Dave,
excellent description for grounding. I'm sure that that setup would
solve Tom's problems. My own grounding scheme is very similar to what
you described, except I never did connect the single point ground at the
house to the tower ground. At first I planned on doing it. I even dug a
trench between the tower and the house for the copper strap. I then got
into a discussion on Tower Talk about it and got talked out of it by a
"former Polyphaser Application Engineer" and a few others. They made it
sound like that ground strap would provide a better path for lightning
to enter the house if my tower ever got hit. I'm not sure I agree, but I
put it off and everything seems fine. No lightning strikes yet though...
--Dave D.
K0QE
> ----------
> From: David G. Henderson[SMTP:daveh@erie.net]
> Reply To: David G. Henderson
> Sent: Wednesday, July 14, 1999 3:29 PM
> To: rfi@contesting.com
> Subject: Re: [RFI] RFI and the TS-850
>
>
> On 14 Jul 99, at 11:01, Branch T SMSgt AFRS
> <Tom.Branch@rs.af.mil> wrote:
>
> > Been trying to track down a problem that has plagued me for months.
> I
> > have a large amount of RF coming into my shack via the coaxial
> shields and
> > the rotor cables
> [snip]
> > 73 de Tom, K4NR
>
> I had a similar problem here and I accidentally fixed it in my quest
> for good lightning protection.
>
> Could I suggest you consider implementing a "single point
> grounding system". PolyPhaser has good information on how to
> construct them. www.polyphaser.com
>
> The basics are these:
>
> 1. Provide a low resistance ground for the tower (many ground rods
> spaced apart at a distance slightly greater than their length, see
> PolyPhaser information), the single point location in the wall or just
>
> inside the wall where the feedlines enter the building, and the
> building service entrances for telephone, cable, water and electric.
> All bonded together with 4 ga. underground, bare, solid copper wire.
>
> 2. Use wide, solid copper strap from the single point ground to the
> tower ground at the base of the tower. The width of the copper strap
> must be equal to or greater than the total of the circumferences of
> all
> the coaxes. This may require several straps--two six inchers in my
> case.
>
> 3. For tower mounted antennas, bond the shields of all coaxes to
> the tower at the top of the tower and the bottom of the tower. For
> wire antennas, skip this step. Otherwise the tower will be part of
> the
> antenna circuit.
>
> 4. All feedlines then come to a single point ground plate (I used a
> 2'
> by 2' by 1/8 inch piece of aluminium) and run through it. Use a
> double female SO-239 bulkhead connector (or N connector as
> necessary) for coaxes not protected from lightning. Use a bulkhead
> mount lightning protector for those always connected to radios.
>
> 5. Use small, light weight copper strap from each radio chassis
> ground to the single point ground plate.
>
> 6. Use a Polyphaser rotor control lightning protector mounted on
> the single point ground plate. The rotor control wire runs down the
> tower and through the protector and then to the control box.
>
> All lightning and RFI stops at the single point ground location and is
>
> shunted to ground. This stopped all my RFI problems.
>
> It's a bit of work, I admit. And it can be very expensive if you buy
> a
> large number of lightning protectors. But it will do the job.
>
> I have attached a picture of my dusty, messy single point ground
> plate. Omitted from the SIG's copy.
>
> Sorry there is no simple fix.
>
>
> 73, Dave, N3EOY
> mailto:daveh@erie.net
>
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