best coax for long runs

[fatsuckertim]

We have a 50-60 ft tower beside a large metal building that houses our offices and buildings. Years ago we had a kenwood trunking base radio and had a short yagi and a CB antennea mounted on the tower. We monitor Mo Highway Patrol Troop A as we sit next to the highway.

I have a 996 P2 and a 996XT, one hooked to the old yagi and one hooked to a scanner antenna, which has one whip straight up and whips below that pointing down like a cone. (Discone?)

I split the MOSWIN towers for troop A between the 2 scanners. Pick up the Daton/Aaron tower mostly as it is the closest, appears to be the busiest too.

One coax says " International wire and cable co #9091 RG 8X " on it and the other looks to be the same diameter but cannot identify it. Probably a 120' run.

What is the best coax and antennas I should use? I know MOSWIN has some 700mhz towers and the others might be in the 100-200 range.

I know that both coax's are 25+ years old.
Any recommendations?

PS- we always monitored Troop A on the low band side before MOSWIN was adopted. not heard much traffic on it for a while. Was in Lee's Summit where Troop A headquarters is located last Friday ( 3-11-22) and noticed that the large radio tower behind the building was completely gone! Might account for not hearing low band traffic any more...

 

[AB5ID]

The tower (new tower) has moved to James A. Reed. If you know what systems you want to hear, you can try using the existing coax to see if it will receive those systems.

 

[belvdr]

RG8X was fine for CB, as it has a loss of approximately 2dB every 100 feet. At 700-800 MHz, you'll probably see 11-12 dB loss per 100 feet.

If you're replacing coax these days, I wouldn't use anything less than LMR-400 on the tower. At 700-800 MHz, you'll see about 3.5 - 4 dB per 100 feet of cable.

Once it is in the building, you can use something more flexible for the short runs. Do it once and do it right.

 

[fatsuckertim]

The tower (new tower) has moved to James A. Reed. If you know what systems you want to hear, you can try using the existing coax to see if it will receive those systems.

Is that the Lee's Summit 700 tower?

 

[fatsuckertim]

If you're replacing coax these days, I wouldn't use anything less than LMR 400 on the tower. Do it once and do it right.

Once it is in the building, you can use something more flexible for the short runs.

Thanks!

 

[ur20v]

Honestly, unless you are doing weak signal DX with a beam on a rotator, you're going to be just fine using RG8 or 8X or whatever you can get cheap since you're only using it for receive.

 

[fatsuckertim]

Honestly, unless you are doing weak signal DX with a beam on a rotator, you're going to be just fine using RG8 or 8X or whatever you can get cheap since you're only using it for receive.

Thanks!

 

[mmckenna]

25 year old coaxial cable should be of concern.
It doesn't last forever.

If your cable/antenna set up works for what you want, then stick with it. Replacing it would be wise if you are actually having reception issues.

If it is RG-8x, the amount of loss in NEW cable at 120 feet and at 800MHz is going to be 15dB, or about 97% of the signal is being lost -just- in the cable before it makes it to your radio. Add in poorly installed connectors, possible water intrusion due to failed weatherproofing, damaged jacket, and you are probably seeing more loss.
Add in a discone antenna, which will have zero gain and a really poor radiation pattern at 800MHz, and it's kind of surprising you are hearing anything at all.
But, if the transmitter is close by, you'll get something. Some of that may be just signal leaking -into- the coaxial cable….

So, it really depends what your expectations are. For a discone antenna at that height, RG-8X is an exceedingly poor choice. 97% signal loss from an already poor performing antenna isn't doing you any good.

If budget isn't a big challenge, then you'll see a huge amount of improvement by using coaxial cable with less losses. LMR-400 is a good starting point. Probably the minimum you should use. It's only going to result in 65% signal loss at 800MHz/120 feet.
LMR-600 will give you about 50% signal loss. If this was a commercial installation, you'd probably want to use something like 7/8" heliax, but that's expensive and overkill for scanner listeners.

If 7/800MHz is your only area of interest, you'll get better performance by ditching the discone and getting a dedicated 7/800MHz antenna.
If you want to keep the discone to make full use of your scanners capability, then upgrading the coax would be an excellent first step.

 

[fatsuckertim]

Thanks for the reply
I can pickup troop D Carthage ( about 90 miles) pretty clear, and most distant weather frequencies come I pretty good also. I feel we might be missing some traffic from other towers in the troop is all.
I've updated my scanners and updated all the new towers in Troop A in. Going to try this SDS 200 in the office to see how it does there as I have had it in my truck the past few days and have been hearing more of both sides of the conversations.
I've been on the phone with the wife and heard traffic over hers and not on mine and vise versa
A

 

[mmckenna]

Thanks for the reply
I can pickup troop D Carthage ( about 90 miles) pretty clear, and most distant weather frequencies come I pretty good also.

That really seems like it's working better than it should for a discone and 120' of RG-8X, but hey, roll with it if it's working.

 

[fatsuckertim]

That really seems like it's working better than it should for a discone and 120' of RG-8X, but hey, roll with it if it's working.

Thanks!

 

[Kiniutech]

check this

Coax Calculator

Coax Attenuation Chart

 

[fatsuckertim]

Thanks!