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21. [TowerTalk] [Fwd: Towers Brought Down!] (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Tue, 16 Jan 2007 20:36:17 -0700
Didn't somebody just ask recently whether the loss of one guy would be fatal to a tower? Here's a convincing bit of evidence (if you can believe the article) ... Dave AB7E Ouch! http://keyetv.com/top
/archives//html/Towertalk/2007-01/msg00485.html (7,376 bytes)

22. Re: [TowerTalk] tower base concrete strength? (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Wed, 17 Jan 2007 15:45:19 -0700
For the most part, a slump test only checks water content. The psi is a function of both water and cement content. A concrete supplier has much more to gain by cheating you out of the required cement
/archives//html/Towertalk/2007-01/msg00514.html (10,927 bytes)

23. Re: [TowerTalk] Antenna Interactions - Reradiated Noise? (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Fri, 19 Jan 2007 15:59:42 -0700
The receiving antennas typically used on 160m and 80m are not very efficient (they make poor transmitting antennas), but they have good directivity and therefore discriminate against noise coming fro
/archives//html/Towertalk/2007-01/msg00558.html (8,072 bytes)

24. Re: [TowerTalk] dipole length adjustment (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Fri, 19 Jan 2007 16:15:39 -0700
That's true to a point. I have used efficient homebrew antenna tuners my entire ham radio life and wouldn't be without one. But you can get some REALLY ugly radiation patterns from trying to use the
/archives//html/Towertalk/2007-01/msg00560.html (10,193 bytes)

25. Re: [TowerTalk] dipole length adjustment (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Fri, 19 Jan 2007 20:12:23 -0700
Sorry, but I wasn't confusing the two points at all. When I said "efficient" I was referring to losses in the tuner. You can have a high SWR on the line and still have low losses there, but if you ha
/archives//html/Towertalk/2007-01/msg00564.html (12,484 bytes)

26. Re: [TowerTalk] TowerTalk Digest, Vol 49, Issue 77 (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Sat, 20 Jan 2007 11:24:47 -0700
Your last comment is incorrect -- the desired signal is typically not reduced by the unused antenna. Your first comment is correct -- that's the whole point ... the other antenna doesn't discriminate
/archives//html/Towertalk/2007-01/msg00582.html (9,746 bytes)

27. Re: [TowerTalk] dipole length adjustment (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Sat, 20 Jan 2007 12:16:50 -0700
Yes, the EDZ is a very nice configuration and it sounds like you have a nice setup. I'd be tempted to try the same thing myself for 80m and 160m except that the long ladder line would have too large
/archives//html/Towertalk/2007-01/msg00586.html (13,108 bytes)

28. Re: [TowerTalk] Ferrite Cores in Trapped Dipoles (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Wed, 07 Feb 2007 14:45:18 -0700
There's an old DOS program called "Coil.exe" that calculates inductance and self-resonance (both parallel and series) for single layer cylindrical air-wound coils. I have no idea how accurate it is f
/archives//html/Towertalk/2007-02/msg00128.html (10,146 bytes)

29. Re: [TowerTalk] 30m moxon (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Wed, 07 Feb 2007 15:07:20 -0700
You probably know this already, but L.B. Cebik -- W4RNL -- has written quite extensively on Moxon antennas (http://www.cebik.com/moxon/moxpage.html) and has generated design figures for various bands
/archives//html/Towertalk/2007-02/msg00129.html (7,948 bytes)

30. Re: [TowerTalk] MonstIR vs Monobander (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Fri, 09 Mar 2007 18:29:09 -0700
I've never owned a SteppIR and don't have any particular affinity for them, but there must be something else going on here. Even a compromise antenna, or a stack of them, shouldn't be down 2 to 3 S u
/archives//html/Towertalk/2007-03/msg00132.html (10,983 bytes)

31. Re: [TowerTalk] Yaesu G2800 Rotor Calibration Question and Complaint (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Mon, 26 Mar 2007 09:08:20 -0700
I agree that nearly $50 is an outlandish price to pay for a replacement plug, especially one that based upon similar reports couldn't have been too robust in the first place. That being said, I think
/archives//html/Towertalk/2007-03/msg00540.html (14,603 bytes)

32. Re: [TowerTalk] Yaesu G2800 Rotor Calibration Question and Complaint (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Mon, 26 Mar 2007 15:59:43 -0700
You are definitely correct. Last year I bought my son a VEX robotics kit, once handled by Radio Shack but now sold direct. Some of the extra piece parts are pretty expensive, so I checked around on e
/archives//html/Towertalk/2007-03/msg00554.html (12,316 bytes)

33. Re: [TowerTalk] DPDT Coaxial Relay question or alternative (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Sun, 08 Apr 2007 09:32:38 -0700
Hi, Cliff. To change from broadside to endfire you need 180 degrees phase shift, not 90 degrees. You can get that with either a half wavelength of coax (adjusted for velocity factor) coax or by switc
/archives//html/Towertalk/2007-04/msg00173.html (9,388 bytes)

34. Re: [TowerTalk] phased 40 meter verticals (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Tue, 17 Apr 2007 00:29:51 -0700
You won't get 135 degree phase shift between two phased verticals using a 135 degree phasing line. The mutual impedance between the two verticals causes it's own phase differential. ON4UN's book show
/archives//html/Towertalk/2007-04/msg00302.html (8,548 bytes)

35. Re: [TowerTalk] Antenna Height (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Wed, 18 Apr 2007 12:26:59 -0700
The terrain modeling program HFTA, written by N6BV and available free with 20th edition of the ARRL Antenna Book, will plot the takeoff lobe for various antennas over whatever terrain profile you spe
/archives//html/Towertalk/2007-04/msg00350.html (8,660 bytes)

36. Re: [TowerTalk] Using Coax as Ladder Line (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Thu, 19 Apr 2007 20:01:43 -0700
What it buys you is a fairly good way to get a balanced line through the wall without severely unbalancing the line or coupling RF to wood, metal, etc. The short length of the coax going through the
/archives//html/Towertalk/2007-04/msg00380.html (8,968 bytes)

37. Re: [TowerTalk] Large Loop Antenna - Electrostatically Shield Loops (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Tue, 24 Apr 2007 10:49:45 -0700
I tried to send you a more detailed direct comment but your spam settings are very restrictive. In brief, you will only end up with the equivalent of a large wire loop for transmitting, and you will
/archives//html/Towertalk/2007-04/msg00501.html (9,443 bytes)

38. Re: [TowerTalk] Large Loop Antenna - Electrostatically Shield Loops (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Tue, 24 Apr 2007 19:21:37 -0700
... and why is that you need to go to all that extra effort to achieve perfect balance in a transmitting loop? I still don't get it. Dave AB7E _______________________________________________ ________
/archives//html/Towertalk/2007-04/msg00510.html (10,998 bytes)

39. Re: [TowerTalk] Horizontal tower movement at the top (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Sun, 06 May 2007 16:04:28 -0700
I'm not a tower expert, but mechanically that sounds like a very bad idea. If the Rohn sections are spaced out from the tree as you propose, the wind against the tower and antenna is likely to put a
/archives//html/Towertalk/2007-05/msg00066.html (11,118 bytes)

40. Re: [TowerTalk] Horizontal tower movement at the top (score: 1)
Author: David Gilbert <xdavid@cis-broadband.com>
Date: Tue, 08 May 2007 09:45:29 -0700
I have exactly the same view of this situation. Why build a redundant support when climbing the existing support is the real issue? I'd also lean toward the crane-on-demand solution, but I'd bet it w
/archives//html/Towertalk/2007-05/msg00098.html (10,077 bytes)


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