[AMRadio] 160 meter antenna

[Brett Gazdzinski]

I have heard ferrite type stuff can cause nasty problems at high power.

Since I run tube rigs, I think I will just cut a dipole for the center of 80 meters, and ditch the tuner, which gets quite warm on the G5RV.

If I am going to heat something up, it might be better that its not in a shielded metal box.

While a balanced setup is best, I don't want to have to tune the antenna every time I change frequencies, as I like to hop around between bands and the phone and CW parts of the bands..
Without a tuner, you can use the antenna's on receive, even on other bands, while with a tuner, if you get far from where you are tuned from, you get a lot of loss...

Brett

  ----- Original Message ----- 
  From: Jim Wilhite 
  To: Discussion of AM Radio in the Amateur Service 
  Sent: Monday, January 12, 2009 6:46 PM
  Subject: Re: [AMRadio] 160 meter antenna


  Remember what balun means, balanced to unbalanced.  This is not some magic device to withstand grand excursion from center frequency of an antenna.  It is to transform on impedance to another.  If you move far enough off center you can wind up with very high voltage in the balun, resulting in what Brett describes.

  Probably the best balun for high power is the choke balun wound on 6" PVC of RG 8U or the beads that fit over the coax.   Since supporting the choke balun at the center of my antenna would be a challenge, I use the beads.  There are there to prevent current of the shield of my coax feedline when I am far off center frequency of the antenna.

  If you are going to move more than 3% of frequency, then forget the W2AU or, even, the so called quality type of balun.  The W2AU I took apart was constructed of RG 58.  Not the best for a HV environment.  When you move from one end of the band to the other, just use a good high power tuner and be prepared for lost power in the tuner.

  Jim/W5JO
    ----- Original Message ----- 


    If you run any power at all, forget the balun unless you gat some sort of monster one, the usual suspects wont work for even moderate power AM.

    Any time I tried traps or baluns on AM, all I got was a fire.
    Some might take 50 watts carrier, but the DX100 blew out many a trap back when I was starting out in AM.


    Brett
    N2DTS


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