Suggested Coax suppliers for custom cables?

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Kumba

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Looking to beef up the cable attached to the Larsen trunk NMO mount for my car. As far as I can tell, Larsen doesn't have anything with thicker/shorter cable, so I figure my best bet is to short the cable length from 17' to 12', which should still be enough to reach the front of the vehicle. I also figured it'd be good to beef the cable up a notch to the thicker RG6 or some of the LMR-240 stuff.

Thought of doing this myself (and I still might), but without the right cable crimper yet, I figured it'd be better to just have one custom made professionally. To start, I figured I'd clip the NMO mount cable about 6" after it leaves the mount housing, and attach a TNC male connector. Then I'd get either the RG6 or LMR-240, and put a TNC female on one end, with a BNC Male L joint on the other, and run that up to the front of my car where I keep my scanner (BCD396T) at.

Sound kosher for one looking to reduce signal loss and try to get a small range boost? Or do I need to look at getting a higher-gain antenna that targets the 800MHz trunked system ranges better (which is what I primarily listen to)? Currently using a Larsen tri-band 150/450/800, and it works really good.

One supplier I found (WPS Antenna, I think) seemed good at first. Their price for a custom 12' 50ohm cable with the above two connectors was about ~$20, plus the extra TNC-M for the cable end on the NMO mount. But they wanted a whopping $26 for shipping, which is absurd for 12' of custom cable and a small connector. So I figured I need to find someone else, but not sure which suppliers out there do good quality work and have reasonable prices, both for the product and for shipping it.

Thoughts?
 

N2JDS

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Until the real techies answer. My opinion is, improve the antenna, I doubt the coax swap would help that much, unless you have bad sections of cable (worn or stressed shielding). I'd think the additional connectors would negate any real improvements. Check around to see if somebody local has an antenna they can loan to see if just swapping out the NMO helps, plus check for shorts in the coax. I'm using a stock NMO hood/fender mount with supplied cable to feed my scanner. Using a 5/8 wave VHF. Absolutely nothing special, and I get 42.XX MHZ . 150.XXX MHZ, 700/800 MHZ, and get that with at least 30-40 miles from base transmitters on the lower, and at least 20 miles on the 700/800 systems. I was quite shocked. Good luck.
 

DPD1

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You could do all that, but unless something is wrong with it to begin with, I doubt you'd hear any difference... Not for something that short.
 

W6KRU

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You could do all that, but unless something is wrong with it to begin with, I doubt you'd hear any difference... Not for something that short.
I agree. If you have excess cable, do not coil it in a loop to stash it. Other than that, I wouldn't worry about it due to the lengths involved.
 

n5ims

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You might try this --> MB240: 3/4" Hole Brass NMO Mount with 17' LMR240 Cable and add the correct connector for your radio after triming it for fit. If you're not comfortable doing the mounting, cable routing, and attaching the connector yourself you may be able to have a professional installer take this assembly and do the install for you for a fee.
 

Kumba

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You might try this --> MB240: 3/4" Hole Brass NMO Mount with 17' LMR240 Cable and add the correct connector for your radio after trimming it for fit. If you're not comfortable doing the mounting, cable routing, and attaching the connector yourself you may be able to have a professional installer take this assembly and do the install for you for a fee.
Well, by trunk mount, I meant more trunk lip mount. Trying to avoid drilling holes in the trunk lid of the car. So far, the Larsen NMO mount has been pretty good.

I asked about this topic, but from a different angle, a few weeks ago. Just a lack of time has prevented me from doing a whole lot of research into it. In the older thread, someone said shortening the cable length and using the thicker cable would probably work better than buying a new antenna, or at least it would identify, for cheaper cost, whether I would need a new antenna or not.

Mostly trying to increase the reception range of my county's local public safety system, which is in the ~868MHz range (after re-banding, should go into the ~851MHz range IIRC). I figured either it'd be the shorter cable length, or a high-gain antenna built specifically for that range, and I either use that exclusively, or use it and the Larsen, and wire in an antenna switch into the car.
 

