[TowerTalk] LMR600 male DIN - baluns, coax and grounding immediately
StellarCAT
rxdesign at ssvecnet.com
Thu Sep 8 10:51:11 EDT 2016
and more than likely ANYTHING you had done to waterproof the connectors
including water proof connectors would have failed with a direct hit. Just
because a connector might be water proof doesn't make them a magic energy
sink capable of thousands of joules... Grounding the shell at the top and
bottom (and middle if over ~75') which is what I plan on doing is probably
the best thing - and I'm sure you had that as well.
Indeed therein lies a problem - how to do this AND seal it ... at the base
I'll have a box on the tower so that connection is inside (metal box with a
separate connection from the inside to the tower as well). All of the
antennas but one are hairpin matches so it will be DC grounded through that
at the antenna and the 2 switch boxes (stacking and then antenna select)
will accomplish two more grounding points ... the 4 element Optibeam 40 will
need a think through.... and the rotary 80/75 dipole at the top - its
hairpin is a coil and is not grounded ... hmmmm....
that brings up a question: Does having a balun at the antenna - assume a
good one - allow one to ground the shield of the coax to the tower
immediately ... i.e. say the DE is out 20' ... there is a balun there ...
can one have another connection at the tower and have that connection shell
grounded - does the balun make this possible? I believe I know the answer
(and I'm trying not to get in to the QUALITY and capability of the balun)
... but would like to hear from the experts - K9YC?
Gary
K9RX
-----Original Message-----
From: Roger (K8RI) on TT
Sent: Wednesday, September 7, 2016 8:24 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] LMR600 male DIN
I've said it many times, I used to feel like you toward connectors,
until a direct lightning strike to the top of my tower removed all of
the weatherproofing and 15 minutes later I had water running out of my
rig onto the desk top. It didn't hurt the rig, but it ruined the desk
top. 40 years total at 3 locations with nary a problem, but one strike
ruined 200 feet of 9913, IIRC 8 connectors, and a desk top
If you are on HF, Unless it is a long line, or you consider the legal
limit as QRP, as far as I can see, there is little to be gained from
using these expensive cables
I found 1/2" Heliax too fragile for kinking, or being stepped on. I gave
away two 100' runs with connectors. and went to LMR600. Now if I could
have found 7/8ths Heliax at a reasonable price, I would have used it for
VHF and UHF. The only time I saw a good price was a pick up load for
the repeater that was free free, but none as an individual.
Total length from my rigs to the top of the tower was 200 feet with
rotator loops and 28' pigtails to the antennas
73
Roger (K8RI)
On 9/7/2016 Wednesday 7:50 PM, Kevin wrote:
> I believe it all started with the superiority of heliax/hard-line from a
> loss perspective and since UHF type connectors for such cable are
> expensive and rare why not use 7/16 DIN, a commercial standard connector.
>
>
> On 9/7/2016 10:26 AM, StellarCAT wrote:
>> Forgive me - I've replied to Gerald's email but this is directed to the
>> thread in general: WHY all the concern for sealed connectors and
>> connector types? I've been using UHF for 49 years and the only time I've
>> had issues with those installed outside it was my fault - either poor
>> wrap of tape or poor solder job ... I've had cables with connectors that
>> were out for years with electrical tape wrapped around them in 2
>> directions - years later when disassembling them for a move they were
>> utterly pristine! I don't get it - why so much discussion?
>>
>> Gary
>> K9RX
>>
>>
>>
>> -----Original Message----- From: TexasRF at aol.com
>> Sent: Wednesday, September 7, 2016 8:56 AM
>> To: john at kk9a.com ; towertalk at contesting.com
>> Subject: Re: [TowerTalk] LMR600 male DIN
>>
>> John, you bring up a valid concern. I am not aware of any coaxial type
>> connector that could be considered waterproof. The fundamental reason is
>> because the threaded connections do not create a hermetic seal when they
>> are
>> screwed together.
>>
>> There are inevitable air spaces inside the connectors and coaxial cables.
>> These air spaces will fill with air. When the air is heated (like outside
>> in full sun) it will expand, creating a positive pressure. Conversely,
>> when
>> the air cools (like at night), it will create a negative pressure. This
>> negative pressure will suck tiny amounts of water vapor through the
>> threads of
>> the connector.
>>
>> If enough water vapor is present droplets of water can condense during
>> the
>> cooling cycle and over the course of days and weeks can collect inside
>> the
>> connector. Once inside, there is no escape and the droplets continue to
>> collect over time.
>>
>> If there are rain or dew drops of water on the outside of the cable, they
>> can also leak through the threads and collect inside the connector.
>> Gravity
>> is not your friend here.
>>
>> Many commercial applications pressurize all of the cables even if they
>> are
>> foam filled types to prevent the problem. You may have noticed many of
>> the
>> Heliax type connectors have air fittings; that is why.
>>
>> 73,
>> Gerald K5GW
>>
>>
>>
>>
>> Over
>>
>>
>> In a message dated 9/7/2016 5:37:52 A.M. Central Daylight Time,
>> john at kk9a.com writes:
>>
>> Is any TX connector really water proof? Are DIN's being professionally
>> installed with no external butyl rubber and tape? On the two outdoor DINs
>> that I have, I weather proofed the connection the same way I did with UHF
>> and N connectors.
>>
>> John KK9A
>>
>>
>> To: towertalk at contesting.com
>> Subject: Re: [TowerTalk] LMR600 male DIN
>> From: "Roger (K8RI) on TT" <K8RI-on-TowerTalk at tm.net>
>> Date: Wed, 7 Sep 2016 01:08:48 -0400
>>
>> Take care!
>> According to the Amphenol page N-Type are not water proof/weather proof.
>>
>> 73
>>
>> Roger (K8RI)
>>
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>
--
73
Roger (K8RI)
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