12/7/2016 8:47 AM, Rudy Bakalov via TowerTalk wrote:
I am thinking of replacing my existing switches with Ranko's Genius product
line.
More than a year ago, I replaced an Array Solutions 6x2 Six Pak with the
older 4O3A unit with the goal of improving isolation between antennas in
my station. I measured the isolation of both units on the bench when I
made the change. The isolation of the original 4O3A 6X2 was 20 dB better
than the Six Pak. When the newer 8x2 was announced, I arranged with the
CO distributor to upgrade to the 8x2, and again measured both. The 8x2
measured 25-30 dB better than the 4O3A 6x2, in the range of 98-105 dB,
depending which pair of antennas were switched. So the total improvement
from the Six Pak was about 50 dB!
I do all isolation measurementswith unused outputs open-circuited,
measuring from one radio port to the other, which I believe best
simulates real world conditions. My test instrument is the
DS8SAQ-designed VNWA 3e that is sold by SDR Kits in the UK.
Quality of both 4O3A units is excellent, and the control circuitry works
as described. I'm not doing anything fancy for switching -- the unit is
simply driven by the line for line band decoder outputs of my two
5B4AGN-designed TXBPF bandpass filter sets.
Don't expect to see that much isolation from one antenna to the other.
In addition to the coupling between antennas, problems with coax and
connectors can degrade it. After making the first change of switches, I
bought a box of Amphenol 83-1SP connectors and a spool of Buryflex and
replaced every piece of coax in my shack. That improved isolation by at
least 10 dB.
73, Jim K9YC
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