NMO2/70SH vs NMO2/70B

[tweiss3]

I currently use the NMO2/70SH which is only 19" tall and has a spring on the bottom. I love the antenna, it's nearly indestructible, and doesn't look too terrible. I am working on rethinking what I have in the car, and was thinking that maybe it wouldn't be so bad to switch out to an antenna for slightly better performance. I like the Larsen stuff, its well made, and at 34.5", the NMO2/70B isn't too much taller. I will be hitting on parking decks though, and I the antenna doesn't have a base spring.

How well does the NMO2/70B hold up to trees, parking decks, overhead obstructions?

 

[trentbob]

I have the 70B... I'm sure you've researched it well, at 35 in, with the pigtail towards the top it is susceptible. It handles a hundred Watts and you're right, it's a Larson, it's quality and performance is as good or better as any.

Depending on your discretion and what you get yourself into regarding obstacles, there's a good chance no antenna will survive certain things LOL.

It's available at GigaParts for $71.00... I have personally dealt with them many times and find them a reputable vendor.

 

[PrivatelyJeff]

I currently use the NMO2/70SH which is only 19" tall and has a spring on the bottom. I love the antenna, it's nearly indestructible, and doesn't look too terrible. I am working on rethinking what I have in the car, and was thinking that maybe it wouldn't be so bad to switch out to an antenna for slightly better performance. I like the Larsen stuff, its well made, and at 34.5", the NMO2/70B isn't too much taller. I will be hitting on parking decks though, and I the antenna doesn't have a base spring.

How well does the NMO2/70B hold up to trees, parking decks, overhead obstructions?

I have that exact antenna and I just put a spring on it and recut it so the length is the same.

 

[mmckenna]

Yeah, adding a spring is always an option. You just buy the spring separately and reduce the whip length accordingly.

I've run the 2/70sh and it's a good antenna. My brother in law ran the 2/70 for a long time, but was happy when I gave him my shorter model. The longer 2/70 makes a lot of wind noise.
The longer flexible whip will reduce the gain a bit when at highway speeds. As the antenna flexes back, some of the energy gets directed high/low based on the tilt of the whip. The 2-70SH won't have that problem. So, yeah, the longer antenna has more gain, but it'll be slightly less while driving. And personally, I've never had an issue with the smaller antennas. The bit of gain difference doesn't really amount to much, and the tradeoffs on a tall truck can be a problem.

 

[n9mxq]

I've beat the living snot out of my 2/70b's over the years, including a stint with a Jeep Wrangler TJ that did almost as much trail as it did road. The only one that got killed was the time I left it on the roof of my minivan and the tire shop lifted the van up to do tires, and shoved the top half down into the coil. Partly my fault for leaving it on...

 

[tweiss3]

I have that exact antenna and I just put a spring on it and recut it so the length is the same.

I didn't think about that. I do see you can buy the spring bases. Makes the antenna more expensive, not that it's not worth it........

Yeah, adding a spring is always an option. You just buy the spring separately and reduce the whip length accordingly.

I've run the 2/70sh and it's a good antenna. My brother in law ran the 2/70 for a long time, but was happy when I gave him my shorter model. The longer 2/70 makes a lot of wind noise.
The longer flexible whip will reduce the gain a bit when at highway speeds. As the antenna flexes back, some of the energy gets directed high/low based on the tilt of the whip. The 2-70SH won't have that problem. So, yeah, the longer antenna has more gain, but it'll be slightly less while driving. And personally, I've never had an issue with the smaller antennas. The bit of gain difference doesn't really amount to much, and the tradeoffs on a tall truck can be a problem.

I didn't think about the bending and noise. That wraps up that idea. I think I will stick with the 2/70sh, it performs great. I was wondering what a bit more help while moving would look like, but the bending in the wind negates that.

I've beat the living snot out of my 2/70b's over the years, including a stint with a Jeep Wrangler TJ that did almost as much trail as it did road. The only one that got killed was the time I left it on the roof of my minivan and the tire shop lifted the van up to do tires, and shoved the top half down into the coil. Partly my fault for leaving it on...

