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" <email@example.com>
To: "John Geiger" <firstname.lastname@example.org>
Sent: Wednesday, January 12, 2011 9:05 PM
Subject: Re: [RFI] Low pass filter opinions
> 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
> 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 <email@example.com>
>> To: <firstname.lastname@example.org>
>> 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.
>> antenna is a G5RV type dipole and goes right over the living room where
>> 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
>> it off completely. Now on the TV in the living room, it will get TVI on
>> 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
>> 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" <email@example.com>
>> To: "John Geiger" <firstname.lastname@example.org>; <email@example.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
>> > 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
>> > 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
>> > 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
>> > operation, but more than that causes problems, then you know that you
>> > 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,
>> > 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
>> > to
>> > the victim (NOT your rig, but your antenna relative to her antenna
>> > 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
>> > low pass filters is almost meaningless. Study your schematics or tech
>> > specs for the rig. Since modern solid state HF rigs mostly use
>> > 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
>> > 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
>> > 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 <firstname.lastname@example.org>
>> >> To: <email@example.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
>> >> _______________________________________________
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>> >> RFI@contesting.com
>> >> http://lists.contesting.com/mailman/listinfo/rfi
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