[amsat-bb] Converter gain and noise..

["Jens H. Jensen" <topcat@xxxxxxxxxxx>]

At 18:22 26-04-2001, you wrote:
 >Jens
 >A couple of years ago I bought a 50 ohm with BNC's decade RF attenuator at a
 >electronic swap meet, for $10. It has three step dials. One is 0-30 (3 
steps),
 >the next is 0-10(10 steps), and the next is 0-1(10 steps) db.
 >It really has come in handy used between the TSI or Drake downconverters. I
 >usually set it between 10 and 13 db. This puts the S meter of my FT-817 at S0
 >with no signal at 2401 Mhz. I believe this is the right way to do it. I guess
 >on could turn down the RF gain control of the rig, but on the 817, this make
 >the S meter unusable. So, I think some sort of attenuator is necessary, for
 >most have downconverters have more than enough IF gain. Some gain 
control >may
 >even necessary between a 2400 Mhz pre-amp(don't have yet) and the
 >downconverter.

Yes, getting the gain balanced to the right levels is going to be essential 
to maintain the large-signal handling capabilities of any link in the chain.

I am not sure how to calculate the needed gain for a given NF, maybe some 
of the Pro's on the list can comment (John, Greg, anyone?)

73 de OZ1LRG

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