[ICOM] Location of low pass filter

[John G.]

I am currently using a Drake Low Pass filter that covers both HF and 6m. 
Still get some RFI on a couple of VCRs in the house when on HF.  Might just 
be overloading the VCR that cant be helped much.  Did wind the incoming coax 
to the VCR around a torrid the other day.  WIll see how that helps.

I figured that a low pass filter couldn't hurt. Was looking at the Bencher 
YA-1 since it gets excellent reviews-people saying how it completely knocked 
out RFI and such.  Figured it would be good insurance just in case. Hate the 
idea of causing TVI or RFI to neighbors.

I am using an Icom 706 original which has only 1 SO239 for HF/.6m. That is 
ok right now, as I have the HF antenna (homebrew doublet similar to G5RV) 
and the 6m yagi (3 element MFJ) both going to the MFJ 949D tuner, then the 
coax going from the tuner to the Drake filter, then to the rig.  The Bencher 
low pass filter is HF only, so couldn't have the 6m yagi going thru it as 
well. That is why I was wondering if I could move it before the tuner-but 
sounds like that won't work.  Could just keep the Drake, or get the Bencher 
in line, but would have to use an antenna switch and maybe another tuner as 
well.

73 John AF5CC
----- Original Message ----- 
From: "Joe K I 5 F J" <jen1joeo at yahoo.com>
To: "ICOM Reflector" <icom at mailman.qth.net>
Sent: Wednesday, May 09, 2012 12:19 AM
Subject: Re: [ICOM] Location of low pass filter


John,
Why do you want to use a Low Pass Filter?
30 Yrs ago they were needed because the purity
of the Tx Power was not as clean as today's modern transceivers.


If you are using a "Older Rig" AKA boat anchor, then the filter might be 
helpful.
I use a old E.F. Johnson LP Filter on the output of a AL-80BQ amplifier.
The reduction of unwanted power greater than 30 MHz is probably unnecessary.

73
Joe O
NNNN




________________________________
 From: Larry Benko <xxw0qe at comcast.net>
To: ICOM Reflector <icom at mailman.qth.net>
Sent: Tuesday, May 8, 2012 5:15 PM
Subject: Re: [ICOM] Location of low pass filter

NO! The lowpass filter is designed to be at a 50 ohm impedance which is
probably not what you would see on the output side of the tuner. Also
the voltages/currents on the line on the output side of the tuner could
damage the lowpass filter.

73,
Larry, W0QE

On 5/8/2012 5:09 PM, John G. wrote:
> I am looking at doing a little upgrading in some parts of the station, and 
> have a question about using a low pass filter. THe current one I have is 
> between the rig and antenna tuner, which seems to be the common place to 
> put one. Can a low pass filter go on the other side of the tuner-between 
> the antenna tuner and the antenna, or might that mess things up since the 
> tuner might now see the low pass filter as the load?
>
> 73 John AF5CC
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Icom Users Net: Sundays, 1700Z, 14.316 MHz
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