While we are talking about inductors, I have a question. I want to build a trap for 40 meters. This trap will be on the top of my 20-meter vertical leading to a top hat that will extend the vertical with another set of radials to 40 meters. I know it in a coincidence of the inductive Xl and the inter winding Xc that brings resonance. How do you test for it? When I wound 28 turns of #14 THHN on a 1.5" pvc form thinking this would be a trap somewhere and I could trim accordingly. I get these results:
At 34 mHz I get a dip to Xs of 200 Ohms on my 269 analyzers in the main or vswr / Xs mode. Using the inductance mode at 43 mHz I get a dip of almost no L. I tried the sniffer as a grid dipper and found no dip Reading the 529 manual I found the advanced mode, Page 16. Hold down the mode and gate button and select advanced one and then step mode to resonance. What I get is like a low pass filter with a shelf at 21 mHz. Not a resonance My Measurements Lab (Millen) Grid Dipper shows a dip at 45 mHz or so. I think I will believe the Millen. The real find was the advanced functions on the 529. Some pretty neat features. I think I need more turns. I think I will try maybe 50 turns of enamel on a 2.5” form and trim it back. I also expect the Xl &Xc will affect the antenna lengths. Any thoughts? Another Question, has anyone tried Flex Seal to waterproof a coax connection? Maybe a layer of tape then spray. John ParmaleeJparmalee@aol.com281-380-3811 K5VGM WI2XLJIn a message dated 6/29/2022 12:51:38 PM Central Standard Time, bvarc@bvarc.org writes: Thanks for info! I ended up figuring out my issue (it was something else) but it’s good to know this stuff. I have that handbook and I’ll take a look. 73, Mike GiannaccioW5REZ On Jun 29, 2022, at 11:09 AM, Rick Hiller via BVARC <bvarc@bvarc.org> wrote: The Radio Amateurs Handbook (aka The ARRL Handbook for Radio Amateurs) gives an excellent explanation of coils, windings, interwire capacitance etc. Pretty much any edition back to the beginning of ham time has it. However, for those living in the 21st century HI, in the 2000 edition i.e. find complete explanations under AC Theory and Reactive Components, Real World Component Data and in the Reference section. A little RF design knowledge for your entertainment this AM. 73...Rick -- W5RH On Wed, Jun 29, 2022 at 9:50 AM Gary Sitton via BVARC <bvarc@bvarc.org> wrote: Yes, that's also another reason for the increased spacing.Gary K5AMH On 6/29/2022 9:00 AM, Joseph Benoit via BVARC wrote: In addition to otherwise stated by K5AMH, as the frequency gets much higher incrementally smaller inductance value is required (wider spacing, turns-per-inch on a given coil diameter) and smaller incremental change is needed to fine-tune if it were. On Sat, Jun 25, 2022 at 11:14 AM Michael Giannaccio via BVARC <bvarc@bvarc.org> wrote: This is probably a basic question but I’ve come up empty in my search and can’t seem to find the answer in the Antenna Book. Can someone explain to me or link me to some reading as to why some roller inductors and screwdriver antennas like the ATAS have less turns per inch on the ends of the coil and more towards the center? I do have the latest edition of the antenna book so if it’s in there I can look it up. Thanks! 73, Mike Giannaccio W5REZ________________________________________________ Brazos Valley Amateur Radio Club BVARC mailing list BVARC@bvarc.org http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org Publicly available archives are available here: https://www.mail-archive.com/bvarc@bvarc.org/ ________________________________________________ Brazos Valley Amateur Radio Club BVARC mailing list BVARC@bvarc.org http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org Publicly available archives are available here: https://www.mail-archive.com/bvarc@bvarc.org/ -- Gary Sitton, K5AMH gasit...@comcast.net SDR/DSP Consultant, "Have FFTs, Will Travel." ________________________________________________ Brazos Valley Amateur Radio Club BVARC mailing list BVARC@bvarc.org http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org Publicly available archives are available here: https://www.mail-archive.com/bvarc@bvarc.org/ -- Rick Hiller e-mail: rickhiller73@gmail.comCell: 832-474-3713Physical: 9031 Troulon Drive Houston, TX 77036________________________________________________ Brazos Valley Amateur Radio Club BVARC mailing list BVARC@bvarc.org http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org Publicly available archives are available here: https://www.mail-archive.com/bvarc@bvarc.org/ ________________________________________________ Brazos Valley Amateur Radio Club BVARC mailing list BVARC@bvarc.org http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org Publicly available archives are available here: https://www.mail-archive.com/bvarc@bvarc.org/
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