2022-01-14, 10:19:48
I found a design chart by Glenn, W9IQ for common mode coax chokes using Mix 31 ferrite toroids, that is simpler than the G3TXQ chart in my presentation. See attached. 12 turns on a FT240-31 looks like the best compromise over most of the HF bands. If you need even wider suppression range, put a 14-turn in series with a 10-turn.
W9IQ specifies very expensive RG400 teflon coax. Good quality RG58 (with solid dielectric & 95% braid) is the same size & should work fine unless you're running a big amp. The stranded center conductor type would be definitely preferred over solid single conductor, for ease of winding. Don't use the foam dielectric type.
Solid dielectric stranded conductor RG58C/U is listed for $0.39/ft at Maple Leaf Comm http://www.mapleleafcom.com/ (although Bob is trying to retire & has moved some products to other sellers)
Cheapest RG400 I've found is Chinese stuff from amazon.ca at $43 for 20 ft. Aircraft Spruce in Chatham has it for $5.40/ft (ouch) https://www.aircraftspruce.ca/
73
Dave, VE3WI
W9IQ specifies very expensive RG400 teflon coax. Good quality RG58 (with solid dielectric & 95% braid) is the same size & should work fine unless you're running a big amp. The stranded center conductor type would be definitely preferred over solid single conductor, for ease of winding. Don't use the foam dielectric type.
Solid dielectric stranded conductor RG58C/U is listed for $0.39/ft at Maple Leaf Comm http://www.mapleleafcom.com/ (although Bob is trying to retire & has moved some products to other sellers)
Cheapest RG400 I've found is Chinese stuff from amazon.ca at $43 for 20 ft. Aircraft Spruce in Chatham has it for $5.40/ft (ouch) https://www.aircraftspruce.ca/
73
Dave, VE3WI