[R-390] Signal Generator Impedence Questions

[rbethman at comcast.net]

Barry,
     The GR-1001A originally came with a 50 ohm adapter.  It, however, was limited to certain outputs to "maintain" its 50 ohm output.

I'll take a GOOD look at min and see if I can look inside and get a schematic drawn of its insides.  May take a week!  I'm just starting a string of 12 hour shifts.

Bob - N0DGN


> Gents,
> 
> The IF alignment procedures for the R390A state to connect the URM-25* to
> the input connector using an impedance matching adapter  (either Test
> MX-1487/URM-25D or CU-206/URM-25F depending on which generator you have).
> Assuming the URM-25* is 50-ohm output, what does this converter do?  I find
> it odd that the adapter is mentioned for the IF GAIN ADJUSTMENT procedure,
> but not for the IF alignment procedures even though the generator is
> connected to the IF module the same way for both procedures.
> 
> I assume the input impedance of the IF module is something other than
> 50-ohms and the adapter is being used to match the two impedances, but I
> don't know what the input impedance of the IF module is.
> 
> I have a GR1001A signal generator which, for most attenuation settings, has
> an output impedance of 10 ohms.  The reason I'm asking about the above
> adapters is I'd like to construct a proper matching network for my 10-ohm
> generator to work the same way as the 50-ohm generators do for the IF
> alignment procedures.
> 
> Another question:  The instructions state to set the output at 150uV for the
> IF GAIN ADJUSTMENT procedure.  If I'm using a different adapter for 10-ohms
> versus 50-ohms, will I need to change the output setting to something other
> than 150uV to account for the different adapter impedances?
> 
> Thanks!
> 
> Barry - N4BUQ
> 
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