[TowerTalk] 1-5/8 inch Andrew Hardline stored outside in New England for 5 years - still good?

[K8RI]

On 5/29/2013 10:36 PM, Jim Brown wrote:
> On 5/29/2013 9:32 AM, William Hein wrote:
>> I have some 1-5/8 inch Andrew Hardline (LDF7-50A) which has been
>> stored outside in New England for 5 years - is it still good and if
>> not can it be rehabilitated?
>
> I'd say it depends on whether water has penetrated it, which in turn
> depends on whether the ends were weatherproofed before that 5 years
> began. It also depends, of course, on whether it might have taken
> lightning hits.
>

I can thinl of two problem with water. If it gets inside the hollow 
center conductor and freezes it could rupture the conductor, possibly 
introducing a discontinuity which would probably be OK for our power 
levels on HF, but it should be thoroughly dried out. OTOH it could be 
quite a problem at UHF and up

The other is end penetration between the dielectric and shield and 
between the dielectric.  As the foam is closed cell it probably wouldn't 
be a serious problem on HF although I think it could create a layer of 
oxide.  It's unlikely the water would penetrate more than a foot or two 
, but not impossible.  In most cases removing a foot or two off the end 
should be sufficient and allow a visual check.

However Jim's suggestion of the VNA is a good one and an important check 
of any old or unknown coax.  It can give you loss at any frequency, a 
profile of the coax for discontinuities within a foot or two, and a 
check of the velocity factor when used as a TDR.

If you know the impedance and velocity factor it can tell you how much 
is in a coil or left on a reel.


> This is a great application for using a VNA (vector network analyzer) to
> measure loss and do a TDR sweep (Time Delay Reflectrometry) to look for
> damage. To do TDR, you'll need connectors on at least one end, and to do
> loss, you'll need connectors on both ends.

It might take adapters, but some VNAs come with calibration resistors.
There are some very good ones
>
> If you don't own a VNA, ask around your neighbors -- there's a good
> chance that someone you know owns one and will volunteer to sweep it for
> you.

VNAs like the AIM 4170 cover up through 2 meters and run just shy of 600 
with all accessories including a nice protective carrying case.

If you really want UHF coverage it'll run close to a grand, but a great 
idea for a club purchase.

I use the less expensive 4170C and not only check the antennas and feed 
lines from the operating position, but by switching it to the tuner I 
can tune far faster and to an SWR beloe 1.0X.  Often to less than 
1.00X:1 and see the return loss at the same time.  Record the traces 
from the VNA and TDR showing the antenna characteristics, write protect 
the files and you can then call up the files and hit retrace which will 
give you a display of the original characteristics withe current ones as 
an overlay to instantly see any changer in the feed lines, switching, 
and antennas.

The device is far more versatile than an SWR meter.
This becomes evident the first time you use a tuner and see what happens 
to the return loss, or the 2:1 points in frequency.

I have a 3 position Alpha delta switch on the input to the tuner. One 
position goes to the rig and the other goes to the VNA.  I can tune the 
amp into the dummy load and the antenna with the VNA, switch back to the 
rig and it's ready to go.

73,

Roger (K8RI)

>
> 73, Jim K9YC
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