2M Antenna Recommendations?

Mashurst

Adventurer
Hi Gents: Long story short, I have an extra antenna on my sprortsmobile which I believe to have been used for HAM radio...
...we use a public safety frequency I have access to (without repeaters) in the 165.000 range.
Assuming it is a HAM antenna tuned for the 2m band 144-148MHz, the answer is yes but not very well. It will probably "hear" better than the handheld inside the vehicle would but it may not get out any better. Also, running that far out of tune has at least some potential to damage the radio. Antennas are cheap and the hard part is running the coax. I would just swap it out for one that is tuned for 165MHz. Alternatively, you may be able to extend it depending on the design.
 

Shoeman

Observer
Thanks Lumpy. Great job of giving a novice the nuts and bolts info needed when shopping for an antenna. You also reminded me that I need to upgrade from my 1/4 wave on my 2M rig.

Geoff
 

Mashurst

Adventurer
Craig,
I think there is some good information here. Thanks for taking the time to put it out here for us.

I do not claim to be an expert but I do question the negative gain on a 1/4 wave. Specifically that half the wire in the air necessarily means 3db loss.

Removing half of the antenna metal reduces the "antenna apeture" by 50%, which results in a 3db loss. Subtract 3db from the dipole gain of 2.15 and you have -0.85 db gain (a loss of .85 db below zero). It's not only half the performance of a dipole, it's below the zero point of that theoretical isotropic radiator.
...The other half of the signal is "thrown away" as ground...
Where does the power go? If it does not come back down the coax (bad SWR), where is it going? Law of conservation of energy and all. Absorbed by the ground plane and turned into heat? The plane must be reflective to work. If all it is doing is, as you posit, "throwing away" or absorbing half the signal, would not the antenna work better without a ground plane? Surly it is being reflected in order to achieve a workable standing wave by "mirroring" the other half of the waveform. Does not the ground plane then becomes part of the aperture? It seems to me that a theoretically perfect plane would not have the 3db loss you assert, but rather that the loss would be a function of the planes inefficacy in reflecting the image of the driven element.

On a somewhat unrelated note; from Personal experience, I can say that higher gain verticals are not always preferable. I generally run the Comet SS-680SB (listed as 2.1 dBi 1/2 wave) on my jeep because it is physically short and the spring makes it very robust but I also carry the longer, higher gain SBB-7 (listed as 4.5dBi 6⁄8 wave center-load) both for redundancy and for mountain top simplex work. From a clear vantage point, the SBB-7 is remarkably better at reaching distant stations but as soon as I come off the mountaintop, it is noticeably less effective at reaching even nearby repeaters. Driving next to a hill will completely block a repeater that I could reach from that same spot with the shorter antenna for instance. My theory is that because the higher gain radiates in a lower, narrower pattern it is causing more power to be absorbed by the near field terrain such as hills and trees. The lower gain half wave sends more power up and over the hills where they have a chance to be reflected or refracted back down toward the listening repeater. In my testing, in addition to being much more practical due to its length, it is a much better radiator for everyday use in the woods.
 
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Uncle Beer

Observer
Damn. I feel informed now. Is this the kind of knowledge that I will receive while studying for my extra?


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Bbasso

Expedition Leader
New to the boafeng radio...
I'd like to listen to more but the stock antenna doesn't cut it.

What 36inch antenna (longest that fits) would be best for mounting on my van's roof?
Also what cable would be needed to connect?

Thanks!
 

MobTuff

Observer
New to the boafeng radio...
I'd like to listen to more but the stock antenna doesn't cut it.

What 36inch antenna (longest that fits) would be best for mounting on my van's roof?
Also what cable would be needed to connect?

Thanks!
I've had great luck with the LARSEN 2/70B. You can see it here. The data sheet is here. It's an NMO style base not a mag mount and is about 35 inches tall.

It's the best dual band antenna I've owned. Very impressive performance.
 

k9lestat

Expedition Leader
I have a a almost 10 in mag mount from my bfang ht. It hits the 2m repeater about 25 miles from my house. And received traffic from repeaters almost 90 miles away. Of course I couldn't transmit to them but they came through crystal clear.

Sent from my QMV7A using Tapatalk
 

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AA1PR

Disabled Explorer
New to the boafeng radio...
I'd like to listen to more but the stock antenna doesn't cut it.

What 36inch antenna (longest that fits) would be best for mounting on my van's roof?
Also what cable would be needed to connect?

Thanks!
NMO body mount is best if you can do that
I have the comet SBB5 which is about 38" & its an amazing antenna so far
& with regards to the HT antenna I've been using nagoya NA771's for all my HT's though they're about 15.5" overall, on my wouxon I keyed up a NY rpt 40 miles away with that antenna

just make sure you get the real McCoy when you buy one since theres so many chinese knockoffs
 

Bbasso

Expedition Leader
Would you mind if you provided links to what fits my needs best?

Nearly one inch thick fiberglass roof or Thule roof rack to mount on. 10 ft length of wire/cable.
 

WhiteH2O

Observer
Quick question:
.
I'm running a 2m/70cm unit currently with a small whip antenna (SBB-1NMO) mounted front and center on a 6'x4' expedition rack with expanded metal floor (ground plane?) that doesn't have a good ground to the vehicle.
.
How big of a difference would a better antenna get me? I originally got this antenna with the idea that it would be good around town and for simplex on group runs, but I'm heading on a trip soon, and I'm debating if I should spend the money on a better antenna since I'll be more in the middle of nowhere and I want to be able to reach out if need be. I've been eyeing a Larson NMO-2/70B, but I can't find good info that can help me decide if it would be worth the $70, or would it be only slightly better than my current set up.
.
Any thoughts/recommendations? Would my rack act as a good enough ground plane that I don't need a half wave antenna- making a different antenna a better option perhaps?
 

MobTuff

Observer
Quick question:
.
I'm running a 2m/70cm unit currently with a small whip antenna (SBB-1NMO) mounted front and center on a 6'x4' expedition rack with expanded metal floor (ground plane?) that doesn't have a good ground to the vehicle.
.
How big of a difference would a better antenna get me? I originally got this antenna with the idea that it would be good around town and for simplex on group runs, but I'm heading on a trip soon, and I'm debating if I should spend the money on a better antenna since I'll be more in the middle of nowhere and I want to be able to reach out if need be. I've been eyeing a Larson NMO-2/70B, but I can't find good info that can help me decide if it would be worth the $70, or would it be only slightly better than my current set up.
.
Any thoughts/recommendations? Would my rack act as a good enough ground plane that I don't need a half wave antenna- making a different antenna a better option perhaps?
It will make a huge difference. I used to run a small 1/4 wave antenna on my truck just like your SBB-1NMO. I upgraded to the Larsen 2/70 and it's a world of difference. Especially for simplex. On the trails with the 1/4 wave I had to almost always have pretty clear line of sight. Now with the 2/70 I can be behind a pretty large hill and have no issue at all. Also the Larsen 2/70 doesn't really need a ground plane. That 1/4 wave you're running probably doesn't have a great ground plane. It's definitely worth the upgrade no doubt about it.
 
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