The AM Forum

  Okay, having a memory lapse, here: some outfit was selling filament choke kits, with which you'd get the ferrite rod, wire, and mounting clamps, but now I can't for the life of me remember who it was. I thought I'd bookmarked the site, but I can't find it. Was it Fair-Rite, or maybe Palomar? I've visited both sites, but so far haven't been able to find it on either.

Go to W8JI ctr engineering.  Best setup available right now.

Otherwise I get a torrid donut and wind my own. 

--Shane
WP2ASS / ex KD6VXI

I think it was Amidon who sold the solenoid-wound filament choke kits.  Tom, W8JI, has superior plate chokes as he designs them to avoid resonances in places where they don't belong.
73 de Norm W1ITT

  Yes, it was Amidon, thank you!  https://www.amidoncorp.com/flc-10-kit/
  I've got an amplifier project in the works that will use a trio of 3-500Z's. The filament chokes I have here in my shop are wound with #10 wire; overkill for using one choke for each tube, but not quite sufficient for using one choke to feed all three tubes (I tested that—the single choke gets really hot at 45 amps). These kits use #14 wire, which should be fine at the 15 amp filament current of the 3-500Z—one choke for each tube.
  I do wish that Amidon would provide specs for the kit on their site, though.

  I didn't see filament chokes on the CTR site, but maybe I didn't look in the right place. I do know that he's got excellent plate chokes.

Email Tom.  He makes them with a slew of beads now.

VE7RF has also stayed making them but not sure if he just copied Tom or what.

I use a FT240-43 for 40 meters and up, or type 31 for full HF.   I have been able to wind #6 wire on a torrid for 4 X 500Z tubes.

The chokes I've built have VNA sweeps in other threads on this site.

But, email to with what you need and he will get you straight.

--Shane
WP2ASS / ex KD6VXI

If anyone is interested, Surplus Sales of Nebraska still has NOS B&W filament chokes.

Darrell

   Okay, after talking with Frank, WA1GFZ, about filament choke design, I'm thinking I'll try the ferrite bead approach, sliding 43-mix beads over heavy gauge conductors (45 amps filament current). Heavy conductors, like #4, are a bear to wind around a core; the bead approach is a good solution. Some good info, along with pictures from KL7OF and K1JJ, can be found here: http://amfone.net/Amforum/index.php?topic=48108.0
   Here's a thought: most have been using the single-hole beads, but would the "binocular" cores works as well? I'm thinking about these: https://www.amidoncorp.com/bn-43-7051/
   There would be a mechanical advantage in that the conductors would be kept physically separated, and since ferrite mixes tend to have a very ohmic high resistance, it wouldn't even be necessary to use insulated wire. But my primary question is whether or not the currents in the wire would still cancel, preventing core saturation, as in the case of a standard bifilar rod-wound choke? I should think that they would, since the induced magnetic flux will permeate the entire core whether both conductors are immediately adjacent or not, since they run through the same core.