I hate tuning CB antennas

[K6GBW]

Just curious, is this one of the newer Jeeps with the aluminum body? My last Jeep was a JK so I had plenty of steel to work with.

 

[smittie]

Mostly aluminum and plastic. The hood is plastic over aluminum. Not sure what the tub is. I miss my CJ-7, all steel everywhere. Never should have sold it.

 

[mmckenna]

So, I bought the Larsen NMO30 and the 64" whip. Got it tuned to 1.1 SWR using the NanoVNA and verified using an SWR meter. And then the center tab broke off.
All done with Larsen. Back to Laird products.

How did the tab break off? Were you pulling on it, or trying to bend it down for better contact?

I had that happen a long time ago, but it was my fault.

Larsen has been slowly migrating to the "pogo pin" for their newer antennas.
Sorry you had a bad experience.

 

[smittie]

How did the tab break off? Were you pulling on it, or trying to bend it down for better contact?

I screwed the antenna on to the NMO and then unscrewed it. At least on this product that I got, Larsen uses cheap, low grade aluminum for the conductor. It is very brittle and breaks easily. The Laird and Tram/Browning product are significantly better built based on what I have in front of me.

The NMO 30 I have was ordered a week ago and arrived two days ago.

Appreciate the sympathy.

 

[mmckenna]

I screwed the antenna on to the NMO and then unscrewed it. At least on this product that I got, Larsen uses cheap, low grade aluminum for the conductor. It is very brittle and breaks easily. The Laird and Tram/Browning product are significantly better built based on what I have in front of me.

The NMO 30 I have was ordered a week ago and arrived two days ago.

Appreciate the sympathy.

I've never seen one made out of aluminum. All of mine were copper, or at least copper coated.

 

[smittie]

I only have two Larsen antennas, one of which is probably pretty old. Both have the same basic design for the center conductor. On the older one the conductor appears to be made of spring steel.

It was an experiment. I learned a few things. Maybe I will be able to recoup some of my losses.

 

[madrabbitt]

i've never had one of those break off on me, even bending them down to make better contact. I wonder if it was just a bad or out of the box defect.
Personally, i prefer larsen and their conductors, over the spring loaded pins. I've had a few cases where the pin had enough corrosion that it was no longer springy and only made contact with certain mounts.

Back to the core of this thread.

OP, i feel your pain. SWR adjustment on 27mhz is somewhere in the spectrum of luck and voodoo. Whomever said REFLECTION has a lot to do with it is absolutely correct. Adjusting SWR on my truck's CB, which has a front fender mount NMO drives me to drink. It can be close to optimal, and then i do something like close the door and its completely off

 

[RFI-EMI-GUY]

i've never had one of those break off on me, even bending them down to make better contact. I wonder if it was just a bad or out of the box defect.
Personally, i prefer larsen and their conductors, over the spring loaded pins. I've had a few cases where the pin had enough corrosion that it was no longer springy and only made contact with certain mounts.

Back to the core of this thread.

OP, i feel your pain. SWR adjustment on 27mhz is somewhere in the spectrum of luck and voodoo. Whomever said REFLECTION has a lot to do with it is absolutely correct. Adjusting SWR on my truck's CB, which has a front fender mount NMO drives me to drink. It can be close to optimal, and then i do something like close the door and its completely off

The first rule is to close all the doors and hatches before tuning. Unless you drive with a door open riding shotgun.

 

[smittie]

Spent 20 years as a software test engineer. Always test it like you use it. Close the door, run the engine, turn the stereo on, the lights. All the things you do.

 

[smittie]

Definitely not impressed with Larsen construction on a couple of levels. However, I also have two Laird that don't seem to work either. The Tram works the best so far.

 

[madrabbitt]

i'm talking about going from 1.1 on channel 19 while testing in situ, to over 3 on the same channel because the door on the passenger side was opened. And not everyone operates the exact same way 100% of the time, so its worth testing several scenarios. However, the CB in my truck gets tuned with the engine on (especially since its an ignition circuit), and all doors and windows closed, because most of the time its being used is on the road.

