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1/2 inch Hard line for repeater ?

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Satelite
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1/2 inch Hard line for repeater ?

Postby Satelite » Wed Aug 19, 2015 9:38 am

Hello:
Been assembling a UHF repeater in the 450 MHz range at 40 watt output with the new 12.5 license I received.
I been looking at 1/2 inch ldf 450 Andrew hard line but at the price im looking around a bit first.
Im figuring right at 120 ft will be needed .
In the past I have had repeaters go noisy from lmr400 spiking cables that at first worked well but give it a couple of years and just plain noisy junky cable from breaking down and leaving brown pin burn spots in the white insulation material so lmr400 is definitely out.
Is there any other cables that youd use for this application for keeping the db losses in reasonable specs ?
Satelite

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Bill_G
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Re: 1/2 inch Hard line for repeater ?

Postby Bill_G » Wed Aug 19, 2015 11:24 am

LDF4-50 is a good investment. As you found out, and especially on long lines, you get what you pay for with LMR cable. All the braided cables noise up over time. For indoor jumpers, you can easily replace one when it fails. But, for transmission line, you have to climb the tower to swap it out. Not a fun thing. Better to put in half inch Heliax that lasts decades.

Save you're money. Look around for deals. Get some Heliax.

Jim202
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Re: 1/2 inch Hard line for repeater ?

Postby Jim202 » Wed Aug 19, 2015 11:26 am

You either do it right the first time or pay twice and have to do it over the second time.

The 1/2 inch heliax type of coax is the way to go. You could even use 7/8 coax that will provide slightly lower loss. Bottom line here as your cable gets longer, the line loss goes up. Just how much line loss you can live with is really the bottom line here.

Make sure you get the correct connectors so you don't have to use adapters to mate with the antenna connector and what you need at the duplexor. This helps limit the line loss between the antenna and the radio.

Jim

Satelite
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Re: 1/2 inch Hard line for repeater ?

Postby Satelite » Wed Aug 19, 2015 4:37 pm

Hello;
Yeah gotta agree with the two above replies.
1/2 inch Andrew LDF 450 is what I was wanting to keep the losses at bay.
Another issue I already made a decision on was dropping from a 10db base/repeater antenna (ASP705 Base Comander) to a 5db base repeater antenna which I felt comfy with but now looking at the coax I really didn't want to sacrifice so much db loss since id already gave up 5db gain as it was on the base/repeater antenna.
Im most likely going to have to back up here and find some used but good Andrew 1/2 inch ldf450 coax and may even just bite the bullet and go the 10db antenna.
License was approved at 10db antenna 40 watt output and aprox 140 ft of coax on the new 12.5 license so had the room and specs approved to do it but wasn't thinking about the coax and 10 db ant being so spendy.
But as already said above buy it right the first time or do it again the second time.
Makes the most sense but still don't like the cost involved.
But if your going to play in the big boy coms department then spose ill have to spend a tad bit more.
I figured the repeater and duplexer and gr500 cabinet would be the costlier items but no it the coax and antenna in my case.
:-( and :-) both if you get my drift here.
Satelite

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Bill_G
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Re: 1/2 inch Hard line for repeater ?

Postby Bill_G » Wed Aug 19, 2015 8:04 pm

The 10db antenna adds another wrinkle. High gain is great if you want to talk beyond the horizon, but can leave you with close in dead spots. 5db is generally sufficient.

LMR400 at 450 has 2.7db loss per 100ft.
LDF4-50 has 1.47db loss per 100ft
LDF7-50 has .8db loss per 100ft

For your purposes, half inch Heliax will be sufficient. You won't notice the less than a db loss difference in performance compared to 7/8ths at 450. OTOH, putting too much gain in your antenna so the main signal is fifty feet over your head will impact you. Add in some terrain masking, and you'll be hating high gain. Stay with the lower gain antenna, and don't worry about the extra db lost in the cable.

RFguy
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Re: 1/2 inch Hard line for repeater ?

Postby RFguy » Thu Aug 20, 2015 6:57 am

Bill_G wrote:LMR400 at 450 has 2.7db loss per 100ft.
LDF4-50 has 1.47db loss per 100ft
LDF5-50 has .8db loss per 100ft


Fixed that for you.

I had just done the same calculation and was going to post it, but you beat me to it.

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Bill_G
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Re: 1/2 inch Hard line for repeater ?

Postby Bill_G » Thu Aug 20, 2015 10:05 am

thx!

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N4DES
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Re: 1/2 inch Hard line for repeater ?

Postby N4DES » Sat Aug 22, 2015 3:41 am

I installed 1/2" LDF4-50 for my HOA's licensed UHF repeater and while the length is only 40' in the pseudo bell tower where the antenna is hidden it works just fine.

Satelite
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Re: 1/2 inch Hard line for repeater ?

Postby Satelite » Mon Aug 31, 2015 7:12 pm

Hello:
Found a coax cable 1/2 inch FXL-540 that's 1.44 db loss at 100 ft for the 450 MHz range.
And brand new only 1.39 per ft.
N male and N female conectors run 20 dollar each so think I found my answer.
Has anyone used this coax and if so what was your experience with it ?
Thanx satelite

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Bill_G
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Re: 1/2 inch Hard line for repeater ?

