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: Coupling Problem - Mosley Pro 57B  (Read 1087 times)
N0GRM
Member

Posts: 24


WWW

Ignore
« on: February 19, 2013, 04:51:06 AM »

I"m using a Mosley Pro-57B up about 45 feet on top of a hill.  I have a high SWR on the 17m and the 10m band.  The manual states: "A coupling problem would be indicated when only one or two bands are unusual and the remainder are within specifications"  This is with respect to the antenna's SWR.  Here's the mid-range swr for all the bands:

20m 1.2:1
17m    4:1
15m  1.1:1
12m  1.4:1
10m     3:1

I'm having difficulty understanding what they mean by "coupling problem" - I'm looking for advice as to where to start solving the problem.  Winter will be done (Minnesota) in a few months hi hi - and I can get back on the tower. 


More infor - bit of a rag-chew...
I purchased the antenna, used, last fall - spent a month refurbishing it (cleaning the aluminum connections, traps, etc) prior to putting it up.  I measured the high SWR at that time, but decided to wait until spring before climbing the tower again.  It snowed the following week - last Thanksgiving.

Thanks in advance for your suggestions or ideas.

73 - Peter N0GRM
Logged
AD4U
Member

Posts: 2177




Ignore
« Reply #1 on: February 19, 2013, 05:28:37 AM »

No offense intended but have you called Mosley?  I recently bought a used Mosley Classic 33 tri-band yagi that was in pieces and without the manual.  When I called Mosley they were very helpful and answered all my questions.

Dick  AD4U
Logged
WB3BEL
Member

Posts: 90




Ignore
« Reply #2 on: February 19, 2013, 06:52:38 AM »

What they mean by coupling problem is that the antenna may be too near other conducting objects.

Perhaps it's too close to another antenna.  Or you have some resonant guy wires.  Or its too close to a metal roof.  Etc.

This may or may not be your problem.  Maybe something is installed wrong or is broken on the antenna ?
Logged
W5WSS
Member

Posts: 1772




Ignore
« Reply #3 on: February 19, 2013, 07:15:58 AM »

The coupling problem relative to the excited by RF interaction between the elements causing out of balance mismatch and or nearby conductors.
 Before proceeding any further Check for this first: For the purpose of determining whether or not there is proper DE coupling of the antenna while resting atop the tower in it's intended final operating position from nearby things such as other antennas power lines electrical systems within your home etc. Do a legal on air continuous carrier SWR test while rotating the antenna The SWR reading should remain unchanged if it changes then the antenna is coupling and presenting.

There is an anecdotal process. If you are sure the antenna is assembled correctly and feed line connectors are corrosion free and dry and feed line routing locates it and is working devoid of re radiation system balance is preserved Then:

Unfortunately you must either DE couple the antenna or re tune the antenna. One suggestion when re tuning the antenna  If you must do this on or near the ground it will be more accurate to point the director towards the zenith while the reflector is pointing towards the Earth surface this is not 100% but can serve as an indicator of coupling to not coupling markers provided the antenna is relocated out in the middle of your property as far away from things as possible.

I hope the problem is something simple.
73
Logged
K3VAT
Member

Posts: 755




Ignore
« Reply #4 on: February 19, 2013, 04:33:27 PM »

... Or you have some resonant guy wires.  Or its too close to a metal roof.  Etc. ...

This would be my guess, provided that you're using conductive guys on the tower.  Are you?  Are they broken up into segments that allow for no coupling to the 17M and/or the 10M band?

73, Rich, K3VAT
Logged
N0GRM
Member

Posts: 24


WWW

Ignore
« Reply #5 on: February 20, 2013, 07:45:49 PM »

Thanks for all the advice - I've tried the suggestions and have been working with the engineers at Mosley.  At this point it looks like at least one of the traps on the 17m driven element may be suspect.  Being it was -6F this morning, I will be holding off on any climbing for awhile. 

73 all
Peter
Logged
W4RS
Member

Posts: 66




Ignore
« Reply #6 on: February 22, 2013, 11:06:27 AM »

having 2 67b's i think its your trap. greg or his son will be able to pinpoint  whitch trap is bad. they are great antenna's
jim w4rs
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!