CELLFLEX Hardline

[VK3ICE]

Hi all,

Has anyone experience with RFS CELLFLEX LCF78-50JA Foam Dielectric Coaxial cable. This is the big stuff 7/8" with some serious performance figures.

I understand this is heavy and requires careful support but I have an option to get an end length (quite long) from a spool for a half decent price IMHO but I would appreciate feedback from actual users of this coax, primarily external exposure issues as there will be a run up my tower (approx 13m). Intended use is for some 40m runs for VHF/UHF.

Thanks

Kevin (VK3ICE)

[VK4TI]

Hi all,

Has anyone experience with RFS CELLFLEX LCF78-50JA Foam Dielectric Coaxial cable. This is the big stuff 7/8" with some serious performance figures.

I understand this is heavy and requires careful support but I have an option to get an end length (quite long) from a spool for a half decent price IMHO but I would appreciate feedback from actual users of this coax, primarily external exposure issues as there will be a run up my tower (approx 13m). Intended use is for some 40m runs for VHF/UHF.

Thanks

Kevin (VK3ICE)

I have never used it exposed as you propose so best ask the manufacturer but internal runs are like any other heavy cable , you might try sourcing the support kit , its obviously difficult but a little care is achievable , fittings require care and cost depending on choices , might need special tools but the supplier may be prepared to fit for you
Barry

[VK2KRR]

Hi Kevin,

I believe the 78-50 is compareable to Andrew LDF5-50 in size and loss specs.

I use it for all my cable feeds here except 1296. It doesn't need careful support as such, but it must be supported and secure, obviously you dont want it blowing in the wind etc. Depending upon your tower structure you can simply tape it to the tower, you can also get the proper stand off brackets, but I'd say the cost would not make that a worth while thing.
You also need to keep appropriate bend radius and if you do tape it be careful of sharp or protruding edges of the tower, dont put to much clamping pressure on it in these spots as it could deform the copper and or cut into the outer sheath.
You could also use cable ties, but they need to be fairly wide ones. I'd use tape rather than cable ties.
I dont think there would be any external exposure issues, its designed to go up towers in all weather conditions.

25mm (I think) saddle clamps also fit over it fairly snug, which is whats holding the very top of this one of mine

[VK2AAH]

I'm very "un-ham" when it comes to this. Appreciating that you may be getting this feeder at a good price I don't know whether people realise how much of a PITA large bend radius feeders like this are if being used for relatively short runs at VHF & (low) UHF. A contractor I deal with used this feeder over a similiar lengths & frequencies (despite my warnings not to) and they will never make the same mistake again. The awful bend radius created an unsightly bird perch for stuff all reduction in loss. But hey I appreciate that hams devoutly believe in "biggest is best" over "it isn't what you have but how you use it...".

Cheers


Richard
VK2AAH

[VK3ICE]

Thanks for your feedback guys, I have spoken to the manuafacturer and been assured it is OK for external installation.

I appreciate securing this type of cable can be challenging and the insights provided are exceptional.

In regard to bend radius and other issues where there will be repetitive mechanical forces I intend to use this cable as the primary feeders from the shack distribution panel in the floor to the top of the tower and then use a more suitable cable for the antenna and radio jumpers. I hope this will overcome potentially huge radius curves at these points that may scare the neighbours and the XYL.

Regards and thanks to all,

Kevin

[VK2XSO]

I work with this cable almost every day.
The bending radius isn't that bad, but it's not RG58 and of course has some practical limitations.
Bending it before it is cut to length is how I work with it.
A sensible person (not a ham) would just use some big a*** DIN connectors on each end and some nice flexible SCF12-50 tails at each end.
These things are dirt cheap on the surplus market.

Lee's example is typical of a good setup. LDF5 to the tower and a tail to the antenna.

http://www.rfsworld.com/dataxpress/Data ... 78-50JA-A0

[VK2AAH]

I question the merit of using 7/8 over 1/2 inch (LDF4-50 or equivalent) over relatively short runs- and I class 40m as "border line". The use of tails is fine & I respect that this approach keeps the top end neat and tidy and the mechanical stress on connectors to a minimum. However I look at what is gained by using 7/8, there has to be some point to stuffing around with a big feeder. Common sense, to me any way, is to adopt a simple rule- if a feed run is shorter than a certain length (I recommended 50m) I specify 1/2 inch. Once it goes beyond that length I specify 7/8inch (this is for sub 1GHz).

My bigger gripe is when techs run 1/2 or 7/8 inch feeders directly into the rack or hut rather than transitioning to a more flexible feeder at the cable entry/lightning protection point.

As usual we have drifted the discussion off Kevin's original topic and he has these issues addressed already. Good luck Kevin!

Cheers

Richard
VK2AAH

[VK3ICE]

Again to each of you have posted replys my sincere thanks.

Although we may have strayed a little from the initial subject I consider everyone's input to be exceptionally valuable and greatly appreciated.

Richard I have spent some time considering the merits of using 7/8"vs 1/2" for these runs but has been predominately a financial decision based on the end roll cost. I do support that for a 40m run we are talking relatively low loss and attenuation results and I will reevaluate these in light of everyone's comments.

As a first poster if this is the quality of feedback received on this forum network, I will be regularly using this medium to seek advice from those of you with far more experience than I.

Thank you and I'll keep you informed of the outcomes down the track.

Regards

Kevin

[VK5PJ]

Hi Kevin,
I have 4 runs of LDF5-50 on my tower (2 of the original Andrew Heliax1 and 2 of the newer Andrew Heliax2 [AVA5-50]), each runs is just under 40 metres in length. While the tower is just 16 metres in height, the cable has to go underground to the nearby shack via a pair of 90mm storm water pipes. Looking back at it I should have used the 100mm pipes as they have a greater wall thickness. the entry and exit points are a work of art, with multiple 45 deg pipe bends to soften the entry angles.

At the bottom of the tower each run does a full loop around before it goes into the pipes, this gives me some flexibility to pull a little bit more up the tower if there is an accident a the top or pull some more either towards or back from the shack. Initially this happened by accident (the cable loop that is) but on the second pair of cables I deliberately duplicated this layout as it dawned on me that doing this removed the stresses between the "up tower" and "to shack" runs of cable.

Looking back at the choice of 7/8" cable, there was a little bit of ego in there BUT it was also a case of what became available in my region. I must admit I wanted to do this once and do it properly having like so many other hams having worked in the industry it seemed silly not to make the extra effort.

As others have indicated, the cable should be supported coming down the tower (your choice how often it is strapped) and not left to hang by a single fixing point up the tower, sideways movement is your enemy on the big cables.

Hope you go ahead with it, I looked at it as an investment if the future as to what higher bands like 2.4Ghz and 3.4GHz I might want to put up the tower. If copper prices go any higher you can cash the cable in for your superannuation

Regards,
Peter, vk5pj

[VK4GHZ]

I...

I'm sorry, I can't add to this, except point out that I am insanely envious of Leigh's antenna horizon!
Not like the burbs here, at all.


That "Rock" is a bastard in our direction though, because you would be a great (enthusiastic and active) station to aim for here in Brisbane.

[VK3ICE]

Peter,

you make some great points here and observations from your experiences that I will put to good use.

The concept of longer term investment has driven me down this path also. I remember being given some advice as an aspiring amateur some 30 plus years ago - "$10 spent in the air is worth $100 in the shack" - I consider the transmission lines to be covered by this philosophy.

And yes I too am insanely jealous of Leigh's outlook.

Regards

Kevin