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To: rfi@contesting.com
Subject: Re: [RFI] VHF/UHF and TVI
From: "Roger (K8RI)" <k8ri@rogerhalstead.com>
Date: Sun, 09 Jan 2011 22:39:57 -0500
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>

On 1/9/2011 10:09 PM, John Geiger wrote:
> I know that HF and 6m can cause pretty good cases on TVI, even with someone 
> on cable TV due to overloading the front end of the TV, but how does 2m and 
> 70cm tend to affect TVI?  Does TVI tend to be less at the higher frequencies?

The only TVI  (from home) I've ever had was from 2-meters on channel 12. 
with no direct harmonic relationship.
OTOH when mobile watch out for leakage on cable Ch 18 as the audio 
subcarrier is 145.25. If we can here them the likely hood they will hear 
us is very high.  This can be particularly bad if some one hooks up 
cable and leaves the outside antenna hooked up directly instead of 
through an A/B switch.

So far I've been lucky on 6-meters as channel 2 adjoins 6-meters 
directly and any nearby 2-meter receiver, including using ch 2 for 
linking VCRs and DVRs is likely to be easily overloaded.  Newer DVRs 
allow using UHF channels up to 73 or 76. Older ones use both ch 2 and ch 
3.  Switching to ch 3 should alleviate *some* 6-meter problems.  Cable 
channel 65 is the same as OTA channel 2. So a set top box listening to 
ch 65 and sending to the TV set on Ch 2 would be hit on both the input 
and output.

OTA UHF channels 45 is 438-444 MHz with channel 44 being just below the 
433 link frequencies.  I've not heard of problems with these but it's 
not unlikely. Cable channels 101 and 102 are in the 432 to 450 range. 
(IOW in or partly in the 440 band)


Roger (K8RI)

> 73s John AA5JG
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