RE: [Repeater-Builder] VHF into aircraft

Thu, 21 Jul 2005 12:13:32 -0700

Mathew,
We had issues with the difference of 2 cell freqs mixing with our output, and landing directly on our input.  When you un-keyed, it would chase it's own tail something fierce.  Many times you could actually hear the cell conversation very clearly, and they were not always "G-rated" conversations!!  Running a split tone system helped a bunch.  Everytime the cell-co's add something to the tower, we have trouble.  Cingular in particular...  seems we were left out of their intermod studies..
 
Lately we have been getting the local sherriff's tactical frequency on the second VHF machine.  It is located on a water tank adjacent to the main site... 
Not cool when the sherriff calls and wants to know why we are re-broadcasting his tac-freq...  We have a close relationship with the SO, and the 911 center..  so they monitor our traffic at the dispatch center.
 
This probably won't help your situation...  but it demonstrates how something can wind-up on your input due to no fault of your own.
 
Good luck in finding the answer..
Mike
K5JMP
-----Original Message-----
From: [email protected] [mailto:[EMAIL PROTECTED]On Behalf Of Mathew Quaife
Sent: Thursday, July 21, 2005 12:31 PM
To: [email protected]
Subject: Re: [Repeater-Builder] VHF into aircraft

I'm starting to think it is either something coming in or the Vocom Amp that is the culprit, but something is funny.  I know my Yaesu FT7736R is a very clean transmitter, and at two watts output, really hard for it to send spurs out.  I'm thinking it might be something that is coming in on the receiever at the same time the transmitter is transmitting.  I am going to feed the repeater into a dummy load today and see if the spurs are still there.  If they are not, then I can only believe something is getting in with the receiver, or there is a inbalance in the antenna system that is causing the problem.  There was indeed a problem with the Maggorie transmitter, but don't think it was the whole problem. 
 
I have used Jan xtals for many of years, and this is the first one the was off.  They all have their problems.  I bought one from International that was put in the wrong casing, they did not want to fix the problem, so I had to solder it to a old large xtal caseing.  Oh well, I'm sure they will fix the problem for me.
 
Mathew


Ron Wright <[EMAIL PROTECTED]> wrote:
Mathew,
 
As far as FAA your repeater with antenna on the ground can easily be heard from an aircraft at even 2000 ft.  We try to get repeaters high to be able to work low mobiles.  We should start insisting on the mobiles being high, hi.
 
Never use JAN crystals in my option.  Have tried them and almost all gave problems...from not working to way off freq to being way off freq 6 months down the road to dying 6 months out.
 
I spend the extra money and save money by using International or Bomar.  International is in some kind of screwed up situation, think due to them buying out Sentry, with 6 + weeks delievery.  Bomar cost more, but both make an excellent crystal. 
 
For a pair of crystals including shipping Bomar $60, International $47, Jan $200 after the overhead.  Bomar does have a $50 min.
 
 
73, ron, n9ee/r

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