Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Wire antenna trimming.  (Read 1512 times)
K6ELQ
Member

Posts: 24




Ignore
« on: May 23, 2013, 05:24:19 PM »

I am now in the process of tuning a half-sloper antenna for 30m. I trimmed the length by folding back the insulated antenna wire back on itself. When I was satisfied on the length I cut off the excess. Now the wire is a bit too short. Apparently the two trimming methods are not exactly the same. Does anybody know of any rule of thumb that would allow me to compensate for the slight difference?

73 de K6ELQ Tony   
Logged
N4JTE
Member

Posts: 1155




Ignore
« Reply #1 on: May 23, 2013, 05:39:14 PM »

Folding back insulated wire will not get the job done will act as a slight capacitance, just add a little wire to each end.
Bob
Logged
K6ELQ
Member

Posts: 24




Ignore
« Reply #2 on: May 23, 2013, 09:22:40 PM »

That was my guess too Bob. That would probably mean there is no simple way to compensate since the capacitance would depend on the length of the fold-back. In my case I cut the antenna long by about two feet and that was the length of my fold-back. When I cut off that two feet of fold-back I was then resonant at a higher frequency. I crimped a splice to add back some length as a temporary fix.

73 de L6ELQ Tony
Logged
K2DC
Member

Posts: 1351


WWW

Ignore
« Reply #3 on: May 24, 2013, 04:35:24 AM »

Tony,

   Here's a trick for wire antenna trimming that's always worked well for me.  Start with a length that is 1 or 2% long for the band of interest, and leave a wire pigtail a couple of feet  hanging down from the end insulator(s).  You can trim off of the pigtail in steps until you get it centered where you want it.  When you're done, just leave what's left of the pigtails in place - they won't hurt a thing.  In fact if it's brand new wire, it may tend to stretch over time lowering the best matched frequency.  You can go back and retrim as necessary.

73,

Don, K2DC
Logged
K6ELQ
Member

Posts: 24




Ignore
« Reply #4 on: May 24, 2013, 09:12:39 AM »

Useful hint Don. Prior to using my fold-back technique I had been looping the wire around the end insulator, tying it off, measure SWR, untying, cutting off a piece, retying, measure SWR, etc. This has been a real pain since I have to climb up about 30 feet on the tower to get to the end of the sloper (after the bottom support end is released) each time to make the adjustment. I'll try your method later today or tomorrow on the new wire. I'll still have to climb the tower but far less to do once I get to the end of the sloper; one snip.

73 de K6ELQ Tony
Logged
K6ELQ
Member

Posts: 24




Ignore
« Reply #5 on: June 01, 2013, 12:49:20 PM »

Don,

Worked like a charm! I didn't end up with much of a pigtail, only about an inch, so it was an easy matter to secure it in the normal fashion around the end insulator. Antenna tuned nicely but NOISY! On to plan C (B was an epic fail  Angry).

73 de K6ELQ Tony
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!