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Building an NMO antenna base, what a serious pain in the ....

Joined
Jan 13, 2019
Messages
24
#1
Gang,
Due to the extended length of cable I needed to run from where I was to locate the antenna, to where the actual radio is mounted, I needed bulk length of RG8X coax and, one PL259 radio end with a reducer for the RG8X and I needed an NMO antenna base fitting for thick mount application, on the other end. Well, good ole' HRO sent me everything I needed in about 2 days, OUTSTANDING service. But, what they didn't tell me was what one serious pain in the petute that NMO is to actually put together and setup. I don't know if any of you have ever had to deal with that situation but, I consider myself as a pretty fair DIY type and have done a lot of things in my life that's quite technical.
I set up the PL 259 with reducer, for the radio end, without any issues whatsoever. What a piece of cake. I then tied it to the radio and ran that cable up, down, around, under, over, and all that, to the rear of our '15 Jeep JKUR. I then fished it through the tail gate so it would come out a pre-existing rubber plug, just behind the spare tire. It's way cool that way and, it's protected and it has a built in seal to keep water out of the tail gate.

Now, I followed the paper instructions to the letter in attaching that RG8X to the NMO thick mount base. I won't bother going through all the instructions here as it would be boring to many of you. But, suffice to say, things just don't fit the way they say it all should go together. I did what Clint Eastwood stated many times in his "Heartbreak Ridge" movie. I "over came, adapted and improvised" severely to make that NMO system work. I finally got it all put together and it works, at least I think it works. I did one radio check by pulling the Jeep out of the garage and asked for a radio check on one of our local repeaters here in Lake Havasu City AZ. I got a reply, yahooooooo, it works. Must have done something right.

But, for those that either haven't done it, and or may be thinking about it, folks, it's not a cake walk. I think, if I was ever to do it again, I'd purchase an NMO mount, with the cable already attached and, if I needed an extra amount of cable, I'd simply get a cable union of some sort and connect the cable in the middle some place. Gotta be easier than what I had to do.
Scott
 
Last edited:
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#2
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Jan 13, 2019
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#3
Doesn't do you much good now, but for next time:

30 foot cable, thick mount:
https://www.theantennafarm.com/catalog/pctel-ke794-7570

Up to 125 feet of cable, thick mount:
https://www.theantennafarm.com/catalog/laird-technologies-mabvto-cable-up-to-125-feet-8341

Or, you can buy a thick mount NMO base that has a UHF or N connector on the bottom:
https://www.theantennafarm.com/cata...e-mounts-270/thick-surface-mount-up-to-1-293/

What was the issue you had?

Hey mmckenna
Thanks for the reply. I should have taken pics of the various steps needed to install the coax onto the base of the NMO thick mount. Now, first off, you can find videos and instructions for attaching coax to a PL259 plug, all day long. But, in my searches which, took me into the night, I couldn't find ONE STINKING VIDEO or, even any instructional pages on how to attach coax cable to an NMO fitting. HRO did send me instructions but, I like to watch videos so I see if there's anything that instruction sheets miss.

AAAAAnnnnnnwaaaaaay, it's a long story but, in short, the coax black housing, was to be trimmed back, from the end of the cut, right at 5/8". The braided shield was to be trimmed back, 3/8" from the cut. The white insulator was to be trimmed back from the cut, 1/8". Then, there's a stainless looking, small, collar that's supposed to fit OVER the entire cable and slid back, out of the way, from the business end of attachment. Got the picture so far? Now, after the collar is slid back, then you're supposed "flare out" the braided section, in the shape of a cone, so that it's no where near the white insulated plastic. Then, the actual NMO mount, has a horizontal snout that is only about 5/32 O.D. and about 1/8" I.D.
What you're supposed to do is, push that cable specifically the white insulation plastic, into the snout, so that the tip of the cable, goes at least partially into a slot, in a center pin, inside the NMO unit. If you look at the bottom of the NMO mount, you can see that small brass piece,with the slot. And you can see if the tip of the cable is mating up with that slot. The white plastic is SUPPOSED to be pushed into that little snout, just enough to bottom out, at the same time, the tip of the cable enters the slot in the center pin.

