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Re: [TowerTalk] Screwdriver driver antenna

To:, Michael Dinkelman <>
Subject: Re: [TowerTalk] Screwdriver driver antenna
From: Jim Lux <>
Reply-to: Jim Lux <>
Date: Wed, 20 Aug 2008 17:39:41 -0700 (GMT-07:00)
List-post: <">>
When I had a screwdriver antenna on my car, I found that having a cross needle 
meter inline made life MUCH easier.  Makes it much easier to tune up, because 
it's obvious when the rig is folding back, and you can just keep the motor 
moving until it stops folding back.

(Obviously, I trust the rig's foldback protection to limit the voltage/current 
in the final amp)

On the other hand, my rig (an FT-757GX at the time) didn't have an internal 
tuner.  I'm not sure how it would work.. I can see the autotuner would keep 
trying to readjust as the screwdriver comes closer to resonance.  Now.. if you 
had a "go to point A for Band X" sort of controller to get the screwdriver 
"close" and just use the tuner to basically do the fine adjust, then that would 
work ok.

I actually tried that, using a AT-100.... it was actually fairly decent, 
because I could "band switch" the screwdriver by eye (it was mounted on the 
front bumper, and I had tape at the positions for the various bands), and then 
let the tuner autotune when I keyed up. All without having to take your eyes 
off the road, etc.

However, I eventually went to a multiband whip and a SGC tuner at the base.  If 
I could only find the time to put together a bandswitch/remote control 
interface from the I-bus to the radio, so I can use the buttons on the steering 
wheel to control the radio.  Either that, or voice recognition (which I think 
would be a better long term solution... "radio, 20 meters, preset 1"  "radio, 
volume up", "radio, one four dot one five zero"  Works in any car, etc.

Same thing for a phased array or rotator on a tower: "antenna, europe"  (or, if 
you have W6AM's farm.. "antenna, South London", <grin>)

-----Original Message-----
>From: Rick Karlquist <>
>Sent: Aug 20, 2008 3:58 PM
>If the rig has a tuner, the internal SWR meter reads the
>SWR on the transmitter side of the tuner, which is different
>than what the in-line meter on the antenna side would read.
>In any event, leaving a meter in-line should have no effect.
>Maybe they don't want you to know the true SWR of their
>Michael Dinkelman wrote:
>> OK - this is only LOOSELY associated with antennas but I'm
>> asking for a friend.
>> Friend has a screwdriver type antenna.
>> Instructions say not to leave a SWR meter in-line between the
>> rig and the antenna and to use the rig's built-in SWR
>> meter when tuning antenna. The rig doesn't have a built-in SWR
>> meter and he can't get a hold of their "technical" support to
>> ask why. I maintain that it isn't an issue, he can leave the
>> SWR meter in-line.
>> I figure they just don't want to bother with explaining the
>> complexities of using an external meter (OMG! - FORWARD SET)
>> and how the power fold back circuits may necessitate him to
>> incrementally reset the meter as he tunes the coil.

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