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TH7DX / 402-cd Info

To: <>
Subject: TH7DX / 402-cd Info
From: (Rod Fitz-Randolph)
Date: Mon, 30 Dec 1996 09:20:31 -0600
>Hello all I wonder if anyone can help with a little info.
>I have a TH7DX at 75 feet with a 402-CD mounted about 12ft above. Both
>booms are in the same plane.
>1. The 15m swr curve seems to mimic the plot for normal settings shown in
>the manual but I have assembled it to the DX setting ( in fact the only
>setting given in the manual) can someone confirm the DX dimensions RDE-2
>=838mm   FDE-2 = 1067mm

Jan, I was compelled (because of the similarity of our setups)
to answer you with the following information.  I, too, have a
TH7DX (at 132') and a 402-CD (at 140').  I had set both the
TH7DX and the 402-CD for the fone portion of the band.  Because
of your SWR readings and query, I measured my 15 meter SWR
(on the meter of the TS-940S - I've found it is verified by
the Drake W-4 SWR meter - with the following results:

21.000  1.3:1
21.050  1.25:1
21.100  1.2:1
21.150  1.28:1
21.200  1.3:1
21.250  1.25:1
21.300  1.2:1
21.350  1.1:1
21.400  1.05:1
21.450  1.05:1

This is being fed with 7/8" Hardline (200') and with 9913 for
the remaining 200' from the Hamshack to the antenna.

The original installation used 225' of 3/4"  CATV 70 ohm (a half
wave on 160 and multiples of half waves on 80 through 10) so that
it would provide 50 ohms impedance matching when fed with 50 ohm
coax.  This was supposed to have worked but it did not.  My
SWR was skewed and not what the charts indicated it should be.
When I replaced the 50/70 ohm combination feedline with 50 ohm
only feedline, my SWR improved considerably.  There may have
been an impedance anomaly in the CATV coax... not sure what
caused the problem.

Don't know if this helps, Jan, but it is a set of data for you
to compare yours to.  Good luck with your project.  73 es Best DX.

Roderick M. Fitz-Randolph
79 Highland Hills Cove,
Jackson, TN  38305
(901) 661-9278 (Phone - after 10 AM and prior to 9 PM)
(901) 664-7539 (FAX - any time of day or night)

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