Spring Base VHF/UHF Dual-Band Mobile Antennas

[K9RNW]

In the world of spring-based NMO mobile antennas when you want to keep things as short/compact as possible...do antennas get any better than this model? I saw it previously recommended on here around 5 years ago. Every other similar atenna seems to be around 33"-35" or incompatible with spring bases.

https://www.dxengineering.com/parts/lsn-nmo2-70sh

I'm thinking of picking up a few Baofeng F8HP's for mixed 2m/MURS/70cm/GMRS use. For instances when they'd be used in a car...it'd be nice to have a better antenna mag mounted on the roof when possible. I specify spring-loaded because we aren't talking 6" or 8" tall UHF quarterwaves, and I'd like to avoid major problems occurring due to inadvertent matings with tree limbs or parking garage beams. They obviously have a higher-than-unity gain, which makes me wonder how they'd fare in hilly environments (northern WI gets pretty hilly).

Thank you

 

[nd5y]

I have used those Larsen 19" dual band antennas (both the open and closed coil types) and I can tell you they do not perform well on UHF.
A straight 2 meter 1/4 wave antenna works better than the short Larsen on UHF (and a 2m 1/4 wave is nowhere near as good on UHF as a UHF 1/4 wave).
If you want a dual band antenna that is good on UHF then you need one of the 3 foot or longer ones.
You probaby won't find a good antenna that covers all of 2m, 70cm, MURS and GMRS.

 

[KK4JUG]

nd5y is right. You can only ask so much of an antenna. Those WV hills can eat up your signal. I know you're concerned about height but you need as much as you can get.

I have a 19" antenna that I use around town because none of the repeaters are more than about 25-28 miles away and there are no mountains to try to get around. Most of the repeaters are within 10 miles. It is not a Larsen. When I go on the road, I switch to a 40" for the extra distance.

Mine is a UHF connector.

 

[mmckenna]

Larsen sells the spring on it's own, and you can adapt any of their antennas to work with it.

I've had good luck with the short Larsen dual band for amateur use, but I'm mostly surrounded by hills, so having high gain antennas isn't a problem.

A simple 1/4 wave VHF antenna, as suggested, would be a good option.
1. it's cheap. You can buy them for less than $10.00
2. they don't need a spring, they are flexible enough as is.
3. they are very broad banded on VHF, a 1/4 wave VHF will easily provide less than 2.0:1 across the 144-174MHz range. Cutting for the top end of the 2 meter band will give you good performance on MURS.
4. they are 3/4 wave on UHF. I used a 1/4 wave VHF as a dual band antenna for years. Worked very well in my area. SWR was better on 70cm than it was on 2 meters.

Not sure how well it would work on GMRS, never checked it down there.

Do keep in mind that the Baofengs don't always have FCC type acceptance for GMRS, so make sure before you purchase it. They also will not have the Part 95J for MURS as they fail to meet the limitations for a MURS radio (2 watts, etc.).
If you don't already have your GMRS license, you may want to hold off for a little bit and wait for the new rule changes to go into place.

 

[KK4JUG]

Do keep in mind that the Baofengs don't always have FCC type acceptance for GMRS, so make sure before you purchase it. They also will not have the Part 95J for MURS as they fail to meet the limitations for a MURS radio (2 watts, etc.).
If you don't already have your GMRS license, you may want to hold off for a little bit and wait for the new rule changes to go into place.

I was gonna bring that up but most of the people on this forum don't care about that. They only want to follow the FCC regulations that they want to follow, whether it's right or wrong.

Their policy is "Go ahead. The FCC isn't listening anyway."

 

[K9RNW]

I have used those Larsen 19" dual band antennas (both the open and closed coil types) and I can tell you they do not perform well on UHF.
A straight 2 meter 1/4 wave antenna works better than the short Larsen on UHF (and a 2m 1/4 wave is nowhere near as good on UHF as a UHF 1/4 wave).
If you want a dual band antenna that is good on UHF then you need one of the 3 foot or longer ones.
You probaby won't find a good antenna that covers all of 2m, 70cm, MURS and GMRS.

If I could ask you...why would UHF not perform as well on what's effectively a 3/4 wave emitter as opposed to a 1/4 wave?

I was gonna bring that up but most of the people on this forum don't care about that. They only want to follow the FCC regulations that they want to follow, whether it's right or wrong.

Their policy is "Go ahead. The FCC isn't listening anyway."

I always follow the law to the letter when it comes to amateur radio operations. Whether the FCC wants to grab me by the neck over a technicality with regards to radio certs when using GMRS freq's, even though I operate within the given restrictions (power/bandwidth/etc), I guess that's a consequence I'll have to live with. Though, it seems like most people don't even *try* to follow the FCC rules at all these days outside of ham radio.

 

[nd5y]

If I could ask you...why would UHF not perform as well on what's effectively a 3/4 wave emitter as opposed to a 1/4 wave?

Because of the radiation pattern. A 3/4 wavelength vertical antenna over a ground plane has a radiation pattern with two lobes. The frequency makes no difference. The main lobe with the most gain is pointed up about 45 degrees above horizontal. The low angle lobe is about 6 dB less than the high angle lobe.