Well, there's TWO MAJOR PROBLEMS HOUSTON! One, the stainless looking collar, in the inside diameter, is the same exact size as the outer black housing of the RG8X coax. So, it AIN'T GONNA SLIDE OVER IT, to get out of the way, so you can do all the work with the braided stuff etc. And TWO, the white plastic is TOO LARGE to fit inside of the snout of the NMO tube. I had to trim, a small amount of that white plastic, for 360 degrees around it, so it would fit inside the tube. What a pain in the ass. And, since the stainless looking little collar would fit onto the black housing of the coax, the only way I could make all this work was to trim more black housing off the cable.

Now, foreseeing the future here, if, IF, I were to complete the attachment of the cable to the center pin, and solder it a tiny bit, THEN, bring the braided "cone" back down and surround the barrel that the white plastic is INSIDE of, now, I'd slide the stainless collar forward 'till it's over the braided section. Then, they (the instructions) want you to crimp that stainless collar, with a very specific, SIX SIDED CRIMPER, that has something to the value of .213.

I had no clue what they were talking about. I know about 6-sided crimping, but, the .213, I had to look that up. Well, it's a special set of crimpers that were on line only. So, I figure'd I'd just deal with that problem when I get to it. But, being the fact that I had to trim excessive black cable housing away, in order to slide that collar back, in order to create working room with the braided shield, that meant when things were all put back, I'd have an exposed section of braided cable. Not good. So, I initially cut the coax and, slid THREE sections of heat shrink tubing over it and back out of the way. Now, when the whole thing is done, I just slide each section of the heat shrink up, 'till it hits the NMO and, apply heat.

When that section has shrunk up, I slide another one up, right over the first one. Heat, done. And finally slide the third one and, repeat. DONE.

Yes, it was a pain in the ass. Eventually, I got it all done.

I most certainly appreciate you finding what I needed. I looked on antenna farm and couldn't find what you found. I guess I'm just not good at looking for stuff. I will keep all that you sent, in a file so, if this home brew attachment of mine goes south, I'll know I can get what I need. Now, if I could just remember where I'd store your stuff. Thank you so much for the tips and the links.
Scott
 

Paysonscanner

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#4
Forgive me if anything I post isn't correct, I'm somewhat new to this hobby, on my own anyhow. My late husband helped me a great deal in understanding the radio hobby, checked my work and was training me. I helped him install two radios in the Subaru Forester I still have it. He had me independently install the NMO mount and run the cable. He helped my hold the drill when I put the hole in the roof, waht a sweetie! He always bought NMO mounts that were sold with a cable assembly that was permanently attached to the brass antenna mount with the radio end absent a connector. We always used, what is it, a PL-359 or is it a 237, to connect the antenna to the radio. In cars we used a reducer adapter for the smaller mobile cable because the 359 is meant for cable that is thicker, for base radio antennas. I watched him and he never bought antenna mounts that the cable wasn't attached to right out of the box. We would route the cable though the body or ceiling first by pulling it through the hole in the roof. Your post sounds like you did the reverse and that is not how my husband showed me how to do it. I don't understand why you used a mount without the antenna cable not already attached. I'm trying to learn here myself, so sorry if I ask you a question instead of me answering yours.
 

Paysonscanner

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#5
I remember my husband running short of cable from the brass mount on one installation and he mounted two 359's, that is all he had at the time, and put in a male/male or female/female connector between the two. He had cut enough extra cable from a wire spool he had in the garage. This is just like Mmckenna described in his post. It sound like your installation wasn't any fun at all! I'll make sure I never try doing that!
 
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#6
I'm trying to learn here myself, so sorry if I ask you a question instead of me answering yours.
Most of the NMO mounts that you find only have 18 feet or so of coaxial cable attached. That's plenty for most installations. Occasionally there are installs where a longer cable is necessary.

There are a couple of ways to do this...
- Like Fireup did, you can buy bare NMO mounts with no cable and build your own.
- I linked to NMO mounts with longer coaxial cable lengths pre-installed.
- Or, like you guys did, pop a connector on the end and just add more cable.

Either one will work. Fabricating your own NMO mounts takes a bit of work, a bit of soldering, and a bit of time. Buying the longer cable'd mounts works for some. Adding a connector (PL-259 - UHF male plug, probably what you are thinking of) will work, too.
 
