LF: RE: 3C85/90 Toroids

["Dave G3WCB" <ganymede444@btopenworld.com>]

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

-----Original Message-----
From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org]On Behalf Of Lee Hudson
Sent: 19 November 2008 18:51
To: rsgb_lf_group@blacksheep.org
Subject: LF: 3C85/90 Toroids

Hi,

 

Any suggestions for suppliers of Toroids made from 3C85/90 material rather than stripping down old SMPS?

 

73,

Lee

M0LMH