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'[EE]: Antenna Feedlines'
2001\07\07@160744 by James R Albers

picon face
Hello Group,

Does anyone know if there is an EIA/TIA standard regarding bringing
antenna feedlines into a radio equipment room?  My boss has instructed us
to bolt a buss bar to the equipment racks and use this as a ground for
Polyphaser lightning arrestors.  I don't think that this is a good
procedure.

Polyphaser recommends using a single point ground that is separate from
the equipment rack and any cable trays.  It seems to me that we should
use an insulated buss bar to mount the arrestors; and then use a heavy
cable to connect this to a ground at the building entrance.

Thanks,

Jim Albers

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2001\07\07@164948 by Bob Ammerman

picon face
I don't know about and EIA/TIA standard, but I might guess that your boss
has pointy hair.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

{Original Message removed}

2001\07\07@172351 by David VanHorn

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face
At 03:01 PM 7/7/01 -0500, James R Albers wrote:
>Hello Group,
>
>Does anyone know if there is an EIA/TIA standard regarding bringing
>antenna feedlines into a radio equipment room?  My boss has instructed us
>to bolt a buss bar to the equipment racks and use this as a ground for
>Polyphaser lightning arrestors.  I don't think that this is a good
>procedure.
>
>Polyphaser recommends using a single point ground that is separate from
>the equipment rack and any cable trays.  It seems to me that we should
>use an insulated buss bar to mount the arrestors; and then use a heavy
>cable to connect this to a ground at the building entrance.

Follow polyphaser.
I wouldn't ground them to anything that I didn't want to share in the
direct hit experience.

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2001\07\08@040230 by Chris Carr

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face
Don't you just love Beancounters. Just agree with him, then write a backside
covering memo crediting him with all the cost cutting engineering.

One of two things will happen. He will get cold feet when he realises that
he would be held responsible for any failure and you get a proper
installation or you are told to go ahead in which case my advice would be to
stay well clear of the tower and equipment room during a lightning storm.

I know not of any EIA/TIA standards. However, I  did a quick look around.

First port of call was http://www.furse.com but most of their site appears
to be under construction 8-(    (their paperware (CDROM) has some good
advice)   so I had a look at Polyphase and the following document gives a
concise summary of the issues.

http://www.polyphaser.com/pdf/PTD1011.pdf

Andrew Antennas http://www.andrew.com also have some useful information

For what it's worth my checklist would be

1. Are all four legs of the Tower connected to a Good Earth. (Use the tower
as a Lightning Rod)
2. Are the cables routed down the centre of the tower and NOT down one of
the legs (Minimise Induced Currents)
3. Are all cables taken through a metal bulkhead and is the protection
applied at that bulkhead (Don't let the Lightning get into the equipment
room)
4. Is the bulkhead directly connected to ground using a very big stranded
cable with no bends. (Keep Resistance and Inductance to earth an absolute
minimum).
5. Are the Equipment Racks bonded to the Entry Bulkhead
6. What about your power supplies. I worked on one station in Africa where a
Battery Room was built under the tower. To save money they routed the cables
to the first floor (that's the one above the Ground Floor 8-) )  equipment
room up one of the legs of the tower. Guess what happened when the tower got
struck by lightning.  Fizzle, Fizzle, Bang.

I would also apply protection at the base of the tower where the vertical
run down the tower changes to a horizontal run towards the building

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2001\07\09@080825 by James R Albers

picon face
Thanks to everyone (especially Chris) for the reply.

> For what it's worth my checklist would be
>
> 1. Are all four legs of the Tower connected to a Good Earth. (Use
> the tower
> as a Lightning Rod)

Yes, it's a monopole, well grounded.

> 2. Are the cables routed down the center of the tower and NOT down
> one of
> the legs (Minimise Induced Currents)

Yes, they come right down the inside of the tower.

> 3. Are all cables taken through a metal bulkhead and is the
> protection
> applied at that bulkhead (Don't let the Lightning get into the
> equipment
> room)

The tower company grounds the coax shield where it leaves the tower; and
then again where it enters the building.

