[amsat-bb] question about the DEM 13 ULNA 2.4GHz preamp

["Mark L. Hammond" <hammond@xxxxxxxxxxxxxxxxxx>]

The details on this preamp are here:
http://www.downeastmicrowave.com/PDF/13ulna.PDF

I have one of these (pre-built) units  in the following configuration:

helix feed->13ULNA premp->Transystem 3373 downconverter on a BBQ dish.

My question is this--does an increase in S-meter background noise 
level/floor (compared to without the preamp installed) on my 2M rig 
guarantee that the preamp is working correctly?

Or is it possible that one of the components has actually failed (like the 
PHEMT), but yet it still causes an increase in the S-meter?

The reason I ask is this--when I first got the unit, I installed the preamp 
BACKWARDS in between the helix feed and the downconverter, and powered it 
up.  (I'm feeding DC into the preamp through the external feed-through cap, 
NOT via the coax)  And AO-40 signals have been quite poor, and I'm not 
certain that my preamp is actually working....

Does having the preamp in line WITHOUT powering it allow signals 
through?  I would expect yes, with perhaps a tiny reduction in signal from 
loss through the unpowered preamp.  Yes, I need to and can test a few of 
these things out, but it's a bit challenging to do it based on my current 
configuration/power scheme.

I know I'm showing my ignorance on how the preamp works, but I hope to 
learn something from constructive replies.

Perhaps somebody has the construction/tuning sheet(s) for this unit from 
when they built it from the kit.  I'd like that information very much...it 
might have some "read the voltage here" type of troubleshooting/tuning 
information...

Thanks for any comments.


Mark L. Hammond  [N8MH]

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org