Can Midland lip-mount and magnetic mount cable be shortened?

[dosw]

Both the MXTA27 lip mount, and the MXTA12 magnetic mount come with a length of fairly thin coax. I think they're each six meters, which is over nineteen feet. I don't know what cable they're using; they call it low profile coax.

 

I have some PL259 crimp-on connectors that are made for RG58, and a crimper tool. Before braving ahead at cutting my MXTA27 cable at six feet, I found some old television coax around the house and cut the connector off of it, just to see if I could use it to practice adding a new connector. I found that the copper braided shield was so thin, and supplemented with even thinner foil, that I couldn't really work with it; any amount of cutting of the outer cover would ruin about half the copper braid, no matter how gentle I was.

 

I assume this was because the cable I tested on was just super cheap stuff, not intended for modification. But that doesn't help me to know if I'm going to be successful with splicing a new connector onto a shortened MXTA27 or MXTA12 cable. Has anyone attempted this? Or am I better off just buying mounts that don't come with cable attached? Such mounts seem less common, in NMO form factor.

[SteveShannon]

40 minutes ago, WRQW589 said:

Both the MXTA27 lip mount, and the MXTA12 magnetic mount come with a length of fairly thin coax. I think they're each six meters, which is over nineteen feet. I don't know what cable they're using; they call it low profile coax.

 

I have some PL259 crimp-on connectors that are made for RG58, and a crimper tool. Before braving ahead at cutting my MXTA27 cable at six feet, I found some old television coax around the house and cut the connector off of it, just to see if I could use it to practice adding a new connector. I found that the copper braided shield was so thin, and supplemented with even thinner foil, that I couldn't really work with it; any amount of cutting of the outer cover would ruin about half the copper braid, no matter how gentle I was.

 

I assume this was because the cable I tested on was just super cheap stuff, not intended for modification. But that doesn't help me to know if I'm going to be successful with splicing a new connector onto a shortened MXTA27 or MXTA12 cable. Has anyone attempted this? Or am I better off just buying mounts that don't come with cable attached? Such mounts seem less common, in NMO form factor.

It’s probably not worth it to shorten that cable.  Calculate the losses and you’ll see that they’re very low, but if you want make sure you buy a good quality pl-259 connector for that exact cable. If the one that’s already on it is removable you might be able to use it.

[tcp2525]

27 minutes ago, SteveShannon said:

It’s probably not worth it to shorten that cable.  Calculate the losses and you’ll see that they’re very low, but if you want make sure you buy a good quality pl-259 connector for that exact cable. If the one that’s already on it is removable you might be able to use it.

I would cut the cable to what is needed, which he said is six feet. Nineteen feet of crappy cable, especially RG-58, is not going to be ideal. If he properly installs a quality connector he will see some improvement that might not be much, but anything is a plus at 465 MHz range. I always use RG-400 in my mobile installations.

[Guest]

Yes one can shorten the cables.  As you’re finding out it is very hard to do by hand.  They do make a tool specifically for this.  I have seen some people that are very good at doing it by hand.  However in the end why bother.  Just loosely coil it and twist it in a figure 8 and zip tie the extra. Yes you have loss in extra cable but is it enough to bother with?   Even with just a 5w hand held it’s going to double or more your distance.  I’d be more concern about using a lip mount with a ground plane antenna and where you plane on mounting it.  I’d bet a cheap mag mount on the roof would do much better then a lip mount on a fender of rear lid.  What antenna re you going to use?  Does it have gain? What wattage is the radio you are using?  5w, 10, 20, 40, 50w    If your loosing even 2 watts on a 5w unit but your doubling your erp then it really doesn’t matter that much. And if you’re loosing 2w or so on a 20w or more radio it REALLY doesn’t matter much.  again placement will matter much more then loosing a few watts in the extra cable. 

[dosw]

16 minutes ago, WRXP381 said:

Yes one can shorten the cables.  As you’re finding out it is very hard to do by hand.  They do make a tool specifically for this.  I have seen some people that are very good at doing it by hand.  However in the end why bother.  Just loosely coil it and twist it in a figure 8 and zip tie the extra. Yes you have loss in extra cable but is it enough to bother with?   Even with just a 5w hand held it’s going to double or more your distance.  I’d be more concern about using a lip mount with a ground plane antenna and where you plane on mounting it.  I’d bet a cheap mag mount on the roof would do much better then a lip mount on a fender of rear lid.  What antenna re you going to use?  Does it have gain? What wattage is the radio you are using?  5w, 10, 20, 40, 50w    If your loosing even 2 watts on a 5w unit but your doubling your erp then it really doesn’t matter that much. And if you’re loosing 2w or so on a 20w or more radio it REALLY doesn’t matter much.  again placement will matter much more then loosing a few watts in the extra cable. 

My lip mount is actually pretty well positioned. Old Bronco, there's eight inches of steel between the rear edge of the hood and the windshield. MXTA26 antenna, SWR under 1.2:1 across the GMRS frequencies. I'm just looking to reduce cable loss because I'm particular, not because it's not working well. Just yesterday I got 19 miles simplex, and would have gotten more were it not for a mountain.

 

[SteveShannon]

1 hour ago, tcp2525 said:

I would cut the cable to what is needed, which he said is six feet. Nineteen feet of crappy cable, especially RG-58, is not going to be ideal.

As I said, calculate the difference between six feet and nineteen feet to see whether there’s any real difference.  I doubt that it will ever make a difference in range, especially if he has no experience with terminating cables. 

