[TowerTalk] Trimming F12 240/340N elements

[James C. Hall, MD]

Hi Dennis:

 

Ouch - this is not so easy, but if it has to be done . This of course will
shift the frequency even higher. There is pretty significant droop on the
ends so I can see that higher is better . but heavier !

 

73, Jamie

WB4YDL

 

  _____  

From: Dennis Vernacchia [mailto:n6ki73 at gmail.com] 
Sent: Monday, October 19, 2009 5:18 PM
To: James C. Hall, MD
Subject: Re: [TowerTalk] Trimming F12 240/340N elements

 

Janie,

For my experience with 40 mtr yagis by F12 ( 2 El EF240 ) - I had t get teh
antenna up
to almost 50 ft before the SWR stopped changing, I don't think 20 ft is high
enuf

73, Dennis N6KI

On Mon, Oct 19, 2009 at 2:53 PM, James C. Hall, MD <heartd0c at nwtcc.com>
wrote:

Hello TT:



Does anyone here have experience with trimming the element lengths of the
driver and/or director of the F12 240/340N ? I have the 3 element version
and each element starts out the same length as the reflector with tips of
38.5". With coax and balun attached, I am to raise each element as a dipole
and trim the driver and director to the correct frequency. I first started
with the reflector to verify that the frequency of 6.90 MHz was correct.
After mounting on a push up mast and raising to a height of 20 feet or so,
my meter indicates a dip in SWR at 7.017 MHz - 117 kHz higher than
expected..
It would seem that the reflector is about 6" too short on each end.



The instruction manual states that the element will shift upward in
frequency about 15 kHz between 15' and 30'. Below this height there is too
much ground coupling. I see the indicated 6.90 MHz at only 7' above ground.



Again does anyone have information on this process ?



73, Jamie

WB4YDL





E-mail message checked by Spyware Doctor (6.1.0.447)
Database version: 6.13510
http://www.pctools.com/en/spyware-doctor-antivirus/
_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk at contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk






E-mail message checked by Spyware Doctor (6.1.0.447)
Database version: 6.13510
http://www.pctools.com/spyware-doctor-antivirus/
<http://www.pctools.com/en/spyware-doctor-antivirus/> 





E-mail message checked by Spyware Doctor (6.1.0.447)
Database version: 6.13510
http://www.pctools.com/en/spyware-doctor-antivirus/