> 4. Is the bulkhead directly connected to ground using a very big
> stranded
> cable with no bends. (Keep Resistance and Inductance to earth an
> absolute
> minimum).

Yes, 000 stranded copper to heavy copper buss bars.

> 5. Are the Equipment Racks bonded to the Entry Bulkhead

No.  This is where things deviate from the recommended.

> 6. What about your power supplies. I worked on one station in Africa
> where a
> Battery Room was built under the tower. To save money they routed
> the cables
> to the first floor (that's the one above the Ground Floor 8-) )
> equipment
> room up one of the legs of the tower. Guess what happened when the
> tower got
> struck by lightning.  Fizzle, Fizzle, Bang.

No batteries (except for the microwave equipment), a generator provides
emergency power.

>
> I would also apply protection at the base of the tower where the
> vertical
> run down the tower changes to a horizontal run towards the building
>

Yes, as above.


It seems that the tower company did a good job.  Now, all that I have to
do is to show my boss the error of his ways.  The drawback is, that if I
do convince him, he'll probably make me do all of the work.

Thanks,

Jim Albers

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2001\07\09@111531 by Bob Barr

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James R Albers wrote:

>
>It seems that the tower company did a good job.  Now, all that I have to
>do is to show my boss the error of his ways.  The drawback is, that if I
>do convince him, he'll probably make me do all of the work.
>

Solid documentation should make that showing a bit easier, though not
necessarily so. (Depending on your work situation, a CYA memo to your boss
might not be a bad idea if he refuses to see the light.)

I, for one, would certainly rather have to do the work than have to explain
to the CEO why the work wasn't done. This especially applies if there's any
chance that 'his way' puts people or a lot of expensive equipment at risk.
Your boss may no longer be there when the stuff hits the fan.

Regards, Bob

_________________________________________________________________
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2001\07\09@174946 by Peter Barick

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Talk about a tight spot ! But James has an opportunity to shine on this
task while still being loyal to his apparent misguided boss.

Let's assume the boss means what he says and is used to getting his
way. James knows what the established engineering practice dictates for
lightning safety. So let's us combine the two. Bob suggests a CYA memo,
that's basic step-1, however it must not be accusatory--no "dumb boss"
talk here. Instead, address it to boss and the project folder, describe
a few points of concern that may impinge on safety and/or equipment
reliability, lastly, offer your engineering-based-and-supported ideas of
what should be. Finally, in the memo ask the boss to reconsider and to
please advise you. Send it.

Next, be prepared and start to plan for the original dumb work order.
The boss may reject your "I have a better idea memo," but now he does so
with some trepidation. [Ha, but he could reconsider!] He also knows that
you have demonstrated leadership and managerial skill that will prove of
value at a future time.

James, you should buy that boss a cigar for this wonderful opportunity
to display your intelligence, not his faults. Go for it! And if he does
give in, do the right thing: Buy Donuts and coffee for the group.
They'll  likely know what'sup anyhow.

Oh, James, do let us know when you move into that bigger office with a
secretary. :-}

Peter

>>> bob_barrspamKILLspamHOTMAIL.COM 07/09/01 10:15AM >>>
James R Albers wrote:
>>>
>>>It seems that the tower company did a good job.  Now, all that I
have to
>>>do is to show my boss the error of his ways.  The drawback is, that
if I
>>>do convince him, he'll probably make me do all of the work.
>>>

>Solid documentation should make that showing a bit easier, though not
>necessarily so. (Depending on your work situation, a CYA memo to your
boss
>might not be a bad idea if he refuses to see the light.)

>I, for one, would certainly rather have to do the work than have to
explain
>to the CEO why the work wasn't done. This especially applies if
there's any
>chance that 'his way' puts people or a lot of expensive equipment at
risk.
>Your boss may no longer be there when the stuff hits the fan.

>Regards, Bob

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