There are two reasons.
1) Many of the screw clamps do NOT tighten enough to keep the element pieces
from slipping. I used to test the clamps but tightening as much as possible
(without stripping the clamp) and then trying to pull out the thinnest element
piece – I succeeded ~ 50% of the time. meaning that over time and the normal
expansion/shrinking cycle due to the seasonal temperature changes (coefficient
of thermal expansion) would almost certainly cause the element tip to extend
and ultimately fall out aided and abetted by any wind.
2) The loose fit would allow the element tip to vibrate, which after a period
of time, would cause metal fatigue which could easily cause the element tip to
crack and/or break off. And, once the element tip begins to crack, moisture
can get in and then freeze which would expand any crack or possibly fracture
the element tip.
These are the two most common types of element tip failures associated with the
Hygain antennas and most other types of antennas.
Using my two Stainless Steel hoseclamp method and flattening the hoseclamp ends
and taping over them, I have never had a failure of this type in 18 years on 11
different Hygain Yagis (105CA, 155CA, 205CA). Which, given the prevalence of
ice-storms (averaging 7 per year!), Nor’easters, violent T-storms and
Hurricanes at my qth, is as good any :”real-world” antenna “test-range”. ;-)
BTW, not all stainless steel hoseclamps will tighten all the way either – I
know this from the same test that I performed on the Hygain Screw clamps. With
the hoseclamps, if they don’t tighten all the way and keep the element
completely unmovable, I replace the offending hoseclamp with one that WILL keep
the element tip completely tight.
73
Bob KQ2M
From: john@kk9a.com
Sent: Thursday, June 22, 2017 8:43 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] HyGain 155CA dampening rope
Why would the screw clamp have any effect on the elements braking? The
parts website seems to indicate that HyGain uses 0.028" wall thickness on
their 20m element tips.
http://www.hy-gain.com/Product.php?productid=174939.
John KK9A
To: "Bill Parry" <bparry@rgv.rr.com>, <towertalk@contesting.com>
Subject: Re: [TowerTalk] HyGain 155CA dampening rope
From: "Bob Shohet, KQ2M" <kq2m@kq2m.com>
Date: Thu, 22 Jun 2017 07:47:51 -0400
Bill,
Did you use the stock Hygain screw clamps at the end of the telescoping
elements or did you use stainless steel hoseclamps like I do?
73
Bob KQ2M
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