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Messages
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#7
Paysonscanner,
I'm very sorry to hear about your late husband. Sounds like a great fella and it was nice that not only did he INCLUDE you in his activities and hobbies, but it also sounds as if you were INTERESTED in them, WAAAAAAAAAAAY COOOOOL!!!! Now, to address your statement(s). First, I've been a DIY type for decades and, am certainly not new to figuring out some technical things on our vehicles. Been stepping "outside the box" so-to-speak, in creating remedies for issues my whole life. But, when it came to mounting this ICOM 2000 in our '15 Jeep JKUR, mounting it was only a slight challenge, more on that later.
Now, I have already mounted a C/B in the Jeep, directly in front of the rear view mirror, very close to the ceiling. In setting up that C/B, and running the cable/coax to it, all the way from the back of the Jeep, on the tail gate, I used a coax that is for C/B and, it came with both ends already installed. Both are PL259. But, a really good part about this particular cable was, it had/has a removable PL259 end but, it sill had the primary connection all soldered up. So, what all that means is, you can run a smaller end, through lots of obstacles and smaller access points, 'till you get to the radio. That was a great help.

But, and here's the leading-up-to issue, that cable was only 17' long. When I completed the final stretch, to the back of the radio, I only had about 1' left!! It worked but, it was really, really close.

Ok, that's the lead up to this install. All that being said, that C/B coax was ran up, through the roll bar padding and over to the wind shield and over to the radio. For the HAM radio, which is mounted in front of the C/B, I did not want to run the HAM coax, right next to the C/B coax. So, its route was along the floor. It's a considerably longer run but ends up very close to the same spot. So, I calculated at least 22' of needed coax for the run. Well, computer searching sometimes eludes me. I usually can find what I want, no matter what I'm looking for. But, in this case, I was basically new to HAM antennas and, their mounting systems and all that.

In looking around, I found that the "NMO" mount was the primary style of HAM antenna mounting for mobile applications. So, I started my search for an NMO mount, with cable/coax attached, that was a minimum of 22'-25' long. I was having ZERO luck in finding it. For some odd reason, I just couldn't come up with the appropriate length of pre-attached RG8X cable/coax to an NMO end.

So, I contacted HRO, Ham Radio Outlet (which has stores all over the U.S.) and told them of my needs. The really nice fella on the phone told me EXACTLY what I needed in terms of all the parts, ends, fittings, coax and all. I asked him since, I needed at least 25' of coax, did they have just an NMO end, that I could attach to a coax? He replied, yep, we gottem'. I said OK, I've got lots of soldering experience and have installed ends on cables before so, how hard could installing an NMO end, to the RG8X cable be? His reply, not hard at all. Roger that, the credit card was given and, the parts were on their way to me, later that afternoon.

I received them 2 days later, great service. Well, you've already read of my experience with the install of that NMO fitting to the end of the cable. No need to repeat it. The components (NMO end) was a tough system to work with because, in my opinion, it was not made correctly.

I would like to see a professional who deals with this sort of stuff on a daily basis, install that same exact end, on the same exact cable, to see how THEY would deal with the improper manufacturing of that component. Again, been doing things like this forever. I've adapted, overcame, improvised for eons of time. I made this system work. But, it was not without a bit of frustration. Sorry for the novel here but, you asked and, this was my answer.
Scott

P.S. I failed to mention in the above novel, that it was later shown to me that there does, IN FACT EXIST, a 30' cable already attached to a "thick mount" NMO end. I needed a "thick mount" because, most NMO applications are through very thin, roof material or even fenders. But, I created a much thicker steel mount, to be mounted on the spare tire rack, for the Jeep. I needed a thicker or, longer threaded mount for this bracket I created.
Scott
 

Paysonscanner

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#8
Paysonscanner,
I'm very sorry to hear about your late husband. Sounds like a great fella and it was nice that not only did he INCLUDE you in his activities and hobbies, but it also sounds as if you were INTERESTED in them, WAAAAAAAAAAAY COOOOOL!!!! Now, to address your statement(s). First, I've been a DIY type for decades and, am certainly not new to figuring out some technical things on our vehicles. Been stepping "outside the box" so-to-speak, in creating remedies for issues my whole life. But, when it came to mounting this ICOM 2000 in our '15 Jeep JKUR, mounting it was only a slight challenge, more on that later.
Now, I have already mounted a C/B in the Jeep, directly in front of the rear view mirror, very close to the ceiling. In setting up that C/B, and running the cable/coax to it, all the way from the back of the Jeep, on the tail gate, I used a coax that is for C/B and, it came with both ends already installed. Both are PL259. But, a really good part about this particular cable was, it had/has a removable PL259 end but, it sill had the primary connection all soldered up. So, what all that means is, you can run a smaller end, through lots of obstacles and smaller access points, 'till you get to the radio. That was a great help.

