Re: Topband: Short Receive Antennas

["Floyd Sense" <fsense@copper.net>]

I've used an MFJ-1026 (think this is the 1025 with a built-in whip) to null 
broadband noise coming from my TV.  I found it worked very well for that 
purpose, but had much less success when trying to null or peak signals on 
160 using two external antennas.  The reason: too difficult to adjust the 
gain and phasing controls on other than constant-carrier signals.  Probably 
not impossible to do, just more trouble than I needed.  The manual warns 
against using the RF sensing to do the T/R switching and urges you to use 
the PTT line to switch the unit.

73, K8AC

----- Original Message ----- 
From: "Jerry Keller" <k3bz@arrl.net>
To: "Donald Chester" <k4kyv@hotmail.com>; <Topband@contesting.com>
Sent: Monday, December 13, 2004 8:41 PM
Subject: Re: Topband: Short Receive Antennas


> Talking about "noise cancelling", what about the MFJ-1025 which claims to 
> provide a "60 db null to wipe out noise and QRM" using a separate external 
> receive antenna (maybe a beverage or a small loop??). It even has an "RF 
> sense T/R switch" that "automatically bypasses the receiver when 
> transmitting".
> Has anyone tried one of these things? Does it work at all?
>
> 73, Jerry K3BZ
>
> ----- Original Message ----- 
> From: "Donald Chester" <k4kyv@hotmail.com>
> To: <Topband@contesting.com>
> Sent: Sunday, December 12, 2004 2:49 PM
> Subject: Re: Topband: Short Receive Antennas
>
>
> > > You might want to look at an article in QST by K6STI, who
> > > experimented/made a "noise-cancelling" antenna. It was
> > > a wire antenna, 25 or more feet on a side, with open wire feed
> > > lines from two opposing corners that went to a center pole and
> > > box with a matching xfmr, etc.  One of the feed lines was twisted 180 deg
> > > to cancel local noise signals.  QST article was Sep 1995, page 33.
> > > and pages following....might be worth a look.
> >
> > I built one of those a few years ago, and still have it.  While it 
> > occasionally provides better reception than my other antennas, most of 
> > the time its performance is disappointing.  I pretty much consider mine 
> > wasted effort.
> >
> >
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