[Elecraft] K1, KX1, K2 antenna tuner high-impedance feed capabilites

[Ron D'Eau Claire]

I've used an end fed dipole (i.e. half wave wire) a lot. I'm currently using
an end fed 80 meter dipole in my fixed-station setup. Such an antenna
presents quite a high impedance at the end, of course. That impedance is
outside the range of the KX1, and probably the K2, although I haven't tried
it on the KAT2 tuner for the K2. However, you don't have to be very far off
of exactly 1/2 wavelength for the tuner to find a match. 

Normally, I use a link-coupled tuner when feeding such antennas.

As you probably know, the closer you can get the antenna to exactly 1/2
wavelength at the operating frequency, the lower the ground return losses.
Indeed, at 1/2 wavelength long it doesn't really need a ground except that
without an RF ground the rig will tend to "float" up to the high impedance
so you will have "rf on the rig". For that reason, it's a very good idea to
plan on some sort of ground: 1/4 wave counterpoise, etc. The antenna is
efficient without it, but the ground will help hold down the RF voltage on
the rig. 

The KX1 tuner has the most limited range of all the Elecraft tuners to date.
That's because of the very small space available for coil/capacitor
combinations on the tiny board inside the KX1 case. 

Ron AC7AC


-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Dave Andrus
Sent: Wednesday, February 20, 2008 10:36 PM
To: Elecraft at mailman.qth.net
Subject: [Elecraft] K1, KX1, K2 antenna tuner high-impedance feed
capabilites


I'm interested in using portable end-fed halfwave antennas when I'm  
out camping.  I have a Norcal BLT tuner that is a absorptive Z-match  
type, suitable for this type of high-impedance tuning and loading.

I'm finishing my build of a K2 right now, just about to add an  
internal tuner to it, and I also plan to build a KX1 in the near  
future (and who knows, maybe a K1 as well?).  I'm wondering whether I  
should add the tuner in, or just carry my BLT around with me?

Since many of you are QRP buffs, and have possibly had occasion to use  
this type of antenna (and maybe even the BLT) in portable locations,  
could you tell me if the internal tuners in these rigs are capable of  
feeding this type of antenna successfully?  I don't just mean to ask  
whether an L-match or T-match type of tuner will handle a high  
impedance load, but also whether the best power transfer is happening,  
such as what the BLT will do?

Thanks in advance,

Dave K7DAA

http://www.k7daa.com

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