Toking advice

Gotta watch those Fresnel zones!
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Dan P
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Toking advice

Post by Dan P » Mon Jul 28, 2014 6:00 pm

Ordering ubiquiti stuff for my 850 foot shot. Have a question re cat 5. Normally, if anything goes on an am grounded tower, must be bonded every 50 feet.Think fm translator, stl etc. How do we bond cat 5 to an am tower (folded unipole, not a hot tower) that has 2 class 4, and at least 1, soon to be 2 250 watt fm translators? Or, does just grounding it near tower base work?
Dan

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Deep Thought
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Re: Toking advice

Post by Deep Thought » Mon Jul 28, 2014 10:47 pm

Run it in conduit and be very careful about bonding that to the tower.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

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kkiddkkidd
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Re: Toking advice

Post by kkiddkkidd » Tue Jul 29, 2014 7:56 am

I agree with the conduit. Make sure that each section of pipe is firmly grounded to the tower. I once found a run of lighting conduit on a 320ft tower to be 100 ohms above the tower steel at the bottom but only 45 ohms away at the middle beacon. At the time, I would probably have argued with someone that it wasn't possible but all 4 towers in this array had varying amounts of resistance between the lighting conduit and tower. They were attached with a combination of stainless straps and u-bolts and had been installed before the towers were painted. Grounding each and every section of conduit on all 4 towers cured many years of array instability.

On the Cat5, I recently installed a "temporary" run of about 225ft on a 1kw AM tower. We did not run it in conduit but we did use the heavily shielded rodent resistant version with a full copper shield. It was grounded at the top and bottom and was supposed to be grounded a couple of times in the middle but the tower crew ran out of daylight. It has functioned flawlessly for several months and has survived a fairly active lightning season.

On another FM tower, a previous engineer had installed a run of about 300ft of common STP Cat5 up to an IP STL dish. It worked great until the first time that the wind blew over about 20mph. At about 20mph, data errors would get high enough that the audio would start dropping. Reducing the tx power from 4 to about 3 kw would usually clear the dropouts but higher winds required more power reduction. I eventually was able to convince management to install conduit and replace the non-outdoor rated Cat5 with the good copper shielded stuff. We did so and the dropouts were permanently cured. We were never able to determine what caused the BER to go up as the cable was well attached and various ground schemes and filters had been tried before I took on this station.

Later,

Kevin
vengineer@kkbc.com
AM Ground Systems Co.
--
Kevin C. Kidd CSRE/AMD
WD4RAT
AM Ground Systems Company
http://www.amgroundsystems.com
KK Broadcast Engineering
http://www.kkbc.com

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kkiddkkidd
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Re: Toking advice

Post by kkiddkkidd » Tue Jul 29, 2014 8:13 am

I guess I didn't really answer your question... I use small coax ground kits to ground the heavily shielded rodent resistant Cat5. In all actuality, a loop of wire pulled around the solid copper jacket would have sufficed but we chose to get the kits since they had the waterproofing materials included and were relatively cheap.

We used these from Tessco:

CommScope - Universal Ground Kit for .1 to .6" cable & CAT5E
TESSCO SKU : 445755 Mfg Part #: GK-SUNV Qty/UOM : 1 EACH UPC: GK-SUNV
COMMSCOPE Uni-Ground Kit for CAT5 and braided cables .1" to .6". Includes 24" ground cable with tinned copper braid, hardware and 2 part weatherproofing.

About $10 each.

If you are using common STP without the substantial outer copper shield these would probably work OK but again a simple loop of wire would suffice.

Whatever you use, remember to bring the ground wire out of the bottom of the waterproofing and keep the ground wire as short and straight as possible.

Later,

Kevin
vengineer@kkbc.com
AM Ground Systems Co.
--
Kevin C. Kidd CSRE/AMD
WD4RAT
AM Ground Systems Company
http://www.amgroundsystems.com
KK Broadcast Engineering
http://www.kkbc.com

stephend2
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Re: Toking advice

Post by stephend2 » Sun Aug 03, 2014 9:30 am

I second the commscope grounding kits. I use them on any AM tower installation. I use the Ubiquiti toughcable carrier cable. It has done well for us coupled with the grounding kits. It's not a copper sheath but a braided shield on top of a foil shield with a tough jacket.

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KPJL FM
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Re: Toking advice

Post by KPJL FM » Tue Aug 05, 2014 1:54 pm

probably need to wind the cat5 on torroids at back of the rack.
Trim to fit, paint to match, tune for minimum smoke.

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Xenirad
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Re: Toking advice

Post by Xenirad » Mon Jan 26, 2015 3:42 pm

KPJL FM wrote:probably need to wind the cat5 on torroids at back of the rack.
I agree. I use the toroids top and bottom. Make sure to use the shielded outdoor UV cable not only for RF but for lightning as well.
Fred Francis, Owner Xenirad Broadcast Engineering http://www.xenirad.com

Dan P
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Re: Taking advice

Post by Dan P » Tue Jan 27, 2015 7:21 pm

Have system in. Want to thank all re shielded cable and grounding kits. Was going to cut over first of this week, but hammered by snow. Long story short, new tower 30 feet at studio (out of old salvage), ubiquiti system sees each end. Bonded to am tower every 50 feet. Going to run barix for 2 existing mono shots, will add more barix units as we add another fm xlator. CP granted last week in Maine.

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