[tcp2525]

19 minutes ago, SteveShannon said:

As I said, calculate the difference between six feet and nineteen feet to see whether there’s any real difference.  I doubt that it will ever make a difference in range, especially if he has no experience with terminating cables. 

Yep, pretty much what I said. I guess we agree. It just might be worth it to some of us to get a fraction of a db more in performance.

[dosw]

I'd be willing to just do it, risking damaging the mount and having to buy a new one. But I can't even figure out if my RG58 connectors are going to fit the cable. I don't see Midland publishing what the cable actually is. That's why I asked if anyone has experience cutting and putting new connectors on these specific mounts. I don't mind fouling it up and having to buy a new one, but if it's known to be impossible due to the low quality of the shielding of this cable I wouldn't bother.

 

If it's RG58U it would be 2db loss over six meters, or 0.68db loss over two meters, I think, for a difference of 1.3db. That's not awful. But if I could use the last meter or so for practice I think I could get the hang of it. I have a crimping tool with jaw inserts for cable from RG6 up to LMR600, and I've used it for LMR400 already.

[SteveShannon]

21 minutes ago, WRQW589 said:

I'd be willing to just do it, risking damaging the mount and having to buy a new one. But I can't even figure out if my RG58 connectors are going to fit the cable. I don't see Midland publishing what the cable actually is. That's why I asked if anyone has experience cutting and putting new connectors on these specific mounts. I don't mind fouling it up and having to buy a new one, but if it's known to be impossible due to the low quality of the shielding of this cable I wouldn't bother.

 

If it's RG58U it would be 2db loss over six meters, or 0.68db loss over two meters, I think, for a difference of 1.3db. That's not awful. But if I could use the last meter or so for practice I think I could get the hang of it. I have a crimping tool with jaw inserts for cable from RG6 up to LMR600, and I've used it for LMR400 already.

The ad on Crutchfield says it’s RG-58A/U which is definitely a high loss cable at UHF frequencies.  The power loss difference between being six feet long and 19.5 feet long is 26%.  At six feet you lose 15% of the power and at 19.5 you lose 41%. So, I have to give @tcp2525 credit that it makes sense to shorten it.

[WRYZ926]

While you definitely have loss with RG-58 at UHF/GMRS frequencies, a good antenna with enough gain will help overcome any loss from the coax.

RG-58A has a a loss of 11 dB or 92% loss at 100 feet for 467 MHz. You are actually looking at a gain of 1 watt (with a 5 watt radio) for a total of 6 watts out when using 19.5 feet of RG-58A coax with an antenna with 3 dBd ( 5.15 dBi) of gain.

So if your antenna has a good ground plane and at least 5 dBi/3 dBd of gain, then I wouldn't worry about shortening the RG-58 coax. Roll any excess up in a nice circle and it will act as a 1:1 balun which helps keep RF from running down the outside of the coax and into the radio.

Here is the coax loss calculator I like to use. https://kv5r.com/ham-radio/coax-loss-calculator/

[dosw]

1 hour ago, WRYZ926 said:

While you definitely have loss with RG-58 at UHF/GMRS frequencies, a good antenna with enough gain will help overcome any loss from the coax.

RG-58A has a a loss of 11 dB or 92% loss at 100 feet for 467 MHz. You are actually looking at a gain of 1 watt (with a 5 watt radio) for a total of 6 watts out when using 19.5 feet of RG-58A coax with an antenna with 3 dBd ( 5.15 dBi) of gain.

So if your antenna has a good ground plane and at least 5 dBi/3 dBd of gain, then I wouldn't worry about shortening the RG-58 coax. Roll any excess up in a nice circle and it will act as a 1:1 balun which helps keep RF from running down the outside of the coax and into the radio.

Here is the coax loss calculator I like to use. https://kv5r.com/ham-radio/coax-loss-calculator/

Thanks. Good information. I'm using a Retevis 40w RA87 radio, and an MXTA26 antenna, most of the time.

 

My SWR readings are very good. And people say I sound loud and clear hitting several repeaters. I just like tweaking things to see where I can make additional improvements. That's all. Thanks again. 

[WRQC527]

23 hours ago, WRQW589 said:

Both the MXTA27 lip mount, and the MXTA12 magnetic mount come with a length of fairly thin coax. I think they're each six meters, which is over nineteen feet. I don't know what cable they're using; they call it low profile coax.

 

I have some PL259 crimp-on connectors that are made for RG58, and a crimper tool. Before braving ahead at cutting my MXTA27 cable at six feet, I found some old television coax around the house and cut the connector off of it, just to see if I could use it to practice adding a new connector. I found that the copper braided shield was so thin, and supplemented with even thinner foil, that I couldn't really work with it; any amount of cutting of the outer cover would ruin about half the copper braid, no matter how gentle I was.

 

I assume this was because the cable I tested on was just super cheap stuff, not intended for modification. But that doesn't help me to know if I'm going to be successful with splicing a new connector onto a shortened MXTA27 or MXTA12 cable. Has anyone attempted this? Or am I better off just buying mounts that don't come with cable attached? Such mounts seem less common, in NMO form factor.

I've installed quite a few connectors on RG-58 and a couple on RG-8X. Like someone else said, it appears to be RG-58 on that mount, and so far I haven't encountered foil on RG-58. That's not to say thre's no such thing as foil-shielded RG-58, just that I haven't encountered it. I've used crimp-on and solder connectors. I prefer crimp-on for RG-58, because they're quick to install and I haven't had one fail yet. I always use marine heat shrink to protect them and give them  little extra strength. I predict that once you cut the coax to the length you need, you will nave no trouble attaching a new connector.