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Re: [RFI] Low pass filter opinions

To: <svetanoff@earthlink.net>, <rfi@contesting.com>
Subject: Re: [RFI] Low pass filter opinions
From: "John Geiger" <aa5jg@fidmail.com>
Date: Thu, 13 Jan 2011 14:01:27 -0000
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
What am I to make of the reviews on eham.net of people who had RFI, then 
bought a TVI filter and that cleared it up?  You can find quite a few like 
these in the product reviews section for RFI.  Not trying to argue but it 
does seem like some people have been able to get a low pass filter to work 
for them. Maybe it will work for me.

The TVI doesn't seem to be on all channels, at least not at my QTH.  Only on 
a few of the lower channels.  When I had a DVD playing it wasn't affected at 
all by my transmitting.  This was with an external DVD player hooked to the 
TV.  Using the external input jacks for it, not channel 3 for input.

73s John AA5JG
----- Original Message ----- 
From: "Dale Svetanoff" <svetanoff@earthlink.net>
To: "John Geiger" <aa5jg@fidmail.com>
Sent: Wednesday, January 12, 2011 9:05 PM
Subject: Re: [RFI] Low pass filter opinions

> John,
> In general, the location of a TV set relative to your RIG is almost a
> non-issue: very seldom is RFI coupled cabinet-to-cabinet, although if they
> share an AC power outlet, noise from the TV set's switching power supply
> could get into the radio.  No, the big issue is distance between the
> ANTENNA and all possible "victims" - those being TV sets and other devices
> that are not supposed to receive ham radio signals.  Again, use of LPFs is
> a waste of time and money.
> Everything you are saying below leads me to suugest relocating that G5RV 
> so
> that it is away from the TV sets (yours and your neighbor's) as far as
> possible.  If you can't move it, you have 2 choices (other than QRT, of
> course):  1, reduce xmit power to below the "threshold of pain" for the
> TVs; 2, apply serious RFI control measures to all affected TV sets (yours
> and the neighbor's) in accordance with info from K9YC (see his related
> postings and web site).  Read and heed his advice.  Also, check all of
> those TVcable connections to make certain there are no poorly connected
> shields and that all fittings are snugged tight.
> Sorry, probably not what you wanted to see but them's the facts.  Bottom
> line:  you MUST get the RF levels from your antenna below the interference
> threshold for the various TVs (reduce xmit power and/or move ham antenna),
> or, lacking that, you must raise the theshold of the TVs by applying RFI
> engineering techniques and materials.
> 73, Dale
> Sr EMC Engineer
>> [Original Message]
>> From: John Geiger <aa5jg@fidmail.com>
>> To: <svetanoff@earthlink.net>
>> Date: 1/12/2011 8:06:07
>> Subject: Re: [RFI] Low pass filter opinions
>> Hi Dale,
>> I have done some checking at the home QTH in the past couple of days as
>> well.  I have a TV in the shack, which is about 5 feet from the rig, and
>> also one in the living room, which is around the corner from the shack.
> The
>> antenna is a G5RV type dipole and goes right over the living room where
> that
>> TV is, maybe 20 feet above the TV.  Also have other TVs in the house but
>> haven't done much testing with them.
>> The TV in the shack get clobbered by TVI on most HF bands and 6m will
> shut
>> it off completely.  Now on the TV in the living room, it will get TVI on
> the
>> lower cable channels when I am on HF, above channel 7 or so seems to be
>> immune most of the time.  Both TVs are on cable and both are the older
>> analog type TVs.  It seems that it is getting into the cable as the TV in
>> the living room is fine when it is playing a DVD. The DVD player doesn't
> use
>> channel 3 for input into the TV, but uses the video input jacks instead.
>> Figured a low pass filter couldn't hurt.  I welcome any other thoughs or
>> ideas you have on this matter.
>> 73s John AA5JG
>> ----- Original Message ----- 
>> From: "Dale Svetanoff" <svetanoff@earthlink.net>
>> To: "John Geiger" <aa5jg@fidmail.com>; <rfi@contesting.com>
>> Sent: Wednesday, January 12, 2011 5:19 AM
