Bob mentioned one point that I would like to emphasize.
160m is a very difficult band to tune on the Model 238 (or similar).
The reason is, the tuning is very sharp and the sweet point is a very tiny
area.
SO MY MESSAGE IS, you may not be tuning carefully enough.
It is really easy to blow right past the sweet spot.
Here's what happened to me:
When I put up my 160m Inv.-L a year ago, its SWR was not bad but not as good
as I would have liked. It ranged from about 1.6:1 to 2.5:1 across between
1.810 and 1.9 MHz.
I got it up and working just a day before the CQWW SSB contest and didn't
have a lot of time to tune the antenna at the feedpoint. Was terrible WX as
well. The Model 238 did NOT find a match. I even tried the extra
capacitor. No luck.
I ran the contest with no ATU, which was no problem because I run my 1000w
amp at 600w and it has a 3-500z (real tube) in the final, not a fire
cracker.
After the contest, and with a lot of time, I decided to try again.
Rather than the antenna analyzer, I used RF, running about 1w out of the
Eagle, driving the linear to about 10w.
After tuning into a dummy load, I applied the antenna through the Model 238
and tried again, but tuning ever so slowly and carefully. I found a sweet
spot where it matched just fine. But it sure was narrow!
For the CQWW I was prepared, knew just where to crank the dials.
My 160m antenna came down is a huge storm a couple months ago and is still
tangled in the tree tops, so I can't check it now. I just peeked at the
back of my 238 and it has the 1000pF cap attached, and I don't recall using
it since then, so it was probably needed for the match.
73
Rick, DJ0IP
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Mike Bryce
Sent: Monday, October 14, 2013 11:53 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Antenna is up, but the coupler doesn't like 160 meters
Jim,
The antenna is a doublet up 50 feet inverted vee style.
It is feed with about 170 ish feet of 600 ohm open line.
None of the couplers can find a tuning solution
All other bands work fine
Sent from my iPad at Aultman hospital.
Mike wb8vge
> On Oct 14, 2013, at 11:09 AM, Jim GM <jim.gmforum@gmail.com> wrote:
>
> Hi Mike, WB8VGE
>
> Hope your surgery goes well for you.
>
> I have gone and still going thru issues with my inverted L on 160M
> like
>
> your having.
>
>
> How long is your antenna? Is it a dipole or Folded dipole? I did not
> see on your post the answers to these questions.
>
>
> How high do you have it?
>
>
> Your going to find or have found that the tuner you have and other
> tuners will not work on 160M. They just cannot handle a near 50 ohm
> match or less no matter what they claim. All they want is your money.
>
> So you need to add additional matching out side the shack with coils
> and homemade capacitors made from coax cable, thats if you have a
> limited junk box like I do.
>
> Any ways the external matching will aid your tuner in the shack to
> take care of the rest.
>
> It will take some time and it is not a quick fix.
>
>
> --
> Jim K9TF
> _______________________________________________
>
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|