But, and here's the leading-up-to issue, that cable was only 17' long. When I completed the final stretch, to the back of the radio, I only had about 1' left!! It worked but, it was really, really close.

Ok, that's the lead up to this install. All that being said, that C/B coax was ran up, through the roll bar padding and over to the wind shield and over to the radio. For the HAM radio, which is mounted in front of the C/B, I did not want to run the HAM coax, right next to the C/B coax. So, its route was along the floor. It's a considerably longer run but ends up very close to the same spot. So, I calculated at least 22' of needed coax for the run. Well, computer searching sometimes eludes me. I usually can find what I want, no matter what I'm looking for. But, in this case, I was basically new to HAM antennas and, their mounting systems and all that.

In looking around, I found that the "NMO" mount was the primary style of HAM antenna mounting for mobile applications. So, I started my search for an NMO mount, with cable/coax attached, that was a minimum of 22'-25' long. I was having ZERO luck in finding it. For some odd reason, I just couldn't come up with the appropriate length of pre-attached RG8X cable/coax to an NMO end.

So, I contacted HRO, Ham Radio Outlet (which has stores all over the U.S.) and told them of my needs. The really nice fella on the phone told me EXACTLY what I needed in terms of all the parts, ends, fittings, coax and all. I asked him since, I needed at least 25' of coax, did they have just an NMO end, that I could attach to a coax? He replied, yep, we gottem'. I said OK, I've got lots of soldering experience and have installed ends on cables before so, how hard could installing an NMO end, to the RG8X cable be? His reply, not hard at all. Roger that, the credit card was given and, the parts were on their way to me, later that afternoon.

I received them 2 days later, great service. Well, you've already read of my experience with the install of that NMO fitting to the end of the cable. No need to repeat it. The components (NMO end) was a tough system to work with because, in my opinion, it was not made correctly.

I would like to see a professional who deals with this sort of stuff on a daily basis, install that same exact end, on the same exact cable, to see how THEY would deal with the improper manufacturing of that component. Again, been doing things like this forever. I've adapted, overcame, improvised for eons of time. I made this system work. But, it was not without a bit of frustration. Sorry for the novel here but, you asked and, this was my answer.
Scott

P.S. I failed to mention in the above novel, that it was later shown to me that there does, IN FACT EXIST, a 30' cable already attached to a "thick mount" NMO end. I needed a "thick mount" because, most NMO applications are through very thin, roof material or even fenders. But, I created a much thicker steel mount, to be mounted on the spare tire rack, for the Jeep. I needed a thicker or, longer threaded mount for this bracket I created.
Scott
Scott, thanks for you explanation and the detail you went into about the job. I learned some things about it from your post. Both my husband's family and mine had some hams, so we both had plenty of help. No one in either family ever had the name "Elmer" as far as we know, but they earned the name. I was talking third party when I was 5 or 6, this on HF. Thank you for your kind words about my husband. There were trade offs that went both ways, he went to chick movies with me, although I think I liked the radio hobby more than he liked those movies! Although, I saw him cry more than once.

Thanks again for the help. I know I will drilling on the roof of the new Honda and will get through it, but on a new car I think I'm going to be nervous. A couple of local hams indicated they would help me.
 
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#9
Paysonscanner,
You're quite welcome and thank you for the nice comments. Now, when it comes time for you to install that NMO antenna base in your roof of your car, might I suggest something, if you haven't already seen or experienced this. Go to youtube and watch a few NMO installs. They use a specifically designed drill that, puts a pilot hole, a 3/4" hole and, there's also a stop built in so you can't accidentally go through the headliner. See what you think.
Scott
 

KE5MC

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#10
Fireup,
Nice novel which I was able to follow and normally I have trouble with my own engineering change order I write reading them a week later.

You are correct it should not be a challenge as outlined. I believe the culprit is the NMO mount you have was expecting RG-58 at a nominal diameter of .195 inches and you were using RG-8X at .242 diameter. The reducer at the radio was for RG-8X and a good fit. Thinking you were good to good, at the antenna end it fell apart not realizing hardware at each end of cable had different expectations. Links supplied in post #2 was the tip-off for me when I saw they were made using RG-58.

