[TowerTalk] Station grounding in a steel enclosure?

[Jim Brown]

Trent,

It sounds like you have a good handle on things.  Since your primary 
concern is from external sources (lightning, noise) I would bond to the 
outside of the enclosure, taking advantage of skin effect to keep those 
external currents "outside the box."

There is, of course, the need for ventilation to allow heat dissipation, 
with the conflicting concern for rain/snow/moisture intrusion.  A tricky 
design problem. :)

I'm guessing you'll be using solar power.  This may seem 
counterintuitive, but I would try to put all electronics for that system 
inside the box, which shields it from antennas. And all power wiring 
outside the box should be twisted pair, to minimize radiation of 
switching transients produced by the charge regulator. Try to choose a 
low noise charge regulator. Genasun makes a line of MPPT charge 
regulators that is very quiet, but, so far, they only make them for 
small systems. Their largest one is rated for 8A for batteries up to 
48V. I'm using one rated for 10A to a 14V LiFePO4 battery.

73, Jim K9YC

On Sun,8/28/2016 5:33 AM, trentkd5ia at aol.com wrote:
> Jim,
> Thank you for your comments.   The plan is to bond all shields and 
> bypass all the conductors coming into the enclosure, but should they 
> be bonded to the outside wall or can they be bonded to the inside 
> wall?  The valve box is made of heavy corrugated steel, and it will be 
> easier to have the connections inside the enclosure rather than 
> outside, under the ground.  Or will it be sufficient to bond and 
> bypass the coax and other cables at the tower base, twelve feet from 
> the enclosure?
> I didn't exactly plan to have a Faraday cage--this big valve box just 
> seemed to be  the most convenient and inexpensive way to keep my 
> equipment safe and secure out on the prairie.
> 73 de Trent   K5XM
> -----Original Message-----
> From: Jim Brown <jim at audiosystemsgroup.com>
> To: towertalk <towertalk at contesting.com>
> Sent: Sun, Aug 28, 2016 7:25 am
> Subject: Re: [TowerTalk] Station grounding in a steel enclosure?
>
> Trent,
>
> Your first problem is that your box is NOT a shield if cables come
> through openings in the box without their shield being bonded to the box
> at the point where they enter. You must also bond or bypass (with
> feedthrough caps) all other leads coming into the enclosure, like power,
> control lines, audio lines, keying lines, etc. Any one of these lines
> that does not have its shield bonded to the enclosure or come through
> the enclosure via a feedthrough capacitor destroys the shielding.
>
> As to where to put the Polyphasers -- I would use the "feed through"
> type and bond them to the enclosure.
>
> The larger question is why you need a Faraday cage in the first place.
> Few stations do. What most stations need is proper BONDING, proper
> grounding, proper power, and proper interconnections between equipment.
> Study http://k9yc.com/GroundingAndAudio.pdf
>
> 73, Jim K9YC
>
> For On Sat,8/27/2016 10:28 PM, trentkd5ia--- via TowerTalk wrote:
> > My remote station is approaching completion. A 70' tower, wireless 
> internet, solar power and RemoteRig with a TS480 is all operational. 
> Still in progress are the antennas to be mounted, and lightning 
> protection. I have a question about grounding. The electronics are 
> housed in a valve box--a galvanized steel cylinder 5 feet in diameter 
> and 4 feet tall, with 3 1/2 feet of that in the ground. A removable 
> steel lid covers it. All cables are in PVC pipe and enter the housing 
> under ground level, and the valve box is 12 feet from the base of the 
> tower.
> >
> > The grounding system will consist of 9 ground rods, 3 connected to 
> each leg of the tower and extending out from the tower. The valve box 
> will also be connected to the grounding system. Polyphasers will 
> protect against surges.
> >
> > My question is, can I install the surge protectors inside the steel 
> housing, or should they be mounted outside the valve box? I'm thinking 
> that the steel cylinder possibly acts as a Faraday cage, and the 
> grounding connection and surge protection should be attached on the 
> outside wall of the housing. Any comments or suggestions, please?
> >
> > Thanks!
> >
> > Trent K5XM on the windy and lightning prone West Texas plains
> >
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk at contesting.com <mailto:TowerTalk at contesting.com>
> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com <mailto:TowerTalk at contesting.com>
> http://lists.contesting.com/mailman/listinfo/towertalk