[NLRS] VHF low pass filters?

[w0zq at aol.com]

I just checked the FCC database and I agree with Chris .... Channel 9 at 186 - 192 MHz and Channel 11 at 198 - 204 MHz are still being used here in the greater Twin Cities area.  My money is that the problem is preamp overload.   Solutions may be

1)  If the preamp can be turned off (probably not), turn it off.  If the gain can be turned down, try that.
2)  Buy a new antenna.  Switch to an non-active antenna using good coax.  No preamp.   RadioShack and Menards have "passive" TV antennas.  See what the picture looks like with this set-up.  Chances are it should be fine.  
3)  If a preamp is needed, use an external preamp and look to find a HP filter that has a cut off above 50 MHz but still passes Channel 9 (186 MHz).  As others have said, place it between the antenna and the preamp, not after the preamp.

One short story to tell.  About 12 years ago my immediate neigbor calls me with a 2m TVI complaint.  While he was on the phone I reduce my power more and more until I was down to 2 watts and still the problem existed !    Since I had not changed anything I asked him if he had made any changes to his "stuff" .... a new TV, move to a new room, etc, etc.  Turns out that he had visited Radio Shack and the sales man sold him a very nice 25 dB gain switchable preamp.  I asked him to turn the preamp off and bingo, problem fixed.  Why he installed a 25 dB gain preamp when we live in Bloomington with P5 picture quality was beyond me, but my advice to him was to return the preamp as its not needed and it only creates problems (for HIM).   PS:  We still talk and the preamp is gone.

73, Jon
W0ZQ



-----Original Message-----
From: Chris Elmquist <chrise at pobox.com>
To: Northern Lights Radio Society <nlrs at mailman.qth.net>
Sent: Wed, Jan 2, 2013 10:44 am
Subject: Re: [NLRS] VHF low pass filters?



I think Kirk is in New Hope, so we're talking about the DTV channels
ere in the Twin Cities right?
This means that the only VHF carriers in play are 9 (186-192 MHz) and 11
198-204 MHz).  I don't think his 6m signal is having an in-band affect
r rather, he's not stomping on a channel that is close to 6m.
Seems more like fundamental overload/blocking due to either a preamp being
aturated or the TV front-end not rejecting off-channel stuff well enough.
Chris N0JCF