Jim Thomson wrote:
> Date: Tue, 13 Apr 2010 21:53:49 -0700
> From: jimlux <firstname.lastname@example.org>
> Subject: Re: [TowerTalk] Coax Question
> Kipton Moravec wrote:
>> On Tue, 2010-04-13 at 07:15 +0000, van wd8aam wrote:
>>> In regards to long runs of coax, has any thought EVER been
>>> given to RG213 to a remote tuned high power amplifier
>>> at the base of the tower. I've thought about it, and for
>>> costs, it might be cost effective. I'm sure someone has this
>>> working for them somewhere. What do you guru's say to this?
> ## it's already been done.. and that was 10 yrs ago !
> The kicker is... if you have say 3 db of loss back to the
> station, then you need an extra 3db of drive power. You
> also LOSE 3 db on RX ! You also require a LONG run of 240 vac
> line, to base of tower, OR a 240-600 vac xfmr at the house..
> then another 600-240vac step down xfmr at base of tower.
> ## getting the power out there is gonna kill it right there.
> 600-240 xfmrs [can be run either way] in 5-10 kva
> variety are available surplus.. then some small ga wire
> could be used. Usually, the xfmr at the far end will have
> taps on it.. like 575v.. or 550v etc.... to factor in the V drop,
> so u end up getting the full 240 vac... but only under full bore load.
> No load, the V will rise > 240vac . BIG ga AL wire between the
> 2 x xfmr's would work.
> ## Ok, now you need a small, secure, heated building, to put the
> xfmr plus 1.5 kw amp, plus any SDR radio, etc.
> ## In the final analysis, cheaper to just use BIG coax.
> ## Most telco's in NA, have what's called an "IRG"
> [inventory recovery group]... usually now run by contractor's, whose
> job it is to store un-used eq.. AND cable. They sell cheap, to dispose of
> junk, at pennies on the dollar. A buddy in W7 land picked up several
> 1000' spools of 7/8" heliax, NEW... for $116.00 per reel. The usual deal
> some proposed cell site new job/addition gets cancelled, AFTER the eq has
> arrived. It then all goes to the IRG warehouse. Meanwhile, the same engineer
> orders all new eq for yet another site ! Most of the contractor's at the
> various IRG's
> wouldn't know heliax from a hole in the grnd. Lot's of other good stuff,
> 19" /24" racks, etc. You have to be in the right place.. at the right
> time.. you
> snooze, you lose. If you see 5 x 5'-6' diam reels of coax... and it sez
> on the side of it, snap it up, pay CASH, and get it outa there asap.
> Andrew also makes heliax in corogated AL shield these days... [ instead of
> Cu] The newer AL stuff still uses a CU tube in the middle.
> ## Plan B is the catv coax route. Most of their stuff is 3/4" OD, with a 8
> ga center
> conductor. Solid AL sheath, so you need the coring tool, to put the fittings
> on em.
> Modified LMR-600 connector's might also work.
This is just one of the ways for adapting 3/4" to UHF
> later... Jim VE7RF
>>> At 06:04 4/13/2010, you wrote:
>>>> On Mon, 12 Apr 2010 21:07:25 -0400, Steve Bagley wrote:
>>>>> I am putting up a tower and will need to run about 500 feet of coax.
>> I would probably put a Software Defined Radio (and computer) at the base
>> of the tower and run Ethernet cable back to the shack. Even with that
>> you will need a switch in the middle as Ethernet has length limit of 300
> Use an 802.11 wireless LAN link with directional antennas. Now all you
> do is run AC power out there.
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