My Alpha 78 TVI goes away if I remove the S-video cable between the DirecTV
receiver and TV. With it in the line 5 watts on 160 meters gives me TVI.
I don't know if it is a bad cable or ??? but I don't see any difference in
quality so I just took it out.
Rick Darwicki -= N6PE =-
=================================================
17775 Elmhurst Circle
Yorba Linda, CA 92886
http://www.stores.ebay.com/n6peradiotubes
http://www.qsl.net/n6pe/
----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: <rfi@contesting.com>
Sent: Friday, June 22, 2007 10:07 AM
Subject: Re: [RFI] N6CW TVI
> On Fri, 22 Jun 2007 08:57:38 -0400, Tom Rauch wrote:
>
>>Station grounds are great for lightning and safety.
>
> I agree with ALL of Tom's comments, including his bonding
> recommendations for TV antennas (and cable TV lead-ins) and about
> his comments on filters. That bonding will certainly divert any
> common mode current on the coax to the power system ground and
> away from the set. BUT: That common mode current CAN re-radiate
> into a set that is poorly shielded. In this situation, a big choke
> could raises the impedance of that coax sufficiently to kill the
> current that is generating the re-radiation.
>
> Nowadays, when we talk about TVI, that may also include RFI to an
> audio system, most of which is the result of the audio cables
> acting as receiving antennas and exciting pin 1 problems. Ferrite
> chokes WILL fix this sort of problem, and are often the most
> effective way of doing it. Proper bonding and using antennas that
> are well matched ARE the right approach, but it doesn't solve
> everything.
>
> Three examples. #1 My home music system is rather simple -- even
> though I'm a pro audio guy, I spend my money on jazz CD;s rather
> than exotic gear. All the power wiring is exposed, so it has line
> filters to prevent common mode coupling. The loudspeaker wiring is
> twisted pair. But it was a 3 ft RCA jumper between my CD player
> and the AV receiver that picked up enough RF from my 10M dipole
> 200 feet away that excited a pin 1 problem in the CD player. A
> choke on that jumper reduced the antenna current enough to fix the
> problem. BTW -- that's a 3-band dipole that I use a lot on 20, 15,
> and 10. No problem on 20 or 15. But the combination of the shorter
> wavelength and the nature of the pin 1 problem inside the CD
> player made 10M a problem.
>
> #2 K6EU, running 100 watts on 2M, was lighting up his neighbor's
> active sub-woofer (that is, a loudspeaker with built-in power amp
> that was part of a home theater system) enough to be annoying when
> he pointed the beam in that direction. Three #43 ferrite clamp-ons
> choked that current.
>
> #3 About six months ago, I acquired an FT-1000MP and started
> contesting with it. I like the radio, but had RF feedback on 15M
> (that same high dipole, roughly 150 ft from the radio). In the
> heat of the contest, I fixed it with a multi-turn choke on the mic
> cable. A few weeks later, I pulled out the RF generator and poked
> around for pin 1 problems. I quickly verified that the mic
> connector has a pin 1 problem in the 4-6 MHz range, and around
> 15M, and the short mic cable (about 6 ft) picked up enough RF from
> that dipole for the radio to detect and generate RF feedback. BTW
> -- I had also gotten RF feedback reports when I checked into an
> NCCC net on 3830.
>
> As to filters: When I started running QRO in Chicago, I chased
> down a good mfr of TV filters and put them in front of the
> distribution for my FM and TV antennas (I didn't have cable
> there). The company is Tin Lee Electronics near Toronto. I found
> them with a google search.
>
> I'll also reinforce Tom's comments about the coax, ESPECIALLY to
> check the CONNECTORS. I reduced the leakage from my cable system
> here in CA to my 2M radio significantly by changing out cheapie
> coax jumpers for good ones that use well installed Snap N Seal
> connectors.
>
> 73,
>
> Jim Brown K9YC
>
>
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