Hee!
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Carl
Braun
Sent: Saturday, February 15, 2014 3:53 PM
To: Tom W8JI; '160'
Subject: Re: Topband: Still in search of resonance
Tom
After reading your post yesterday I had a dream that I woke up and saw one
of those flying monkeys on top of my tower laughing and sawing away.
Carl AG6X
-----Original Message-----
From: Tom W8JI [mailto:w8ji@w8ji.com]
Sent: Friday, February 14, 2014 6:02 PM
To: Carl Braun; '160'
Subject: Re: Topband: Still in search of resonance
Hi Carl,
It sounds like you are trying to find 50 ohms on the tower without any
series capacitor by looking at R and X. I would not try to do that. The
reactance puts you out of range on the MFJ bridge. You are down to a few
bits difference between data points the PIC needs in the MFJ.
Look at this below. You said:
<<<<seen at the other levels too as long as I brought the R down with a
variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms
on the MFJ) I was able to put the big variable inline to bring the reading
to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr
on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with
just the 1000D. BUT...again...I'm bringing the R down with the
capacitor...not finding 50 ohms anywhere on the tower>>>>
Stop trying to find 50 ohms without the capacitor!!!!!
Right now at 46 ft you were at 24 ohms with the capacitor. That should tell
you and everyone on this reflector :-) that you are tapped too low now!
Let's look at this in simple terms. Here is what you said:
<<<<<When I had the gamma arm mounted at the 90' level. I was able to put my
baby variable 160pf inline to bring the 425 ohm impedance down to about 60
ohms and the antenna heard very well; especially on the 1700 KHz broadcast
band, with a 2.4:1 Vswr. Similar results could be seen at the other levels
too as long as I brought the R down with a variable cap. >>>>>
That is NORMAL. You will always need the capacitor. Always. The only way to
eliminate the capacitor is to saw your Yagi antenna off the tower so the
tower moves above 2 MHz. Then you will probably find a 50j0 tap without any
capacitor.
You also might use a large skirt, but why??????
Just use a capacitor!!!
If you are trying to eliminate the capacitor, you will have a lot of work to
do.
73 Tom
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