The 340N is a great antenna. We have one up at N6NF's place, and it plays
like a maestro!
***dan
----- Original Message -----
From: <towertalk-request@contesting.com>
To: <towertalk@contesting.com>
Sent: Tuesday, April 02, 2002 6:46 PM
Subject: Towertalk digest, Vol 1 #93 - 16 msgs
> Send Towertalk mailing list submissions to
> towertalk@contesting.com
>
> To subscribe or unsubscribe via the World Wide Web, visit
> http://lists.contesting.com/mailman/listinfo/towertalk
> or, via email, send a message with subject or body 'help' to
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>
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of Towertalk digest..."
>
>
> Today's Topics:
>
> 1. (no subject) (K8fu@aol.com)
> 2. 40 meter beam (Bruce Makas)
> 3. Test ... Please excuse (Jim Thompson - W3LAP)
> 4. Re: Grounding mast to tower (Red)
> 5. RE: portable communications (George Shaw)
> 6. How To Hold Up A 20' Mast On The Ground? (Robin Midgett)
> 7. 4130 Masts For Sale (Robin Midgett)
> 8. Hazer windload/weightload? (brewerj@squared.com)
> 9. Re: Low-Angle Scattering (Steve Miller)
> 10. Re: 40 meter beam (Bruce Makas)
> 11. Re: How To Hold Up A 20' Mast On The Ground? (K7LXC@aol.com)
> 12. Re: near tradedy Redux (n4kg@juno.com)
> 13. Re: How To Hold Up A 20' Mast On The Ground? (Jerry Kincade)
> 14. Re: How To Hold Up A 20' Mast On The Ground? (n4kg@juno.com)
> 15. Re: Hazer windload/weightload? (Barrie Smith)
> 16. Re: Grounding mast to tower (Pete Goudreau)
>
> --__--__--
>
> Message: 1
> From: K8fu@aol.com
To: <towertalk@contesting.com>
> Date: Tue, 2 Apr 2002 12:10:52 EST
> To: towertalk@contesting.com
> Subject: [Towertalk] (no subject)
>
> Cheers 'Ya All..............
>
> Does anyone hv a source for 600 Ohm Ladder Line ?? Preferably insulated
like
> the 450 ohm.
> I'm trying to learn the "Ladder Line Twist" but Chubby Checker will not
> return my calls.
> Many Tnx
>
> Mark K8FU
> Charlies Whisky...When U Care Enough To Send the Very Best.
>
>
> --- StripMime Report -- processed MIME parts ---
> multipart/alternative
> text/plain (text body -- kept)
> text/html
> ---
>
> --__--__--
>
> Message: 2
> From: "Bruce Makas" <k1my@msn.com>
> To: "Towertalk submital" <towertalk@contesting.com>
To: <towertalk@contesting.com>
> Date: Tue, 2 Apr 2002 10:42:54 -0800
> Subject: [Towertalk] 40 meter beam
>
> I am putting up a 100 foot Rohn 45 with a single 40 meter beam on top.
What
> do you recommend for an antenna?
>
> I have been looking at M2 40M4L 4 element and the Force 12 MAG340N 3
> element.
>
> I am primarilly a DXer but also play in contests. Reliability is as
> important to me as is performance. Once up I don't want it to break. The
QTH
> is in the mountains at 7000 foot elevation.
>
> I also believe it is the consensus of the reflector that the Orion
> OR2800P-DC is the rotor of choice. Is this correct? Reliability is the
most
> important consideration for me.
>
> Thanks in advance.
