[amsat-bb] Pre amp question

Steve Raas sraas at optonline.net
Tue Dec 12 18:30:12 PST 2006

As I prepare for getting on the birds.. I decided to test out this AG-25
preamp that came with my new radio. Now my experience with preamps is
limited, but this one is rather baffling me.


I connected everything in line.. and powered up the preamp and at 1st glance
it appeared that it worked fine, however after about 10 seconds I started
questioning a few things. 


#1 My noise floor went up 10db ( I've never seen this before I guess my
experience with preamps is just the good ones )


#2 My Received signal quality was unchanged all it did was make the signal
'appear' stronger on the meter.


Now I know if the preamp was dead.. I would hear nothing.. so I am going to
go out on a limb here and assume that its either:


a)       an incredibly broad band pre-amp with a completely fictitious ' Low
noise floor ' claim or

b)       Detuned


 I guess what Im going after is a few things with this email .. has any one
ever taken one of these AG-25's and given it a proper tuning? Or is this
what I should expect with this particular item?


In my previous experience (terrestrial weak sig stuff) a decent preamp may
up the noise floor from a s-meter reading of mabey 0 or 1 to a s5, but with
a significant increase in received signal gain. and intelligibility.


I really want to do this the correct way.. and if this thing is un-fixable
junk.. its going in the junk drawer fast. I don't want to configure rx
system around sompthing that wont produce results.




I'd like to thank everyone for their input so far.. Ive learned a lot w/o
even Transmitting and R.F. yet!



-Steve Raas


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