DPD1

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I would try a dedicated higher gain 800 antenna. Other stuff should still come in so so, but the 800 should be as good as possible. Cable loss is an issue, but many people sort of over do it. Lets say you compare RG8X and RG58. Even at 1 GHz, that would be about .11 db loss per foot for RG8X, and .16 db for RG58. So for 17', it's 1.87 db vs 2.72 db. Nothing anyone's ear is going to hear. RG8X is nice just because it's more hardy and flexible, but it's not a huge loss difference. Also a fallacy that gets raised by people sometimes is the 'hose effect'... They think that if you take say... 100' of RG8, then bring that into say... 8' of RG8X or even RG58, that somehow a huge loss will occur in the smaller cable, as if it's a smaller hose that restricts the flow. It doesn't work that way. The loss occurs in multiples of the length.
 

KT4HX

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Hose effect? I have to admit Dave that is the first time I'd heard that term applied to coax. I guess I don't get out of the house enough! :lol: Interesting that someone would even consider that an issue.
 

W6KRU

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I have some coiled up that way. Why should I not do this? (RX-only, RG6)
Coiling up coax is one way of choking off some frequencies. It might or might not affect your reception. I have seen it cause severe SWR on vhf-hi. I err on the safe side and don't coil coax.
 
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N_Jay

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Coiling up coax is one way of choking off some frequencies. It might or might not affect your reception. I have seen it cause severe SWR on vhf-hi. I err on the safe side and don't coil coax.
If coiling the coax is causing any change in the antenna system it is s sure sign of some other issue.
 

W6KRU

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If coiling the coax is causing any change in the antenna system it is s sure sign of some other issue.
In 2 cases I saw vhf-hi showing lots of reflected power in a mobile using my Bird watt meter. These were race vehicles and the coax was zip tied in a bundle to a support bar in the roll cage. To fix it I pulled the bundle off the bar, removed the excess cable, and put a new connector on. That cured the problem in both cases. The antenna in both cases was a 5/8 wave with a proper ground plane and they were both pretty close to proper length. ???
 
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N_Jay

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I would guess a bad ground plane or bad ground.

In an antenna system with a decent match, the RF flows inside the coax and coiling the cable will have no effect.

In a system with a significant mismatch or where a required groundplane is missing or not properly grounded, the outside of the coax becomes a radiating element and coiling the coax cats as a choke to this current flow.
In this case, where the SWR changes with the cable coiled it is the coiled reading that is most likely correct.

In the uncoiled state the RF flowing on the shield of the cable is also flowing on the case of the SWR meeter and is not being measured.
 
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W6KRU

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I would guess a bad ground plane or bad ground.
Thanks Jay. I'll keep that in mind next time and look around a little more. Anyone reading this thread should disregard my previous advice against coiling excess coax.
 

Kumba

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I would try a dedicated higher gain 800 antenna. Other stuff should still come in so so, but the 800 should be as good as possible. Cable loss is an issue, but many people sort of over do it. Lets say you compare RG8X and RG58. Even at 1 GHz, that would be about .11 db loss per foot for RG8X, and .16 db for RG58. So for 17', it's 1.87 db vs 2.72 db. Nothing anyone's ear is going to hear. RG8X is nice just because it's more hardy and flexible, but it's not a huge loss difference. Also a fallacy that gets raised by people sometimes is the 'hose effect'... They think that if you take say... 100' of RG8, then bring that into say... 8' of RG8X or even RG58, that somehow a huge loss will occur in the smaller cable, as if it's a smaller hose that restricts the flow. It doesn't work that way. The loss occurs in multiples of the length.
There a specific type of antenna I should look at? I'm assuming I want something with high gain, but I'm trying to keep it small, too (I think the Larsen is about ~16" tall). I haven't found a good explanation yet of what the terms "1/4th wave" or "5/8th wave" means in regards to antenna functionality, as well as the other bits that one has to factor into understanding what a good antenna looks like. The Wiki here doesn't seem to cover the little details like that, just provides links to popular antennas.
 
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