Needed Info: 100-250 Coil, GD-1B

[al winfrey]

Hi Steve,

That coil is the one that always falls out when you open the box. If I remember right ,
it is just a "hairpin loop" made from 12 or 14 ga wire and having a length of maybe 3 cm
or a little over an inch.  It would be nice if someone else having an actual coil could
give you the exact measuerments.  You could adjust the calibration by squeezing the coil
a bit.  Hope that helps.

Al - wa9hsl
....

Steve Harrison wrote:

> Howdy,
>
> I've obtained a great-condition GD-1B from a very kind fellow in
> Connecticut; but it is missing the 100-250 MHz coil and manual. I probably
> don't need the manual too badly (there isn't much to a GDO, after all!);
> but I would like to try to duplicate the original 100-250 MHz coil if
> possible. Also, I'm curious about any alignment instructions that Heath may
> have had (so the manual might be useful, after all). And, I found the
> original 82-ohm cathode resistor shorted with a jumper for some reason. I
> want to get this thing halfway calibrated and working on the 100-250 MHz
> range in particular to give to a good buddy in Maine so he no longer has
> reason to complain "I can't tell if it's oscillating, nor where, if it is!".
>
> SO: can anyone describe to me what the original 100-250 MHz coil looked like?
>
> And, can anyone briefly describe any alignment instructions?
>
> And, was shorting that cathode resistor some mod to enable more consistent
> oscillation across the V/UHF range, or what?
>
> Also, what is the claimed value of the two mica DC blocking capacitors
> between the tube grid and plate, and the tuning capacitor??
>
> Finally... does the 6AF4 tube have to be in especially-good condition in
> order that this GDO operates reliably across the entire range? I recall the
> 6AF4 was used extensively as the local oscillator in UHF tuners some 30-40
> years ago, pre-Nuvistor days. I'm half-tempted to try a FET since I don't
> have any 6AF4s left (got lots of acorns for my own Measurements Corp.  GDO,
> though!).
>
> TNX Much,
>
> Steve K0XP
>
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