Dual band 5/8 wave?

[ClemsonSCJ]

Hey guys, I’ve searched the webs over and can’t find a NMO mount dual band antenna that’s 5/8 wave on 2m. Anybody got any suggestions?

 

[nd5y]

When you say dual band which other band besides 2 m?
A 5/8 wave 2 m antenna with a series coil will function as a 1/4 wave on 6 m. If you are looking for a straight whip 5/8 wave 2 m antenna that also works on 70 cm then that's physically impossible. The closest thing would be something like a Comet SBB-7 NMO.

 

[ClemsonSCJ]

When you say dual band which other band besides 2 m?
A 5/8 wave 2 m antenna with a series coil will function as a 1/4 wave on 6 m. If you are looking for a straight whip 5/8 wave 2 m antenna that also works on 70 cm then that's physically impossible. The closest thing would be something like a Comet SBB-7 NMO.

Sorry, I was referring to 2m/70cm dual band. I was just hoping to get a little more range out of my setup. I had put a Larsen NMO 2/70 that I was just playing on with a UV-5R until I could get a good mobile radio installed. Got a ICOM 2730A installed last week and it will easily reach out to repeaters that are 25-30 miles away. But on simplex I hooked up the UV-5R to a magnet mount dual band antenna on top of my gun safe and set up an IP camera to it to see when it was picking up and I got the exact same distance with the 50w mobile radio as I did with the 5w baofeng before it starts cutting out, which was about 3 miles, best case. I assumed that if I’m hitting repeaters at 30ish miles then my handheld should pick up at least half that distance inside my house. Or at the very least double or triple the handheld’s transmit distance.

 

[mmckenna]

I got the exact same distance with the 50w mobile radio as I did with the 5w baofeng before it starts cutting out, which was about 3 miles, best case. I assumed that if I’m hitting repeaters at 30ish miles then my handheld should pick up at least half that distance inside my house. Or at the very least double or triple the handheld’s transmit distance.

A couple of things….

I'd not rule out something with the Baofeng. They have known poor receivers and any high RF levels in your vicinity can screw them up.

As for the repeaters, they have really good antennas up high.

You limitation may not be the radio, it may be your location. Power output doesn't fix everything.

 

[alcahuete]

I assumed that if I’m hitting repeaters at 30ish miles then my handheld should pick up at least half that distance inside my house. Or at the very least double or triple the handheld’s transmit distance.

You are never going to get 15 miles simplex (or anywhere close) with an inside magmount antenna. Not going to happen. Decent outside antenna? Very doable depending on terrain and obstructions.

 

[kny2xb]

Dual Band 2 Meter/440 Mobile Antenna

Specs Gain: 2.4 dBd VHF-5.5 dBd UHF Pattern: Omni-directional Wavelength: 1/2-5/8-5/8 Elements: 2 Tuned: 144-148 & 430-450 MHz Band: VHF/UHF Rated Watts: 150 Cable: RG58U Cable Length: 17 Feet Mount Type: NMO Height: 38" Magnet Size: 3 5/8" Features Tuned to 2 Meter and 440 Ham...

dpdproductions.com

 

[jonwienke]

5/8-wave antennas have an an impedance of around 75 ohms and require a matching network, while 1/4-wave antennas (or odd multiples thereof) have an impedance of about 50 ohms. 5/8-wave at 144 is about 2 full wavelengths at 440, which means it's not going to resonate correctly, and the impedance matching network tuned for the wrong frequency band will bork things even worse. That's why such dual-band antennas don't exist.

 

[mrweather]

Dual Band 2 Meter/440 Mobile Antenna

Specs Gain: 2.4 dBd VHF-5.5 dBd UHF Pattern: Omni-directional Wavelength: 1/2-5/8-5/8 Elements: 2 Tuned: 144-148 & 430-450 MHz Band: VHF/UHF Rated Watts: 150 Cable: RG58U Cable Length: 17 Feet Mount Type: NMO Height: 38" Magnet Size: 3 5/8" Features Tuned to 2 Meter and 440 Ham...

dpdproductions.com

That antenna appears to be 1/2 wave on 2m and 5/8 over 5/8 on 70cm. Same thing as the Larsen NMO2/70.

 

[ClemsonSCJ]

That antenna appears to be 1/2 wave on 2m and 5/8 over 5/8 on 70cm. Same thing as the Larsen NMO2/70.

So the weird thing about that is DX Engineering has the Larsen NMO2/70 as a “1/2 + 3/8” wave or 1/2 wave over 3/8 wave. Do you have something you’re referencing to get that spec?

 

[mrweather]

So the weird thing about that is DX Engineering has the Larsen NMO2/70 as a “1/2 + 3/8” wave or 1/2 wave over 3/8 wave. Do you have something you’re referencing to get that spec?

