On 25/08/2011 9:03 PM, clifford wright wrote:
I have some very nice 12.5mm toroids (violet) which work Very well from
1 to 20 MHz but take a severe dive in performance above there. What I
need is a source of toroids of the same size but with a frequency range
with high Q from say 15 to 60 Mhz. These are for the bandpass tuned rf
filter and the 1st IF @ 45 MHz.
Anyone got any ideas where I might obtain a few out here in NZ. None of
the local suppliers have anything like this and they are also generally
very ignorant of the proper use of toroids especially at HF. Any
suggestions very gratefully received.

I got a few HF/VHF toroids recently from http://rockby.com.au.

Just make sure you verify that the mix you select is correct for the
purpose (resonant, not transformer) you need, and has the permeability
you want. There's a lot of confusing information on the net about what
different mixes are good for, and I'm only just starting to get my head
around it.

Rockby stock # 25651 is smaller than you want, but mix 12, mu=3, which
should be good in resonant circuits from 20-200MHz, if I have my facts
straight. I also have some stock #25298, mu=40 and mix 63, which should
be ok in resonant circuits from 10-80MHz, and in transformers to 800MHz.

If anyone can verify or discredit the above suitabilities, I'd like to
know before I spend too much time playing with circuits around these
(I haven't found time yet, still trying to figure out how to make decent
PCBs, necessary to get a ground plane at 2m).

Clifford Heath.