[AMRadio] I'm not an antenna expert

John Lawson jpl15 at panix.com
Wed Jan 11 11:43:30 EST 2006

I don't even play one on TeeVee...

   So, in advance of a lot of EZNec work (and I don't have the experience 
with that program to derive much 'good' out of it right now) - I'd like 
to ask what may seem to be a rather obvious HF antenna question.

   Due to the usual reasons - my HF antenna is a loop suspended from my 
backyard fence - approx 430' total, closed loop, 5' off the ground, fed by 
450 ohm ladder line back into the shack, using an Ameritron ATR-15 tuner 
to match the system to my Valiant.  The tuner and transmitter are bonded 
to a very heavy ground system via an 8' stake less than 3' from the gear. 
There is no ground system under the antenna, other than that which Nature 
provided - and with the current winter conditions, the ground is rather 
wet and conductive.

   This antenna system exhibits the following SWR:

160M - 1.3:1
  80M - 1.1:1
  40M -  +3:1
  20M -   2:1
  15M -  +3:1
  10M -  +3:1

  The tuner capacitors end up being  all-the-way-meshed on the 
'misbehaving' bands - not so on 160, 80, and 20.

   So I'll see Y'all on 3880 and just fergit the rest.   ;}

   No but seriously folks: obviously the feedpoint resistance is outside 
the tuner's ability to cope with it at various frequencies.

   I'm thinking the first unscientific experiment might be to go to the 
opposite side of the loop from the feedpoint and cut it into a big 
horizontal bent dipole - mainly because that will take about 45 seconds to 
accomplish - one of the benefits of having one's entire antenna at 

   But I'd like to get some other opinions - I know there's an electrical 
Pattern here from the info - and I have some other ideas based on that.

   And no, I can't put up a "real antenna" so I'm pretty much comiited to 
making this one work as well as I can. Until I move the QTH to somewhere 
with a few acres and room for Lots of Wire.


John  KB6SCO

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