PAR antenna on 80 meters

[Grif-2]

Greetings, all-

Here is a small tidbit of possibly useful information in this period of low sunspot activity, which probably everybody but me knew anyway.

The PAR EndFedZ is a popular backpacking or portable semi-QRP (25 watts maximum) multi-band antenna covering 40, 20, and 10 meters. (It will also cover 30, 20, and 10 if the wire "stinger" is shortened.) Being a half-wave antenna, no radials are needed.

I found that if both sides of the coax coming out of the PAR matchbox are tied together and treated like a random wire, the internal tuner in my Icom IC-703 would match it on 80 meters, with a resulting SWR of 1.2. I used about a 34 ft. counterpoise with this setup. I'm looking forward to seeing if the internal tuner in my KX-1 with the forthcoming 80 meter board will also match it.

The IC-703 was unable to get a match on the WARC bands or on 15 meters. Sorry. I think a more robust tuner could probably match those bands as well. An experiment for another day.

73, Grif, KF4JG

Sorry, the previous attempt to send this had unacceptable formatting embedded in the text. I don't know how much went through, but some of it got bounced.
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[EricJ-2]

I sometimes do that to use my TH7DX on 30m. The K1 and K2 have no problem
loading it on 40m and 80m too, but it doesn't hear or radiate very well.
Still it's usable in a pinch.

Eric
KE6US
www.ke6us.com

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Grif
Sent: Wednesday, February 01, 2006 7:41 AM
To: [hidden email]; [hidden email]
Subject: [Elecraft] PAR antenna on 80 meters

Greetings, all-

Here is a small tidbit of possibly useful information in this period of low
sunspot activity, which probably everybody but me knew anyway.

The PAR EndFedZ is a popular backpacking or portable semi-QRP (25 watts
maximum) multi-band antenna covering 40, 20, and 10 meters. (It will also
cover 30, 20, and 10 if the wire "stinger" is shortened.) Being a half-wave
antenna, no radials are needed.

I found that if both sides of the coax coming out of the PAR matchbox are
tied together and treated like a random wire, the internal tuner in my Icom
IC-703 would match it on 80 meters, with a resulting SWR of 1.2. I used
about a 34 ft. counterpoise with this setup. I'm looking forward to seeing
if the internal tuner in my KX-1 with the forthcoming 80 meter board will
also match it.

The IC-703 was unable to get a match on the WARC bands or on 15 meters.
Sorry. I think a more robust tuner could probably match those bands as well.
An experiment for another day.

73, Grif, KF4JG

Sorry, the previous attempt to send this had unacceptable formatting
embedded in the text. I don't know how much went through, but some of it got
bounced.
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[Ron D'Eau Claire-2]

You can often get a match to a difficult antenna system by making it LESS
efficient. Many have posted how they have been able to load up this or that
antenna after using fewer radials in the counterpoise or through some
similar means.

That raises the resistance of the system which helps the tuner. The bad news
is that the added resistance is loss resistance, not RF being radiated. But
as Eric observed, it can make a system usable in a pinch.

Of course low SWR is *not* an indication of antenna efficiency. As others
have pointed out many times, were that true our dummy loads would be the
best antennas ever!

Probably the best indicator is the "Q" or sharpness with which our antenna
systems tune, especially when using an antenna that is less than 1/2 wave
long. Efficient short antennas have high "Q", tuning sharper and sharper
(have less bandwidth at the 2:1 SWR points) as they get shorter. For
example, I have a  doublet that is only about 80 feet overall. It works FB
on 80 meters, but I have to retune if I move more than 5 or 10 kHz to keep
the SWR down below 2:1. That is a sign that it is working efficiently.

If you have a short antenna that seems to work over a broad range in the
band, you can be sure that there is a lot of loss resistance in the system.
Be happy if your short antenna requires that you to wait while the tuner
finds a new match after moving a few kHz!

Ron AC7AC

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