[Elecraft] ATU vs. External Tuner

[Sandy]

I have a situation that is similar!  I have a 40 meter dipole in the attic 
of a single story ranch type home.  Diope elevation about 12 feet, with ends 
bent at 90 degrees to make it fit in attic.  It is fed with 75 ohm twin 
lead.

I am using it as a dipole on 40/30/20 meters OK with a K1 and a T1 external 
tuner.  Results pretty good considering on those bands.  I have also used it 
on 80 and 160 meters by shorting the feeder and connecting to the  "hot" 
(center conductor on BNC jack) and a counterpoise to the ground connection 
on the T1.  Results were usable on 80 meters and 160 even though it is a 
"stretch" on 160! Could fairly constantly work a station 200-250 miles 
distant with weak signals on that band.

I haven't a lot of "radio time" available these days as my XYL had a stroke 
last year and duties around the house keep me busy and away from getting on 
the air.

I do have an "HF Packer" amplifier I built a few years ago, and it gives me 
around 25-35 watts on all bands with around 2 watts drive from the K1. 
Eventually I plan on getting an "Inverted L" antenna up on that side of the 
house in the trees and working it against a counterpoise and ground rod.

73,

Sandy W5TVW

----- Original Message ----- 
From: "John Buck" <kh7t at arrl.net>
To: "Frank MacDonell" <kd8fip at gmail.com>
Cc: "Elecraft" <elecraft at mailman.qth.net>
Sent: Sunday, October 26, 2008 4:19 PM
Subject: Re: [Elecraft] ATU vs. External Tuner


> Frank,
>
> Since the dipole is in the attic, you are probably not getting perfect
> swr without a tuner.  The antenna is a compromise unless you have a very
> large attic with little metal near by.  If you have trimmed it for
> resonance at 40 meters I assume it is quite a bit shorter than a
> standard dipole due the proximity of the roof and wood work.
>
> If the dipole is actually resonant at 40 meters then it will work poorly
> on 20 meters even if you can match it at the radio with some combination
> of feedline and tuner.  Please note that a perfect dipole up high in the
> clear will not be 1 to 1 swr at resonance but will be 70 to 90 ohms.  Do
> not fall into the trap of trying to obtain a perfect match on every band.
>
> I would try a non resonant length (g5rv style) fed with coax.  It will
> be more effective on multiple bands and the SWR will not be too high to
> tune as it is on the second harmonic with a resonant dipole.  The
> antenna center impedance of the g5rv lengths (102' or 88' if in the
> clear) avoids extreme high impedances on several of the HF bands.   The
> coax losses should be be acceptable on most bands.  I would certainly
> try that with the K3 tuner   If you have carefully trimmed the 40 meter
> for resonance in place in the attic, try adding about 25% length and if
> necessary folding the ends to fit.  There is nothing wrong with trying
> fan dipoles if you have the space and can trim appropriately.
>
> I am sure others will correct my ball park numbers.  I also would not
> get carried away about the perfect feedline length for feeding a g5rv.
> The best feed line is the shortest one that goes from the antenna to the
> tuner.
>
> That said, if the coax line is very long, then a remote tuner is nice.
> The K3 tuner is excellent.  I would use it .  If you fall into a good
> automatic remote tuner use that.
> But consider the fact that resonant antennas to not necessarily radiate
> better than properly tuned non resonant lengths.
>
> John KH7T
>
> Frank MacDonell wrote:
>> I have a k3 with internal antenna tuner connected to a 40 meter dipole
>> in the attic. Will the internal ATU work for me visiting other bands
>> or would I be better off installing a tuner between the rig and the
>> antenna? Is an auto tuner more preferred than automatic? Thanks to all
>> for your time.
>>
>>
>
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