After doing some work on the franken-hustler 6-BTV, I thought I'd replace the old home brew choke at the feed point with a different version.   I had run across a supplier with a pretty decent selection & pricing for ferrites: http://www.kf7p.com/KF7P/Ferrite_chokes.html  and picked up a few, including some FT240-31 toroids specifically for HF chokes.   Type 31 has similar characteristics to type 43, but a broader range that extends into the lower HF freqs.

This time around, I went with a teflon jacketed coax rather than a bifilar wrap.  I ended up using RG-316 for ease of wraps & what looks to be adequate power handling for my uses.   Anyway, this is what the finished product looks like:



I made up two, one for the feed point on the vertical & one on the 6 way antenna switch.  The one in the shack was left open so I could see if any power issues might crop up.  I did test with 1KW cw key down into the dummy for about 45 seconds & only a very slight degree of warmth in the coax.   I also swept the choke, terminated w/50 ohms,  from 1 Mhz -> 30 Mhz with the AA-170.  SWR was <= 1.02:1 for the full range.

Sweeping the sheath through the same range was showing impedance numbers of > 1000 ohms (multiples) for the majority of the range, dropping to 850 - 900 at about 30 Mhz.
(I know it isn't the proper tool for a real test of the wound toroid impedance, but it is what I have, so I took a look ....)

We'll see how it pans out over time.  I haven't really ever run into common mode RF issues, but figured I might as well be pro-active.

There is some serious ham radio in this thread!!! Good job.

They look great!

Fantastic job. I have found running chokes at various points cuts down on noise coming from the shack at the antenna. When I run field day at the EOC i can kill 2-3s-units of noise by putting them right at the outside of the building.

That looks first class!