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Author Topic: SWR shift after upgrading coax - what gives?  (Read 10422 times)
KM3F
Member

Posts: 788




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« Reply #30 on: March 10, 2010, 12:38:21 PM »

Absolutely agree with Eric.
As stated in my last reply above, measure all parts of the system for performance and after connection to the antenna, you can see where an issue is without question.
My M2 12 element beam is flat at the end of nearly 200 feet of feedline consisting of short LMR 600 to 7/8" hardline back to a short LMR 600 to a coax relay to LMR 400 flex around the rotator to the beam. The other antenna is a 6m beam. All hardware is N type connections.
Using a tuner is a copout and does not address the losses in the system you alrady have plus the tuner adds some insertion loss on top of it all.
If you want less then the best for the effort then we failed to get you to understand!
Good luck.
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KB1GMX
Member

Posts: 1482




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« Reply #31 on: March 11, 2010, 08:56:12 AM »

Likely a coax issue.  Been through this with other antennas as well over the years.

As someone that uses the OSJ146/440 for both portable and fixed uses there are things I've noted. I use it as it's simple, rugged and for field use it can take
a terrible beating and it's dual band.

It's a good flat antenna and should not exhibit an
unacceptable SWR.  Mine were verified on a short
ground mount at 6ft and well clear of other objects
and I found that 1.1-1.2 was good enough for 435-450.
Vhf was a non issue.

Even 25ft of 8x made any SWR disappear due to losses.
Also made really weak signals go away too.

For short runs I use premium RG213 even for UHF as
the loss in 25-35ft is low enough.  For greater runs
than that 9914, Buryflex or LMR.  Cheap cable has a
long term payback in pain.  I never buy with
connectors installed as I can't QA the work done
and they maybe just wrong ones for my use.  I buy
bulk usually 250ft or more at a time and test it
on the roll.

Played with 9913, hated it too touchy and susceptable to mechanical damage. That and larger foam core cable was not that much more costly and far more durable.
 
The SO239 equivalent socket is the antennas supplied connector and is part of the feed and not easily changed.  Testing says PL259 of quality is not that
big a loss at 440 well under a half DB.  It has other liabilities (not water tight) but for local FM repeater use it's fine.  For anything more stressful
I'd not only be doing N connectors but a higher gain antenna as well.
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K5MBV
Member

Posts: 265




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« Reply #32 on: May 14, 2010, 12:44:57 PM »

PL259s aren't recommended for use at UHF. Actually they can be unusable
at UHF. All the testing and trouble for nothing. Just don't use them... and
stick with LMR400 or better above 2 meters.

Nickle or chrome plated type N connectors aren't much better. Use silver plated
ones if you can afford them.

Ken  K5MBV
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