[AMRadio] Antennas for AM (was Legal limit AM amplifier, homebrew)

[Rick Poole]

At 11:17 AM 11/13/2011, Rob Atkinson wrote:

 >>>>>
>Is it one of those carolina windom jobs?
<<<<<

Good morning, Rob.

Not exactly.  It doesn't have the vertical radiator or the choke 1/4 
wavelength down the coax.  It is fed at about the 1/3-2/3 point with 
a 4:1 current balun and 50-ohm coax to the shack.  Works pretty well 
on the fundamental and even harmonics.  Currently it is mainly used 
for 80 and 40 but I plan to put up another one for 160 and 80 and use 
that with the AM station.  I suspect most or all of my AM activity 
will end up on those two bands anyway.

 >>>>>
>If you can ever get a
>center fed ladder line 1/2 w. dipole up to around 50 feet and fed with
>a KW Matchbox, things will work out a little better I think.
<<<<<

I had a KW Matchbox and sold it several years ago.  Probably 
shouldn't have done that!  I still have two NyeViking KW tuners I 
could use, but both of those are what Bernie characterized as a "POS 
that place a balun on the output" :-).

Of course open wire balanced feeder antenna couplers are simple 
enough to build so I suppose I could build one.

I have a 160-meter inverted V fed with ladder line and a tuner, but I 
think I'm going to try to avoid open wire feeders this time 
around.  The position of the AM station and the general layout of the 
shack would require perhaps 15-20 feet of open wire feeder to be 
strung around the shack to where the matchbox would have to go, and I 
don't have much confidence in being able to avoid RF-in-the-shack 
problems, especially since I have three computers running here, two 
of which are used for mission-critical business purposes (I'm a 
medical device software engineering consultant in my other 
life).  I've seen what can happen to computers if you try to run them 
in a high RF environment, and it was not pretty.  So I think I'm 
going to stick with coax and a resonant antenna for this one... an 
OCF antenna carefully tuned for 1.9 MHz will also resonate on 3.8 MHz 
and that should put me about where I need to be on both bands.

I plan to rent an 85-foot cherry picker next spring and use it for 
some projects around the property, including putting up some new 
antennas.  I did that once before with a 45-foot cherry picker and it 
worked quite well.

The 35-foot OCF is mainly used for NVIS stuff and I'll still need that.

Rick WA1RKT