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From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: sci.electronics,rec.ham-radio
Subject: Re: Eico dip meter - Help!!
Summary: Pestering Larry Lippman to do some of the hard work...
Message-ID: <8066@milton.u.washington.edu>
Date: 25 Sep 90 01:55:15 GMT
References: <4049@kitty.UUCP> <3113@vela.acs.oakland.edu> <4052@kitty.UUCP>
Organization: University of Washington, Seattle
Lines: 27

In article <4052@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes:
>In article <3113@vela.acs.oakland.edu>, swood@vela.acs.oakland.edu ( EVENSONG) writes:
>> Hey! The 710 is the very animal that I have. (Eico 710
>
>	Get some 0.75" OD plexiglass tubing and cut it in 2.5 inch lengths.
>
>	The grid dip meter is tuned *solely* by the inductance of the
>coil; there is obviously no bandswitch on the instrument.  While the
>3 lower frequency coils may be tricky since they are tapped and I cannot
>estimate the turns, the higher frequency coils from 2.9 MHz to 250 MHz
>should be easy to build.
> ... [more helpful information, followed by]
>
>	I can't do much more than tell you the above.

	But if you've got a working grid dip meter, you can tell him
the inductance of the taps on the coils; just clip a capacitor
onto the taps and measure away with ... a grid dip meter.  Since the things
are low frequency coils with the inbuilt tuning capacitor (circa 50 pF),
this will likely require using either another grid dip meter, or measuring
only the higher-frequency tapped coils ('cuz you're unlikely to be able
to estimate the stray capacitance better than a large fraction of
that 50 pF.)
	The inductance, of course, goes as the square of the turns
ratio.

                   John Whitmore