[R-390] Mechanical Filter Repair

[Tim Shoppa]

VE3TS asks:
> Well, I have a 4 KC mechanical filter  apart here, and it is at the stage I 
> need the correct magnetic wire to rewind the coils. The finest size  I have 
> is 38 gauge but the filter  requires 42 gauge .0025 mil.
> Does anyone have, or know of a source for this stuff?  (In a reasonably 
> small quantity?)

42 AWG is what's used for guitar pickups etc. In the $25 range
for a half-pound roll you can get it at:

  http://www.stewmac.com/shop/Electronics,_pickups/Supplies:_Wire,_cables/Pickup_Coil_Wire.html

42 AWG copper is about 1750 ohms per 1000 foot, and
from memory a mechanical filter is about 120 ohms, so
you would only need about 70 feet for each end.

A half-pound is 25000 feet (five miles) so you'd have some
left over after doing all our filters :-).

I do know that smaller and larger rolls show up on E-bay sometimes.

Please keep us updated on your progress with the filter
rebuild. I am very, very interested!

Tim.