Mobile 2 meter antennas

[Turbo T]

I'm considering studying for my tech license to operate on the 2 meter band. When I finally get my ticket, my goal is to install a 2 meter radio in my pick up truck.

A few questions I have to ask...

1. How tall is a 2 meter antenna required to be for a proper operation on a vehicle? (if this sounds like a wierd question, consider a CB requires a true 108 inches to work correctly...how many required for a 2 meter to work correctly on a vehicle)

2. Do most mobile mount 2 meter antennas work the same way as a CB antenna? Meaning when you transmit the antenna requires a ground plane as "the other half of the antenna"?

3. Do 2 meters require an SWR check when setting up like a CB does? If so can I use an SWR meter (that I use for CB antenna tuning) to check the SWR's on a 2 meter radio antenna?

4. Do 2 meter radios use the same SO-239 connectors and PL-259 connectors like a CB does?

 

[74IN]

1 About 19 1/4 inches.

2 Yes

3 You need a meter that is capable of VHF.

4 Yes, but some use NMO or LM mounts for the antenna but will accept a PL 259 and the radio will as well.

Larsen makes very good antennas for your need. A 1/4 wave whip will work fine as well.

 

[W5LZ]

'74IN' answered your questions, this just expands on those answers...

1. A 1/4 wave at 2 meters is about 19 inches long, considerably shorter than that 102 inches at 11 meters. (About 2.5 times that 19 inches, about 48 inches, would be a 5/8 wave length at 2 meters.) How many would you need? For typical communications use, you'd need at least one antenna.

2. All antennas require at least two 'terminals', a (+) and a (-), to work. That "groundplane" can be almost anything, another 19 inch conductor, the metal of the vehicle's body, or even the feed line in the case of those 'NGP' antennas.

3. A 2 meter antenna, just like any other antenna, should be 'tuned' for resonance and a good impedance match with the feed line and transmitter (SWR). Since 2 meters is such a high frequency, adjusting for it is a bit more 'touchy' than for low frequencies, the differences are much smaller. A quarter inch one way or the other at 11 meters isn't as bad as it can be at 2 meters. A typical SWR meter made for HF probably won't do well at VHF.

4. Do 2 meter radios use the same SO-239 connectors and PL-259 connectors like a CB does? In general, yes they do, but there are other type connectors that might also be used. That's both for antenna mounting and just connecting things.

And to touch on a few other aspects, the same modes are used as with other bands, AM, SSB, FM, and a bunch of 'digital' modes. It's not as common to find an 'all-mode' VHF/UHF radio as it is with the HF bands, more of them are FM, less capable of the typical HF modes like AM and SSB. They are around, just not as common since there are a lot of repeaters on 2 meters that only use FM mode. Output power isn't a huge biggy on VHF/UHF bands. Antenna height above ground will make much more difference than higher power. That's because 2 meters really is a 'line of sight' band. Various things can 'block' VHF/UHF signals much more than at HF. that's another reason why a higher antenna that can 'see' over things, makes much more sense than just bumping up the power.
There are lots of differences between HF and VHF/UHF. None of them particularly 'hard' to manage, they're just different, not what 'HF people' are used to. It can be a lot of fun, and can cause a few head-aches until you figure out what those 'differences' are.
- 'Doc

__________________

 

[kd-5-bgt]

Looks like all your questions have pretty well been covered....

For a 2 meter antenna I would recomend a Larson nmo-150 for a good single band antenna.I have used one for years and I really do like it.A Mag mount will help simplify thye set up

There are several 2 meter antennas to choose from,but for me personally that one is my favorite

and good luck on passing your test

 

[Turbo T]

Thanks. Yes this did answer my questions.

I do want to ask the real difference between 1/4 and 5/8 wave besides the physical lengths? I see this all the time and never could figure it out...I'm going to guess one is better than the other in terns of TX and RX?

Once I got my ticket, I wanted to try to do a hard mount if at all possible. Coming from the 27 mHz CB side of the house, I was after seeing if anyone makes a solid one piece non coil style antenna, similar to a 102 whip. Obviously shorter though.

Also does the "height is might" rule apply on 2 meter antennas?

Thanks!

 

[kd-5-bgt]

"height is might" does apply to the base antennas for 2 meter ....

Mobile...not so much since 2 meters uses repeaters most of the time to extend their range

 

[W5LZ]

Probably the biggest difference in the performance of a 1/4 wave and a 5/8 wave antenna is the shape of the radiation pattern. The 5/8 wave tends to have a 'flatter' pattern, which can certainly be advantageous at times. They all use some type of matching coil, usually at the base, and not large at all.
A 1/4 wave antenna (that 19 inch thingy) doesn't normally use any matching coil, it's just a straight 'stick'/wire. It tends to have a shorter 'range' than a 5/8 wave antenna, which isn't a huge liability at times. Which you might use is a matter of 'taste' and needs.
That 'hard mounting' is the way to go with any antenna is you can. If you can't, do what you can.
- 'Doc

 

[ranger56528]

I have a radio shack 6m,2m,70cm mag mount that works ok with my T70A but just orderd a MFJ-1729 to try out in my other veh also ordered a TM-271A 2m rig to go with the MFJ-1729.

 

[Turbo T]

Thanks, what hard mount 2 m antenna do you prefer?

 

[kd-5-bgt]

For me personally I am sold on Larson ....the NMO-150 antenna has at least 3 different mounts...mag mount,trunk lip mount and a trunk mount that requires screws to make it solid,oh yea,the hard mount that you have to drill a hole as well...I have used the mag mount and the trunk mount that requires screws and they both work great !!

There are more brands of antennas out there that will work just fine..Diamond,Hustler,Comet just to name a few.... all of them are good solid antennas.

Take your time and do your homework to find the antenna/mount that will work for you

 

[office888]

I use an MFJ-1728B base loaded 5/8 wave 2m antenna.

It's about the size of an atypical CB antenna, and the range on it is unbelievable.

It works great for simplex and repeaters...If you're talking to bases, or off of repeaters, 10w is all you need with a 5/8 wave!