>> Subject: RE: [RFI] Low pass filter opinions
>> > John,
>> >
>> > Having read your initial post yesterday (on the 10th), I'd like to make
> a
>> > few comments regarding the situation.
>> >
>> > First, what is the location of your antenna to either your neighbor's 
>> > TV
>> > set or to her TV antenna (or cable/satellite box)?
>> >
>> > Second, if the problem really is RF fundamental overload, then a low
> pass
>> > filter will NOT help the problem.  (Fundamental overload occurs when 
>> > the
>> > fundamental RF signal is enough to disturb the victim device [her TV or
>> > related equipment].  Harmonics may or may not have any effect.)  The
> best
>> > suggestion is, in fact. to try reducing power.  You mention 25 watts,
>> > reduced from your normal 100 watt level.  If 25 watts results in proper
> TV
>> > operation, but more than that causes problems, then you know that you
> are
>> > fighting a 6 dB reduction issue, which is not too bad.  However, if you
>> > have problems down to even lower levels, such as 10 watts or 5 watts,
> then
>> > you have 10 dB or 13 dB problems.  In short, you need to find the
>> > threshold
>> > of pain for that TV.
>> >
>> > Remember, curing these types of problems involves working the issues of
>> > Source emission frequencies and power level (your rig), Source
> proximity
>> > to
>> > the victim (NOT your rig, but your antenna relative to her antenna
> and/or
>> > TV and related equipment), and Threshold of disturbance for the victim.
>> > The problem will go away if you reduce power enough, move your antennas
>> > away far enough from her house and/or equipment, and provide shielding,
>> > choking, and by-passing on all I/O connections to the TV.  However, is
>> > that
>> > realistic?  Probably not, so work the one or two issues that you can
>> > control and see what happens.  Keep us posted.
>> >
>> > Final note: if your rig is a modern solid state one, the use of
> addditonal
>> > low pass filters is almost meaningless.  Study your schematics or tech
>> > specs for the rig.  Since modern solid state HF rigs mostly use
> broadband
>> > PA stages, thay employ low pass and/or bandpass filter networks as
>> > integral
>> > components of their design in order to meet FCC spur and harmonic 
>> > specs.
>> > The only places I use low pass filters these days is on my classic tube
>> > rigs and after a linear tube-type amp.  After all, you can not filter
> the
>> > fundamental and when a rig has harmonics down by 60 dB or more, keep in
>> > mind that 60 dB down from 100 watts (which is +50 dBm into 50 ohms) is
> -10
>> > dBm, which is 0.1 milliwatt!
>> >
>> > I suspect that either your antenna (or part of it) is much too close to
>> > her
>> > equipment, or her TV and related equipment has a problem that either
>> > requires a lot of work to fix or that should be checked for bad
>> > connections
>> > (at all cable fittings).  Good luck.
>> >
>> > 73, Dale
>> > WA9ENA
>> >
>> >
>> >
>> >
>> >> [Original Message]
>> >> From: John Geiger <aa5jg@fidmail.com>
>> >> To: <rfi@contesting.com>
>> >> Date: 1/11/2011 7:49:23
>> >> Subject: [RFI] Low pass filter opinions
>> >>
>> >> What have list members found to be the best low pass filters to 
>> >> prevent
>> > TVI?  I currently have a Drake TV-1000 in line but that allows RF up to
>> > 52mhz, and actually above that because I have used it successfully on
>> > 52.525mhz for 6m FM.  Today I borrowed a Kenwood LF-30A from a friend. 
>> > I
>> > can't find too many specs on it other than it has 90db of attenuation
>> > above
>> > 90mhz.  It didn't make any difference compared to my Drake.  I was
>> > thinking
>> > that it might do better since it should have a lower cutoff frequency.
>> >>
>> >> I see that Drake also made a TV3300 filter that is rated at 80db above
>> > 41mhz.  And the ICE filters get good reviews on eham.net.  So, any
>> > opinions
>> > as to what low pass filters work best?
>> >>
>> >> 73s John AA5JG
>> >> _______________________________________________
>> >> RFI mailing list
>> >> RFI@contesting.com
>> >> http://lists.contesting.com/mailman/listinfo/rfi
>> >
>> >

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