While RG-58 is not the best for VHF-UHF in mobile installation because of the short runs it's common. Another cable used depending on manufacture is RG317 PTFE. My experience is RG-8X is more common for HF setups and what I use in my shack.

As mentioned earlier its a done deal, but maybe in the future my post might help. Keep the rubber side down on the jeep. :)

Mike
 
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Messages
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#11
Fireup,
Nice novel which I was able to follow and normally I have trouble with my own engineering change order I write reading them a week later.

You are correct it should not be a challenge as outlined. I believe the culprit is the NMO mount you have was expecting RG-58 at a nominal diameter of .195 inches and you were using RG-8X at .242 diameter. The reducer at the radio was for RG-8X and a good fit. Thinking you were good to good, at the antenna end it fell apart not realizing hardware at each end of cable had different expectations. Links supplied in post #2 was the tip-off for me when I saw they were made using RG-58.

While RG-58 is not the best for VHF-UHF in mobile installation because of the short runs it's common. Another cable used depending on manufacture is RG317 PTFE. My experience is RG-8X is more common for HF setups and what I use in my shack.

As mentioned earlier its a done deal, but maybe in the future my post might help. Keep the rubber side down on the jeep. :)

Mike
Mike,
Thank you Sir, for taking the time to respond here. It's very much appreciated. Not knowing that much about coax, its variations, fittings, antenna ends and all that, I was given some components to put together and, well, it was as you read, a bit of a nightmare but, I mustered through it. So far, in the very limited contacts I've made, here in this small town, I'm not getting any negative feedback that would indicate I've got problems transmitting, due to poor installation practices. Now, knowing the size differences in the coax, yep, that much would have made it seriously easier. Oh well, next time. Thanks again.
Scott
 
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#12
Used to be a test for communications installers. They would give you a PL259 Connector, small soldering iron, and the reducer, and ask you to install that on the coax cable. Correct answer?????
 
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#16
More than likely yes.
I agree. Compared to some of the crap the amateur/hobby manufacturers have come up with, and comparing it to the older mobile mount designs, the NMO is pretty dang good. Waterproof, able to handle much higher frequencies, easy to install, designed from the ground up to be a mobile antenna mount, cheap, etc.
 
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#19
Gang,
Before I entered this installation, I had never heard of an NMO mount/base/antenna before. All I'd ever dealt with in any form, mostly C/B, was the PL259 design. But, I consider that kind-a normal. As far as I know, NOBODY'S born knowing every bit of information, pertaining to every aspect of HAM radio there is to know. Everyone who's interested in HAM, LEARNS more and more as they progress in the hobby. An NMO mount, that is normally FACTORY installed on the cable/coax end, is more than likely probably a great design. Had I been a bit more diligent in searching, I'd have found what I needed, an NMO mount, pre connected to a 30' cable/coax with an open end for my connection when I determined the final length.

But, I didn't and was shown later that it did, in fact, exist. Oh well, live and learn. Now, from what was explained to me a from a couple of posts above, it appears my install issues, were not because I was just not a very good installer. The problems I encountered were quite possibly because I was given the incorrect components to fit together. And since the interaction was a form of mail order, I was not able to run down the street, to the local HRO and ask what's up with improperly fitting equipment. I merely presumed I was just having difficulty with fitment. And, as usual for me, I made it work. One way or another, I was not going to let that NMO mount win.

As for me asking questions about the wiring of my ICOM 2000 for power, again, been doing stuff kinda like this for a long time. But, as stated, I've never ever seen a fuse on a NEGATIVE side of wiring a radio, ANY radio, C/B or otherwise. This is/was my first HAM radio to mount and power up. I know and realize that the power this radio puts out, maxed at 50 watts, is more than your average junk C/B so, I realize there may be a need for a bit larger wire diameter. I know and realize that larger wire carries more watts/amps so, the load on it can be greater. But, I'm unschooled on the requirements of a HAM in this kind of situation. So, I asked. And I got great answers. So far, with 14GA wire, a total length of about 7', seems to be working Just fine. The fuses that came with the original wiring, were the glass tube type.

I installed waterproof blade type on both the negative and positive, 15A each. Ain't blown yet.
Scott
 
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