Postby Bill_G » Mon Aug 31, 2015 7:19 pm

No. We haven't. That's the new aluminum cable from Commscope. Haven't worked with it yet.

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Astro Spectra
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Re: 1/2 inch Hard line for repeater ?

Postby Astro Spectra » Sat Sep 05, 2015 11:25 am

FXL works but there are a few cautions. The one that probably doesn't apply here is that you can only use the special connectors designed for it otherwise you will have IM and corrosion issues. The second issue is that it is more fragile and unforgiving than copper Heliax. Carefully follow the installation instructions particularly on maximum unsupported vertical runs and use the recommended clips.

Jim202
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Re: 1/2 inch Hard line for repeater ?

Postby Jim202 » Sat Sep 05, 2015 12:52 pm

I will add another point of caution to be very careful of when installing the connectors. You will need to remove the outer jacket and have some of the outer shield available. If you score the aluminum outer shield, it will fracture at the score if it's bent there. So be careful not to score the outer shield as you work installing the connector.

Loss wise the cable is good. But the precautions of bending the cable and supporting it correctly are a must.

Given the choice, I would go after the copper heliax coax.

Jim

Satelite
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Re: 1/2 inch Hard line for repeater ?

Postby Satelite » Sun Sep 13, 2015 9:36 am

Hello:
I did purchase the FXL-540 1/2 inch hard line aluminum coaxial cable for the repeater which was at 450mhz area and 140 foot long.
My experience with this coax was pretty favorable as to the quality of construction.
The cable is round without the corrugated ridges normally seen on Andrew LDF-450 coax.
Id say its just as stiff and rigid as ldf-450 in my opinion.
As Jim202 already mentioned you don't want to score the outer aluminum but the aluminum outer shield is pretty thick and quite strong so no real biggie if you just take care.
The rf connectors are a bit different but still quality but you do need to be fairly close on the cutting to length so that the connectors outer body will ground to the aluminum outer part of the cable and cut the very good quality plastic protective plastic jacket ( Seems to be same as found on LDF-450 cable) so that the coax has the connectors grounded through the coax outer aluminum shield.
LDF cable connectors had several fingers that compressed to do this but on the FXL-540 cable connectors when you tighten the connector on the connector pushes back hard against the outer aluminum shieding and seals as a flared type contact against the outer and then sorta funnel shapes and if you cut it right then the connector makes contact and as a way of trying to describe it clamps down onto the flare just produced.
So the specs are extremely good and while not by much or even worth mentioning this coax is just as good if not by the specs just a smidge better by the db loss tables I compared the two against.
Im at the moment pretty impressed with the coax and time will tell but I cant see where the aluminum over the copper outer will be a problem as long as careful attention to rubber splice covered with black tape to qarantee no moisture to eliminate any possibility of corroding and to make sure you use a flexible spiking cable at the base/repeater antenna to compensate for any cold hot weather expansion or contracting forces on the cable connect to prevent the possibility of losing the flared clamped aluminum outer shields contact by being pulled out etc.
Don't know if it would ever do that but I do know I wont be climbing up the tower to find out knowing I have a looped spiking cable to allow for any coax movement thus preventing the possibility.
The coax for the money was in my opinion well worth the savings over ldf-450 but you do need to just as I would any cable secure to eliminate moving and bending which is not big problem and normal install practices for me anyway.
Pretty decent stuff and it will bend as in curves but plan on doing it in long sweeps rather than in 6 inches which isn't going to be good by my thinking.
Id really plan on bending the coax cable in say a 90 degree bend but in 18 inches of cable and be gentle and do the bend in all of the 18 inches gradually to accomplish it.
I cant remember now but think the specs said you bend it in a shorter length than 18 but I myself would say - NOT MY CABLE IM NOT.
Bending it in the 18 inch just simply lets the coax bend very easily with almost no stress on the cable with insurance to spare from kinking or splitting the outer conducting shield.
And installing the connectors DID NOT need any special tools to cut ect but would be nice but I did it with wrenches /pliers/ hack saw/Dremil cutoff tool with metal cut off disc(wasn't really needed but made it nice to do over hack saw) and a utility knife to cut the outer plastic jacket.
So you can install the connectors with normal bench tools if you needed to.
No soldering required.
At this point I WILL GLADLY BUY IT AGAIN FOR THE NEXT INSTAL.
Satelite

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Bill_G
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Re: 1/2 inch Hard line for repeater ?

Postby Bill_G » Sun Sep 13, 2015 12:09 pm

Excellent. Thx!

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kf4sqb
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Re: 1/2 inch Hard line for repeater ?

Postby kf4sqb » Fri Sep 25, 2015 6:01 pm

3/4" 75 Ohm CATV hardline is usually cheaper than the standard 50 Ohm hardline we use for radio comms, but will perform almost as well. You may even be able to find a CATV provider local to you that is selling out (quite a few smaller carriers are being ran out of business by the "big boys" these days) or upgrading to fiber optic that will sell you cable for cheap. Connectors are a bit tricky (if anyone makes standard RF connectors for the stuff, I'm not aware of it), and the same caveats that apply to the FXL cable mentioned above also apply to the CATV cable, as it also has an aluminum shield. The dB losses caused by using 75 Ohm cable in a 50 Ohm system are fairly insignificant, and should be made up for by going from 1/2" to 3/4" line. Just a little food for thought.
kf4sqb "at" wetsnet "dot" com



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