[R-390] Signal Generator Impedence Questions

[David Wise]

It's not like that, Roger.  The output from the oscillator
goes to a meter.  You goose the oscillator until it's on
the SET mark, then you get a specific voltage by setting
a downstream attenuator.  It's a decade step atten plus
a 0-to-2.0 vernier.  So as I said to Barry, you'd set the
step atten to 100uV and set the vernier to 1.5 .

For the current task it's beside the point, as others
have mentioned.  Adjust for best S/N if you care; if you
don't, well, you don't; set it midrange and forget it.

73,
Dave Wise

> -----Original Message-----
> From: Flowertime01 at wmconnect.com [mailto:Flowertime01 at wmconnect.com]
> Sent: Thursday, June 02, 2005 3:52 PM
> To: r-390 at mailman.qth.net
> Subject: Re: [R-390] Signal Generator Impedence Questions
> 
> 
> Barry,
> 
> I have not used a GR1001A .
> Consider stepping the output up to the next output range 
> and setting the adjustable attenuation control back under
> 100% to what would be 150uV. Just because the dial goes
> up to 150% the generator may not be able to put that out.
> Not that the generator will not do it, but the attenuation network
> and maybe current / voltage limiting of an output stage hits
> a ceiling before you 150% of output at the low ranges.
> 
>  Kludgy, !! Is there some other way?
> ----------------------------
> I was disappointed that with 150uV(?) at the input, I was not able to
> get -7V on the diode load.
> 
> Something is wrong, either low output or IF deck needs some work.
> The gain adjust should let you get about -15 volts with the 
> pot cranked
> over full gain and 150 uV in. 
> 
> You are just not going to look at 150uv on a scope or measure 
> it with a
> meter. How does the signal gen perform at 1 - 10 uv on 
> another receiver?
> 
> As the other mail pointed out, due to lack of shielding you 
> cannot really 
> run the 150uv output through an attenuator and see how it 
> performs as a 1- 10 
> uV
> drive for a receiver.
> 
> You will know when you have it right, the R390 will 
> definitely not be deaf.
> -----------------------------
> 
> I was thinking that the 10-ohm impedance mismatch might be
> affecting my ability to set the gain by the manual properly.
> 
> Not likely. Either the generator output is low, or you do have
> IF, Audio deck problems. Pop the VFO on and you should get 
> about -30 volts on the diode load.
> 
> ---------------------------------------------
> I was just trying to get something close to the procedure 
> that's in the 
> manual.
> 
> Understandable Barry, when every thing is not going well, 
> Try reading the manual. 
> 
> -----------------------------------------------
> One thing I did notice that was rather humorous.  In the section for
> aligning Z503, the manual states that if Z503 is defective, 
> replace it.  I'm
> not sure why they felt the need to include that blurb.  Kind 
> of obvious,
> isn't it?
> 
> Lots of little bits of humor in those TM's dry reading but some error 
> included.
> ____________________________________
> 
> Roger KC6TRU
> 
> 
> 
> 
> 
> 
> 
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