[BC] Changing channels

[Phil Alexander]

On 24 Feb 2006 at 13:00, Scott Cason wrote:

> Having a separate box like an LPB or Crown gives you a place to go should
> the main fail.  It will also allow you to take the main off the air for
> routine maintenance instead of it taking itself off and then having to
> perform emergency maintenance.  Think of the cost of the amplifier as
> insurance.  Cheap insurance.

Very good point Scott. A LPB-30 is a neat little transmitter and when
correctly set up and fed by modern processor, it can achieve remarkable
results. The keys are correct alignment of the transmitter itself,
proper matching to the antenna and a good audio feed. With a couple
of minor modifications, remote control and metering are also possible.
The problems I've seen with them are poor output when improperly tuned
or matched. The transmitter is essentially low level modulation with 
linear amplification, and unless the box is happy, + modulation tends
to get rounded off to < 100%.

One thing to remember for remote control installations is the RF
switch must handle the same level static discharges as the full power
daytime system, thus, a small coax switch may not be the best idea.
Consider a real RF contactor if you need to switch remotely. They have
a better survival possibility in a lightning region.


Phil Alexander, CSRE, AMD
Broadcast Engineering Services and Technology 
(a Div. of Advanced Parts Corporation) 
Ph. (317) 335-2065   FAX (317) 335-9037





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