>
> Bruce K1MY
>
>
> --__--__--
>
> Message: 3
To: <towertalk@contesting.com>
> Date: Tue, 02 Apr 2002 13:16:15 -0500
> From: Jim Thompson - W3LAP <w3lap@america.net>
> Reply-To: w3lap@america.net
> Organization: W3LAP SYSTEMS AND SOFTWARE
> To: towertalk@contesting.com
> Subject: [Towertalk] Test ... Please excuse
>
> Test ... Please excuse
> --
> Jim Thompson - w3lap
>
>
>
> --__--__--
>
> Message: 4
> From: "Red" <RedHaines@centurytel.net>
> To: <towertalk@contesting.com>
> Subject: Re: [Towertalk] Grounding mast to tower
To: <towertalk@contesting.com>
> Date: Tue, 2 Apr 2002 12:33:43 -0600
>
> Hi;
>
> A modestly high impedance between the mast and the tower will send more of
> the current down the feedline, thus increasing the voltage at the
lightning
> arrestor, suppressor, or attenuator (of course, you have one of those!).
>
> It is desireable to bypass the current through as many paths as possible.
> Each additional path reduces the overall impedance and reduces the voltage
> on the feedline. Model every path with a complex impedance and calculate
> the effect of changing impedance. Read Polyphaser's book on the subject.
>
> I recommend connecting a flexible lead from the mast to each tower leg.
Pay
> attention to corrosion prevention in the connections, in accordance with
the
> materials used. Inspect such connections at least annually.
>
> 73 de WO0W
>
>
> --__--__--
>
> Message: 5
> From: "George Shaw" <george.shaw@ukf.net>
> To: <towertalk@contesting.com>
> Subject: RE: [Towertalk] portable communications
To: <towertalk@contesting.com>
> Date: Tue, 2 Apr 2002 19:49:12 +0100
>
> Found it
>
> http://www.smc-comms.com
>
> Hilomast
>
> George Shaw MI3ZEN
>
> Mobile: +44 (0) 7740 361 163
> Email: george.shaw@ukf.net
>
>
> -----Original Message-----
> From: towertalk-admin@contesting.com
> [mailto:towertalk-admin@contesting.com] On Behalf Of K7LXC@aol.com
> Sent: 02 April 2002 01:41
> To: thoele@txcyber.com; towertalk@contesting.com
> Subject: Re: [Towertalk] portable communications
>
> In a message dated 4/1/02 12:48:11 PM Pacific Standard Time,
> thoele@txcyber.com writes:
>
> > Anybody know of a good source for pneumatic masts, in the 30 to 50
> foot
> > range? Any suggestions or comments most welcome.
>
> Force 12 has introduced a line of smaller non-pneumatic tubular
> aluminum
> crank-ups that would be worth looking at. www.force12inc.com I think.
>
> Cheers,
> Steve K7LXC
> TOWER TECH
> _______________________________________________
> Towertalk mailing list
> Towertalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
> ---
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
To: <towertalk@contesting.com>
> Version: 6.0.343 / Virus Database: 190 - Release Date: 22/03/2002
>
>
>
> --__--__--
>
> Message: 6
To: <towertalk@contesting.com>
> Date: Tue, 02 Apr 2002 13:04:30 -0600
> To: towertalk@contesting.com
> From: Robin Midgett <robin.midgett@vanderbilt.edu>
> Subject: [Towertalk] How To Hold Up A 20' Mast On The Ground?
>
> Greetings TT,
> I'm seeking constructive advice on how to hold a 20' mast upright on the
> ground while antennas are installed onto the mast. The plan is for a crane
> to place the mast & antenna assembly into the tower top once the tower is
> built & the antennas are on the mast. A stake through a plate driven into
> the ground is easy enough to keep the bottom of the mast from moving
> laterally; how should a person keep the thing upright without hindering
the
> antenna installation?
> I have an idea of using guy wires to hold the mast upright & of using
> scaffolding as a work platform to install the antennas, working from the
> top of the mast downward. What say you?
>
> Thanks,
> Robin Midgett KB4IDC
> VHF+ Glutton
>
>
> --__--__--
>
> Message: 7
To: <towertalk@contesting.com>
> Date: Tue, 02 Apr 2002 13:25:11 -0600
> To: towertalk@contesting.com
> From: Robin Midgett <robin.midgett@vanderbilt.edu>
> Subject: [Towertalk] 4130 Masts For Sale
>
> I may have a pair of new, never used masts for sale soon. If anyone is
> interested in acquiring one or both at Dayton, please let me know & I can
> make arrangements to bring them to the flea market at Hara Arena.