Good to hear, will keep it in the back of my mind.

 

[mmckenna]

I didn't think about the bending and noise. That wraps up that idea. I think I will stick with the 2/70sh, it performs great. I was wondering what a bit more help while moving would look like, but the bending in the wind negates that.

The impact of the antenna flexing back at highway speeds isn't huge, but it's not zero, either.
I see you are in Ohio, so to this West Coast guy, that means lots of flat lands. Higher gain antennas would have an edge in that environment since the additional gain is achieved by focusing the radiation pattern at the horizon. That can be a benefit.
But, if the shorter antenna is working well, the additional cost of the new antenna may not add up. But, then again, this is a hobby...

I ran the 2/70SH for a long time, and it worked well, but I'm pretty much surrounded by hills and mountains. Hard to get anywhere here where the true horizon is visible.

 

[tweiss3]

The impact of the antenna flexing back at highway speeds isn't huge, but it's not zero, either.
I see you are in Ohio, so to this West Coast guy, that means lots of flat lands. Higher gain antennas would have an edge in that environment since the additional gain is achieved by focusing the radiation pattern at the horizon. That can be a benefit.
But, if the shorter antenna is working well, the additional cost of the new antenna may not add up. But, then again, this is a hobby...

I ran the 2/70SH for a long time, and it worked well, but I'm pretty much surrounded by hills and mountains. Hard to get anywhere here where the true horizon is visible.

Actually, I'm on the Appalachia side of the state, and will be making trips to PA more often. I have a split in my commute that I'm blind to the other side of the ridge. I just have been driving so much more, it's made me rethink it. The wind noise would drive me crazy.

 

[Firekite]

I just have been driving so much more, it's made me rethink it. The wind noise would drive me crazy.

I have a 2/70SH and a 2/70B should be here next week. I’ve never noticed any road noise from the 2/70SH, but to be fair I’m in an F250 diesel, not an S-class. I’ll be sure to report if it’s suddenly an issue

The 2/70B is mostly for road trips. The SH version works well as it is. Always wondered if I were missing some range. I’m also curious to see if one tests out a little better than the other when hooked up to GMRS, though that’s not specifically what they’re meant for, but closely adjacent.

 

[PrivatelyJeff]

I didn't think about the bending and noise. That wraps up that idea. I think I will stick with the 2/70sh, it performs great. I was wondering what a bit more help while moving would look like, but the bending in the wind negates that.

The spring is fairly stiff so there isn’t much flex at highway speeds and as for noise, the only time I’ve ever heard anything, I was driving into very strong winds (the kind that push your car around on the road) at highway speeds. With just normal driving, I don’t hear a thing.

 

[mmckenna]

Actually, I'm on the Appalachia side of the state, and will be making trips to PA more often. I have a split in my commute that I'm blind to the other side of the ridge. I just have been driving so much more, it's made me rethink it. The wind noise would drive me crazy.

OK, sounds like the sh model might be a good choice. The noise isn't terribly offensive, but it is there as a whistle. The open coil is the culprit and you can always stick some heat shrink over it. That'll quiet it down quite a bit.

I've tried many different antennas over the last 30 or so years, and for my applications at work and personally, I've never seen a big enough difference between a 1/4 wave VHF antenna and a 5/8th's wave antenna to make it worth the trade off. Your milage may vary.
I've also tested with UHF and extensively with 800MHz, and the differences you'll find really only matter if you are right on the fringes of coverage. It's the difference between a horribly scratchy signal that you can barely understand and absolutely nothing.

 

[mmckenna]

The 2/70B is mostly for road trips. The SH version works well as it is. Always wondered if I were missing some range. I’m also curious to see if one tests out a little better than the other when hooked up to GMRS, though that’s not specifically what they’re meant for, but closely adjacent.

Ask and ye shall receive:

Here's the UHF sweep of a Larsen NMO-2/70SH:

It's best at 443MHz, and the SWR climbs a bit as you go away from that point, but still under 1.5:1 around the 462/467 range. This was a permanent mount NMO centered on the roof of a 2019 Chevy Silverado crew cab. In other words, a nearly perfect ground plane.

