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Author Topic: Nine (9) Inch Diameter coax cable!  (Read 5662 times)
G7MRV
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« on: May 21, 2014, 10:55:55 PM »

Ok, so I work in high power UHF broadcasting. We use cables made by RFS to feed up the 1000ft tower here, and we use very large 6inch cables!

But, ive just been looking at the RFS website and see they make a NINE INCH diameter 50ohm coax!
9 inch! Thi stuff is rated at around 5MW at MF, and hundreds of kW's at TV UHF frequencies! with loss figures that if you could get them in a 10mm cable would start a new religion! Grin

RFS HCA900-50T 9" HELIFLEX® Air-Dielectric Coaxial Cable
http://www.rfsworld.com/product-solutions-results,560,1.html&sol=1671

6inch is the biggest coax I have ever seen in an actual cable (we have 8 inch but thats rigid line!)

Has anyone nine inch or bigger semi-flexible coax, actual 'cable', in use, and if so where and how?
« Last Edit: May 21, 2014, 11:00:28 PM by G7MRV » Logged

KD8MJR
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« Reply #1 on: May 22, 2014, 01:48:39 AM »

Has anyone nine inch or bigger semi-flexible coax, actual 'cable', in use, and if so where and how?

 Cool  Cool
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DL8OV
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« Reply #2 on: May 22, 2014, 07:53:00 AM »

The link does not work so well. For anybody interested here is the link to the pdf datasheet.

http://www.rfsworld.com/WebSearchECat/datasheets/pdf/?q=HCA900-50T

This amazing 'cable' can be used up to 590 MHz and for amateur use we could transmit 268KW as high as the 70cm band without any technical issues.

Peter DL8OV
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G7MRV
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« Reply #3 on: May 22, 2014, 08:54:26 AM »

Thanks for the better link Peter

I have a 'patch lead' some 5m long, made from their 4inch product with connectors. I can barely lift it!
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W9FIB
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« Reply #4 on: May 22, 2014, 07:50:05 PM »

Must take 1 hell of a winch to pull up 6" coax 1000'!
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K8AXW
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« Reply #5 on: May 22, 2014, 09:27:20 PM »

1000' of 9" weighs over 3 tons.  It's incomprehensible to me how it's handled!
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G7MRV
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« Reply #6 on: May 22, 2014, 10:22:34 PM »

Must take 1 hell of a winch to pull up 6" coax 1000'!

Actually, It takes two! One pushes it up from the bottom, the other (which is actually on the ground and very well tied down!) pulls it up from the top, via a big pulley! The top one has to run everso slightly faster than the bottom one, to avoid kinking the cable,

and believe me, you dont want to kink this stuff! Its not something you can simply shove a barrel connector on!

We buy this stuff cut exactly to the length needed, even forgetting to take account of the extra space needed for the connectors can totally ruin a job! Its not so bad if you've ordered it slightly long, but if its even a few millimeters short... Embarrassed

And when your pumping 50kW at 700MHz up it, you really dont want any extra loss, and certainly no impedence bumps! Shocked

Incidentally, our cable runs are about 1100ft up the tower, but the towers about 300ft from the transmitters! And this isnt even our tallest structure!

Now, imaging an 'offcut' of the 4 or 6inch stuff, about say 60ft long, with the appropriate adaptor/connector fittings, including a right angle, made nice and straight, with a few of the support brackets modified as guy rings....  (and yep, you can get adaptors direct down from the 6inch to an N type!!! I know, ive got some!) It really is rigid enough that you could make a self feeding mast! Grin

It would be a great comeback to those people who point out that all the loss in your G5RV is from the coax! I wonder how a G5RV fed with 9" coax would perform?
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G7MRV
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« Reply #7 on: May 22, 2014, 10:26:09 PM »

The link does not work so well. For anybody interested here is the link to the pdf datasheet.

http://www.rfsworld.com/WebSearchECat/datasheets/pdf/?q=HCA900-50T

This amazing 'cable' can be used up to 590 MHz and for amateur use we could transmit 268KW as high as the 70cm band without any technical issues.

Peter DL8OV

Although the two connectors would probably cost the same as a new FT-857D Cheesy
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K7KBN
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« Reply #8 on: May 23, 2014, 10:41:46 PM »

The link does not work so well. For anybody interested here is the link to the pdf datasheet.

http://www.rfsworld.com/WebSearchECat/datasheets/pdf/?q=HCA900-50T

This amazing 'cable' can be used up to 590 MHz and for amateur use we could transmit 268KW as high as the 70cm band without any technical issues.

Peter DL8OV

Although the two connectors would probably cost the same as a new FT-857D Cheesy

How about the SMA adapter so I can use it with my new Chinese Superradio?
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73
Pat K7KBN
CWO4 USNR Ret.
DL8OV
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« Reply #9 on: May 24, 2014, 08:25:47 AM »

I'll hold it with my pliers whilst you solder it on  Grin

Peter DL8OV
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G7MRV
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« Reply #10 on: May 24, 2014, 01:19:50 PM »

Think you'll have to use two adapters, they do one from the 9" heliflex down to an N type, so just bob an N to SMA onto that!  Cheesy
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G7MRV
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« Reply #11 on: May 24, 2014, 03:25:39 PM »



Theres two 4" to N type adapters there, lower left and upper left, beside a bit of rigid 4" feeder used as a filter and sampling point. The 'inner' of the coax is to the right. Im in the process of sectioning this piece as a demonstration and teaching aid.
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W2IBC
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« Reply #12 on: May 26, 2014, 11:45:13 AM »

got to wonder what the price per foot is on that 9"
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I AM THE VOICE OF THE VOICELESS!
KA5PIU
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« Reply #13 on: May 31, 2014, 05:15:18 PM »

Hello.

Newer cell towers only have DC and a fiber optic line.
All of the RF stuff is on top.
The old coax is not removed Cry
Yes, the little hut gets removed, replaced by this set of panels.
The cable company does remove coax when they put in fiber.
But, that is 75 ohm hardline.
The problem with 6" line is that it would weigh more than most ham grade towers weigh, and they could not support it!
Even the heliax that cell towers use would be too heavy.
But, the idea of putting the rig on top of the tower, that might work.
Can you imagine an access point in a cooler mounted on a tower? I have seen just that!
It looks silly, but it does work.
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KV7W
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« Reply #14 on: May 31, 2014, 07:03:05 PM »

45G could probably handle up to 1 1/4", but 7/8" is a lot easier to work with! I couldn't imagine working with 6" heliax, let alone 9". How the heck you suppose to route that? Ratchet straps and come-alongs must be the norm.  The feed line ladder must be mounted on the outside of the tower, too. Can't imagine the cost - or the pressure to get the connector on right the first time.
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