[Elecraft] Looking for a way to switch an antenna input to the KAT500
john at kk9a.com
john at kk9a.com
Mon Feb 18 09:59:55 EST 2019
W2VJN and N3RD from Top Ten Devices are great helpful guys. I have been
using their band decoders for decades and we have both operated from the
same station in St Croix. I also have a Top Ten 6 way antenna relay box
that I only use only on contest expeditions with a single radio. It is
small, light weight and easily fits in my suitcase. This is not a
heavy-duty relay, you cannot run legal limit RTTY though it. Also the
SO-239 center connectors are recessed which might cause an issue with some
crimped PL-259's. To use their relays for an SO2R station would require a
lot of relay boxes and they claim isolation >40dB. For me a single 2 x 6
box is a better choice, Array Solutions SixPak claims >55dB which Jim
confirmed.
John KK9A
Jim Brown K9YC wrote:
On 2/17/2019 6:26 PM, Randy Farmer wrote:
> I concur with the comments on the Top Ten 2-way switches. I'm using
> about 10 of them at various places in my SO2R contest station antenna
> and BPF switching networks. They work well and have good isolation. I
On the basis of my measurements with a Vector Network Analyzer, I am NOT
impressed with these switches, and consider them poorly designed. The
major design flaw is that they depend upon the chassis for signal
return, so the signal path gets increasingly badly mismatched at 15M and
above. I didn't measure crosstalk, but this design error would certainly
impact it. I reduced the mismatch by about half by adding braid from the
coax connectors to the circuit board and following (as best I could) the
signal path to provide a return. Why? Because the "ground" layer is
broken under the top layer, so it can't act as a return either!
Someone cited 50 dB as "good isolation." When I replaced my WX0B 6x2, I
measured isolation of about 55 dB. The replacement, a 4O3A 6x2, measured
75 dB worst case. And other one I'm using now, the 4O3A Antenna Genius,
measures better than 95 dB worst case.
If you look inside a well designed power amp, you'll see transmission
line running from input and output for both TX and RX path. My Ten Tec
Titans were built that way, and so is the KPA500. You'll also see
mini-coax jumpers tying sections of the K3 together.
73, Jim K9YC
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