Question about the Comet SBB-5

[4x4mike]

I'm in the market for a higher gain dual band antenna with an NMO base. It appears the Commet SBB-5NMO fits my needs but I see it's a fold over design. I don't need the fold over option but it looks as if there is no avoiding it.

Question about the fold over portion. How does it work? Google images isn't really showing me much. How durable is the joint? I'm not planning on ramming the antenna into trees but I also don't plan on folding it over much ,if any. Is it strong enough for me not to worry about it being a weak point?

My other option is the SBB-2NMO but it doesn't have gain numbers much more than I already have with my B-10. The SBB-2 is only 18" and has an option of a spring base but I like the 3 dbi on 2m that the SBB-5 has.


Any input on this matter from those with experience?

 

[DaveInDenver]

First thing is don't pay attention to gain numbers, in the real world they don't mean much. If you do want to compare numbers make sure you're comparing apples-to-apples, dBi or dBd between both. You convert dBd (decibel gain relative to a real dipole) to dBi (gain relative to a theoretical isotropic radiator) by adding 2.15dB. IOW dBd = dBi - 2.15dB. By specifying gain compared to a isotropic radiator a manufacturer can inflate the number. Problem is an isotropic radiator cannot exist in the real world so it's disingenuous.

For example, the SBB-5 is listed at 3dB gain on 2m in a 1/2 wavelength configuration. When you compare that to a Larsen NMO2/70, which has the same configuration and essentially the same construction (open coil), it's listed at 1.6dB. Reason for this is Comet spec in dBi and Larsen in dBd. They will each show exactly the same 1.6dB in gain compared to a 1/4 wavelength whip, which is half a dipole and taken as no gain baseline antenna (e.g. unity gain or 0 dB). FWIW both the NMO2/70 and SBB-5 are also collinear 5/8 wavelength antennas on 70cm yet Comet claims 5.5dB of gain and Larsen 3.5dB. Same reason, one comparing to a theoretical and the other to a real life baseline.

The important thing to see is that no manufacturer can cheat physics. A 1/2 wavelength is a 1/2 wavelength. They can come up with complex designs with several elements to realize large gains but this comes at the expense of something, generally bandwidth and beamwidth. IOW, if they do some funky 4 element design that shows 13dB of gain, that means it will have a very narrow pattern, probably being next to deaf as you increase elevation if the pattern is omnidirectional in azimuth.

I had a Comet antenna with the fold-over that got loose after a couple of years. I used it fairly often, though, since it was to fold over parking in the garage. After that I started using commercial antennas with great success, they are much more durable.

 

[4x4mike]

Thanks for the insight. The dual band I currently run is the Comet B-10 NMO. I was having some range issues in the Mojave and wished I had my Larsen 150. It just seems the B-10 has a few limitations due to it's short size. I'll keep my 150 and my Larsen 1/4 wave but I'd like a dual band that will get me a little more range in varying terrain.

A couple suggestions would be nice, even the commercial models.

Thanks

 

[DaveInDenver]

In dual bands it's tough IMHO to beat a NMO2/70 (or SBB-5 in the Comet) as an all around antenna. The range will be fairly similar to your NMO150 on 2m. There's no magic to it, you'll get about 2 to 4dB of gain over a 1/4 wavelength and anything more you really need to be thinking about using a directional.

 

[4x4mike]

Thanks. I had a 2/70 when I got my first radio but that first radio was only a 2m and the antenna was way too floppy. It didn't fit my needs so I sold it. Length isn't a huge issue but the floppiness combined with the twig grabbing coil wounds killed the deal.

Thanks for the help.

 

[DaveInDenver]

The Comet is AFAIK essentially the same, so the open coil and flexibility might make it less good. Keep in mind that if the antenna is any stiffer you'll risk pulling the NMO out of the roof when you hit stuff. Larsen does sell a closed coil version of the 2/70 for this reason, BTW.

 

[Robert Bills]

. . . Keep in mind that if the antenna is any stiffer you'll risk pulling the NMO out of the roof when you hit stuff. Larsen does sell a closed coil version of the 2/70 for this reason. . . .

Dave,

I am ordering a new 2m/70cm mobile antenna in the next few days for a roof rack installation and have the 34.5" Larsen NMO-2/70B in my shopping cart. I had not considered the 19" closed coil Larsen NMO-2/70SH because until recently most of my offroading was in the desert where clearance is almost never an issue. However, now I am in NorCal where there are often overhanging oak or pine branches.

Are you saying that the Larsen NMO-2/70SH 19" closed coil antenna would be a better choice than the 34.5" open coil 2/70B in areas where foliage might catch in an open coil? Are there any strength or performance issues with the closed coil 2/70SH vs. open coil 2/70B?

