Batboard

need to run approximately 40-60 feet of coax for a base station setup at our stations for VHF and 800. Antenna will be attached to a pipe about 20 ft mounted to side of metal building. No repeater, just a simple base.

I am putting polyphasers on the lines and of course grounded. What do I need to use for coax? LMR400, 1/2 inch, 3/8 inch Heli.

Thanks guys

1/2 inch hardline or 7/8 superflex if money is available

Jban-

LMR-600 or 1/2" Heliax (LDF4) would be more than sufficient for your application.

Bruce-
LDF4 (1/2") is 2dB per 100ft. at 824.
VXL5 (7/8" Superflex) is 1.22dB per 100ft. at 824.

So, for a 60ft. run, we're talking about 1.2dB vs. 0.732dB, for a net difference of 0.468dB. Completely inconsequential to overall system performance, which requires jumping to significantly larger and more expensive cable/connectors.

As always, Thank you gentlemen for your assistance.

One more question. We are also going to put up a 70-90 ft pole on a hilltop to relocate our repeater. Estimating at this point of a coax run of 120 ft to the polyphaser. About 6-8 ft from the polyphaser to the repeater. 100 watts out of the repeater to a 6db antenna.

I assume we would want to use 7/8 hardline?

Jban-

What band? 800, for a 120 foot run, 7/8" is reasonable... 1/2" would be tolerable. UHF or VHF, 1/2" is fine.

Sorry about that. VHF

your 1st post says VHF and 800
Thats why the 7/8th.

at the end of the day thats all I run except a couple of locations where 1 1/4 and 1 5/8 is required .

Bruce1807 wrote:your 1st post says VHF and 800
Thats why the 7/8th.

Two different configurations, one a base, one a repeater.

1/2" loss at VHF - 0.815dB/100ft.
1/2" loss at 800 - 2.090dB/100ft.
7/8" loss at VHF - 0.449dB/100ft.
7/8" loss at 800 - 1.180dB/100ft.

Now, keep in mind the cost... (my distributor price)
1/2" - $1.48/ft.
1/2" N-Male connector - $34.07/ea.
7/8" - $3.60/ft.
7/8" N-Male connector - $115.38/ea.

For your purposes, I'd run 1/2" for your base station. It's a short run, and the cost/benefit from going to 7/8" is low. Hopefully you'll be mounting the Polyphaser at the building entry point to an existing halo ground... if the length from Polyphaser to radio is short, consider 1/4", 3/8", or 1/2" Superflex for the jumper (base this on length and loss)

For the repeater, if you have the budget, go ahead and run 7/8". Again, from the Polyphaser to the cabinet, based on the length/loss, consider running 1/2" Superflex jumpers.

Sorry for the possible confusion on the questions. Here is what we are doing.

I have a vhf and an 800 modile radio that is going to be installed in each of our 2 fire stations as a simple base. The building is metal. I am planning on attaching a mast to the side of the building (about 10-20 feet) to mount the VHF antenna. After thinking about it, I may just use a mobile antenna mounted directly to the metal roof for the 800 rig. I don't need much for the 800 side. I am still debating on how to do the grounding since it is attached to a building. I am open to suggestions on this.

The repeater is VHF. We are relocating for better coverage (finally got permission to use property we wanted in the first place). A local utility company is suppling the pole and setting it. I don't know at this point if the pole is wood or metal. We plan on constructing a small cinder block building for the shack. This will be grounded via halo. Question: does the shack need to be part of the halo ring or just the pole?

I had planned on using 7/8 for the repeater run but if 1/2 will work that would be a $ advantage. I want to get it done as properly as possible, however, so if 7/8 is it, that is what we will do.

As always, I appreciate your assistance and am open to any and all suggestions or insight.

Other than that, this Texas boy is COLD right now! I can deal with 110 temps but I don't like 29.

halo is generally clased as internal.
External grounding should go round the pole and the shack

get hold of Motorolas R56 standard. It tells all

All grounding for telecommunications is covered by the
NEC (Natational Electrical Code). There are a couple of
sections that you need to pay attention to. Check out the
250 and the 800 sections.

These are very clear on just how and where the grounding
needs to be done. Motorola's R52 does sort of cover the
part of grounding the antenna structure and inside the
equipment room. I think it is some what unclear on the
power side of things though.

Jim