[TowerTalk] lightning arrester suggesstions

[Jim Brown]

On 12/15/2025 7:18 PM, J. Hunt via TowerTalk wrote:
> A Bias Tee device inserts /  removes a DC signal from a feedline.  This Bias Tee device also creates an impedance bump (seen by an IFR oscilloscope) = signal loss.  Hence, I do not use them, use a separate control cable as needed.

Some of those losses exist only in the mind of those looking at TDRs, 
and/or only working at UHF. More than ten years ago, I made about twenty 
cables for a DXpedition using an RG8-size coax manufactured by Commscope 
designed for use at VHF/UHF with loss specs like LMR400. Solid #10 
copper center, dense tinned copper braid and robust Al foil. It came to 
me around 2003 from a distressed sail to a friend who bought half of a 
truck-load of it after a dot-com bankruptcy. Over the years, I probably 
bought more than a dozen 1,000 ft spools of it, passing some along to 
friends. The non-plenum version is Commscope 3227, the plenum version 
was something like 2726K (I'm 84, and memory fades). I bought mostly the 
plenum version, which is TFE to meet fire codes, and those DXpedition 
cables were the plenum version.

To test the cables, I spliced 13 of them, each with Amphenol 83-1SP 
connectors, with Amphenol barrels, and measured the loss by substitution 
using HP gear, at spot frequencies in log increments from about 500 kHz 
t0 200 MHz. The loss of that 1,300 ft transmission line at 200 MHz was 
slightly less than the mfr's spec. That's for 28 83-!SPs and Amphenol 14 
barrels.  ("By substitution" is an old-school method in which you 
connect generator and voltmeter directly, record the loss, then repeat 
with the DUT  added. It's what we did before we had gear with greater 
precision than a well-calibrated VNA.

This sort of loss is VERY strongly dependent on the operating frequency, 
and can, indeed, be quite significant at high VHF and UHF. Most serious 
ham antennas are for HF, where such losses are far lower. Please don't 
offer VHF/UHF advice to folks working HF. The nature of transmission 
lines makes them two very different worlds.

Because I live in a dense redwood forest, with antennas having to shoot 
through several hundred feet of trees and their foliage, operating at 
UHF and high VHF is masturbation. The highest frequency I take seriously 
is 6M. The lowest is 160M. The 300 ft runs from shack to the top of my 
tallest tower are all 7/8-in.

Good engineering is NOT dancing on the head of a pin, using worst case 
analysis that doesn't apply to the problem at hand. It's not using the 
product that has the greatest advertising budget, or "is the industry 
standard." Or that has the budget to pay the high cost of UL testing. It 
is using solid scientific principles to solve specific problems. The 
former results in $150 hammers (it used to be $80 hammers). The latter 
is how we can do stuff well, at far less cost.

As a retired design professional for systems that are going to get 
inspected, I would be specifying the UL Listed Polyphaser products. But 
as a ham, with a finite budget, the arrestors I've bought in the last 
ten years to replace them are all the Morgan-design that Array Solutions 
was selling.

73, Jim K9YC

73, Jim K9YC