Topband: Antenna analysers in close proximity to BC station.

[Shoppa, Tim]

At my QTH, many of the local (just a few miles away) AM BC stations cut back power a lot at sunset.

The cleanup is remarkable on my transmit Marconi. Before sunset and without any reject filters, I literally have 50V RMS between antenna and ground. It can light up a neon light on modulation peaks of the nearest stations (OK I cheated and built a tuned circuit for 630 WMAL to make that happen! But it does happen.) At night it clears up dramatically and is closer to 10V RMS.

It may be as easy as waiting for sunset to do the antenna analyzer thing. (Not sure if this helps the original poster in the UK... don't know if UK/Euro stations have the same day/night switcheroo that NA stations coordinate. And I think clear channel stations do not cut back power at night... do clear channel stations actually still exist?).

Tim N3QE
________________________________________
From: Topband [topband-bounces at contesting.com] on behalf of ZR [zr at jeremy.mv.com]
Sent: Friday, November 02, 2012 8:11 PM
To: Tom Boucher; 160 reflector; Chris G3SVL
Subject: Re: Topband: Antenna analysers in close proximity to BC  station.

MFJ sells a filter for that but I dont know how well it works around serious
BCB RF; 10KW at the high end of the band in 2 directions in about 7-8 miles
doesnt bother my unfiltered 259B nor do the FM and UHF TV sites about 2
miles away.

Carl
KM1H




----- Original Message -----
From: "Chris G3SVL" <Chris at G3SVL.com>
To: "Tom Boucher" <tom at telemetry.demon.co.uk>; "160 reflector"
<topband at contesting.com>
Sent: Friday, November 02, 2012 6:42 PM
Subject: Re: Topband: Antenna analysers in close proximity to BC station.


> At 21:21 02/11/2012, Tom Boucher wrote:
>>...... but how to use the antenna analyser in the presence of a high BC
>>station field. Anyone any ideas?
>
> Hi Tom,
>
> I have 2.4KW of MW BC transmitter 300m from the base of my 160m antenna,
> so I know the problem.  I've found an ICE BC filter to be pretty good -
> but I've only ever used it to tweak a matching system, not to take
> absolute readings.
>
> I've used a loaned N8LP LP100A and that worked fine - but of course that's
> an entirely different measurement system.
>
> 73 Chris, G3SVL
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