John,
Jim Brown, K9YC, answered your first question very well. Again, I repeat,
using a LPF in your situation will NOT help the RFI problem. The filters
within the rig (assuming a modern solid state rig) have already reduced the
out-of-band spurs and harmonics to a milliwatt, or less! Put your efforts
elsewhere.
As for the second issue, you have already answered that question yourself.
The DVD player was coming into your set via the direct IN jacks - NOT the
tuner. That should tell you that the problem, is in fact, an RF problem
with the tuner. The good news is that your TV itself is apparently not
affected by the RF fields. Get your G5RV further away from your TV set or
the TV antenna (if you are using one). If you have cable or satellite,
check those cable connections (again) to make certain that they are snug
and use an ohmmeter to verify shield continuity at each Type F connector.
Note that it is very easy to have a bad (open) connection to the cable
shield when crimping on those F connector ferrules.
I doubt this will help, but if you are absolutely hung up on filtering some
RF, get a decent HIGH pass filter and install it right at the input to the
TV set tuner. Be sure to get one in a metal, not plastic, case. Maybe it
will sufficiently attenuate the HF RF that is coming into the set via the
coax center conductor. If you have common mode coupled RF on the cable
shield, then the HPF will not help and you need to see K9YC's web site for
info on common mode choke materials to add over the TV coax cable. Note
that you must use materials that are effective at HF - not the often-used
Type 43 materals that work best for VHF.
73, Dale
WA9ENA
> [Original Message]
> From: John Geiger <aa5jg@fidmail.com>
> To: <svetanoff@earthlink.net>; <rfi@contesting.com>
> Date: 1/13/2011 8:01:34
> Subject: Re: [RFI] Low pass filter opinions
>
> 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
> > WA9ENA
> > 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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