GMRS coax length

[Guest 8NannyFoe]

Hi guys, another newbie here.  I am an old CB'r from a few decades ago and a recent discovery of GMRS has awoke an old flame of alternate communication.   Anyway I am setting up new base station.   I have about a 33' run (absolute minimum).   Its a fairly long run for this frequency and I don't see any readily made antenna cable runs made from RG58.   Loss is most likely the reason I am assuming.  From what I am getting cable length can and will make a difference in the GMRS experience.  To long or to short can effect performance.   I found two articles that implied this however neither gave the lengths which probably means its not an easy answer.   From what I understand a 1/2 wave length cable vs a 5/8 vs a full wave length cable will impact transmit and receive performance.   Given my absolute minimum length 33 feet  ( a longer than usual run) can anyone please advise me a good length and better quality cable to make this job complete and very good.   RG58U is the cable a friend recommended but he didn't expand on why and suggested just cutting it at any length and length doesn't matter.  I'm fine with the cost of this cable, but would really like the best performance out of my purchase even if it means I need to purchase a longer run to make sure it is efficient as possible.  May be over kill or underkill, so feel free to comment on that as well.   What length is the proper length of cable I need to fit my job?   Thanks in advance!!

[Lscott]

Do not use RG-58 cable at these frequencies for anything other than short runs. You are much better off using RG-8, LMR-400, Beldin 9913 or some type of heliax, typically 1/2 inch or larger, for the run. Also it is strongly advised to use "N" type connectors. You may need an "N" type to a PL-239 adapter for the end going into the back of the radio unless you make a cable with it on the end.

 

You can check here for coax cables. They may custom manufacture a cable for you.

 

https://www.theantennafarm.com/catalog/index.php?main_page=index&cPath=344&sort=20a

 

http://www.cablexperts.com/cfdocs/index.cfm

[axorlov]

Do not use RG58U, loss is very significant on 460MHz. Just look at what Lscott listed. Another reputable company that sells cables with connectors is dxengineering.com They have 25', 50', 75' runs of their LMR400 equivalent with with N-connector or PL259. Coax loss charts: https://w4rp.com/ref/coax.html

 

If radio-cable-antenna-connectors system is well-matched through all the components, the length of the coax will not matter. The 1/2 wavelength cable allows you to tune your device (usually antenna) more precisely with some equipment. Once match achieved, coax can be any fraction of wavelength. So, don't worry about it unless you plan to invest into instruments and knowledge. And 1/2 wavelength on GMRS is roughly 325mm, so quarter-inch less or quarter-inch more and you are out of optimal length anyway. Velocity factor is also needed to be considered...  Do not worry about coax length. The shorter the better, but that's it.

[Guest 8NannyFoe]

Thank you.   I went with LMR-400.   The antenna I bought has the N type connector and I had Times custom make me the cable with N type connector and the 259 on my radio side.   I jumped the gun a bit when buying the antenna though.  I bought a 6db gain antenna.   I didnt know what that meant.   It is now my understanding that Unity gain would actually have been a better choice for hilly areas?   

Do not use RG-58 cable at these frequencies for anything other than short runs. You are much better off using RG-8, LMR-400, Beldin 9913 or some type of heliax, typically 1/2 inch or larger, for the run. Also it is strongly advised to use "N" type connectors. You may need an "N" type to a PL-239 adapter for the end going into the back of the radio unless you make a cable with it on the end.

 

You can check here for coax cables. They may custom manufacture a cable for you.

 

https://www.theantennafarm.com/catalog/index.php?main_page=index&cPath=344&sort=20a

 

http://www.cablexperts.com/cfdocs/index.cfm

 

[axorlov]

... It is now my understanding that Unity gain would actually have been a better choice for hilly areas?   

Depending on how tall the hills are and how close you are to them. It's likely be fine, if they are hills and not El Capitan (https://en.wikipedia.org/wiki/El_Capitan) and you are not at the bottom of it.

