[RFI] RFI and the TS-850

Dave D'Epagnier Dave D'Epagnier" <DAVED@ctilidar.com
Thu, 15 Jul 1999 08:32:30 -0600

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.
> ----------
> 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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