[TowerTalk] 40 Meter Yagi

[Jim Thomson]

Date: Mon, 19 Jun 2017 06:56:09 -0700
From: "Jim Thomson" <jim.thom at telus.net>
To: <towertalk at contesting.com>
Subject: [TowerTalk] 40 Meter Yagi

<<<<   If you use Termans  formulae, the coil Q is even less,  but this is all debatable.  

## oops.  termans  formulae depicts the coil Q being a lot more than the k6sti results,
IE: lower ESR.  On one of these small air core hb 40m coils I wound, just 3.5 uh, the ESR per k6sti came out to
.76 ohm  using  .375 OD  CU tubing....and .70 ohm using silver plated .375 cu tubing. 
Using Termans formulae, bare  .375 cu tubing came  out to .5 ohm ESR.   What the actual ESR is,
who really knows.  Q =  XL  /  esr       hb silver plated .375 cu tubing coil, with ends flattened, will handle
a  .25-20  SS bolt.   SS bolt used to bond the ends of the HB coil onto the threaded AL hex shaped standoffs.
Other end of al standoff is bolted to the 40M ele  with another .25-20 SS bolt.  Anything has to be better than
12 gauge magnet wire, wound tight, on a fiberglass or pvc form. 

Jim  VE7RF