[TowerTalk] [Bulk] Re: 90 degree coax bend atop a crankup tower

Sat Jun 6 21:43:13 EDT 2015

There are fairly deep cuts in the concrete, but the whole thing is full 
of1/4" steel mesh.

The whole works needs to be resurfaced as it was poured on a 90 deg plus 
day with not a cloud in sight.  They used too much water to keep it from 
setting up too soon.  Even with keeping it wet, the whole surface was 
spalling badly.
within a year. To resurface it is almost as expensive as redoing the 
entire apron.  I have several diamond blades for the saws along with a 
heavy duty industrial, worm gear drive saw. Unfortunately, neither my 
leg or back will permit working in a kneeling position for more than a 
few minutes.

The point where the concrete abuts against the garage floor does need to 
be cut with an expansion joint (foam or 2 part Silastic) expansion joint 
inserted.  Cutting a close as possible while maintaining a straight cut 
will remove a strip about 3" wide. That would be doable and allow the 
installation of a ground "ring" around the house.  The electrical  
ground and service entrance and the station SPG would still be on 
opposite sides of the house.

If the leg and arm were useful, I'd rent a grinder and resurface the 
apron with the liquid used to get a flat, lever surface.  It would give 
us a really nice surface on the apron that would need some sort of 
additive to keep it from becoming too slippery.  The cost would be 
between $3,000 and $4,000 just for the apron.  The big expansion joint 
and extra 100' of bare #2, plus the extra ground rods and CadWelds with 
labor would probably be another $1,000 or more.  So that puts us at 
roughly another $5,000 (give or take)  to add a ground ring and fix the 
apron.

"I think" I may start a cut across the front of the garage.  It might 
take me the entire summer to make the one cut, but it'd solve several 
problems.It would also join the current ground system close to mid point 
eith the distance from the 45G to the entrance ground about the same as 
from the tower to the station SPG..  Then, I'm not sure the budget will 
stand more than getting around the N end of the garage and to the 
entrance.  The rest of the ground ring and resurfacing might have to 
wait.  Just too many expensive projects going on at one time.  including 
the replacement of about 7 large N2 filled tripane windows.  We recently 
had to dig up the weep tile around half the house and reinforce the 
basement walls as well as some major roof work (due to a poor job done 
in the past) and replacing the 100' 45G with a major, crank up and tilt 
over tower.

Good thing I quit flying and sold the airplane.  <:-))
Still...this would have been a lot easier when I was still working <LOL> 
but hind sight works so much better than foresight.

73

Roger (K8RI)

s
On 6/6/2015 7:33 PM, Roger (K8RI) on TT wrote:
> Migration where the coax is laying on the ground is specific to 
> several types of coax where the materials for the center conductor and 
> outer  (jacket, shield, and braid) have substantially different 
> coefficients of expansion, 9913 is one.  I've never seen it in the LMR 
> series with Al inner and outer construction which OTOH  is very poor 
> about migration in vertical runs.  I've found LMR-600 to be very bad, 
> but single turn loops  16 to 18" in dia about every 50 feet or so, 
> seem to cure it.
>
> I used all, 9913 and was an advocate of proper weather proofing, until 
> lightening blew off all the weatherproofing and less than 15 minutes 
> later /I had water running out of the 2-meter rig.
> Back then I used coax seal, or the 3M equivalent covered with 88 
> tape.  It not only removed all the weatherproofing, but the silver 
> plating as well, leaving the connectors looking like sand blasted 
> brass.  Blowing dry air or N2 through it would have repaired it, but I 
> gave all, or almost all of it away.
>
> 73
>
> Roger (K8RI)
>
> On 6/5/2015 11:15 PM, Richard (Rick) Karlquist wrote:
>>
>>
>> On 6/5/2015 8:00 PM, Roger (K8RI) on TT wrote:
>>
>>
>>> My experience shows "to me" that those using N-type connectors on
>>> vertical runs without problems are quite lucky.
>>>
>>
>> Coax with type N connectors is quite capable of center pin
>> migration in or out just laying on the ground.  About
>> 20 years ago, I bought a bunch of 43 foot long 9913 cables
>> with type N's at a swap meet.  They came coiled up and I
>> just threw them in storage.  By now, every single one of
>> them has the center pins sticking out both ends like
>> pinocchio.  The ones that I used early on that got
>> straightened out for a while, but then were rolled up
>> did better.
>>
>> I had some 500 foot runs of coax laying out on the ground
>> and over time, the center conductor migrated.
>>
>> Going forward, I use PL259's exclusively to avoid this problem.
>> Except on my 7/8 inch coax.
>>
>> Rick N6RK
>
>

-- 

73

Roger (K8RI)

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