NMO2/70SH vs NMO2/70B

[prcguy]

I have a tree that overhangs the street on my main path out of town and my Larsen NMO2/70B has probably hit it hundreds of times with no problems. I've scraped under many other trees and have seen leaves sheared off by the whip and coil in my rear view mirror but no damage.

I should mention this is my first mobile install so this is for sure a uphill learning experience right now, I originally was going to use a comet ant but it has an epic large coil right in the middle of the ant, I want this in a rig that goes off-road so coil loops mid ant height I fear will just be damaged by trees. Larsen seems to be well liked and bullet proof options. So I'm torn between the NMO2/70B much smaller coil trun at the top and the NMOQWB

The TH-D710GA is actually the radio I want to use in my rig, I should have mentioned that. APRS will more then likely be running as well.

When you said NMOQWB I assume your referring to NMOQB I'm not finding any listing in the Larsen for NMOQWB.

Appreciate the help

 

[mmckenna]

I should mention this is my first mobile install so this is for sure a uphill learning experience right now, I originally was going to use a comet ant but it has an epic large coil right in the middle of the ant, I want this in a rig that goes off-road so coil loops mid ant height I fear will just be damaged by trees. Larsen seems to be well liked and bullet proof options. So I'm torn between the NMO2/70B much smaller coil trun at the top and the NMOQWB

Yeah, I don't think you'd have a problem with the open coil on the NMO-2/70. My brother in law used his off road and never had a problem. Wouldn't be my own personal first choice for an antenna, but that's just me.

When you said NMOQWB I assume your referring to NMOQB I'm not finding any listing in the Larsen for NMOQWB.

Appreciate the help

Yeah, sorry, misread your post. There is a WB model for the 1/4 wave antennas. It's the 'Wide Band' version. It has a thicker whip and a spring at the base. It gives some better useable bandwidth, but it's not necessary for a ham radio. These are primarily designed for public safety radios where it may be programmed with frequencies down in the 151MHz range as well as federal stuff up around 171MHz. Not necessary for what you are doing.

The basic NMOQ will work fine for 2 meter VHF. It'll resonate as a 3/4 wave on UHF, but on UHF the radiation pattern shoots a bit above the horizon. Not an issue if you are using a lot of mountain top 70cm repeaters, but probably not ideal if you are looking to do simplex 70cm.

 

[tweiss3]

Am I correct in my understanding that the "B" model being a center loaded 1/2 wave + 3/4 colinear that it does not require a ground plane, but the "SH" model does? Or am I mistaken and both require a ground plane.

 

[mmckenna]

Am I correct in my understanding that the "B" model being a center loaded 1/2 wave + 3/4 colinear that it does not require a ground plane, but the "SH" model does? Or am I mistaken and both require a ground plane.

Larsen usually uses the "B" model to indicate a black antenna whip.
The Larsen NMO-2/70 is the colinear. It is 1/2 wave on VHF, so a ground plane isn't necessary. Not sure how that impacts UHF, though.

The NMO-2/70SH model is a 1/4 wave on VHF, and it does require a ground plane.

 

[W7GEL]

Decided to order the the $75 NMO-2/70 .... must be covid pricing. Wish I had a local HAM store.

Appreciate the help from everyone especially mmckenna with your cool charts and info. I will verify my 3/4 is 3/4 before I drill as well

 

[Firekite]

Decided to order the the $75 NMO-2/70 .... must be covid pricing. Wish I had a local HAM store.

I've had the 2/70SH for a while and find it to be very good. The 2/70B just arrived, so I look forward to seeing if it makes any difference. Around here there aren't true mountains, just hills, so flattening out the radiation might actually help.

 

[mrweather]

$75 for a Larsen NMO2/70 is money well spent. Up here in VE-land it's over $100.

But, it's the best dual-band antenna out there, IMHO.

 

[tweiss3]

It appears I shot myself in the foot with this thread. Finding one might be rough (I know they are out there, but $120 at DX is a no go).

 

[Firekite]

It appears I shot myself in the foot with this thread. Finding one might be rough (I know they are out there, but $120 at DX is a no go).

Is this what you’re referring to?

https://www.theantennafarm.com/catalog/index.php?main_page=product_info&products_id=1712

 

[mmckenna]

It appears I shot myself in the foot with this thread. Finding one might be rough (I know they are out there, but $120 at DX is a no go).

Yeah, no reason it should cost you $120.00.

 

[tweiss3]

Yeah, no reason it should cost you $120.00.

Exactly. The big kicker is shipping costs. I ended up finding it with free shipping for 74. I figure at a minimum, it will have other uses when an out of the normal situation occurs.

 

[tweiss3]

The 2/70B has been installed since Tuesday (Monday night), and I'm not sure if there is any improvement at all. It's hard to tell with the weather we have been having and all the tropo and temperature inversion. I had a solid YSF contact with a UHF repeater today that was 97 miles, and no way there was line of site (I was at 800 ft, repeater at 600 ft, and ground grew to 1400 feet between us).

I'm also not hearing any whistling, but maybe I just haven't noticed.

Overall, I think I'll leave it on untill either the truck goes in for service, or is replaced, mostly cause I don't feel like switching it out just yet.

 

[K6GBW]

I had one of those antennas years ago. It works well enough, but I had it in the center of a pickup truck roof and I frequency hit things with it. It just go irritating so I switched it out for a 12" Comet B10MNO. I swear that little antenna worked almost as well and never hit anything. I ran that antenna for over ten years and it just worked. But I live in Los Angeles where I'm usually driving around from sea level to 700 feet. The local repeaters are on mountains that range from 3500 to 5700 feet, so for me I don't need a huge amount of gain. It basically comes down to finding a balance between convenience and utility. If I lived in a desert with repeaters on poles I'd opt for a high gain antenna. But I find having less gain to be helpful in my situation. I honestly think too many people look at antennas with an eye toward max gain when it may not be the answer they are looking for. Anyway, I hope the antenna works well for you.

 

[Firekite]

I'm also not hearing any whistling, but maybe I just haven't noticed.

It’s totally dependent on placement and vehicle. Just because there’s a breeze nearby doesn’t mean every beer bottle on the outdoor table becomes a musical instrument. In my case there is some resonant wind noise that picks up about 65mph where I have it on my roof. I’ve experimented with twisting it around, and it produces a different tone. I’ll also experiment with put it in a different spot on the roof. I’ve stuck a wrap of duct tape around it just temporarily and will probably end up getting some larger heat shrink tubing to cover the coil just so it looks a little nicer. I may also swap it out for the 2/70SH for local work.