Topband: antenna analyzers

[Richard (Rick) Karlquist]

On 10/12/2018 12:02 PM, AC0RL via Topband wrote:

> I have found that antenna analyzers can get screwed up on long antennas if
> there are nearby transmitters; AM stations or any other transmitter that can
> swamp out the input to the analyzer. I live 1/4 mile from a 1kw am station
> and I cannot use any brand of analyzer on the HF bands. I must use a SWR
> bridge and a transmitter.
> 
> Jerry Kahn
> AC0RL

Don't lose hope!

I live 6 miles from a 50 kW BCB station.  Most analyzers are useless.
Then I bought the Rig Expert AA-55 zoom.  All I can say is:  it works
flawlessly at this QTH on a 90 foot top loaded vertical.  Also, the
AA-55 can be protected with a BCB reject filter, which can then be
calibrated out.  If you play that card, I'm sure you will be OK even
at your high QRM QTH.

You can also use an N8LP digital wattmeter which reads out impedance,
not just SWR.  Larry tells me that you have to locate the device's
coupler at the antenna (not in the shack) and the cables between
the coupler and main box cannot exceed 20 feet.  With those caveats,
this is a bulletproof way to make R + jX measurements.

A poor man's retro solution is to build a noise bridge for 160 meters.
AFAIK, no commercially made bridge works on topband.  You can take
a published design for the higher bands and just extrapolate it to
160, by replacing the variable capacitor with a triple 365 pF broadcast
receiver unit.  You might have to increase the amount of ferrite
in the bridge transformer.

Rick N6RK