Topband: 160m Inverted L High SWR

Charlie Cunningham charlie-cunningham at nc.rr.com
Thu Oct 3 18:28:31 EDT 2013


Hi, Bill

In your first post, you indicated that min VSWR was 2.9:1 at 1833 KHz, indicating that the system was resonant exactly where  you wanted I to be.

Could I respectfully suggest that at 1.8 MHz, even with a really long coaxial feed-line, the excess loss with a 2.9:1 VSWR over a "flat"  (!:1 VSWR) line is really not much at all? The fact that your transceiver is throttling back due to the 2.9:1 VSWR could be easily dealt with by using a tuner between the transceiver  and the feed-line, rather than doing all that work at the antenna.  Not much of a problem at all if you are only running a couple hundred watts. A lot less work and frustration! And the excess loss would be relatively insignificant at 160m.

73,
Charlie, K4OTV

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Bill Stewart
Sent: Thursday, October 03, 2013 3:48 PM
To: topband
Subject: Re: Topband: 160m Inverted L High SWR


To all who responded...many thanks. 
I am now in the process of reading over all the suggestions, which were plentiful. 
  
So far I have tried folding back (shortening) the C-P wires by 2 ft....no change, but I'm gonna make a more drastic change and see what that does. I changed the coax run also, with no change. SWR still just shy of 3:1. I will move on to some of the other suggestions. 
  
Question 1: there was mention of tuning the C-P wires. Does that mean to trim them to the desired operating freq (swr min)...leaving the vert as is? 
Would the method be to apply rf between one wire (all others unhooked) and the vert and adj the C-P wire for the desired freq. 
  
Question 2: there was also mention of using a choke at the feed point. 
Recommendations were 30T of 9913 on 8" dia & 30T of RG8 on 6" dia. 
I'm using RG8X so I guess abt the same T/dia would work..doesn't seem too critical.  
  
I can only extend the horiz. section abt ten more feet before the end gets into the support tree so will probably have to leave it around 130' long. 
I will only be running a max of 200w so no hi-pwr coax or other HV devices should be needed. 
  
Again, thanks for all the helpful comments...now out to the back yard..again. 
73 de Bill K4JYS
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Topband Reflector



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