[scorpion1200]

Hi guys, another newbie here.  I am an old CB'r from a few decades ago and a recent discovery of GMRS has awoke an old flame of alternate communication.   Anyway I am setting up new base station.   I have about a 33' run (absolute minimum).   Its a fairly long run for this frequency and I don't see any readily made antenna cable runs made from RG58.   Loss is most likely the reason I am assuming.  From what I am getting cable length can and will make a difference in the GMRS experience.  To long or to short can effect performance.   I found two articles that implied this however neither gave the lengths which probably means its not an easy answer.   From what I understand a 1/2 wave length cable vs a 5/8 vs a full wave length cable will impact transmit and receive performance.   Given my absolute minimum length 33 feet  ( a longer than usual run) can anyone please advise me a good length and better quality cable to make this job complete and very good.   RG58U is the cable a friend recommended but he didn't expand on why and suggested just cutting it at any length and length doesn't matter.  I'm fine with the cost of this cable, but would really like the best performance out of my purchase even if it means I need to purchase a longer run to make sure it is efficient as possible.  May be over kill or underkill, so feel free to comment on that as well.   What length is the proper length of cable I need to fit my job?   Thanks in advance!!

 

In my opinion RG 213 will be more then enough for your application assuming GMRS@50 watts.

Since your cable run is min 33 feet. Now if you were running 100 feet of cable especially underground then you would use LMR 400. GMRS is max of 50 watts of power@tt. I can see if you were running 100 watts.

 

[smalpierre]

Thank you.   I went with LMR-400.   The antenna I bought has the N type connector and I had Times custom make me the cable with N type connector and the 259 on my radio side.   I jumped the gun a bit when buying the antenna though.  I bought a 6db gain antenna.   I didnt know what that meant.   It is now my understanding that Unity gain would actually have been a better choice for hilly areas?   

 

Real Times LMR-400 is probably the ticket for that application. If you can solder coax connections and the radio side is a UHF connector (pl-259/so-239 I forget which is which) you might consider cutting the N connector off and putting the right one on to not have any adapters. N is the way for exterior for sure.

 

Depending on how hilly it is, yes, less gain could perform better since it's not as focused on the horizon - but unity might be a wee bit excessive. Gain is good if you can stay in the radiation pattern of the antenna. Its so flat where i'm at, a machinist might not be able to get it any flatter so I want as high of a gain as I can get.

 

If you want to do some horse trading or whatnot I might be interested in a 6db uhf antenna, then you could get something else.

[OldRadioGuy]

The exact cable length does not matter.  Shorter is better.

The only exception would be if you were using a matching network on the radio end of the cable.

But still, it would have a random effect... as long as your radio is pretty close to nominal 50 ohms (non reactive Z)

I won't get into smith charts so just trust me.

 

Pasternack makes custom cables and Digikey might also do customs.

Not cheap but maybe worth it for the quality etc.

Digikey would be cheaper than Pasternack.

 

Keep in mind you could use a much heavier cable outside and run something smaller for the last few feet coming into the radio.

Mix and match can make sense.

 

Vince

[ClassicCarGuy]

Thread resurrection. I'm setting up in installing a home base J-Pole antenna. Its probably gonna be a very short rum with no more than 50 ft. Anyone had experience or takes with Belden 9914. I  never tried this on a two way radio but I been using Belden interconnect on Hi Fidelty system  and its just wonderful in so many ways. This company have been in business for a long time as always one of the top notch.

Going back, I wanted to use a solid core cable that has an excellent shielding. As I understood, this is originally on of the high standard real RG-8 coax cable that has a 99% braiding. I was wondering too what is the flexibility of this cable vs  the high grade LMR 400? I will have to have the company cut and install the  Amphenol PL259 to have it done professionally.

Any takes would be great and thank you!

[BoxCar]

Belden is a well-known name for wire products. Look at the cable specs and see what the minimum bend radius is for all the cables you are considering. Compare that to the path your cable needs to run, and use that as one of your selection criteria. The bend radius will tell you how sharp a corner you can make with the cable while maintaining any loss figures.

[SteveShannon]

Here’s the spec sheet for the 9914: https://www.belden.com/products/Cable/Coax-Triax-Cable/50-Ohm-Coax-Cable/9914

It’s the same diameter as the LMR400 and has a 10 AWG single solid copper center conductor.  

The minimum bend radius is 4 inch.

I think it’ll be heavier than LMR400 and just as stiff. 

