Topband: Antenna analysers in close proximity to BC station.

[Tree]

It is a common solution to put a 160 meter band pass filter on the SWR
meter and it will work.

I had to do this on both 160 meters and 80 meters at A73A.  The high power
AM station was miles away.

Tree N6TR

On Fri, Nov 2, 2012 at 3:22 PM, HAROLD SMITH JR <w0rihps at sbcglobal.net>wrote:

> MFJ makes a filter for their Antenna analysers. I am sure that if it does
> not
> work for you, you can get your monies back.
>
> 73......Price W0RI
>
>
>
> I have the same problem with a 50KW FM station a couple of miles away
> affecting my Palstar ZM-30.  It is useable on the rig side of an antenna
> tuning unit, but most of my antennas are self resonate therefore the FM
> broadcast RF rides right into the bridge making it mostly worthless when
> directly attached to any antenna such as a dipole, vertical, yagi, etc.
>
> Sometimes I can get a useable reading if I turn the antenna 90 to the
> broadcast tower, but that only works with the rotatable antennas.
>
> Experiments with filtering using small value caps, small pi networks, a
> series FM trap, or ferrites have been unsuccessful.  Any filter I put in
> front of the analyzer influences the reading substantially.  BTW... this
> broadcast station also comes in on my frequency counter too, with no
> antenna
> attached.
>
> Please let the group know if any of you have come up with a "transparent at
> ham frequencies" inline filter.
>
> 73
>
> Lloyd - N9LB
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com]On Behalf Of Tom
> Boucher
> Sent: Friday, November 02, 2012 4:21 PM
> To: 160 reflector
> Subject: Topband: Antenna analysers in close proximity to BC station.
>
>
>
>
> A ham friend asked me to design a matching network for his 160 metre end
> fed
> quarter wave, so I asked him to provide an impedance reading using his
> MFJ-259B. I would then use the Berkley site
> (
> http://bwrc.eecs.berkeley.edu/Research/RF/projects/60GHz/matching/ImpMatch.
> html<http://bwrc.eecs.berkeley.edu/Research/RF/projects/60GHz/matching/ImpMatch.html>) to provide the necessary values for an 'L' network, as I have done
> many times at my own station.
>
> The readings he provided were total nonsense and quite erratic, so we
> concluded his MFJ-259B was dead. He assured me that he always does a static
> discharge before connecting the MFJ.
>
> So I paid him a visit, taking along my Palstar Antenna analyser thing,
> which
> has always performed well at home, and what-do-you-know, the readings on
> that were also erratic, total nonsense and it behaved in a way I have never
> seen before.
>
> Than someone suggested the problem may be due to a 50Kw BC station on 909
> KHz, situated less than 5 miles away, causing both antenna analysers to
> misbehave.
>
>
>
> We ended up with a good old-fashioned link coupled parallel tuned circuit
> with the antenna tapped a few turns up from the ground end. This works fine
> but he is power limited due to arcing across the tuning capacitor. So we
> would ideally like to revert to the 'L' network plan, but how to use the
> antenna analyser in the presence of a high BC station field. Anyone any
> ideas?
>
>
>
> 73
>
> Tom G3OLB
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