Hi Roger,
I'd suggest all the failures you cite aren't actually related to the issue of
joint conductivity.
Solder deteriorates when exposed to weather. We know that, so why F12 didn't
account for it, I can't say.
Rough handling damages joints. Still not related to the hand-wringing over
whether a joint between two parts of an element is capacitive or resistive or
some combination both. My point was simply history suggests, absent damage or
poorly chosen fastening methods (such as plain solder or clamping unslitted
tubes with hose clamps), whatever electrical characteristics may exist at a
joint of two parts of a tubular element are of little consequence. At least at
the time of assembly.
A poorly placed rivet that allows for slop to develop is also unrelated to the
question of whether noalox serves to introduce a fatal amount of reactance.
The right choice of fastener is important for the longevity of the connection,
no question. But at the time of assembly, all of the current fastening methods
(rivets, hose clamps, compression rings, screws, etc.) should all render
differences in joint conductivity to below our ability to discern on the air.
I guess if one really wanted to be picky, the ultimate solution would be to
invent a device that could extrude tubing on site with a built-in taper. No
joints!
You could build your yagis the same way eavestroughers manufacture seamless
gutters on site. With enough adjustability to the extruder, you could even
manufacture one-piece booms.
73, kelly, ve4xt
ps: the on-site extruder was a joke. Please, no comments on whether the
metallurgy is sound!
Sent from my iPad
> On Mar 9, 2016, at 10:59 PM, Roger (K8RI) on TT <K8RI-on-TowerTalk@tm.net>
> wrote:
>
> It would certainly seem like it, but I'm not so sure. Most of the better
> antennas work well once tuned up and may work great for some years. The C3i
> antennas were great performers for some years. Yet when taken down, the coax
> match on all had the solder dissolved to the point where the matching section
> was no longer connected. They would have stayed up for 4 or 5 more years
> before they failed, but a flock of Cormorants decided "THAT C3i 7L 6-meter
> antenna" was going to be their roost. So I think failures are often
> attributed to the weather or age rather than design.
>
> I found a broken element tight at the first rivet on the C19XR. Admittedly it
> was from rough handling. My wife had some neighbors move the antenna (on saw
> horses) when I wasn't available to help. Holes in elements weaken them at
> that point, so I'd want that first rivet a little farther back so the larger
> tube would support the smaller at the weakest point.
>
> Loose rivets? I wonder if that was an installation problem? With pop rivets
> even cleaning the hole out with even a 1/64th over size drill would likely be
> a source for problems. Pop rivets should be snug. If installed one-at-a-time
> the following rivets may not want to go in, resulting in a hole being
> redrilled
>
> 73
>
> Roger (K8RI)
>
>
>
>> On 3/9/2016 Wednesday 8:21 PM, Kelly Taylor wrote:
>> Isn’t a lot of this talk a bit of picking the pepper?
>>
>> If joint conductivity of aluminum elements was a serious issue, wouldn’t we
>> have heard something about it in the, what, 60 years we’ve been using
>> aluminum tubing for antenna elements?
>>
>>
>> 73, kelly, ve4xt
>>
>>
>>> On Mar 9, 2016, at 6:36 PM, George Dubovsky <n4ua.va@gmail.com> wrote:
>>>
>>> If you weld the aluminum tubing, you destroy the heat treatment in the Heat
>>> Affected Zone, resulting in a much weaker element.
>>>
>>> 73,
>>>
>>> geo - n4ua
>>>
>>> On Wed, Mar 9, 2016 at 6:43 PM, Tom_N2SR via TowerTalk <
>>> towertalk@contesting.com> wrote:
>>>
>>>> If you weld the tubing together, what is the wind rating then? Kind of
>>>> difficult to get apart, but very little risk of losing electrical contact,
>>>> rivets failing, rusted screws, etc.
>>>>
>>>> Someone should try it and report their results.
>>>>
>>>> Tom, N2SR
>>>> _______________________________________________
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>
>
> --
>
> 73
>
> Roger (K8RI)
>
>
> ---
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