[TMC] GPR-90RXD stuff

[James A. (Andy) Moorer]

If somebody has an L38 from a parts unit or is willing to unsolder 
theirs, you can use a modern ohmmeter to figure out where the tap is. 
There won't be a lot of resistance, but the ratio of resistances from 
tap to end points should be related to # turns. That plus the overall 
inductance should be all you need. Hmm. I wonder how critical the 
winding technique is? Basket-wound versus pi-wound? The point of those 
"loose-looking" winding techniques is to reduce the self-capacitance of 
the windings. You can wind one by hand, or on a vintage Miller coil 
winder if you can find one and figure out how to make it work.
-A

On 8/6/2021 5:01 PM, John Poulton wrote:
> Just for the heck of it, I looked up the drawing for this coil (L38, BFO
> output coil).  From the parts list, it's TMC part # CL-231, which is also
> the TMC drawing number.
>
> Here's the drawing URL (I've scanned most of the drawings for smaller coil
> assemblies):
>
> https://tmchistory.org/tmc_drawings/drawings_db/cl/cl_200_299/cl-231.pdf
>
> The drawing is singularly unhelpful.  It shows a 3-rank pi-wound coil with
> an inductance of 585uH (in agreement with the schematic, but not the parts
> list) with a powdered iron core, but it doesn't even mention a tap or
> indicate where it might be..  Arghhh.  Maybe the wire type and Q will be
> useful to you.
>
> Chris, hope you're able to find a photo of the coil.  I'd be interested to
> know what you find out from it.
>
> 73, John K4OZY


-- 
James A. (Andy) Moorer
www.jamminpower.org