[Elecraft] Ferrite Torroid RF filters

[Ed Cole]

I used a F140-43 torroid with three turns to filter switching noise from 
my HP 226519-001 "blade" 50v 50A PS:
6m_control_panel_back_3.jpg (825×619) (kl7uw.com) 
<http://www.kl7uw.com/6m_control_panel_back_3.jpg>
used clamp-on ferrite filters on the 240vac hot wires.

So when I obtained a new Meanwell RSP-3000-48 switching supply to 
replace the HP, I used a similar method using two ferrite torroids sized 
for RG-8x with two clamp-on beads for good measure.  On the 48v output I 
used two torroids sized for RG8 in series with an extra loop thru them both:
http://www.kl7uw.com/6M-EME-CONTROL.jpg

I see no switching noise on my K3 that is only two foot from the PS.  
The coax beads are probably mix-31 as they are sold for the general HF 
ham market as common mode RF filters on coax lines.

The original tip for filtering the HP PS came from Lance-W7GJ who did 
many of the first conversions of the Harris ch.2 TV linears to 6m ham use.

I am building a 1200w MRF1K50H HF/6m (W6PQL) linear to replace my Harris 
to use with my K3/10 driving with 3w to the new amp.  So I will be 
running QRO on HF in a couple months.

73, Ed - KL7UW