[R-390] Signal Generator Impedence Questions

[David Wise]

Point well taken, Barry.  I skipped past your words and went
straight to the task.  The 1001A meter is not calibrated
in uV.  For what it's worth, it does have a "relative" scale.
The SET CARRIER line is 1.0, and there are marks for 1.2, 0.8,
and so on.

It doesn't matter what the 10 ohms sees; since it and the
40-ohm series resistor are not separated by any cable,
there's no "termination issue" between them.  The cable
sees 50 ohms, and the generator+series R (which can be taken
as one contiguous blob) sees 50 ohms, everybody happy.
Note that you _will_ have to do some arithmetic to figure
out what the output voltage is.  This kind of "wart" was
endemic to GR instruments.  Good stuff, but quirky.

73,
Dave Wise

> -----Original Message-----
> From: Barry [mailto:n4buq at aol.com]
> Sent: Thursday, June 02, 2005 3:18 PM
> To: R-390 at mailman.qth.net
> Subject: Re: [R-390] Signal Generator Impedence Questions
> 
> 
> Dave,
> 
> Looks like I'll be finding a 40-ohm resistor post haste.
> 
> I didn't say the 1001A does not have a calibrated attenuator; 
> I said it
> doesn't have a microvolt meter.  Your instructions to get 
> 150uV are exactly
> what I did.
> 
> I am confused on one issue, though.  If a 40-ohm resistor is 
> in series with
> the output and then a 50-ohm resistor is in parallel with the 
> output, the
> 10-ohm output sees 90-ohms, right?  I don't quite understand this.
> 
> Thanks and 73!
> 
> Barry - N4BUQ
> 
> ----- Original Message ----- 
> From: "David Wise" <David_Wise at Phoenix.com>
> To: <R-390 at mailman.qth.net>
> Sent: Thursday, June 02, 2005 4:43 PM
> Subject: RE: [R-390] Signal Generator Impedence Questions
> 
> 
> Roy Morgan beat me to the punch in saying that the GR1001A
> "impedance matching adaptor" was nothing more than a 40 ohm
> resistor.  The connector assembly it's embedded in costs
> about 100x what the resistor did.
> 
> But I want to take issue with your statement that the
> 1001A does not have a calibrated attenuator.  It most
> certainly does, unless early production omitted it.
> To get 150uV (assuming it's terminated right), using
> the CARRIER control you set the meter to the SET CARRIER
> line, then set the step attenuator (MULTIPLIER) to 100uV,
> and set the vernier (OUTPUT) to 1.5 .  Simple.
> 
> 73,
> Dave Wise
> 
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