LinkBack Thread Tools Search this Thread Display Modes
Prev Previous Post   Next Post Next
  #1   Report Post  
Old April 4th 06, 11:08 PM posted to rec.radio.amateur.antenna
AK
 
Posts: n/a
Default Antenna RF choke questions

Putting together a new Cushcraft A4S (10,15, 20m) beam.

Cushcraft recommends using an 8-turn, 6-inch diameter RG8U coax cable coil
as an RF choke for feeding the driven element. HyGain suggested the same
thing for the TH2MK3 antenna I used many years ago -- only using 12 turns of
RG8 (with the 6-inch outside diameter), rather than 8 turns. I have a few
questions on the best way to do this.

1) Is it fair to assume that the more turns the better?

2) Should the coil be as close to the antenna feedpoint as possible, or is a
foot or two of straight coax between the antenna input and the coil OK?

3) Would placing the coax coil around the mast (instead of taping one side
of the coil to the mast as suggested) be a bad thing to do?

4) Is there a good website or book that describes the technical tradeoffs of
a coax RF choke? ( I am sort of wondering if the choke can be skipped. Some
time ago, I used a W2AU balun on a multiband dipole. All it did was create
TVI when I went on 10 meters. Took the balun out, and the resonant points
didn't change. I figured that if there were antenna currents on the coax,
they would bring down the resonant frequency without the balun. Since that
didn't happen, I figured the balun wasn't helping - - but balun core
saturation at 30 MHz (with the KW on) was what was racking up the TVs.)

5) One last question - not having to do with the coax RF choke:
Cushcraft "operating tips" say to not use vinyl tape on SO239 or PL-239
connectors. Why? What problem would the tape cause??

Thanks for any info - AK


 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Passive Repeater Bryan Martin Antenna 13 February 10th 06 02:03 PM
The Long and Thin Vertical Loop Antenna. [ The Non-Resonance Vertical with a Difference ] RHF Shortwave 0 December 27th 05 06:03 PM
Questions -?- Considering a 'small' Shortwave Listener's (SWLs) Antenna RHF Shortwave 1 January 24th 05 09:37 PM
Antenna Advice Chris Shortwave 5 September 20th 04 02:04 AM
Outdoor Antenna and lack of intermod Soliloquy Scanner 11 October 11th 03 01:36 AM


All times are GMT +1. The time now is 07:29 PM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 RadioBanter.
The comments are property of their posters.
 

About Us

"It's about Radio"

 

Copyright © 2017