Topband: Isolated F81 F Barrel Connector

[lee at k7tjr.com]

   Hello Paul and others. You are quite correct as there is common mode
protection on all of those Hi-Z 8 circle antenna input lines. One problem
with 8 element arrays is that there is a significant problem of common mode
due for one thing the long length of the element connecting cables.
Personally I would not recommend using an isolated barrel connector to a
metal panel as you suggest. I think the capacitance to ground and to the
other elements as a result might decrease the common mode rejection. I think
it would be better if you could make a small panel for all 8 connectors of
single sided circuit board to fit into your aluminum plate. Then remove any
copper around the use of more common type barrel connectors for a through
connection. 
 The fewer connections inline will be better so I don't recommend using
different series adapters. Not only is the extremely low signal levels on
these lines but there is also 13.8 VDC at 40 ma. The fewer connections the
better to limit any possible micro arcing on these low signal lines.
   P.S. Do not use cheap Chinese barrel connectors or you WILL have a
problem with connection. Experience speaking.

Lee   K7TJR
Hi-Z Antennas

-----Original Message-----
From: Topband <topband-bounces at contesting.com> On Behalf Of Paul Christensen
Sent: Sunday, October 21, 2018 12:08 PM
To: topband at contesting.com
Subject: Topband: Isolated F81 F Barrel Connector

Google isn't my friend today...

I am looking for an isolated "F" barrel connector, commonly known as the
F81.  I am designing an aluminum interface plate for use with a Hi-Z
8-circle receive array.  The panel will contain multiple F81 barrel
connectors that attach to the side of a large PVC tool box with gasket
weather seal.  An isolated F81 is probably a very odd item since it's a
connector that's not normally used for baseband signal distribution like
video and data.

Each of the RG-6 lines run into a Hi-Z switched phasing box where each line
is connected to a toroid transformer.  As such, measuring resistance from
the ground of one antenna port to another shows about 30 ohms resistance,
necessitating isolation at my connection plate.  The Hi-Z phasing box is
made of PVC material and each antenna input is isolated by virtue of the
plastic box.  

In the alternative, I could use isolated BNC or TNC connectors with F
between-series adapters.   Insulating each F81 with its own insolation strip
is definitely not an option in this application.  The last option is to run
all lines directly into the large box and make a direct connection to the
Hi-Z phasing unit.  However, I would really like the option to disconnect on
the *outside* of the box so that it can be quickly wheeled in for
maintenance.  

Thoughts?

Paul, W9AC

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