> 20' 4130 2" OD 3/16" wall, galvanized
> 20' 4130 2" OD 5/16" wall, galvanized
>
> Thanks,
> Robin Midgett KB4IDC
> 615-477-8976 cellular
> 615-322-5836 office
> 615-773-4198 home
> rmidgett@bellsouth.net
> robin.midgett@vanderbilt.edu
>
>
> --__--__--
>
> Message: 8
> To: towertalk@contesting.com
> From: brewerj@squared.com
To: <towertalk@contesting.com>
> Date: Tue, 2 Apr 2002 14:37:22 -0500
> Subject: [Towertalk] Hazer windload/weightload?
>
> Does anyone have any practical experience in loading down a Hazer
> with a fairly good sized antenna? I'm considering putting up a TH6DX
> on the heavy steel model Hazer, and while this is well within the weight
> limit and windload limit, is it practical? I've got a sturdy boom, and I
dont
> plan on raising the antenna too far up past the thrust bearing so as to
minimize
> the torsional load.
>
> I guess compared to winching up many hundreds of lbs of crankup
> tower, pulling up 125 lbs of antenna, hazer, rotor and cable is
> not much, but I'd appreciate some first hand experience.
>
> Many thanks
> John wb5oau/4
>
>
> --__--__--
>
> Message: 9
> From: Steve Miller <millersg@dmapub.dma.org>
> Subject: Re: [Towertalk] Low-Angle Scattering
> To: towertalk@contesting.com
To: <towertalk@contesting.com>
> Date: Tue, 2 Apr 2002 14:50:42 -0500 (EST)
>
> N4ZR wrote:
>
> > At the very-low-angle peak, the modeled signal is 17.8 dBi at 1.75
degrees
> > above the real horizon. At the same elevation angle above flat terrain,
> > the same antenna shows approximately 1.8 dBi.
>
>
> Pete,
>
> These low angle 'inflated gains' are modeling artifacts. I saw similar
> behavior after entering a rather detailed topography for my location.
>
> To check the model, I took the original terrain profile and broke it up
> into smaller segments (interpolating between the original data points).
> This should have provided the same pattern, however the interpolated data
> set also showed inflated gain behavior at low angles. Too bad, I could
> have used another 16 dB! ;)
>
> 73,
> Steve N8SM
>
> P.S. Many scattering/diffraction algorithms become numerically tricky
> at 'near-grazing' incidence angles.
>
> --__--__--
>
> Message: 10
> From: "Bruce Makas" <k1my@msn.com>
> To: "Towertalk submital" <towertalk@contesting.com>, <kb9cry@attbi.com>
> Subject: Re: [Towertalk] 40 meter beam
To: <towertalk@contesting.com>
> Date: Tue, 2 Apr 2002 16:14:40 -0800
>
> But how are you going to turn the ;lower antenna? I hope you are not
> planning on using a TIC ring. If you are, let me know . I'll give you a
> great price on my 3rd failed one. NEVER AGAIN.
>
> 73, Bruce K1MY
> ----- Original Message -----
> From: <kb9cry@attbi.com>
> To: "Bruce Makas" <k1my@msn.com>
> Sent: Tuesday, April 02, 2002 11:22 AM
> Subject: Re: [Towertalk] 40 meter beam
>
>
> > Bruce I'm planning the same thing as, but 120 ft., and
> > was also planning on one big antenna. Then at a recent
> > W9DXCC Convention I heard Jay, W0XB, Array Solutions,
> > give a presentation on stacking two smaller 40M beams
> > and phasing them. That's now my plan. You get maybe a
> > more bang by phasing two together plus you can drive
> > them separately; the one at a lower height will work
> > better for domestic use. Finally the installation and
> > maintenance of two smaller beams is much less than one
> > big beam. Hope this doesn't put you back to square one
> > but that's my new plan. Gd luck, I'll be interested in
> > your decision. 73 Phil KB9CRY
> > > I am putting up a 100 foot Rohn 45 with a single 40 meter beam on top.