Here's the full sweep from 100MHz to 900MHz.

Here's the VHF sweep from 130MHz to 174MHz. You'd have to get up to 170MHz before it climbs above 2:1 SWR.

Since these are 1/4 wave on VHF, they are naturally very broad banded.

 

[Firekite]

Ask and ye shall receive:

Ha! That’s awesome. Thank you for sharing that!

 

[mrweather]

Theoretically, the NMO2/70B will have an advantage over the NMO2/70SH because it has more gain. In practice, it may not be all that noticeable. Compared to the shorty, I've gotten similar performance on both 2m and 70cm using a regular 19" whip. And the price was cheaper.

The SWR sweeps mmckenna posted above are similar to the ones I've obtained with my RigXpert AA-600.

 

[tweiss3]

Just so all this is in the same thread for future reference.
NMO2/70SH is 19" tall, Pulse Larsen claims 2.14 dbi gain for 2m (unity gain), and 4 dbi gain for 70cm
NMO2/70B is 34.5" tall, Pulse Larsen claims 3.8 dbi gain for 2m and 5.2 dbi gain for 70cm

If I have used these calculators correctly, at 50 watts input that translates to roughly 19.5 miles vs. 21 miles line of site (check my math please), provided the whips stay straight and vertical.

One thing I am interested in, the whip material is quite thick for the SH model, is it equally as thick on the B model?

I still think I'm not going to see any cost/performance/aggravation benefit from the switch, but it's always good to review and explore if there may be a better option.

 

[mmckenna]

If I have used these calculators correctly, at 50 watts input that translates to roughly 19.5 miles vs. 21 miles line of site (check my math please), provided the whips stay straight and vertical.

Too many variables to calculate like that. It's not x watts = x miles.

One thing I am interested in, the whip material is quite thick for the SH model, is it equally as thick on the B model?

The NMO-2/70SH has a thicker whip material. The NMO-2/70 is a bit thinner and more flexible.

I still think I'm not going to see any cost/performance/aggravation benefit from the switch, but it's always good to review and explore if there may be a better option.

You can always buy one and try it for a bit. If you don't like it, sell it to some ham that'll enjoy it.
But, yeah, on my full size truck, the longer higher gain antennas didn't make enough difference to be worth the drawbacks.

 

[n5ims]

Also note that there are two versions of the longer 2/70. One has an open coil (looks like the old cell antennas but longer) and the other has a closed coil. They both appear to work well and very similar (I have both and use them interchangeably) so only the look is different. It's been a while since I got either but think the open coil is the "B" version and the closed coil version is the "C" version. Also note that there is also a commercial version of the "C" model that is cut for the commercial bands and is not appropriate for ham use. Check the specs to be sure prior to purchase!

Both B and C versions have stood up to many years of use, often on top of an SUV so it's in the range of tree limbs. It does make a nice thung when you hit a limb but I've never seen damage. I swap the antennas out on both a standard NMO mount and my NMO Mag mount base. I use the version that is needed for what I'm doing (short antennas when I'll be garage parking regularly, a 5/8 wave VHF-Hi antenna when I'm only using VHF and need the extra gain, and one of the 2/70s for regular V/U use). Which I pick is very technical - which ever black antenna of the right length I happen to pick out of the stack at the time).

Since you have the SH version already, the B or C version will be a good version to have when you need the gain. You can swap them out as needed.

 

[N4KVE]

I’ve been using the longer one with the closed coil since 1991. It’s outlasted many cars. Like a Timex watch, “it just keeps on ticking”.

 

[mrweather]

The closed coil NMO2/70 whip hasn't been available for many years (Volume 6 of my Larsen Antenna SourceBook lists it but Volume 10 does not). Electrically there's no difference between it and the "curly cue" black whip (NMO2/70B).

 

[jwt873]

I've had my closed coil 2/70B since the mid 80's. I did have one problem with it. The flat spring tab in the plastic base recently broke and I had to replace it.

I recall reading somewhere that the whip with the open coil is prone to whistling on the highway. Don't know this to be true since I've never used one.