Ken Bessler wrote:


Now (finally!) to my questions:

1) How good are radio shack chokes?
2) I was only able to get 4 turns around the feedline's choke
- is that enough?
3) Am I just messing too much around trying to get a 40m
dipole to tune on 10m?
4) Would I do better to add a balun and run the 450 ohm
ladder line direct to the tuner?

--
73's es gd dx de Ken KG=D8WX
Grid EM17ip, Flying Pigs #1055,
List Owner, Yahoo! E-groups:
VX-2R & FT-857

Hi Ken, I have had that problem with Auto tuners myself, and could not
get a satisfactory solution. The Vendors solution is Ferrite on the
coax, and make sure you have a good RF ground at the tuner.
The problem is almost certainly RF feedback getting into the tuner.
Since you have elimated current on the shield of the coax by the Radio
Shack cores (they should work, don't know of any recent studies of
these cores on 10m) that is not the problem.
The problem may be RF potential at the tuner by direct radiation. To
eliminate this you need a very good RF ground directly at the tuner.
For 10M this is a very short connection to a good earth ground. A 20'
long ground connection is not the answer.
You might try hooking a fan 10m dipole in parallel with the 40m
dipole. This would provide a better match for the Auto Tuner. If the
problem is still there, then it is direct radiation. Better RF ground,
or reduce power.
Gary N4AST

wrote in message
ups.com...

Hi Ken, I have had that problem with Auto tuners myself, and could not
get a satisfactory solution. The Vendors solution is Ferrite on the
coax, and make sure you have a good RF ground at the tuner.
The problem is almost certainly RF feedback getting into the tuner.
Since you have elimated current on the shield of the coax by the Radio
Shack cores (they should work, don't know of any recent studies of
these cores on 10m) that is not the problem.
The problem may be RF potential at the tuner by direct radiation. To
eliminate this you need a very good RF ground directly at the tuner.
For 10M this is a very short connection to a good earth ground. A 20'
long ground connection is not the answer.
You might try hooking a fan 10m dipole in parallel with the 40m
dipole. This would provide a better match for the Auto Tuner. If the
problem is still there, then it is direct radiation. Better RF ground,
or reduce power.
Gary N4AST

================================================== =========
Thanks, Gary.

I messed around with different chokes on different positions
until I had eliminated 90% of the problem. One of the biggest
helps was putting both a snap on square choke *and* a coaxial
choke right at the back of the rig where the HF coax attaches.

I used 2 standards - I had my son listen on the computer with
headphones and rate the FM buzz from 1 to 100. We started
at 75 and ended up at 2. I also switched from 20m to 10m and
kept track on what power level would cause problems on trying
to tune 10m. I started with 65 watts and ended with 95 watts.

I have a Cuscraft R7000 that KB0OMQ gave (!!) me - when
I get that up, I imagine my problems will be solved, at least as
far as trying to get my 40m antenna to load on 10m

--
73's es gd dx de Ken KGØWX
Grid EM17ip, Flying Pigs #1055,
List Owner, Yahoo! E-groups:
VX-2R & FT-857

Ken and Gary;

Coax fed auto tuners have a range of about 3:1 SWR. This means that for
a 50 ohm feed the greatest antenna input that it can match is 150 ohms.
If you want to feed any type of antenna with a generally unknown input
impedance you need to use open wire feed line. Using this feed line you
can auto match a wider range of miss match 10 or 15 to 1. For matching
absolutely any impedance use a manual tuner.

Dave WD9BDZ


Ken Bessler wrote:

wrote in message
ups.com...

Hi Ken, I have had that problem with Auto tuners myself, and could not
get a satisfactory solution. The Vendors solution is Ferrite on the
coax, and make sure you have a good RF ground at the tuner.
The problem is almost certainly RF feedback getting into the tuner.
Since you have elimated current on the shield of the coax by the Radio
Shack cores (they should work, don't know of any recent studies of
these cores on 10m) that is not the problem.
The problem may be RF potential at the tuner by direct radiation. To
eliminate this you need a very good RF ground directly at the tuner.
For 10M this is a very short connection to a good earth ground. A 20'
long ground connection is not the answer.
You might try hooking a fan 10m dipole in parallel with the 40m
dipole. This would provide a better match for the Auto Tuner. If the
problem is still there, then it is direct radiation. Better RF ground,
or reduce power.
Gary N4AST

================================================== =========
Thanks, Gary.

I messed around with different chokes on different positions
until I had eliminated 90% of the problem. One of the biggest
helps was putting both a snap on square choke *and* a coaxial
choke right at the back of the rig where the HF coax attaches.

I used 2 standards - I had my son listen on the computer with
headphones and rate the FM buzz from 1 to 100. We started
at 75 and ended up at 2. I also switched from 20m to 10m and
kept track on what power level would cause problems on trying
to tune 10m. I started with 65 watts and ended with 95 watts.

I have a Cuscraft R7000 that KB0OMQ gave (!!) me - when
I get that up, I imagine my problems will be solved, at least as
far as trying to get my 40m antenna to load on 10m

David G. Nagel wrote:
Ken and Gary;

Coax fed auto tuners have a range of about 3:1 SWR. This means that
for
a 50 ohm feed the greatest antenna input that it can match is 150
ohms.

That's roughly true for the usual (lousy) ATUs sold by the likes of
Yaesu as rig accessories. It is most definitely not true in the cases
of most of the third-party "coax-fed" autotuners. My LDG AT-11MP easily
matches the high VSWRs presented by my G5RV on all the HF ham bands
with the exception of 30M. I forget which band it is but the feedpoint
impedance at the shack end of the coax falls outside the ability of my
MFJ antenna analyzer to measure it which means that the AT-11MP is
successfully dealing with a VSWR in excess of 12:1. The servo-tuned ATU
in my old TS-940SAT is almost as good as the LDG autotuner in this
respect.

If you want to feed any type of antenna with a generally unknown
input
impedance you need to use open wire feed line. Using this feed line
you
can auto match a wider range of miss match 10 or 15 to 1. For
matching
absolutely any impedance use a manual tuner.

Dave WD9BDZ

w3rv