Ironically, I also have the Comet B-10 NMO in my shopping cart (PayPal balance from the sale of "offroad parts I no longer need" depending), so that I can have something shorter and more "stealth" for running around town or when there is too much overhanging foliage to deal with the hassle. However, depending upon your response to my questions it may make more sense just to buy the 18" Larsen NMO-2/70SH and be done with it. It would sure save a pile of money.

Antennas I am considering or have considered:

Comet B-10 NMO 12” open coil $42.95
Comet SS-460SB NMO 18” closed coil with spring $43.95
Diamond NR72B NMO 14” open coil $39.95
Larsen NMO-2/70 SH 19" closed coil with spring $49.95

Comet SBB-5 NMO 38” open coil $58.95
Larsen NMO-2/70B 34.5” open coil $79.95

Your thoughts on any/all of these antennas?

BTW - This is the Breedlove NMO mount I will be using, through 1/8" steel. It should be strong enough.

 

[4x4mike]

Your list is similar to what I'm looking at buy, already have or have already owned.

For the most part the B-10 is a great antenna. I bought it based on the reviews I read and folks claims that it performed similar to antennas twice it's size. I have yet to snag it on something and it's a stiff little antenna. I owned a Larsen 2/70 and it was really floppy. The open coil can get caught on something but it can also be covered with a piece of shrink wrap. I didn't like how it would flop and hit my other antenna or items on my roof rack.

Another thing about the 2/70 is that it has 2 hex screws that hold the whip in the coil. Even tight it's possible for a twig to get caught in the coil and the ship be pulled out. You won't know you've lost your whip until you've lost communications. The B-10 whip is part of the base.

If the brush was really tough I'd probably just run my 1/4 wave 2m as it's short and flexible. Most my buddies run 2m but I use cross band repeat with my radio and still need a nice dual band antenna.

 

[DaveInDenver]

There are 3 Larsen antennas:

NMO2/70B = open coil, 35" tall

NMO2/70C = closed coil, 37" tall

NMO2/70SH = closed coil, 19" tall with base spring

I personally have used The NMO2/70B, NMO2/70SH, NMO150, a Comet C767 and currently the STI-CO Flexi-whip. I run dual whips with a duplexer now and this has worked well for me, but before I mostly used the 1/4 wavelength tall 2/70SH most of the time. In any case if I need range for whatever reason I use the NMO150 but that might be once a year, maybe. I have the antennas in the middle of my roof and seem to get decent range.

The Breedlove NMO is substantial but I've only ever used standard issue NMO bases.

 

[Robert Bills]

I don't want to hijack 4x4Mike's thread about the Comet SBB-5, so I've started a new one regarding the choice I am trying to make between the Comet SS-460SB NMO and the Larsen NMO-2/70SH.

http://www.expeditionportal.com/for...-or-Larsen-NMO-2-70SH-Is-One-quot-Better-quot

Please help!

 

[Frdmskr]

The NMO270B is fantastic and indestructible. Had one for over five years and never a leak or swr issues.


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[Frdmskr]

Something to consider based on your perceived need, the same I had a while ago, is are you needing a higher gain antenna or and higher takeoff antenna. I used to live in Northern VA and had issues hitting local repeaters in the urban jungle. No problem hitting the machine 70 miles away though. Switched from my diamond high gain dual band to the Larson and it was night and day. Hit all the local stuff fine. Was marginal into the far off machine once I got east if a certain point. Thing is I needed to talk locally, not very often 70m away.

On a trail you will have a similar need. If you really need to hit a machine from the boonies bring a beam- 4-6 ele max - or use HF on 40 and call for help there.


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[Orbital Debris]

I've got both the SBB-2 and the SBB-5, but in a PL-259 configuration on a lip mount. Since they are not NMO, neither is a foldover. I've had great performance from both, I use the SBB-2 for daily use so I never have to worry about clearance around town. It will hit 30ft height above terrain (on top of bldg) repeaters out to about 15-20 miles.

I use the SBB-5 for field events when I want extra coverage such as tracking. It has performed well, doesn't flop much at 70 mph, and survived at least one low clearance hit bending it over about 60 degrees. I really got it for a little bit of extra reach out on the eastern plains of Colorado, but for everyday, the SBB-2 has performed well. One thing that is nice about the SBB-5 at 38in length, I store it in a pvc tube behind the rear seats when I've swapped it with the SBB-2. It is just the right size to lay across the cargo area.

 

[Stevenson]

Here is what I have
http://www.universal-radio.com/catalog/hamantm/3907.html

It works great, looks great, and i can fold it over or take it off if needed. I have the pl-259 and not nmo.

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[Stevenson]

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