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| Subject: | LF: RE: 3C85/90 Toroids |
| From: | "Dave G3WCB" <[email protected]> |
| Date: | Wed, 19 Nov 2008 22:11:19 -0000 |
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Hi,
Lee, LF
I have
found that the core material used for the output transformer and feedpoint choke
isn't too critical in push-pull FET transmitters like the G0MRF and other
designs. I've used a variety of dodgy toroids made from EMC-choke
grade material with good results. However, you absolutely do need to use the
right material for the 56-uH inductors in the low-pass filter, otherwide they
heat up alarmingly.
As
well as the famous Phillips 3C85 material, I find that Micrometals toroids
type T130-2 (1.3 inch) and T200-2 (2-inch) toroids work quite well at 137
kHz. I bought some from a stall at Kempton Park rally, and I'll post the name of
the vendor here just as soon as I can remember who it was! You can also use
air-cored solenoid windings for these inductors, but if you use wire that is too
thin, they will also heat up as the circulating currents within the LPF can be
quite high.
Look
out for them at rallies if you get the chance. The T130-2 and T200-2 toroids are
coloured red with one grey cheek.
Good
luck and 73
Dave
G3WCB IO91RM
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