> What
> > > do you recommend for an antenna?
> > >
> > > I have been looking at M2 40M4L 4 element and the Force 12 MAG340N 3
> > > element.
> > >
> > > I am primarilly a DXer but also play in contests. Reliability is as
> > > important to me as is performance. Once up I don't want it to break.
The
> QTH
> > > is in the mountains at 7000 foot elevation.
> > >
> > > I also believe it is the consensus of the reflector that the Orion
> > > OR2800P-DC is the rotor of choice. Is this correct? Reliability is the
> most
> > > important consideration for me.
> > >
> > > Thanks in advance.
> > >
> > > Bruce K1MY
> > >
> > > _______________________________________________
> > > Towertalk mailing list
> > > Towertalk@contesting.com
> > > http://lists.contesting.com/mailman/listinfo/towertalk
> >
>
>
> --__--__--
>
> Message: 11
> From: K7LXC@aol.com
To: <towertalk@contesting.com>
> Date: Tue, 2 Apr 2002 20:07:41 EST
> Subject: Re: [Towertalk] How To Hold Up A 20' Mast On The Ground?
> To: robin.midgett@vanderbilt.edu, towertalk@contesting.com
>
> In a message dated 4/2/02 11:08:20 AM Pacific Standard Time,
> robin.midgett@vanderbilt.edu writes:
>
> > I'm seeking constructive advice on how to hold a 20' mast upright on the
> > ground while antennas are installed onto the mast. The plan is for a
crane
> > to place the mast & antenna assembly into the tower top once the tower
is
> > built & the antennas are on the mast. A stake through a plate driven
into
> > the ground is easy enough to keep the bottom of the mast from moving
> > laterally; how should a person keep the thing upright without hindering
> the
> > antenna installation?
> > I have an idea of using guy wires to hold the mast upright & of using
> > scaffolding as a work platform to install the antennas, working from
the
> > top of the mast downward. What say you?
>
> WAY too much work and screwing around. Since you're going to have the
> crane there, have him do all the work. What you need is a man-basket and
> someone in it. To install the mast, you need to be on the tower as the
crane
> lowers it. You just have to guide it in. Make sure there are no pieces of
> galvanizing to prevent lowering it through the thrust bearing (inspect
every
> inch and file if necessary) and use a LONG sling (the crane operator will
> have them) so the headache ball is above the top of the mast and it'll
hang
> vertically. Of course you did check the TB/mast fit on the ground
beforehand.
>
> Then the crane delivers the bottom antenna as you're standing on the
> tower. That's a slamdunk.
>
> Use the man and the man-basket to pick up each of the other antennas
> until you top out and the antennas are done. You can hang them from the
> headache ball or man-basket - just rig them so that you can work on them
at a
> decent work height so you can attach them to the mast. Have someone on the
> ground help you line up the booms.
>
> It doesn't matter which way they're all pointed since one of the last
> things you'll do is rotate and calibrate the beams to a known direction
> (probably north - DON'T ASK - hi) and then tighten the rotator mast clamp.
>
> You should have jumpers that extend from the feedpoints to the top of
the
> tower; then all you have to do is use barrel connectors and hook up each
coax
> to the shack. Please wxproof appropriately.
>
> This whole process will take about an hour or so - much less time than
> you'll spend fooling around with the mast on the ground. Couldn't be
easier.
>
> Cheers,
> Steve K7LXC
> TOWER TECH -
> Professional, affordable tower services for industry and amateurs
>
> --__--__--
>
> Message: 12
> To: TOWERTALK@CONTESTING.COM
To: <towertalk@contesting.com>
> Date: Tue, 2 Apr 2002 16:51:44 -0600
> Subject: Re: [Towertalk] near tradedy Redux
> From: n4kg@juno.com
>
> On Mon, 01 Apr 2002 14:57:11 -0700 Peter Larsen <ve6yc@shaw.ca> writes:
> >
> > Going around/over guy wires is probably the most dangerous
> > part of your climb. You should look into some device that will allow
> > you to clip into the tower above the guywire (or obstruction) before
> > you unbelt from the tower. I have a "seat belt" style lanyard with
> > a carabineer (sp?) on the side of my belt for this.
