Steve,
After calculating loss when studying the different feed lines, then thinking
about the connectors,
it is painful to then think about introducing loss back in with connectors. I
see the insertion loss
is extremely small with the connectors, so no worries.
I am definitely going with BuryFlex for the rotator loop and up to the ant
connections. The run is fairly
short and I found the loss is not that much different compared to LMR400
especially for a short run like this.
Now to decide feed line to the tower. I have some good options to consider
thanks to you and and
the other posts. I wont be burying the feed to the tower and Cellflex looks
attractive. Nice low loss, comparable to
Heliax, and more flexible than Heliax I understand.
Thanks for the info Steve, much appreciated.
73,
Bob
K6UJ
> On Aug 2, 2015, at 9:43 AM, Stephen Davis <sdavis@davisrf.com> wrote:
>
> John and Charlie are correct, no need, and physically impractical, to be
> running one type of coax all the way to top and or to antenna. Noted was
> Bury-Flex ™ . At HF & VHF , the attenuation difference is minimal, LMR400 vs.
> Bury-Flex ™ (I'm partial to Bury-Flex ™ ….maybe say I'm biased because I
> designed it). Although I don't know the length you have to run, thus the
> actual attenuation difference. I can provide that to you for any choice of
> cable you want to analyze, just need freqcy range of the application and
> length. Bury-Flex ™ can be used as a rotor loop, just add about 20% more
> length than you would for an RG-213 or similar loop. LMR 400 UF for a loop:
> NO, the outer jacket is TPR, won't last as long as Bury-Flex ™ or 9913F7.
> We can equip you with any coax you want. 1/2" Heliax you can direct bury
> (same for LMR-600, the 600 also comes in a DB (direct bury) but you will be
> OK using their std. 600, it has exactly the same outer jacket PE, the DB just
> has the "Grease" which is only there to fill any knick in the outer jacket if
> you just happen to drive a stake, or roto till (yikes, in the area of your
> cherished buried cable HI) in errant fashion.
> The grease will also act as a thermal barrier against wide swing temperature
> inversion… but that usually is only an issue where moisture is already inside
> and the temp drops a lot. Or you take the reel of cable from your 70 deg F
> , into cold outdoor temps.
>
> Grounding the shields: we have some not so expensive grounding kits which
> you just cut away the out coax insuation, clamp it on and the other end of
> the grounding wire that comes with it
> can be clamped to tower leg. Yes, it is real good idea to ground at top and
> bottom, but that theory usually is associated with using an inline surge
> protector, Polyp[haswer, at top and bottom. Without the surge protector, the
> only thing you are really giving a ground path for is the outer shield
> conductor vs. the center conductor would also be protected with a Polyphaser
> device.
>
> Lastly, don't worry about putting connectors into the coax feed line, i.e.
> bottom and top of tower, at the entrance panel to your house or shack, and
> a transition at the drip loop. So many hams worry about insertion loss of
> connectors and adaptors. THe max insertion loss of a good commercial grade
> connector or adaptor is only .200 dB
> at the MUF of the connector. UHF females and males (SO 239 and PL 259 ) are
> MUF 300 MHz. The X to Y is linear so if you are operating at 30 MHz, you
> insertion loss would be
> 30/300 = .10 X .200 at MUF = .02 dB per connector or adaptor.
>
> 73 Steve, K1PEK DAVIS RF Co.
>
>
> On Aug 2, 2015, at 9:42 AM, towertalk-request@contesting.com wrote:
>
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>> Today's Topics:
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>> 1. Re: LMR600 up to the top of tower ? (Charlie Gallo)
>> 2. Re: LMR600 up to the top of tower ? (Steve Sacco NN4X)
>>
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Sat, 1 Aug 2015 22:02:45 -0400
>> From: Charlie Gallo <Charlie@TheGallos.com>
>> To: john@kk9a.com
>> Cc: towertalk@contesting.com
>> Subject: Re: [TowerTalk] LMR600 up to the top of tower ?
>> Message-ID: <1210224415.20150801220245@TheGallos.com>
>> Content-Type: text/plain; charset=iso-8859-1
>>
>>
>> On 8/1/2015 john@kk9a.com wrote:
>>
>>> I would never run one piece of coax underground that far and then up the
>>> tower, especially with a crank-up. The tower piece will likely get damaged
>>> at some point. LMR600 is not that flexible and certainly would not be good
>>> for your rotator loop. I would direct bury large Heliax underground and
>>> then use something flexible and tough (like Belden 8267) on the crank-up
>>> tower.
>>
>>> John KK9A
>>
>> Yep - Remember, your coax shield should be tied to the tower at the
>> bottom AND the top. (Gee, yes you can carefully strip the outer jacket
>> and bond,
>> but easiest way is something like a PL-259 bulkhead connector mounted
>> to the tower (or polyphasor or similar - at least at the bottom)
>>
>> You can easily transition from one type of coax to another at these
>> points - tun the 600 to the bottom of the tower, and then buryflex (or
>> say LMR400) up, and then transition to something flexible at the top
>> ground point. All done, simple, and you are on your way to the start
>> of proper grounding too
>> --
>> 73 de KG2V - Charles Gallo
>> Quality Custom Machine-shop work for the radio amateur (sm)
>>
>> www.baysidephoto.com
>> www.thegallos.com
>>
>>
>>
>> ------------------------------
>>
>
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