[Elecraft] T1 Remote Tuning and Power Supply

[Vic K2VCO]

I did an experiment in which I connected an open-wire-fed 88 foot dipole to my K3 through 
a large balun. The KAT3 matched it perfectly on all bands, but I wondered about the 
efficiency of this system compared to a balanced tuner like my old Johnson Matchbox.

So I measured the temperature rise of the balun after transmitting for a minute and 
recorded it. It was several degrees. Then I added a pair of capacitors in series with the 
feeders to tune out the reactance (it happened to be inductive on the band that I was 
testing) and re-ran the experiment (after waiting several hours for the balun to return to 
room temperature). The temperature rise was much less, almost unmeasurable!

I think this showed that the "tuner-to-balun" system can be inefficient under some 
conditions. I went back to the Matchbox, even though I had to give up the automatic tuning 
provided by the KAT3.

On 3/11/2011 12:22 AM, David Cutter wrote:
> Jim
>
> I like the idea of a battery operated remote tuner and a simple relay
> change-over to provide a top-loaded vertical.  I'm often bothered by
> connecting the antenna feeder into a 1:1 balun and then to the tuner.  I've
> read that the very large impedance mis-match can lead to large losses in the
> balun on some frequencies, though you might not *feel* it with low power.
> With a self-powered little tuner, it would be easy to raise it off the
> ground a little and connect the ladder line feeder directly to the tuner;
> then coil some thin coax through a ferrite toroid to make a choke (see Jim
> Brown's excellent articles - K9YC) for connection to your RG213.  This
> should also result in less noise pick up on receive.  Some folks add a
> further choke at the shack end to further reduce received noise.
>
> David
> G3UNA
>
>
>> I've been running my T1 remote out under my 88ft dipole which is just
>> short
>> of 50ft in the air at the midpoint. The ends are a bit higher. The T1 is
>> down at the ground under a plastic container and connected to the
>> windowline
>> via a Elecraft 1:1 balun. I remote control it via the circuit on my
>> website
>> www.jtmiller.com . I find it gets a 1:1 match on 80-6 meters. It is
>> connected to my K3 about 60ft away via RG213.
>>
>> Obviously the pattern is a bit of a daisy above 20M and is mostly a cloud
>> warmer at 80M and below. But that's just what this length dipole does
>> independent of match.
>>
>> I've lately been using the windowline as a vertical with the 88ft as a
>> capacity hat on 80-160 and found it works quite well. The T1 is very happy
>> matching that on 80M and gets to about 2:1 on 160. I use my K3 internal
>> tuner to remove the remaining mismatch on 160 to ensure proper power meter
>> readings. The loss due to this level of SWR on 160 with RG213 is
>> meaningless.
>>
>> When used in this vertical configuration the two ends of the windowline
>> are
>> tied together to one terminal of the tuner and the other side connects to
>> 8
>> 60ft buried radials.
>>
>> 73
>>
>> Jim ab3cv
>
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-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/