Topband: antenna analyzers

[Wes Stewart]

I can vouch for the AA-55 Zoom, although it is not without flaws. I live 5.9 
miles from a 50KW BC station on 1550 kHz.  On my 160-meter inverted-L they are 
70 dB over S9 on a calibrated K3, that's 70 dB above -73 dBm or -3dBm. As long 
as I don't sweep through that frequency, the analyzer is unfazed.  As an aside, 
I have yet to find a low cost SDR that will stand up to this.  I had to return a 
RSP2 Pro that even with BC band filtering folded up like a cheap suitcase.

My N2PK VNA works fine as does the DG8SAQ VNWA.  I just last night finished 
building a DG5MK designed FA-VA5, which I suspect will do okay.  It will run 
using the VNWA software too.  Good thing, since so far, the standalone interface 
is wanting, but that could be my failing.  (It's really tough to run an 
instrument this powerful with just three push buttons)

Note that all of these are vector analyzers.

Wes  N7WS

On 10/12/2018 12:20 PM, Richard (Rick) Karlquist wrote:
>
>
> 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
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