>
> N4KG: My solution to going around antennas / guy wires
> is to have TWO lanyards so that I ALWAYS have
> a line around the tower. I use a single 10 ft 1/2 inch
> nylon rope folded and looped around one D ring
> with 5000 lb rated clips on each end. The loop
> can be adjusted so that I have one shorter and
> one longer lanyard where the shorter end holds
> me close to the tower and the longer end is
> the primary climbing lanyard. Tom N4KG
>
>
>
> ________________________________________________________________
> GET INTERNET ACCESS FROM JUNO!
> Juno offers FREE or PREMIUM Internet access for less!
> Join Juno today! For your FREE software, visit:
> http://dl.www.juno.com/get/web/.
>
> --__--__--
>
> Message: 13
To: <towertalk@contesting.com>
> Date: Tue, 02 Apr 2002 20:12:50 -0800
> From: Jerry Kincade <w5kp@swbell.net>
> Subject: Re: [Towertalk] How To Hold Up A 20' Mast On The Ground?
> To: towertalk@contesting.com
>
> It also helps to pay attention to the size crane you order up. I thought a
> 100' boom truck was fine for my 80' R45 + 15' of mast, but because of the
> headache ball and attached rigging, we lost about 3-4 feet of actual
lifting
> height. Since at max height the boom is near vertical, maneuvering the
beam
> around up there was a bit touchier than I liked. At one point we had to
> swing the antenna boom over the top of the mast, which was at 95' plus 18"
> of copper air terminal, for a total clearance height of about 96-1/2 feet.
I
> guess I needed another 1/4" of boom truck, because the antenna boom
actually
> scraped the tip of the copper air terminal - it was that close with the
boom
> maxed out. :-) It all worked because of an experienced boom operator, but
> I'll make sure I have something in the 125' range next time, so I'll have
a
> little more leeway and working room up there. Gotta love those cranes,
> except when you have to write the check!
> 73, Jerry W5KP
>
> ----- Original Message -----
> From: <K7LXC@aol.com>
> >
> > WAY too much work and screwing around. Since you're going to have
the
> > crane there, have him do all the work. What you need is a man-basket and
> > someone in it. To install the mast, you need to be on the tower as the
> crane
> > lowers it.
> (snip)
> > This whole process will take about an hour or so - much less time than
> > you'll spend fooling around with the mast on the ground. Couldn't be
> easier.
> >
> > Cheers,
> > Steve K7LXC
> > TOWER TECH -
> > Professional, affordable tower services for industry and amateurs
>
>
>
>
> --__--__--
>
> Message: 14
> To: TOWERTALK@CONTESTING.COM, robin.midgett@vanderbilt.edu
To: <towertalk@contesting.com>
> Date: Tue, 2 Apr 2002 20:08:10 -0600
> Subject: Re: [Towertalk] How To Hold Up A 20' Mast On The Ground?
> From: n4kg@juno.com
>
> I have a 10 ft mast holding / storing two 3L20's, a 5L10, and 3L10.
>
> It sits in a 30? inch hole in the ground formed by pounding a short
> thin wall steel tube into the ground, six inches at a time, removing
> the tube, clearing out the dirt, and pounding it in another six inches,
> until the desired depth is achieved.
>
> For a 20 ft mast, I would suggest going deeper, say 4 to 5 ft.
>
> Tom N4KG
>
> On Tue, 02 Apr 2002 Robin Midgett <robin.midgett@vanderbilt.edu> writes:
> > Greetings TT,
> > I'm seeking constructive advice on how to hold a 20' mast upright on
> > the
> > ground while antennas are installed onto the mast. The plan is for a
> > crane
> > to place the mast & antenna assembly into the tower top once the
> > tower is
> > built & the antennas are on the mast. A stake through a plate driven
> > into
> > the ground is easy enough to keep the bottom of the mast from moving
> >
> > laterally; how should a person keep the thing upright without
> > hindering the
> > antenna installation?
