[TowerTalk] 402CD

[Mark Pride via TowerTalk]

As I recall, if the SWR dips (2 or 3:1?) around 7.8 MHz, then one of the DE traps (coils) is out of the circuit and the problem lies in the screw terminal on the coil (become open circuit).
Definitely not related to height above ground. Regards,
Mark, K1RX



 
 
 

    





      From: "john at kk9a.com" <john at kk9a.com>
 To: towertalk at contesting.com 
 Sent: Friday, December 5, 2014 3:33 PM
 Subject: Re: [TowerTalk] 402CD
   
I am not sure how low the antenna is, but moving from 30' high to 70'
should not make any significant SWR change.

John KK9A


To:    towertalk at contesting.com
Subject:    Re: [TowerTalk] 402CD
From:    Roger Cooke G3LDI <roger at g3ldi.co.uk>
Reply-to:    roger at g3ldi.co.uk
Date:    Tue, 02 Dec 2014 20:20:00 +0000

Hi.

Many thanks to all who replied. I have kept all the emails and it looks
like there are a couple of
possibilities.

1 The loading coils are not making proper connection, some corrosion may
have crept under the insulating sleeving covering them. This seems a
common fault so I will be having a look at those.

2 A couple of you suggested that it could be too low. I have it installed
on a 70ft crank-up tower which I have to finish roping as yet in order to
crank it up. I'm not sure if this would have accounted for the 3:1 SWR,
which seems very high to me. My linear would baulk at that!!

I did clean the beam thoroughly before putting it up and I used aluminium
graphite anti-seize compound on the elements when assembling it. I used a
1:1 toroidal balun at the feed point and
I used Westflex 50 ohm low-loss coax.

Thanks again to all who replied and I will follow up on all the
suggestions. Hopefully they will work out! I shall crank the tower up to
70ft before testing again. Even that is low for 40m I do realise! I am
just too much of a coward to stack it above my 4-el steppir which is on my
120ft
tower. I guess it might be an idea to swap them around!!!!

73 de Roger, G3LDI


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