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[RFI] Televisions and RFI; info needed, pse

To: <rfi@contesting.com>
Subject: [RFI] Televisions and RFI; info needed, pse
From: dgsvetan at rockwellcollins.com (dgsvetan@rockwellcollins.com)
Date: Mon Mar 31 10:37:29 2003

I noticed that while you got plenty of replies about general RFI, no one
addressed your questions about 50 MHz operation.

Bear in mind that all TV tuners are, by function, broadbanded devices.
Sadly, the 6m band is less than a full TV channel below Channel 2.  The
effects to a TV set for Ch. 2 reception are more a function of the
situation than of set characteristics.  For example:  what is the strength
of the Ch. 2 signal?  How much power will be run on 6m?  What mode (SSB/CW
or FM) do you plan to run?  What antenna type(s) will be used on 6m?  What
is the relative location of those antennas to the TV antenna?

>From my personal, limited experience with operating 6m in a Ch. 2 area, I
can tell you the following:

1.  Operating SSB at the low end of the band is safer than operating FM in

2.  Even though FM uses vertical polarity, the FM operation is only about 2
MHz below Ch. 2 and that is not enough.  I received a TVI complaint from a
person more than 2 miles away when I was using 6m FM because his TV antenna
points in my direction to "see" the Ch. 2 signal.

3.  Separate the 6m antennas from the TV antenna as much as possible.  Do
not expect to place both antennas on the same roof or tower.

4.  Consider installing a 6m suck-out trap in the TV 75 ohm cable.  K1UHF
makes one, and I think they are available from Down East Microwave, and
other vendors.  I need to get one.  I already have the K1UHF trap for 2m
SSB.  Note that these are NARROW traps.  The 6m covers the SSB part of the
band only, as does the 2m one.

5.  Run the lowest power you can on 6m.  When the band opens, I do very
well with 10 watts.  (I got 20 over 9 reports from the East Coast during
the January VHF contest.  I am located in Iowa.)

I am planning a complete filter package to install in-line with the
downlead from my TV antenna.  This package will include filters for each
VHF and UHF ham band, 6m thru 70cm, and the main head-end TV pre-amp.  All
the stuff will be in a weather-proof, RF-tight box mounted on the tower.
It is important to keep strong ham sigs from crunching the pre-amp's input.
All cables and connections after the pre-amp must be first class so that
ham RF does not get into the TV system.  if that happens, I'll have to put
in more filters at the individual TV sets and/or my inside distribution
amplifiers.  Anyway, be prepared to stay the course and work the TVI issues
one by one.

FYI:  I live in a moderate zone for Ch. 2 signal strength  - about 40 or 50
miles from the xmtr.  I am in a rural area, and rotate a deep fring TV
antenna because we watch a lot of TV that is in the range of 75 to 100
miles away.

Best luck.

73, Dale

                      <wa2bpe@infoblvd.        To:       "rfi@contesting.com" 
                      net>                     cc:                              
                      Sent by:                 Subject:  [RFI] Televisions and 
RFI; info needed, pse                                   
                      03/29/2003 09:08                                          


...Just had the family TV smoke itself - literally - and it isn't worth
fixing.  The stench of burning epoxy is *not* nice!!

Perhaps this was discussed some time ago, but does anyone have any
experience with the EMI/RFI susceptibility of the various brands
presently available? Experience of sensitivity to 50MHz is of special
interest.  I am specifically interested in anyone's experience with
Samsung; both high definition ready and standard analog models.


Tom - WA2BPE

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