> > I have an idea of using guy wires to hold the mast upright & of
> > using
> > scaffolding as a work platform to install the antennas, working from
> > the
> > top of the mast downward. What say you?
> >
> > Thanks,
> > Robin Midgett KB4IDC
> > VHF+ Glutton
> >
> > _______________________________________________
> > Towertalk mailing list
> > Towertalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> ________________________________________________________________
> GET INTERNET ACCESS FROM JUNO!
> Juno offers FREE or PREMIUM Internet access for less!
> Join Juno today! For your FREE software, visit:
> http://dl.www.juno.com/get/web/.
>
> --__--__--
>
> Message: 15
> From: "Barrie Smith" <barrie@centric.net>
> To: <towertalk@contesting.com>, <brewerj@squared.com>
> Subject: Re: [Towertalk] Hazer windload/weightload?
To: <towertalk@contesting.com>
> Date: Tue, 2 Apr 2002 19:41:34 -0700
>
> I've had over 250 lbs on the aluminum hazer on my 18" face aluminum tower,
> at 70'.
>
> That may have been too much, but I had no problems.
>
> 73, Barrie, W7ALW, Missoula, Montana
> ----- Original Message -----
> From: <brewerj@squared.com>
> To: <towertalk@contesting.com>
> Sent: Tuesday, April 02, 2002 12:37 PM
> Subject: [Towertalk] Hazer windload/weightload?
>
>
> > Does anyone have any practical experience in loading down a Hazer
> > with a fairly good sized antenna? I'm considering putting up a TH6DX
> > on the heavy steel model Hazer, and while this is well within the weight
> > limit and windload limit, is it practical? I've got a sturdy boom, and
I
> dont
> > plan on raising the antenna too far up past the thrust bearing so as to
> minimize
> > the torsional load.
> >
> > I guess compared to winching up many hundreds of lbs of crankup
> > tower, pulling up 125 lbs of antenna, hazer, rotor and cable is
> > not much, but I'd appreciate some first hand experience.
> >
> > Many thanks
> > John wb5oau/4
> >
> > _______________________________________________
> > Towertalk mailing list
> > Towertalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
> >
>
>
>
> --__--__--
>
> Message: 16
> To: K7LXC@aol.com
> Cc: towertalk@contesting.com
> Subject: Re: [Towertalk] Grounding mast to tower
> From: Pete Goudreau <goudpj@mac.com>
To: <towertalk@contesting.com>
> Date: Tue, 2 Apr 2002 20:44:35 -0600
>
> K7LXC@aol.com wrote:
>
> > In a message dated 4/2/02 6:42:22 AM Pacific Standard Time,
> > goudpj@mac.com writes:
>
> >>> The mast is metal, the TB and its holding bolts are metal, it's
> >>> attached to the metal tower - seems like that's enough for me.
>
> >> Well, the only contact between the mast and the tower is through
> the
> >> point contacts across the balls, or rollers, in the bearing, which
> >> doesn't seem like a low impedance path.
>
> > There are over a dozen ball bearings in the Rohn thrust bearings so
> I
> > suspect that it's a pretty good contact. Even if there are some ohms
> > of resistance, there is virtually no gap for the strike to arc
> across
> > so you still wind up with a decent path.
>
> OK, thanks for that, had no idea if these bearings are ball, roller,
> tapered roller, or bronze bushing. The problem with anything other
> than a bronze bushing is that the point contact of the balls, or the
> line contacts of the rollers, is just that, a tiny contact area.
> This creates a large contact resistance and an incredibly large
> current density at that point.
>
> My guess is that the overall dc resistance is low enough to keep the
> mast at the tower's potential so it can't build up a charge, but is
> too high to handle any surge currents.
>
> > Look at it like this - where else is the strike going to go?
> Putting a
> > strap from the mast to the tower won't work because of the inductive
> > resistance (?) so you're stuck with that path anyway.
