Steve,
Three more questions for you:
1) What is the location of YOUR transmit antenna relative to the neighbor's
house? In particular, what's the horizontal plane distance?
2) Your first post says that the problem occurs when you are on 80m. From
that, I assume that the 2 element yagi is for 80m, making it quite large.
Does the direction in which you aim the antenna make any difference with
respect to the reactions of your neighbor's TV?
3. What RF power are you running on 80m? Have you tried varying your xmit
power level to see if there is a point at which the interference stops?
Here's my take on this: While Tom, K8TB, might be going in the right
direction about a possible interaction between any florescent lamps (which
could include CFLs) and your RF to trigger the TV's IR sensor circuits, I
am thinking that you just might be radiating enough power to affect the IR
detection circuits directly. Remember, all semiconductors have the
capability to be RF detectors in one form or another. If turning the
antenna and/or dropping power causes the problem to go away, you then will
have determined the threshold value for this issue.
Assuming that the problem goes away if you drop power to 10 watts, that's
10 dB below 100 watts, but 20 dB below 1000 watts. So, you may have to
figure a way to maintain the net RF field to the TV (or the TV's sensor)
below the trigger point when you are running whatever your full power level
is. Obtaining a margin of 20 dB will not be easy (if tests to find the
threshold show such high isolation to be required). Since the only
external avenue left appears to be the AC power cord of the TV, then either
filtering the power cord right at the back of the set or providing RF
shielding to the IR sensor (INSIDE the TV) would be logical approaches.
Alas, I suspect that shielding is out because that would mean cracking the
set open and doing stuff inside, not a likely option with equipment that is
not yours. I hope the power cord is the culprit. (Note that any set with
a remote control requires a small amount of "keep alive" power so that the
remote sensor is always ready for a command. Perhaps there is RF coupling
between the power connections [inside the set] and the IR sensor circuits
of this particular TV set.)
Good luck and please let us on the list know what happens.
73, Dale
WA9ENA
Sr. EMC Engineer
> [Original Message]
> From: VE6WZ_Steve <ve6wz@shaw.ca>
> To: David Bowker <david.bowker@yahoo.com>
> Cc: <rfi@contesting.com>
> Date: 12/31/2011 2:51:12
> Subject: Re: [RFI] TV turns on-off when TX
>
> Thanks for the few responses I have received already.
>
> I repeat as stated in my original post....I have isolated ALL connections
going to the TV.....there is NOTHING connected to the TV except the power.
> I understand the common mode problem, and have much experience using
torroids for RFI ingress. I am well supplied with various Type 31 material
snap-ons and large torroids.
> This "seems" like a unique situation were ingress is not via external
connection, but I will try a brute force filter in case ingress is via
differential mode on the power line....tnx Dave.
>
> BTW...This is a new problem, and I have no problem with any TVs in my
house...it is just my neighbors which is a very late model (only one month
old) unit.
>
> A bit more info on the station:
>
> My antenna is perfectly resonant homebrew 2 el. Yagi at 100'.
> There are 2 very robust choke baluns in series at the feedpoint, (one
> solenoid and another material 31 torroid).
> The antenna is matched at the feedpoint to accommodate the narrow
bandwidth
> of the Yagi.
> http://www.qsl.net/ve6wz/intro.htm
>
>
> Steve ve6wz.
>
>
> From: David Bowker
> Sent: Saturday, December 31, 2011 1:15 PM
> To: ve6wz@shaw.ca
> Subject: [RFI] TV turns on-off when TX
>
>
> Steve,
>
> A bit more info would be helpful to assist in diagnosing the possible
methods of ingress of RF into the TV, such as:
>
> * Does the TV receive it's input signal from CATV, SATELLITE DISH, or OTA
antenna?
>
> * Does it turn ON/OFF and VOL change with the (antenna/CATV/satellite) TV
signal input disconnected?
>
> A toroid choke on the power line entrance to the TV may not be effective
if the RF is entering into the power utility system as a differential mode
signal traveling on the utility entrance to the dwelling. If this is the
case, only a brute force power line filter would be effective.
>
> I have a Samsung 37" LCD TV and run 1.5 kW to 4 element vertical arrays
on 80M & 40M which are 150' from my DirecTV satellite dish and when the
array is pointing directly at the dish (~ 6 kW ERP) I do not experience any
abnomalies.
>
> 73, Dave, K1FK
> Fort Kent, ME
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