[NLRS] Tower, or silo as tower?

[David Palm]

Thanks to all for the great feedback on using a silo as an antenna support,
both on and off list.  Basically it was unanimous that I should use the silo
for an antenna support.  Here's a quick summary of the good info:

K9KL made some great points on safety.  My silo is empty and the doors are
open, so there's no poison gas problem.  I hadn't really considered the
possibility that, being empty, it might eventually cave in.  It is cemented
on the inside, but I don't know how much additional strength that adds to
the structure.  The ladders are all in very good condition, but as you say,
I'll be careful.

Several folks suggested putting just the transverters, pre-amps, and PAs at
the top and running the IF from the shack, rather than having to remote
control the IF rig as well.  Great idea.  I figure the run from the shack to
just under the dome would be about 250 feet, so that's very do-able with a
28 MHz IF.  Then the feedlines from the VHF-UHF-SHF stuff would still be
nice and short.

N0JCF thought that having separate runs for receive and transmit IF would be
worthwhile; I'll have to see what the budget might support.

W0TLE mentioned the potential lightning problem, something I had thought of
but didn't mention.  Yup, I'll definitely have to make serious provisions
for that, especially with all that gear at the top.  If anybody has specific
feedback on this issue, I'd love to hear it.

Logistically one of my big questions is how to manage a tall mast with
stacked antennas.  This really goes for both towers and a silo-tower.  I can
see on either a tower or a silo having a nice stable place to work at the
base of the mast and having good access to the lowest beam on the mast, but
how is it best done to get the mast lowered so that you can work on the
antennas that are higher up?  Can anybody describe how they manage this?

Thanks and 73,

David  W9HQ




On Thu, Aug 27, 2009 at 9:28 PM, Dr. Gerald N. Johnson
<geraldj at weather.net>wrote:

> On Thu, 2009-08-27 at 15:16 -0500, David Palm wrote:
> >
> > Okay, thanks for the good feedback on the Icom PCR receivers.  Now, if
> you
> > all don't mind, I'm looking for some feedback on an idea I've been
> tossing
> > around.
> >
> > I have a very favorable location here.  I'm at about 1280 ft. ASL, right
> > smack on top of the ridge.  My only real problem in terms of an RF
> horizon
> > is that there is a horseshoe of very tall mature trees (60 - 70 feet)
> around
> > the house, spanning from the west to the east, leaving out the south.  So
> > I'm sure I get some attenuation on 2 meters and up and it'll only get
> worse
> > as I try to add bands.
> >
> > Putting up a tower over the tops of those trees is a possibility, but
> > obviously that doesn't come cheap.  But there is another possibility.
> >
> > I have a silo on the property and the top of the dome sits at about 70
> feet
> > above the ground.  I have often thought about building a platform just
> under
> > the dome and setting up a PC, wireless router, computer-controlled rig
> and
> > rotor, and whatever other amplifiers and transverters I want to mess
> with.
> > There are a number of up sides to this, as I see it.  For starters, the
> > structure itself gets antennas at 80 feet above the ground (with an
> > appropriate mast) basically for free.  Second, the feed lines to those
> > antennas would be trivially short, like in the 25 foot range, so line
> losses
> > would be kept to a minimum.  Third, not only is it above the trees but
> it's
> > physically away from them as well, so all of that foliage attenuation
> goes
> > away.  Fourth, even factoring in a remote-controllable rotor, it would
> > surely be a lot cheaper to do a set-up like that than it would to put up
> an
> > 80+ foot tower.  Fifth, I think it would be easier and safer to work on
> > stuff up there than it would on a tower, because the only way this silo
> is
> > coming down is in a serious earthquake.  And it is protected from the
> > elements under the dome.
>
> I've considered that a few times. There are radios like TenTec Orion and
> Omni VII that are already set up to run HF by ethernet control. It would
> take a computer to take care of antenna rotation, antenna selection, and
> operation of transverters, but there have been some fancy computer
> controls set up with the Flex radio by KM0T and others. Hovwever I think
> he uses it only for local control, but for many microwave bands.
> >
> > The downsides as I see them are these: I think I would miss having the
> > physical radio in the shack.  With the PC and the WiFi and the remote
> > control software and such there's a lot more to go wrong and it could get
> > pretty annoying to have to climb that beast and troubleshoot something,
> > especially in the winter and/or during bad weather.  And the temperature
> > extremes would be much greater up there than they would be in my shack.
>
> You might need to control temperature extremes, winter and summer. And
> you might find a remote master reset switch at the bottom of the silo to
> be really handy, especially when running windoze.
> >
> > So, if you had my situation, what would you do?
>
> Coax for that run isn't bad though with the shelter up top, it would be
> handy to put transverters, LNA, and PA up there with LO controls sent up
> a coax from an environment with better temperature control.
>
> I'm sure I could find a few farm silos in this neighborhood with TV
> antennas up top and at least one supported a FM band translater for a
> religous network.
>
> The hardest part would be making structure to hold mast or rotor, but
> that's possible. And if the silo wasn't cleaned out well the last time
> it was used for silage, there might be some residual gasses that will
> need to be vented, so you can survive inside. If its vented, then there
> may be problems of bird access leaving marks behind.
> >
> > Thanks and 73,
> >
> > David  W9HQ
>
> 73, Jerry, K0CQ
>
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