A more flexible alternative would be a cable with a stranded center conductor.  Messi and Paoloni make some but I’m sure others do as well. Their Ultraflex 10 is good cable.  Here’s a link to information about it: https://www.buytwowayradios.com/messi-paoloni-mp-uf10-mr.html

[ClassicCarGuy]

5 hours ago, Sshannon said:

Here’s the spec sheet for the 9914: https://www.belden.com/products/Cable/Coax-Triax-Cable/50-Ohm-Coax-Cable/9914

It’s the same diameter as the LMR400 and has a 10 AWG single solid copper center conductor.  

The minimum bend radius is 4 inch.

I think it’ll be heavier than LMR400 and just as stiff. 

A more flexible alternative would be a cable with a stranded center conductor.  Messi and Paoloni make some but I’m sure others do as well. Their Ultraflex 10 is good cable.  Here’s a link to information about it: https://www.buytwowayradios.com/messi-paoloni-mp-uf10-mr.html

 

Is this a good cable assembly. I just need 25 feet for LMR-400. My radio draws a real 50 watt and will be hooked up to a Jpole antenna.

https://www.hamradio.com/detail.cfm?pid=H0-012001

 

[SteveShannon]

1 hour ago, WRZM228 said:

 

Is this a good cable assembly. I just need 25 feet for LMR-400. My radio draws a real 50 watt and will be hooked up to a Jpole antenna.

https://www.hamradio.com/detail.cfm?pid=H0-012001

 

Yes, I like ABR and that’s their flexible cable. Should be fine. 

[ClassicCarGuy]

1 minute ago, Sshannon said:

Yes, I like ABR and that’s their flexible cable. Should be fine. 

its a good thing youre here... I'm about to get this. I double measured and everything and I only need 19 feet. So I'm getting a 25 foot LMR-240 and 3 foot extra for SWR meter testing. Here is the lost and what do you think?

Just to say... I really want a good line. But in reality, as a former two way radio user.. There's no way I will get this thing squared in 1 shot. I'm thinking I will I'll just go with the LMR-240 and if I got everything dialed then later on I'll get the most promising LMR-400 that I can achieve. If I continue working on this, I'll be losing money on my job.... Do you think thats a good plan?

I have a very nice 50 watt radio. We tested it in the shop. It was drawing around 50 on max. I'll show it to you later.

I am also Thinking about getting an okay radio for the car like AnyTone AT-778UV so I can just leave the other one for base station.

 

[WRYZ926]

I'm using LMR400 Ultra Flex for my GMRS and 2m/70cm antennas. The coax going to my GMRS antenna is 32 foot long and the one going to my dual band antenna is 82 foot long.

[SteveShannon]

18 minutes ago, WRZM228 said:

its a good thing youre here... I'm about to get this. I double measured and everything and I only need 19 feet. So I'm getting a 25 foot LMR-240 and 3 foot extra for SWR meter testing. Here is the lost and what do you think?

Just to say... I really want a good line. But in reality, as a former two way radio user.. There's no way I will get this thing squared in 1 shot. I'm thinking I will I'll just go with the LMR-240 and if I got everything dialed then later on I'll get the most promising LMR-400 that I can achieve. If I continue working on this, I'll be losing money on my job.... Do you think thats a good plan?

I have a very nice 50 watt radio. We tested it in the shop. It was drawing around 50 on max. I'll show it to you later.

I am also Thinking about getting an okay radio for the car like AnyTone AT-778UV so I can just leave the other one for base station.

 

It’s a good plan. It’s short enough that losses won’t hurt you too bad. There are always some losses but most of us will never suffer from them. 

[ClassicCarGuy]

2 hours ago, Sshannon said:

It’s a good plan. It’s short enough that losses won’t hurt you too bad. There are always some losses but most of us will never suffer from them. 

I just got back and picked up some groceries... I bought some extra PL-259 connectors in case if I need to cut the home base coax later on. The antenna is gonna be mounted like right in top of our bonus room. On a straight line is not even 10 feet from my desk. This like some work. I have an old Palomar power supply that I bought in my old CB days. I should recap it next week. I was looking at the newer power supply and It feels so light. That's why I didn't buy a new one yet. Well see whats gonna happen. There's only one way to know if this is gonna work or not. If no, I'll be using a smoke signal for back up.