 

[prcguy]

Definitely not impressed with Larsen construction on a couple of levels. However, I also have two Laird that don't seem to work either. The Tram works the best so far.

First off I will bet $1.00 there has never been an aluminum contact tab in the base of any Larsen mobile antenna. Its almost always beryllium copper and maybe silver plated. They would never use aluminum as most mating tabs on the NMO mount are brass or silver plated and aluminum would cause a huge dissimilar metal corrosion party. The internal loading coils are either solid copper wire or copper clad steel and there is no good way they can interface an aluminum spring tab to that.

Second, touting a Tram over a Larson or Laird is kind of like praising a Yugo over a Toyota. The Tram/Browning label has been a Chinese copy cat brand for quite some time now. I've been heavily involved with most types of mobile antennas since the mid 70s installing, range testing, etc.

 

[smittie]

OK, not aluminum. Still brittle and broken. Experientially, the Larsen lasted a day. The Laird units lasted a month or so and the Tram still works. I'll go with experience over recommendations in almost every case.

The "Chinese knock-off" denigration holds no water with me. Most if not all of the radios we are using are 'Chinese knock-offs'. I care far less about reputation than what works.

 

[mmckenna]

OK, not aluminum. Still brittle and broken. Experientially, the Larsen lasted a day. The Laird units lasted a month or so and the Tram still works. I'll go with experience over recommendations in almost every case.

Well, things break. It happens.
I've got 30 year old Larsen antennas that have never given me issues. I use them at work and have them on probably 60+ vehicles. I had one with the tab fail, but that was because I was pulling on it when I shouldn't have been. I've disassembled some of their coils, including the NMO27 coil and they are well built.

As for experience, keep in mind that some of us have been doing this stuff for decades, and it's not just rattling off brand names to sound good, it comes from actual experience with the products. I won't recommend something without good reason.

If you found something that works for you, that's all that matters.

 

[smittie]

As for experience, keep in mind that some of us have been doing this stuff for decades, and it's not just rattling off brand names to sound good, it comes from actual experience with the products. I won't recommend something without good reason.

I understand that. Your recommendation was the reason I spend $178 on a Larsen antenna. In the meantime, I have a Tram on my truck that has been working for months. You tell me. What should I do based on this experience?

 

[madrabbitt]

WTF larsen is $178?

The damn panthers dont even cost that much, and i'm looking at retail.

 

[smittie]

WTF larsen is $178?

The damn panthers dont even cost that much, and i'm looking at retail.

Purchased through Antenna Farm; NMO 30 base, two 64" whips and one spring. Plus shipping. For the parts I wanted to get, I didn't see any other retailers offering.

 

[mmckenna]

Ouch! $178?

Like I said, if the Tram works for you, run it until it fails.

 

[madrabbitt]

now you have me wondering how much i spent on the CB antenna and mount on my truck.

$54 for vehicle specific mount + nmo and coax,
$105 for the antenna

 

[K6GBW]

Jeeze, have antennas gone up THAT much? You say you're using the NMO30, I'm wondering if you might be better off with the NMO27. I have one that I used to run on my pickup and it was excellent.

Antennas aren't magic, they are usually just stainless rod and coils. Nothing super scientific about them. The quality differences are in the materials and the details of the workmanship. Some antennas are so simple you can go with lower quality brands without really hurting anything. I still have a Tram dual band NMO mount antenna that works great because there's just not a lot to screw up. If the Tram you are running looks like it's decently made and it's tuning up and performing well then there's really no reason to change it.

Also, keep in mind that a super low SWR of 1.1 on all channels is almost impossible to get in a mobile installation. If you are getting 1.8 on your desired channel of operation then you should be good to go. Especially if you're just using it for trail communications and or listening to the trucks for traffic then it should work fine.

In the radio world we all want low SWR but there's a point when better becomes the enemy of good enough!

PS: DX Engineering has the Larsen NMO27B for $71.00 right now.