In article .com,
kg0wx wrote:

Thanks, Dave! Lot's of great info. I just bought a mint GD-1B in the
original box with 7 inserts.

That sounds like a really nice find! I'd be very interested to learn
how you find its sensitivity. There seems to be a big range in dipper
output and sensitivity, with most of the modern transistorized units
coming up looking rather wimpy compared to classic firebottle types
such as the Measurements 59.

I understand what freq range the 1st 5
inserts do as they are marked and there is a picture in the manual.
Problem is the last two inserts - they have a lot of wire (looks like
AM antenna micro wire). One has 1 coil of wire, the other 2 coils.

Unlike the regular coils, these are wound inside the plastic form
and sealed. Any idea what they are for? Is that the 341-A coil set?
How do I use them (what range)?

That's probably the additional coil set mentioned in the manual (which
you can download from http://bama.sbc.edu or its less-heavily-loaded
mirror site at http://bama.edebris.com/

The standard set of 5 coils goes down to 2 MHz. The manual says that
the extra coils extend the frequency range to 350 kHz, but doesn't say
how many coils are included in the extended range. Since it appears
that each of the coils in the standard set covers a frequency range of
about 2.5:1, I'd guess that one of your extended coils covers from
somewhere around 800 kHz up to 2 MHz, and the other covers from 350
kHz to 800 kHz. The one with more wire, is probably the latter. You'd
use these coils in just the same way that you use the other five.

If you have access to a reasonably sensitive RF frequency counter it
shouldn't be difficult to confirm this. I use an MFJ 269's freq-counter
function, with a few inches of wire soldered to a BNC connector, in
order to do fine calibration of the output of my Measurements 59 grid
dipper. Just plug in the coil, turn on the dipper, hold it near the
frequency-meter wire probe, and the probe will probably pick up enough
RF to give a good indication.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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