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Total 950 documents matching your query.

181. Re: [TowerTalk] WTB: GAP VOYAGER and a ???? (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Fri, 09 May 2008 12:18:57 -0700
I'm sure it is. The manufacturer's description says it needs to be used with a tuner (excerpt from the manual reproduced below) as well as the 4:1 balun. Personally, I find the comment about coax len
/archives//html/Towertalk/2008-05/msg00113.html (10,146 bytes)

182. Re: [TowerTalk] excavator (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Mon, 12 May 2008 14:19:04 -0700
What makes you think it is discretionary for the average ham? 1. Backhoes generally dig square holes. An auger large enough to dig a large hole is going to be much larger and more expensive than a ba
/archives//html/Towertalk/2008-05/msg00218.html (7,815 bytes)

183. Re: [TowerTalk] Square vs Round Holes (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Mon, 12 May 2008 17:18:34 -0700
I agree. Calculating equivalences (round versus square) almost for sure requires a competent engineer, and it might even (maybe even probably) be significantly different depending upon location. For
/archives//html/Towertalk/2008-05/msg00233.html (9,773 bytes)

184. Re: [TowerTalk] Tower grounding (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Wed, 28 May 2008 21:36:13 -0700
I have an Ohms Law question for you with respect to that comment. Let's assume the tower base is secured within the concrete (and therefore the lightning has an extremely low impedance path into the
/archives//html/Towertalk/2008-05/msg00501.html (9,315 bytes)

185. Re: [TowerTalk] tower ground question (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Thu, 29 May 2008 01:45:31 -0700
Why? If it is indeed a low impedance path (and it would be useless if it wasn't), why is it less desirable to run it through the concrete than around it? Why? The tower legs (or the tower base or the
/archives//html/Towertalk/2008-05/msg00503.html (10,017 bytes)

186. Re: [TowerTalk] tower ground question] (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Thu, 29 May 2008 09:48:30 -0700
The tower is Cadweld bonded to every single stick of rebar at the bottom of the cage, representing 16 cross pieces each 9 feet long (eight sticks in each direction) plus the bottom perimeter rebar co
/archives//html/Towertalk/2008-05/msg00523.html (9,598 bytes)

187. Re: [TowerTalk] tower ground question (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Thu, 29 May 2008 11:03:21 -0700
Per your comments, the two towers you refer to were isolated from the concrete base. That is the same condition described by Polyphaser for the single semi-verified claim of an exploding base they co
/archives//html/Towertalk/2008-05/msg00528.html (12,813 bytes)

188. Re: [TowerTalk] tower ground question (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Thu, 29 May 2008 11:15:54 -0700
I've never understood that comment either. I fully agree that rebar or anything made of steel will rust and the rust will propagate along the rebar into the concrete, but copper doesn't do that. Some
/archives//html/Towertalk/2008-05/msg00530.html (10,350 bytes)

189. Re: [TowerTalk] Rebar (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Thu, 29 May 2008 11:33:26 -0700
I could be wrong, but I don't think it is the water infiltration by itself that causes the problem. Concrete is inherently porous and there are typically thousands of microcracks in it anyway. In the
/archives//html/Towertalk/2008-05/msg00534.html (8,310 bytes)

190. Re: [TowerTalk] tower ground question (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Thu, 29 May 2008 12:13:33 -0700
Actually, we may be approaching some common ground here ... Yes, I would agree that a good shunt path outside the foundation would be desirable for the reasons you mention (ability to monitor corrosi
/archives//html/Towertalk/2008-05/msg00538.html (13,646 bytes)

191. Re: [TowerTalk] Faraday Cage (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Sat, 31 May 2008 13:36:25 -0700
Hi, Warren. I was going to suggest that 1/10 wavelength grid spacing at the highest frequency you want to shield would be sufficient, but I found this reference that recommends 1/20 wavelength. http:
/archives//html/Towertalk/2008-05/msg00590.html (8,599 bytes)

192. Re: [TowerTalk] Faraday Cage (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Sat, 31 May 2008 16:57:26 -0700
To what attenuation level? The attenuation is logarithmic with spacing, and I can't believe that a quarter wavelength would provide more than about 3db or 6db attenuation. Dave AB7E _________________
/archives//html/Towertalk/2008-05/msg00592.html (11,160 bytes)

193. Re: [TowerTalk] Faraday Cage (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Sun, 01 Jun 2008 13:47:14 -0700
Just a cautionary note here. Somehow I assumed you were talking about ambient RF shielding, but if you are talking about lightning protection, my guess is that the greatest jeopardy from a strike com
/archives//html/Towertalk/2008-06/msg00021.html (8,810 bytes)

194. Re: [TowerTalk] Identify Hardline (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Wed, 18 Jun 2008 19:43:08 -0700
I'm not sure you're going to be all that thrilled with it. Here's what the Tessco web site says about it: "Radiax slotted coaxial cables solve wireless communication problems in confined areas, such
/archives//html/Towertalk/2008-06/msg00382.html (9,135 bytes)

195. Re: [TowerTalk] Help with "stringer" rope...... (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Sat, 21 Jun 2008 17:29:59 -0700
I'd try dacron fishing line: http://tinyurl.com/3ekt64* *Soaking it in some black ink should color it fairly well. 73, Dave AB7E* * fraz1 wrote: _______________________________________________ ______
/archives//html/Towertalk/2008-06/msg00429.html (7,983 bytes)

196. Re: [TowerTalk] Mounting roof-top tower on tile/shake roof (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Sun, 22 Jun 2008 10:15:23 -0700
In general, tiles and shakes are not intended to provide the primary rainproofing for a modern roof. A heavy underlayment typically provides the rainproofing, and the tiles/shakes provide mechanical
/archives//html/Towertalk/2008-06/msg00468.html (10,400 bytes)

197. Re: [TowerTalk] Lock nuts revisited (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Mon, 23 Jun 2008 13:59:27 -0700
Accepting Roger's empirical results at face value, how about the following hypothesis: I don't know for sure, but I suspect that most of the friction that hold a threaded bolt in a threaded hole is t
/archives//html/Towertalk/2008-06/msg00496.html (11,742 bytes)

198. Re: [TowerTalk] lighting protection setup (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Fri, 27 Jun 2008 13:42:50 -0700
That is all good and valid info, but the problem Jorge described is static buildup on the wire dipole itself, resulting in a spark jumping across the end of the coax connector (from pin to shield) in
/archives//html/Towertalk/2008-06/msg00656.html (12,450 bytes)

199. Re: [TowerTalk] Transmission Line theory (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Tue, 01 Jul 2008 14:02:48 -0700
I found a program called "atlc" (arbitrary transmission line calculator) by searching on Google. If you can wade through how to use it, it supposedly will calculate the transmission line impedance of
/archives//html/Towertalk/2008-07/msg00017.html (9,625 bytes)

200. Re: [TowerTalk] Coax Comparison Chart (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Tue, 01 Jul 2008 21:46:15 -0700
Don't forget TLW, the transmission line software that comes (free) with the (not so free) ARRL Antenna Book. TLW won't give you voltgae or power ratings, but it will give you loss and impedance trans
/archives//html/Towertalk/2008-07/msg00027.html (8,778 bytes)

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