>
> Well, that's my question actually, where do surge currents flow
> during a strike to an antenna or mast?
>
> Adding jumpers of some kind has been recommended, but that strap
> would only be good for static grounding, and not very helpful for
> surge currents. Braid or stranded wire won't hold up to strike
> currents and solid wire or strap would eventually fail no matter how
> carefully applied and the inductive nature of the loop around the
> rotator would naturally, as you say, impede fast risetime surge
> currents anyway.
>
> This is one of the points I was trying to find an answer to. That
> is, if the paths to the tower are all relatively high impedance, a
> strike to an antenna element, boom, or mast isn't as straightforward
> a thing to manage as one to the tower. And this isn't covered in the
> Polyphaser book or any other source I've researched so far. Just an
> engineering problem is all.
>
> >> Sure, that's the plan, but if the tower is grounded and the mast
> >> isn't well grounded to the tower, the surge current from a strike
> to
> >> an antenna or the mast has to jump the connection point to get to
> >> tower ground so a transient high potential can exist.
>
> > Believe me - those bearing contact points (which wouldn't suffer any
> > real damage due to a strike anyway) would be the least of my
> worries.
>
> They're the least of my worries as well. My worry is in earthing
> everything at the top of the tower so as to inhibit charge buildup
> that could trigger a strike. If that's something that's possible,
> then the probability of a strike is then reduced closer to the
> region's random strike probability. I'd feel a lot better if this
> was something that could be reduced to an engineering problem with a
> cost effective solution.
>
> >From what you've said, it appears that the bearing itself provides
> adequate earthing of the mast for charge dissipation. The other half
> of my original question was in wondering how effectively capacitance
> of the antennae and mast is coupled to the top of the tower for use
> in shunt loading it as a vertical. It seems that it's not a problem
> either although it strikes me that it could be quite variable.
>
> > The main point of a ground system is to keep harmful transients out
> of
> > the building so I think you're getting too hung up on something at
> the
> > extreme OTHER end of the scenario.
>
> No, I guess I just didn't state my givens clearly. The entire
> arrangement is to be installed by the book, according to Polyphaser
> and appropriate codes. The coax feedlines will be grounded to the
> tower at the top and the bottom using LMR-400 grounding kits on
> BuryFlex. The tower will be well grounded and attached to an
> earthing field of strap connected ground rods. All feedlines and
> control lines will be buried and earthed at an external master ground
> bar carrying Poylphaser dc blocked suppressors, etc., etc.
>
> I wasn't worried about the mast end of the system in terms of damage,
> just trying to find out if there was a way to optimize earthing of
> the rotating parts so as to avoid charge buildup that could trigger a
> strike. Just engineering it to death.
>
> >>> Everything except the insulated elements are connected to the
> tower
> >>> and to the tower ground so they should be okay. You get arcing
> when
> >>> you have potential differences between conductors - that's why
> >>> everything in the ground system is tied together so they all rise
> >>> and fall at the same rate. Then you don't have any arcing.
>
> >> Understood. But if the mast isn't well grounded to the tower, there
> >> will be arcing. I'm assuming that even the minimal contact to the
> >> tower via the thrust bearing and rotator bearing is adequate to
> keep
> >> the mast grounded to the tower, just that it isn't a low impedance
> >> path for surge currents and thus some arcing could conceivable
> occur.
>
> > It's well grounded - okay? Yes - lightning is pretty unpredictable
> and
> > yes - some arcing could conceivably occur but I'd suggest spending
> > your time, energy, and money on the more important *other* end of
> the
> > system.
>
> Well, yes, lightning can be pretty unpredictable but there are ways
> to mitigate its likelihood as well as its damage. And at the
> potentials and charge densities associated with a strike, there isn't
> so much arcing as there is vaporized metal fed plasma that
> essentially electrically short everything within reach, and it will
> reach whatever it takes. Nasty stuff. As long as its made as
> unlikely as possible and the damage constrained to places well away
> from the house and the equipment, I'll be happy.
>
> Thanks very much,
> Pete, AD5HD
>
>
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