 

[K9RNW]

Larsen sells the spring on it's own, and you can adapt any of their antennas to work with it.

I've had good luck with the short Larsen dual band for amateur use, but I'm mostly surrounded by hills, so having high gain antennas isn't a problem.

A simple 1/4 wave VHF antenna, as suggested, would be a good option.
1. it's cheap. You can buy them for less than $10.00
2. they don't need a spring, they are flexible enough as is.
3. they are very broad banded on VHF, a 1/4 wave VHF will easily provide less than 2.0:1 across the 144-174MHz range. Cutting for the top end of the 2 meter band will give you good performance on MURS.
4. they are 3/4 wave on UHF. I used a 1/4 wave VHF as a dual band antenna for years. Worked very well in my area. SWR was better on 70cm than it was on 2 meters.

Not sure how well it would work on GMRS, never checked it down there.

Do keep in mind that the Baofengs don't always have FCC type acceptance for GMRS, so make sure before you purchase it. They also will not have the Part 95J for MURS as they fail to meet the limitations for a MURS radio (2 watts, etc.).
If you don't already have your GMRS license, you may want to hold off for a little bit and wait for the new rule changes to go into place.

Thanks for the reply! I guess this, along my with other thread, is leading me to the conclusion that the best solution is to simply buy both VHF and UHF quarterwaves... A set of two true 1/4 waves would cost less than a "dual-band" antenna anyway. Do you have a thought on how "panoramic" sunroofs effect their operation? It seems like a lot of cars (including one of my own) are moving towards most of the roof being glass.

Though now this makes me wonder with regards to using them on-foot...will the antenna that comes with the Baofeng from suffer the same "it sucks on VHF, but is okay on UHF" (or vice versa) problem? Supposedly Baofeng is shipping their radios with better antennas these days...but who knows.

 

[mmckenna]

Thanks for the reply! I guess this, along my with other thread, is leading me to the conclusion that the best solution is to simply buy both VHF and UHF quarterwaves... A set of two true 1/4 waves would cost less than a "dual-band" antenna anyway. Do you have a thought on how "panoramic" sunroofs effect their operation? It seems like a lot of cars (including one of my own) are moving towards most of the roof being glass.

I make sure I purchase my new vehicles without a sun roof, however my wife wanted on on her Ford Escape. It's only got one panel, and as an SUV, lots of room towards the rear of the vehicle.

A ground dependent antenna will want (at least) 1/4 wave length of ground plane in all directions under the antenna to work ideally. Reality is that it'll work fine without a "perfect" ground plane. So, as long as you have some good ground under the antenna, it's going to work. You just have to work with what you have.

Two 1/4 waves (one VHF, one UHF) is a good solution, but you'll need to add a diplexer if your radio only has one antenna output. These diplexers will sap a bit of power from your signal, but having proper antennas will probably still show an improvement. This also lets you tune your antennas for the ideal frequency. If you are going to use 70cm and GMRS, tuning your antenna for something near the middle between the two is a good compromise. Trim for around 454MHz, and that'll land you between the 440MHz and 467MHz areas. If you favor one over the other, adjust accordingly. As I mentioned above, quarter wave antennas are very broadbanded, so they are forgiving when working outside their tuning points.

Though now this makes me wonder with regards to using them on-foot...will the antenna that comes with the Baofeng from suffer the same "it sucks on VHF, but is okay on UHF" (or vice versa) problem? Supposedly Baofeng is shipping their radios with better antennas these days...but who knows.

Probably. There's two things, the design of the antenna and the size of the ground plane underneath it. On VHF hand held antennas are often helically wound, which reduces efficiency,but makes it a bit more user friendly. You can get longer antennas, closer to 1/4 wave,which helps performance.
As for the ground plane, the metal frame of the radio and capacitive coupling to your hand "sort of" gives a ground plane, but it's less than ideal on VHF. One solution is to add a 19" long piece of wire to the grounded part of the antenna base. There was a company used to sell these, called "Tiger tails". They are really easy to make on your own.
On UHF, it's less of an issue as fitting a 1/4 wave UHF antenna (6 inches) onto a portable radio is easy, as is getting a ground plane.

 

[AI7PM]

Comtelco A1531. Better built commercial grade, and less expensive if you buy it through RFWIZZ.

I've used the Larsen model, and found the Comtelco more broad-banded, as well as better built.

A1531B - COMTELCO Communication Products

 

[nd5y]

Comtelco A1531. Better built commercial grade,

It might be better built but it's the same size and electrical design as the Larsen and probably just as bad on UHF.

 

[AI7PM]

It might be better built but it's the same size and electrical design as the Larsen and probably just as bad on UHF.

"..just as bad on UHF" ? Your mileage may vary. I found the Larsen worked a bit better than a 1/4 wave on UHF. Not as good as a 1/4 on VHF. I NMO mount atop a pickup truck.

My experience has been the Comtelco A1531B is better in both bands over the Larsen 2/70SH. The solid brass bottom and larger spring may be a factor. (capture?) I also like the Comtelco push pin contact over the Larsen and PCTEL flexing tab method.