2 meter ham antenna analyzer/tuner

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jonheld

jonheld

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So I'm trying to do the right thing and purchase an analyzer/tuner for my setup with multiple antennae.
I have a Diamond NMO mount with 2 Diamond antennae and 1 Larson whip.

The Diamonds work fine, but the Larson requires me to cut it to length for min SWR.

I have been told that an NMO base will always show a 1:1 SWR due to the load coil in the base, and that this makes it difficult to "tune" an antenna. The common thinking is that any 2M antenna is fairly close out of the box, and that has been my feeling on the Diamond products. However I don't know how to properly deal with the Larson.

I'm looking for insight as to what unit will work for my needs and will it be accurate?
 
jonheld said:
So I'm trying to do the right thing and purchase an analyzer/tuner for my setup with multiple antennae.
I have a Diamond NMO mount with 2 Diamond antennae and 1 Larson whip.

The Diamonds work fine, but the Larson requires me to cut it to length for min SWR.

I have been told that an NMO base will always show a 1:1 SWR due to the load coil in the base, and that this makes it difficult to "tune" an antenna. The common thinking is that any 2M antenna is fairly close out of the box, and that has been my feeling on the Diamond products. However I don't know how to properly deal with the Larson.

I'm looking for insight as to what unit will work for my needs and will it be accurate?
Click to expand...


I can't give you a ton of info, but I run a Larsen 150 on an NMO mount and did tune it with an excellent SWR meter lent to me by DesertDude. Larsen has a cut chart on the website, and I cut the whip to just longer than that, and then took off 1/4 inch at a time until it was perfect. it's been good ever since. The length on the cut chart was within 1/4 of being correct as I recall. In the future, I'd likely cut to length and forget it.
 
Yea, I followed the cut chart that came with my 150. It's exactly 42" and it performs worse than the Diamond in my highly scientific experiments ;)

"How do I sound now?" Right now it's all I got.

The Larson 150 is a 5/8 wave, the Diamond NR770HBNMO is a 1/2 wave and the Diamond NR72BNMO is a 1/4 wave. Both the smaller antennae perform better than the Larson.

Are all NMO bases the same or do they vary from manufacturer to manufacturer?
 
The Larsen 150s are some of the best antennas you can get. If it's the 5/8 wave model, you need to have a good ground plane, where as the 1/2 wave antenna is not dependent on a ground plane in the same way.

I would guess your whole system needs something and the first place I would look is the ground of the NMO mount. That Larsen should outperform the other 2 antennas easily.

If you can't figure it out, it's a POS and you should remove it and send it to me for disposal.
 
I'm using the venerable MFJ 259-B, which not every purist likes but it's done well for me with a variety of home and vehicle installations.

MFJ Enterprises Inc.

With it, I have never seen an NMO at 1:1. I'm running a Larsen NMO-150 1/2-wave on the spare tire carrier of my 40, and it works great after some very minor trimming of the length. Really happy with that antenna. One thing to look out for is that Larsen uses the NMO-150 model number for both 5/8-wave and 1/2-wave antennas; you have to pay close attention to the catalog to get the right one for your application.
 
I think the problem here is a loose nut behind the keyboard ;)

I remeasured and looked again at the base coil for the Larson. It is a 1/2 wave that I cut to 5/8 specs. Apparently I wasn't really paying attention to what I was reading or what I was measuring.
The first cut was to 48". This would have been correct for 5/8 at 146 MHZ. Last night after looking at my invoice and comparing it to the base coil, I realized my mistake. I cut it down to 40 1/8". I will have to test it to see what kind of difference it made.

Sorry for the misinformation on this thread.
 
jonheld said:
I think the problem here is a loose nut behind the keyboard ;)

I remeasured and looked again at the base coil for the Larson. It is a 1/2 wave that I cut to 5/8 specs. Apparently I wasn't really paying attention to what I was reading or what I was measuring.
The first cut was to 48". This would have been correct for 5/8 at 146 MHZ. Last night after looking at my invoice and comparing it to the base coil, I realized my mistake. I cut it down to 40 1/8". I will have to test it to see what kind of difference it made.

Sorry for the misinformation on this thread.
Click to expand...

Ha! That is so something I would do. I'm looking for a new antenna and have been poking in this thread.
 
jonheld said:
I think the problem here is a loose nut behind the keyboard ;)

I remeasured and looked again at the base coil for the Larson. It is a 1/2 wave that I cut to 5/8 specs. Apparently I wasn't really paying attention to what I was reading or what I was measuring.
The first cut was to 48". This would have been correct for 5/8 at 146 MHZ. Last night after looking at my invoice and comparing it to the base coil, I realized my mistake. I cut it down to 40 1/8". I will have to test it to see what kind of difference it made.

Sorry for the misinformation on this thread.
Click to expand...

At least you originally cut it long... :)

cheers,
george.
 
jonheld said:
I cut it down to 40 1/8". I will have to test it to see what kind of difference it made.
Click to expand...

If you get a chance, I'm curious about what you found with the antenna analyzer and how the antennas compare in practice and/or on the analyzer.
 
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