My mistake, a Larsen antenna book I have from 2005 lists the NMO2/70 as a centre-loaded 1/2 wave on VHF and collinear on UHF.

But the Larsen has almost the same physical length as the dpdproductions listing (37 1/4" vs 38") suggesting it's electrically the same.

 

[nd5y]

So the weird thing about that is DX Engineering has the Larsen NMO2/70 as a “1/2 + 3/8” wave or 1/2 wave over 3/8 wave. Do you have something you’re referencing to get that spec?

Get your specs from the manufacturer not dealers. Even then you need to be suspicious of published specs sometimes.
I have never see a NMO2/70 described as a “1/2 + 3/8” on 2 meters.

 

[jonwienke]

How exactly is 3/8 wave going to resonate correctly?

 

[ClemsonSCJ]

Get your specs from the manufacturer not dealers. Even then you need to be suspicious of published specs sometimes.
I have never see a NMO2/70 described as a “1/2 + 3/8” on 2 meters.

It’s listed as “1/2” on 2 meter and “1/2 + 3/8” on 70cm. Not 2m.

 

[jonwienke]

It’s listed as “1/2” on 2 meter and “1/2 + 3/8” on 70cm. Not 2m.

That's obviously wrong, because the ratio between 2m and 70cm is very different than the ratio between (1/2) and (1/2 + 3/8).

 

[ClemsonSCJ]

That's obviously wrong, because the ratio between 2m and 70cm is very different than the ratio between (1/2) and (1/2 + 3/8).

Yeah everything else I’m looking up has “collinear” listed under the UHF frequencies which I take to mean 2 x 5/8.

So assuming I wanted to run 5/8 on both VHF and UHF, has anyone had any success utilizing a duplexer like the comet duplexer to use a single dual band radio on 2 separate antennas?

 

[jonwienke]

So assuming I wanted to run 5/8 on both VHF and UHF, has anyone had any success utilizing a duplexer like the comet duplexer to use a single dual band radio on 2 separate antennas?

That is common standard practice. There are plenty of options to split UHF and VHF to separate antennas.

 

[nd5y]

So assuming I wanted to run 5/8 on both VHF and UHF, has anyone had any success utilizing a duplexer like the comet duplexer to use a single dual band radio on 2 separate antennas?

You can do that but it's probably a waste of money.
On a vehicle you are not going to see a noticeable performance increase between a NMO-2/70 and separate 2 m 5/8 wave and 70 cm collinear antennas.

 

[ClemsonSCJ]

You can do that but it's probably a waste of money.
On a vehicle you are not going to see a noticeable performance increase between a NMO-2/70 and separate 2 m 5/8 wave and 70 cm collinear antennas.

I’ll admit my knowledge on this, while progressing, is super fresh and limited. However from the reading I’ve done and applying it to my environment, I can’t imagine why 70cm performs exponentially better than 2m, yet it does. I’m going to do some more testing to make sure I’m getting accurate results, but I’m getting 2-3x, possibly even more distances out of 70cm than 2m. This is in an area with far more land/woods than houses and rolling hills, not much else, and my SWR is also much better on 2m than 70cm. The only factor that I can think of is that the antenna I have now is radiating more towards the horizon on 70cm and on 2m its strongest radiation is into the open air where no receiving antennas are located. Again, super limited understanding on this stuff so feel free to tell me if I’m sounding like an idiot and reaching. I won’t get my feelings hurt.

 

[jwt873]

On a vehicle you are not going to see a noticeable performance increase between a NMO-2/70 and separate 2 m 5/8 wave and 70 cm collinear antennas.

I can confirm this I have several vehicles equipped for ham radio (and I like collecting things), so I have more than one mobile antenna. As below:

Larsen 2/70 dual band,
Larsen 2 meter 5/8 wave
PCtel MUF4305 UHF collinear
NMO 1/4 Wave for 2m
NMO 1/4 wave for 70cm
NMO 1/4 wave for 220

There isn't much difference at all between the 2/70 and the 5/8 on 2 meters. On the highway the 2/70 is a bit better than the 2 meter 5/8. Perhaps because the wind doesn't bend it over as much.

The 440 collinear is a 5/8 over 1/4 wave with a claimed 5 dBi gain. For UHF performance, I see little difference between it an the Larsen 2/70.

So, out of my collection above, I find the Larsen 2/70 has been the best all around performer. (The quarter wave antennas are for when I want to travel light).

 

[WB9YBM]

Hey guys, I’ve searched the webs over and can’t find a NMO mount dual band antenna that’s 5/8 wave on 2m. Anybody got any suggestions?

How 'bout some kind of signal splitter, then feed two different antennas?