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To: k1dg@ix.netcom.com, CatWhiskR@aol.com
Subject: Re: [RFI] TVI
From: dgsvetan@rockwellcollins.com
Date: Thu, 21 Jun 2007 13:47:28 -0500
List-post: <mailto:rfi@contesting.com>
Doug and Terry,

At the risk of being flamed (nothing new - I have my Nomex suit on), I'd 
like to say that I sure wouldn't mind having that Sylvania TV. Considering 
how much it is withstanding at frequencies other than 50 MHz, it is a 
pretty good set, IMHO.  Yes, compared to high end communication receivers, 
lab instruments, and military radios, most TV sets are junk.  However, 
accepting that as a fact and trying to find out which ones are lesser 
junk, there's the trick. 

I suspect that there are two problems with 6m operation, both of which are 
related to the fact that the TV is designed to receive RF starting at 54 
MHz.  No TV tuner that I know of is going to reject the kind of front end 
overload that your set is getting when you are on 6m.  Terry, you didn't 
say which channels your XYL watches while ironing, but if she is watching 
off-air local channels in the low VHF group (ch 2 thru 6), then the tuner 
is getting hammered pretty good.  It may benefit from a high pass filter 
placed right at its input connector, but that filter better have a pretty 
steep slope below 54 MHz to very useful.  On the other hand, if she 
watches cable or channels not in the VHF low group, then you may need more 
shielding within the set, more effective by-passing on the external leads 
(meaning ferrites + by-pass caps), or greater separation distance between 
the antenna and TV set. 

As for in-line filters, another good source (for me) has been MCM 
Electronics, in Ohio.  Google them and go to their CATV and Satellite TV 
stuff.  They carry a lot of commercial (as opposed to only consumer) grade 
stuff.  As for that HP filter at the TV input, I believe prior postings on 
this reflector have talked about I.C.E. as a source.  As I said, you'll 
need a very steep filter slope to be useful if tuner front end overload is 
the problem. 

Please let us know what works.

73, Dale

"Doug Grant" <k1dg@ix.netcom.com> 
Sent by: rfi-bounces@contesting.com
06/21/2007 12:10 PM



> Here is the problem. TV on second floor. Tower is about 5 feet away, on 
> other side of the wall. I have had TVI issues with this TV (Sylvania 32 
> color) on HF but have tamed it with toroids on the cable lead in and the 
> cord. Even with the KW.
> On 50 mhz, with my 5 element yagi 30-50 feet above the TV, and the roof, 

> depending on how high I have it cranked up, I take the TV sound 
(primary) and 
> picture (not so critical) out with 2 watts. This happens when the 
antenna is 
> pointed directly over the house. When the antenna is at right angles to 
the house, 
> no TVI, even with 100 watts. This is on all channels and with cable TV. 
I have 
> had new cable run, quad shield, with no improvement.
> I have added all kinds of toroids to both AC line and the cable with 
> slight improvement. There is a seamless aluminum rain gutter, 30 feet 
> running along the roof a few feet above the TV. In the same direction as 
the TVI. 
> Grounding it has not helped. 

While we have all discovered common-mode ingress (which is what toroids on 
line cords and cable fix), don't forget good ole differential-mode 
ingress. Insert even a dumb old Radio Shack High-pass filter in-line with 
the coax. Just fixed my own TVI at my new vacation house that way.

Radio Shack does not appear to carry such filters nowadays (I had a few 
old ones left over), but cable TV shops like Coast CATV Equipment Supply, 
Inc. in Corona, CA 92880 Tel: (800) 800-2770  appear to carry suitable 
filters. Check out http://www.coastcatvsupply.com/Pico/picomacom.htm

GL and 73,

Doug K1DG
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