On 2025-05-20 3:07 PM, Tim Duffy wrote:
Many times guys would catch the 80 meter mast insulator on fire at
the top of the tower section (24 ft.). when running high power in
the CW section of> 80 meters. Substituting Teflon for the PVC
insulator fixed that issue
Had it happen years ago (with just an SB-220) ... the carbon black in
the plastic made the insulators less than good insulators. When they
got dirty and damp they would start to "track" and eventually burn.
Make the replacement insulators a couple inches longer than the original
and move the bottom insulator as close to the attachment point of the
75/80 meter wire as possible.
The HyGain CW mod is actually the 160 Meter loading coil LC-160Q -
4 turns per inch, 3 inch ID x 10 inches long (#10 solid wire IIRC)
mounted on an insulating board (through the center). 80 meter
operation is conducted with the tap near the top - adjusted for
your choice of "sweet spot". Construction is shown in Figure 13
(page 16) of the HyTower Instruction Manual. It would not be
difficult to calculate the overall inductance of that coil and
build a version with - say - 3/16" tubing.
73,
... Joe, W4TV
On 2025-05-20 3:07 PM, Tim Duffy wrote:
One other comment is that the original HyGain 80 CW mod (loading coil) that
MFJ sold - had its challenges.
Many times guys would catch the 80 meter mast insulator on fire at the top
of the tower section (24 ft.). when running high power in the CW section of
80 meters. Substituting Teflon for the PVC insulator fixed that issue
73
Tim K3LR
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
Brown
Sent: Tuesday, May 20, 2025 3:01 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 80m loading coil for 18-HT
On 5/20/2025 11:42 AM, n5xz@earthlink.net wrote:
I'm looking to installed an 80m loading coil in my 18HT tower
If you can't find one, or info on one, you might want to try sweeping
the antenna with a complex impedance analyzer (VIA) that can export a
file to one of the versions of NEC, and design your own. The general
approach would be to find the suitable inductance, then go to inductor
design tools to come up with its physical design. SimSmith is also a
useful tool for designing something like this.
73, Jim K9YC
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