The antennas are fine and normal for those bands. Well maybe not quite
normal as they are fan dipoles, but you are simply talking about remote
tuning the antenna. Close to what a remote tuner would do. You can
also just switch in series coils to essentially lengthen the antenna.
It's just not continuous like the compressible coil. But both methods
are essentially changing the ant frequency IOW, retuning.
73
Roger (K8RI)
On 12/14/2016 9:40 AM, Jim Thomson wrote:
Date: Wed, 14 Dec 2016 02:59:16 -0500
From: "Roger (K8RI)" <k8ri@rogerhalstead.com>
To: amps@contesting.com
Subject: Re: [Amps] Yes SS needs ant tuner.
On 160, 74, and even 40 those built in tuners are incapable of wide
frequency changes. I have 4 SS rigs. One is 200W while the others are
all 100W out. None can cover all of those three bands unaided. The big
Palstar tuners take care of the tuning with the aid of an AIM.
73
Roger (K8RI)
## and just how far outa whack are your ants for 160 /80 / 40m ?
Feed the SS xcvrs into the amp, then let the amp worry about the swr,
which may well not work out....so u end up with having to manually tweak
an external tuner in the shack.
## id try an fix the ants using whatever method will work. Seco systems
even makes a tornado drive, that only compress / expands one tubing coil.
That would work good for vert ants. Then with the 10 x pre-sets, you
could quickly cover the entire band on either 160 or 80..or even 40m.
Bring up the closest pre-set, then manually tune the compressible coil
from there, with its up /down function. It uses the Ameritron
SDC-102 screwdriver control box. 12 vdc motor inside the
seco tornado drive compresses the coil or expands it.
## But they are not like a roller coil...which will go down to 0 uh.
The compressible coils will provide for a 2:1 ratio for max to min uh.
IE: 12-6 uh...or 8-4uh... or 20-10 uh etc. You wont blow up
plastic coated .25 inch OD cu tubing any time soon. The digital
turns counter on the SDC-102 works superb.
## thats one option. Vac relays and coils at the feedpoint is another option.
Another option is a motor driven vac cap, we did that on a buddys 160m
vert. Which consisted of a T type top loading on a 100 ft tall wire..with
elevated
grnd plane. Flat swr across the entire 160m band.
## On any of these schemes, no tuner required in the shack, swr is always flat
across 160 /80 /40m..... so the tube or SS amp or SS xcvr is always happy..
and ditto with coax and coax connectors.
## then swr BW becomes a non issue.
Jim VE7RF
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