I've been watching a lot of The Smokin Ape's youtube about cmc chokes, baluns, ununs, etc.

I ordered a couple 240-31 toroids and wrapped one with a 2 left 2 right 1:1 and the other one with a 6 forward crossover 7 backward 1:1 (14ga THHN)

I'm still learning the NanoVNA.  The 6 forward 7 back has more S21 attenuation across the HF range, which surprised me after watching so many videos that test and prove the 2 left 2 right method.

When I look at the smith chart for the S11 it has an arc that is way off 50 ohms.  I'm trying to wrap my head around impedance matching.  My radio and coax is 50ohm, my Hustler 5 BTV is something less (25 to 30 I think, but I'm making changes to the install...)  

How do you all look at CMC chokes and impedance matching?  Any advice on which setup/measurements are important on the NanoVNA (other than the calibrating at the reference plane)? Anyone recommend videos that explain why difference between the S21 logmag when reading one wire vs both?  (I know they balance each other, just trying to figure out is the 2 wire S21 is useful).

http://k4sx.com/CommonModeChokesW1HIS2006Apr06.pdf

10-12 turns of RG 58 through one of those toroids would do it, as well as winding 12 bifilar on each side and soldering them color to color. In my experience, the swr will rise a bit in the higher bands, but nothing concerning with a 31mix.


I made one with 31 mix beads like this one. It works pretty well.

I'm lazy, and have a 50 ohm resistor jig I use to do a quick test with a rig expert to check my work.
I hook them up with the antennas and then test and adjust the antenna.

I'm more curious about impedance matching than how to wrap. What kind of analysis do you all do on your antenna and components?

For my antenna, I use the NanoVNA:
S11 LOGMAG for resonance
S11 SWR for swr
S11 smith R+L/C for impedance
For choke:
S21 LOGMAG for attenuation

I'm trying to decide if I should short one side of toroid, put a couple 100ohm resistors across 1 side for 50ohm resistive load, or load it with antenna to see impedance.

My guess is that I can just load it with antenna and see what happens. I'm going to try to make more progress on the install today and see what measurements I get.

I use my rig expert for testing. For a 1:1, I use a 50 ohm resistor on the "antenna" side. For a 9:1, I have 450 ohm resistors, for 49:1 2450 ohms, etc. They aren't perfect, but It will let you know pretty well how it is going to perform. I get smith chart readings, pretty much everything you can get from the nanovna on their free software.
I will adjust the windings on the toroids if they aren't working as well as they should, or even redo them if they suck. It's part of the fun of making your own antennas, and helps with troubleshooting the whole system. If I know that the transformer is performing and my readings are way off I can look at things like the coax or connectors as an issue.

Do you impedance match the choke, or just get decent attenuation? I'm trying to decide if this is overboard (like matching null on feedline) or if it effects antenna efficiency.

I check the transformers with my jigs, hook everything up and trim my wire. If I have obvious issues, I have a good base to see what the problems is. I don't go overboard as I know what should work and what shouldn't.
Edit: I used to shoot for 1:1 with every antenna, and that just gets frustrating. I will take 1.5:1 with 50 ohm impedance over 1.1:1 with 30 ohms impedance.

My bifilar cmc shows 50-ish ohms resistive on the smith chart in S21, but S11 resistive is over 1 kohms. I'm guessing that a S21 of 50 ohms means I don't need to worry about a transformer between the cable and choke. I am still curious if some kind of transformer to match the 50 ohm coax to the 30-ish ohm antenna would help.

I got a 4x4 in the ground for a more solid mount. Bought some of that pet fence wire and made new radials. 8 are 33ft long and 8 are 17ft long. They barely fit in my limited space. I went out today and used my shorter section of RG8 to check the antenna.

I'm very happy with logmag and swr on 10m. 15m is also good. 20m is ok.  I inserted my homemade coil and got a section of 40m under 2 swr and about -15 dB logmag.

I need to figure out a better way to contain the choke. My next step will be to try tuning up each band without the choke, then adding it and seeing what difference it will make. I still don't have my feedline installed, so that's what I'm piecing together.

Also, if anyone has recommendation on which part of 80m I should try to tune my resonator, I'm interested in the what and why.

Decide what portion of 80/75m is most important to you. Do you want to work digital, or CW, or SSB?

No digital capability right now, don't know CW yet, so just SSB

I saw a video recently where a guy tested the big snap-on mix 31 beads.  He ran attenuation tests with various number of beads and found that he got better attenuation, naturally, with more beads.  But beyond 7 beads there was so little increase as to be meaningless.  Diminishing returns and all that. So there you have it, seven beads.

5 solid beads as illustrated above from fair rite will do the job.

For my vertical, I put down 32 16' radials, as I had hoped to add 80m to it, but I couldn't get it to work well enough. I haven't seen how many you have down at this point.