Looking for (IM-11)

[Gary L. Sanders]

Most DVM's have 1MOhm input impedance, which is adequate for today's modern
low Voltage circuits; but 1MOhm will load down many tube circuits. A VTVM is
better for tube circuits because of it's higher input R. Even oscilloscopes
have 1MOhm input R; it's the x10 probe that gives it a 10MOhm input R.

--
Regards,
Gary L. Sanders, Staff Analog Eng., gsanders at csidaq.com
Celerity Systems, Inc. --- http://www.csidaq.com
Cupertino, CA USA (408) 873-1001 fx (408) 873-1397
Ultra Fast Acquisition & Data Generation Systems

Stewart D Lyon wrote:

> Sean -- a digital voltmeter will work just as well, or better. The IM-11
> has an input impedance of 11 megs and most DVMs are higher than that. If
> the test also calls for a "RF Probe" than that's a different story. The
> RF Probe was sold as an accessory to the VTVM and will only work (at
> least easily) with a Heath VTVM. However, the only place a Probe is used,
> on a SB-101, is during the alternate (and preferred) method of
> neutralizing the 6146s (and maybe the balanced modulator -- I can't
> remember).
>
> You can buy a pretty good DVM for $40-50 at most radio stores and they
> are lot more accurate than a VTVM.
>
> I have a Heath VTVM and  RF Probe and never use them on my SB-101s.
> Instead I use a DVM and an oscilloscope. I think the gear will remain
> original even if you use modern test equipment on it !!
>
> Hope this helps &
> 73, Stu - W6CUX
> Winnetka, CA
> ARRL Life Member
>
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