[TowerTalk] 135 foot dipole, 300 ohm twinlead

[K4SAV]

"Outside it hangs from the antenna, drops to about a foot above the ground
and comes into my window along with several pieces of coax.  It goes under
my desk about 6-8 feet and wraps back to the top to the tuner. "

OOH - missed that comment before. You need to have some seperation between twinlead and other stuff.  If you lay it against other lines, you can couple common mode signals into the other lines.  These currents can get into your house wiring and cause RF overload of TV sets, VCRs, etc

Jerry, K4SAV



K4SAV wrote:

>Let me take a stab at this.  Due to the fact that your TVI is on all 
>channels everywhere in your house, a lot of causes are rulled out. It 
>probable doesn't have anything to do with the fact you changed 
>feedlines.  As others have said, the balanced line should work fine. I 
>would say that most likely the source of your problem is either:
>
> 1. A loose connection, or broken wire, in your feedline.  Could be 
>anywhere along the line but most probably at the connection to the antenna.
>
> 2. Your cheap VCR
>
> 3. A loose cable connection to a cheap VCR.
>
>
>Number 1, broken wire, can turn your dipole into something that looks 
>like a vertical with ground return currents through your house wiring.  
>The easiest way to determine this is to drop the antenna and get out the 
>ohmmeter.
>
>Number 2, cheap VCR, is usually never suspected.  Many of these VCRs put 
>a diode across the antenna terminals.  I guess they figure they are 
>protecting the antenna inputs.  This serves as a great rectifier, which 
>generates tremendous quantities of harmonics, then applies this into 
>your cable system, which goes all over your house.
>
>You can test for this by unplugging all the stuff connected to you cable 
>system, then one by one, add them back and see if you can find a 
>culprit.  Usually the problem is created by RF overload.  If this is the 
>case, put several ferrite beads on the input cable to the TV/VCR 
>equipment which is causing the problem.  You may also have to put some 
>on the AC line as well.
>
>Number 3 is obvious.  This allows common mode signals into the VCR which 
>rectifies them, and the rest is the same as #2.
>
>Jerry, K4SAV
>
>Buck - N4PGW wrote:
>
>  
>
>>I had a 129 foot dipole fed with CATV coax.  It did ok, but where the
>>aluminum met the copper, it oxidized and I have been suffering with AM
>>broadcast band bleedover on all frequencies below 14 MHz.  I recently
>>replaced it with a 135 foot dipole fed by 300 ohm TV twinlead to my tuner on
>>which my IC-706 sits.  The problem I have now is TVI.  When I get the
>>antenna tuned and run more than 30 watts, the TV pictures turn red, green,
>>or blue.  We are on Cable TV and I cannot recall the last time I had TVI
>>other than when I operated 6 meters and the rig is sitting less than two
>>feet from my TV.  (the TVI now is all over the house.)  I don't know if it
>>is getting into neighbors homes at this time.
>>
>>I figure I am getting less loss tuning that antenna with twinlead as opposed
>>to coax, but I have a piece of RG-8 foam I am thinking about feeding the
>>antenna with instead.  
>>
>>Any suggestions or ideas?
>>
>>thanks,
>>Buck
>>N4PGW
>>
>>
>>
>>_______________________________________________
>>
>>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
>>
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>> 
>>
>>    
>>
>
>_______________________________________________
>
>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
>
>_______________________________________________
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>http://lists.contesting.com/mailman/listinfo/towertalk
>
>  
>