[VHFcontesting] Coax

[Nate Duehr]

On Jul 23, 2008, at 6:18 AM, David wrote:

> I am putting up a 70cm array at 50 ft in the future. I have on hand  
> three 25
> ft sections of Andrew FSJ4-50B coax with connectors attached that  
> was given
> me to me when a local cell tower was moved.  It was used inside and  
> is in
> excellent shape. To use this I would have to use two barrel  
> connectors.
> What would be the loss in the barrel connectors.  Would I be just as  
> well
> off using one section of LMR-400 or the equivalent.
>
> Thanks,
>
> David Hinton
> KE4YYD

Since no one answered your query...

Are you saying you're not familiar with the math and need some  
assistance with it, or are you looking for a definitive answer as to  
how much loss your particular barrel connectors are at UHF?

The list can provide anecdotal numbers for "generic" barrels, but  
here's the real deal...

You're not installing a repeater or something at an unattended site,  
or many of us would say the problem is the possibility of water- 
ingress at all those junctions.  (Especially seeing that 4-land  
callsign... you guys have some wicked humidity and rain, depending on  
where you are.)

If you were, we'd probably say -- use one length of coax/hardline.

But in reality, since it's a home tower... you can put up the free  
stuff, do the math to calculate how LMR-400 would work in the same  
setup, measure your losses and see if you think the hardline is  
performing as well as it should be/could be improved.  Especially if  
you already have the barrels and the cable.

Oh another thought... you don't have to run it up the tower to test  
it's loss... string it out in the back yard, the front porch, the  
street... whatever!  (GRIN)

It's ham radio, after all.  "Cheap" is the order of the day in  
anything at your QTH, unless you're engineering for max performance  
from day 1 of the installation.  If you're like most of us, you'll be  
tinkering with it for years...

If you already have the stuff, just try it.  "Get 'er done", and just  
measure it and see how it performs.  (GRIN)  You can even put it up,  
enjoy it until you can afford to replace it with LMR-400 if you don't  
like how it's behaving, and swap it out later.

Have fun,

--
Nate Duehr, WY0X
nate at natetech.com