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[aprssig] Positive Earth RC-D710?

Robert Bruninga bruninga at usna.edu
Mon Sep 29 14:36:46 UTC 2008


Showing the D710 Display head connected alone to an HT was a big
hit at the DCC converence.  Making it an all-in-one package was
cute, but I think I will make the audio cord about 4 feet long
so I can hand-hold the Display head like a game boy and the
battery and HT can sit by the window for better RF.

> Positive Earth RC-D710? 
> www.aprs.org/D710-HT.html Does not have a diode in the supply.
> www.ew.usna.edu/~bruninga/aprs/RC-D710-connx-pwr.GIF Has a
diode in...

Thanks Dave!

I have now added the reverse diode protection  to protect the
Display Head if you connect power up backwards.  (Always use a
fuse, otherwise the diode gives no protection).

The original series diode voltage drop is not desired, because
it reduces the amount of battery life.  My D710 display head
drops out on 8.3 volts and that represents 1.04 volts per NiCd
cell which is a good cutooff.  Fully charged, the voltage is
11.2 volts which is still safe. 





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