NMO Woes

[jwt873]

So my 20+ year old Larsen NMO-2/70 dual band antenna finally bit the bullet.

I've always had several vehicles and I've moved the antenna back and forth between them quite often. I also remove and replace it whenever I'm parked for longer periods in pubilc areas to prevent theft. Over time the spring contact in the middle lost a lot of its 'springiness' and wasn't making a good contact with the center pin on the mount'. I took to bending it out with my fingernail before I installed the antenna so there would be a better contact.

Well.. Bend a piece of metal back and forth long enough and it will eventually break. And, after long faithful service, mine did. I notice the gasket has perished as well. I was thinking of soldering the broken tab back on, but that's only a stopgap fix. Time for a new coil. Just wondering if anyone else has had this happen to them?

 

[Mikejo]

This is why we tell people to use “Mag- Mounts”!

yuc,yuk,yuk!

 

[Mikejo]

Seriously, just soldering it would be the weak point. Looks like you do need a new coil!

 

[mrweather]

Better to just get a new coil, they're not that expensive.

I'm on my second NMO2/70 coil. The first one last about 5-6 years then just died. I think something broke inside as I swept it with an antenna analyzer and it didn't seem to resonate anywhere. I have come across some stories of a small internal disk capacitor failing.

My current NMO2/70 coil is 15 years old and going strong.

 

[mmckenna]

So my 20+ year old Larsen NMO-2/70 dual band antenna finally bit the bullet.

Yeah, one of the known weaknesses with the spring tab contacts. Do it enough and that will happen. Metal fatigue.

Soldering wouldn't fix it for long. On it's own it would be a good electrical connection, but not a good mechanical connection.

I did have it happen with one antenna that I removed a lot, probably 25 years ago. It was not a issue limited to Larsen antennas, I've seen it happen on other brands.

The newer Larsen antenna designs use a 'pogo' pin. Basically a spring loaded pin that maintains contact. The older style antennas haven't adapted this, however. I have seen the old Motorola antennas that used the pogo spring contact fail also, so they are not a perfect solution. This is one of those places were paying attention to maintenance is important.

Just get a new coil if that's the issue (if you can find them).

 

[Mikejo]

Perhaps if you can rustle up a small diameter spring that would sit on the base pin (not larger than a pin), perhaps that would suffice until you can locate another coil?

 

[N4KVE]

I always stick a small piece of rubber under the tab to prevent it from bending in. My 2/70 is 30 years old.

 

[FFPM571]

you got your money worth buy a new one

 

[merlin]

Why not a new antenna and mount ? I know they can be had under $50 on ebay.
I guess like me, I am still trying to find a base for a vintage Motorola 5 db mobile antenna.

 

[n9mxq]

I've got one that old.. Haven't had that issue >yet<. Did have one ruined by my local tire shop. Forgot to take it off the vehicle when I took it in for tires. When they lifted the van up to work on it, the squished the loading coil in the middle.. Wasn't mad, just as much my fault as theirs..

 

[jwt873]

Well, I definitely did get my money's worth..(Main reason for posting this was to show what can happen to older Larsens).

Got a new one coming in the mail as I type this

 

[fineshot1]

FYI - AS well as the above I have also had some of the Larsen coils fill up with water
so I changed them with MaxRad antennas - that was about 20+ years ago that I made
this water infiltration discovery. MaxRad was gobbled up by PCTel I think.

 

[jwt873]

Interesting... We have a large LMR provider that covers a lot of Western Canada. (Ham friendly too.. We have free repeater space on a couple of their commercial towers).

They sold Larsen antennas for years. But they recently switched to MaxRad/PCTel. I'm guessing it was probably more for profit than reliability.

 

[kayn1n32008]

Why not a new antenna and mount ? I know they can be had under $50 on ebay.
I guess like me, I am still trying to find a base for a vintage Motorola 5 db mobile antenna.

No need for a new mount. He simply needs a new base. They can be bought separate from the whip.

 

[kayn1n32008]

Interesting... We have a large LMR provider that covers a lot of Western Canada. (Ham friendly too.. We have free repeater space on a couple of their commercial towers).

They sold Larsen antennas for years. But they recently switched to MaxRad/PCTel. I'm guessing it was probably more for profit than reliability.

Maxrad/PCTel are decent antennas. I've used them for LMR, and not had an issue.

 

[jwt873]

He simply needs a new base. They can be bought separate from the whip.

Actually, that's what I have coming..

 

[jwt873]

Maxrad/PCTel are decent antennas. I've used them for LMR, and not had an issue.

I have a Maxrad MUF4305 in my mobile antenna collection. It's a 5/8 wave over 1/4 wave UHF collinear. Supposed to have 5dB gain. Don't use it much, but it's not a bad antenna.

 

[cmdrwill]

So my 20+ year old Larsen NMO-2/70 dual band antenna finally bit the bullet.

Common problem with the older Larson antenna base/coil contacts.

 

[kny2xb]

Does this help?

https://www.hamradio.com/detail.cfm?pid=H0-000617

 

[cmdrwill]

Does this help?

No, way overpriced