Hi Larry,
> "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote:
> I'd like to find a continuous-duty MSR-2000
> 450-470 MHz PA Deck (any level, but 20-40
> watts would be more than enough).
It's all about the PA heat sink, which IMO
doesn't support high duty cycle operation
above say... 25-35 watts without a fan.
The Lower power MSR UHF PA's have different
circuits, but the heat sink is the same as
the 110 watt version. A small ball bearing
boxer type fan is prudent. I put a pair on
the cabinet rails underneath the side vents
blowing air out the top sides. I place house
heating/AC filter material over the front
vents to keep the dust intake under control.
> I'm trusting that they would directly swap
> out with the one that I'm using now -
Yes and no... the power supply included with
the low power MSR unit is the consolette
type layout and the mounting hardware is a
bit different. If you use the 110 watt MSR
power supply, you'll be wasting a lot of energy
in the transformer, by the way it operates.
It would be more practical to run the low
power PA in the repeater and run the repeater
off an external supply so your utility bill
is mucho less. A typical MSR and Micor high
power supply can and will gobble a lot of
energy while space heating your cabinet.
Keeps the mice warm if you don't have the
rodent cable port screen/panel in place.
> I have a 100-watt intermittent duty MSR-2000
> Repeater on a UHF Ham channel, but don't want to
> cook the PA deck.
If you really trust your antenna system, turn the
110 watt pa down to ~60 watts and put a fan on it.
(provided you're using the original MSR internal
duplexer, properly adjusted).
> Most people I know that have used these in Ham
> (continuous-duty) service have fried the
> intermittent-duty PA deck numerous times, even
> with fans blowing continuously on the heat sinks.
> When we had these in service with the local Police
> Dept., we always had to keep plenty of the PA
> Deck repair kits in stock ($450+ for each one!)
> Larry
>
There are power, voltage and current controls on
the PA control board. When the mentioned controls
are properly dialed in at the 65 watt value, you
should be able to run higher tx duty cycles. The
limit and power controls function very well, understanding
their setup and operation via the manual instructions is
not an easy first read.
I have not lost an MSR PA in decades from heat
falure since pulling back on the throttle and
setting the protection pots for the lower value.
I actually don't even run fans much except in/on
busy trunking MSR-2000 conversions.
You don't really need the 40 watt PA. Feel free to
Email me direct off the list if you have specific
questions.
cheers
skipp
www.radiowrench.com
skipp025 at yahoo.com
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