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Down East Microwave converter problem


This is to alert those using the latest version of the Down
East Microwave 2400-144 

We have discovered that the 3-terminal 9 volt regulator goes
into thermal overload because it has no heat sink. In this
condition, the converter essentially shuts down (gain goes
to -dB). (This also explains why we were having so much
trouble hearing AO-40 on our initial attempts).

The time to shutdown depends upon the voltage you feed it.
At 13.6V, it takes about 8 minutes. At 18V it takes only
about 3 minutes. Power consumption of the converter is ~320
ma so it does generate a moderate amount of heat.

We solved the problem by attaching a small L-bracket from
the regulator to the case. The straight piece goes on the
regulator tab; the "L" gets bolted to the case. Copious
amounts of heat sink compound should be applied to both
ends. The case does get slightly warm, but the regulator
seems happy. Time will tell if a hot, sunny day will warm
the case to the point where the same effect occurs.

We have advised DEM of the problem and are awaiting their

Art, N3OY
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