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Re: [TowerTalk] 43' Vertical - Feed Point Tuner or Shack Tuner?

To: Richards <>,
Subject: Re: [TowerTalk] 43' Vertical - Feed Point Tuner or Shack Tuner?
From: Dan Zimmerman N3OX <>
Date: Sat, 7 Feb 2009 00:13:46 -0500
List-post: <">>
> Nothing special, but it does allow me to work 80-20 rather well with
> just the one one big stick and a big Palstar tuner.   I have used it
> sparingly on 160,  so I am not sure how well it works on that band,
> but STILL, the fact it works at all means I have workable antenna on
> that band, and it works better than anything I tried for that band before.
> I am making contacts where I did not before.

I think that is many peoples' experience.   And in the end, ham radio
without making contacts is just electrical engineering.  But I think a lot
of people (and I'm not saying you do) follow this line of logic:

Postulate:  Full legal limit effective radiated power is basically
requirement to make lots of 160m contacts

Observation : I'm making lots of 160m contacts

Conclusion: I must be radiating a non-negligible fraction of my 1500W.

It's just that first step that's the "gotcha."  To be a *really* successful
(200-300 countries) 160m DXer you need to get close to 1500W ERP.  To place
in domestic contests and make DXCC at least from the relatively easy East
Coast, though, especially from a good location?  10W or 20W will do it, I

What it basically means is that the range of "workable" antennas is
EXTREMELY large.  Makes ham radio a lot of fun.  But it also potentially
leaves a lot of room for improvement with workable antennas.

Is it a great antenna - well... probably not,  and you make a good point,
> but in a world of compromises, I feel I have come up on the better end
> of the stick this time.  My yard only 100 feet wide by 55 feet deep, so
> this is a GREAT OPTION because it IS easy to erect, has a very small
> foot print,  has very low visual impact, and is omni directional.

There's a box you could put at the base of it to greatly improve 80m/160m
performance.  That box would contain a big copper tubing coil and a few
vacuum relays.

If I ran a ham radio company, I'd probably sell one for $250.  I don't want
to do that.  You can get the relays from Max Gain or someone, and the tubing
from Home Depot ;-)

I ran a 40 footer with a base loading coil on 80.  Killer antenna even on my
tiny lot.   Best DX antenna I ever had for 80 until I put up the 60 footer
(which really didn't give me any  noticeable performance boost, because it
probably was only a couple dB stronger).  I did put a loading coil on it for
160m and had great fun in the Stew Perry contest, but had a pretty hard time
getting the attention of the DX I was hearing.  But like you said, it was
better than nothing, and that's important.

And you probably actually get *saved* by your small yard to a certain
extent.  Coax loss probably swamps radial field smallness loss if you have a
long coax run, but you probably don't have a particularly long coax run, I'd

But at the same time, that UNUN and coax must be eating a noticeable amount
of signal.  If you want to try something simple, 20 feet of 3/8" copper
refrigeration tubing wound in a coil of 15 turns about 5 inches diameter and
about a foot long is in the ballpark of what you need to load it to
resonance on 80m at absolutely obscene power levels even full duty cycle.
1/4" should be more than sufficient for kW, and I used #10 wire with no ill
effects with 100W, but I'm pretty sure that's going to be undersized for kW
levels, at least with long transmissions.

I do have to wonder why no one's selling one yet.  Sounds like a business

But adding loading inductors might be an admission of weakness?    There's
also the fact that a 160m base loading doohickey would lead to a very, very,
very narrow bandwidth and a very hazardous feedpoint.  Even over my minimal
radial system, I think I got 10kHz to 15kHz between the 2:1 SWR points on
160m and the antenna with my MFJ-259B plugged in made a great proximity
detector.  If I got within 6 feet of the antenna, it detuned 20kHz.  Same
with the rain, etc.  And it probably would have caught fire if I had an amp
;-)  Until the fire, though, it would have been a lot louder.

I am sold on it until I can  1) afford, and 2) erect
better.  And, yes,   I AM working on it!

That's just the thing.  What it needs is mostly that you cancel its
reactance out, at least on 80m.  160 is the same story, but since it's so
short it's hard at high power.  Be careful if you try it, because the base
insulator may not be too happy with you.  You'd be looking at something in
the ballpark of 9kV at the top of the coil at 1500W.

And that 9kV is what you NEED to force a 43 foot unloaded antenna over a
small ground system to radiate something like 300W on 160m.  If you had a
great ground system and an impressive loading coil, you could eke out about
a kilowatt radiated, and you'd have to stand off like 12kV across the
inductor.     And these numbers aren't particular to a coil loaded antenna.
They're the feed voltages you need after whatever matching device in order
to radiate those powers from a 43 foot radiator, and  I don't see these
antennas coming with warnings regarding the 10+kV at the feedpoint ;-)  I
wonder why...

If you become very fond of 160m, I'd probably recommend figuring a way to
add a top loading wire to turn the thing into an inverted L temporarily when
you want to have a big sig on Topband.  A nice, strong 43 foot aluminum
stick in the backyard installed over a great radial field has a lot of
potential to be a great antenna for the lowest ham bands.  It's just not
done yet ;-)  If you ever go from having fun to being frustrated, don't go
buy something else, just try some time-tested loading methods.


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