mike wrote:
Gentlemen,
I work for a student transportation company using UHF radio
communications. While I have played around with CB radios several years
ago I have no experience with UHF.
Our system operates on either of 2 channels near 470MHz. Channel 1
transmits via a repeater located in the hills a few miles away, while
channel 2 is direct.
For most of the last school year we have operated on channel 2 as
channel 1 wasn't working. A company recently came out (not following
known company authorization proceedures), and apparently repaired a
faulty repeater. Our company was charged about $185.00 for parts and
over $600.00 for labor. The rate worked out to be $80.00 per hour over
7.5 hours. Not only does this seem a wee bit steep to me, but the
communications are still poor on channel 1.
Assuming that the repeater is fine now, the problem seems to be more
related to the individual busses. Over the course of time our mechanics
have swapped-out radios, mics, and probably antennas as well. Given the
nature of the problems and my previous (limited) experience with CB, my
suspicion is that the antennas on the busses need to be tuned.
I used to tune my CB antennas with an SWR meter and get good results. I
understand the basics enough to be able to do that and could probably
teach our mechanic as well. However, since I have no experience with
UHF I don't know if there's more to it with UHF over standard CB and if
there is more equipment required than an SWR meter. I am just having a
real difficult time paying $80.00 an hour for someone to do something I
used to do quite easily.
Mike
$80 per hour isn't a bad price if the work is good. UHF requires more
expensive instruments than CB, they amortize that in the labor costs --
in other words that $80 per hour is for the guy _plus_ the equipment.
Assuming the radios in the busses are in good shape (you could send them
out for servicing and alighnment/checking for much less than you could
have the guy come out and do it) you are left with antennas and cabling.
I wouldn't expect that it's _just_ the antennas - coax can be pretty
lossy at those frequencies, if it's been beaten up it'll show.
So get an SWR meter that'll work reliably at 470MHz, and try adjusting
some antennas. Try replacing coax as well, and if either fix seems to
work then keep it up.
--
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Tim Wescott
Wescott Design Services
http://www.wescottdesign.com