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General Antenna Question


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#21 zap

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Posted 20 January 2015 - 11:37 AM

I actually have two (if you want to really get into the reasoning of why that particular antenna is installed where it is)…the other was on my Trailblazer, on the roof. One night I was coming down a dimly lit city street and hit the antenna a little more than half way up on a low hanging tree branch traveling roughly 15 MPH, which is frankly slow to me. By then, the damage was done. The antenna had actually pulled the NMO mount out of the roof of the vehicle. 

 

Notice now, Comet sells a spring for that antenna. I guarantee you I'm not the first one who has pointed out to them (out of first hand experience) that the antenna they market as a Search and Rescue antenna, is way too stiff to be useful in a real Search and Rescue environment. They may have also been looking like they were facing several lawsuits. 

 

Back to the antenna being on my Trailblazer. While it was on the roof, I actually took the time to hook the antenna up to an analyzer and the results I got, are what I quoted in my previous post. 

 

Now back to where that antenna happens to be on my Jeep. I'm not sure if you've ever spent a lot of time in heavily wooded areas, especially driving vehicles through them, but you're always gonna hit antennas on something. After witnessing what happened to the roof of my daily driver, I carefully picked a mounting location that would both be sturdy enough for that antenna (until I found a different antenna solution that would suit my bandwidth needs). So I chose to sacrifice some signal to mount the antenna on something much more sturdy than the roof. I might also add, the only current use for that VHF 1/4 wave antenna on the roof of that Jeep, is for an APRS tracker I have in that Jeep.

 

Here is another interesting little tit bit to look at. A quarter wave antenna (VHF or UHF) cost roughly $5-12 (or I can even get a Larsen NMO150WB for $30). My wideband UHF knobs, $30. The last CA2x4SR I bought cost roughly $75. However, if roof mounted, the CA2x4SR can cost you several hundred dollars at a body shop if one was to hit the antenna on something in the right spot. For the other options, you'd be worrying about dragging the roof before you ever even considered the antennas doing damage to the roof from snagging on something.

 

That is the primary difference between commercial antennas and amateur antennas. Commercial antennas are designed to take a beating through a parking garage, in the woods, over rough terrain, even survive a roll over. You break a base, you can usually buy a base without buying a new antenna. You snap a whip, you can generally get another for less than $10. You just don't get that kind of quality out of an amateur antenna, and you definitely don't get that out of the 2x4SR.



#22 roadrunnernm

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Posted 20 January 2015 - 01:18 PM

Zap, 

 

Would you please post the make and model of your  " My wideband UHF knobs".  I'd like to see a picture of it. 

 

Thanks in advance.



#23 zap

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Posted 20 January 2015 - 02:27 PM

MLPV430

About a few inches smaller than a 1/4 wave 450-470MHz antenna.

88f265ff22f14183171c7ff060ecf318.jpg


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#24 DoctorZ

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Posted 21 January 2015 - 02:04 AM

I actually have two (if you want to really get into the reasoning of why that particular antenna is installed where it is)…the other was on my Trailblazer, on the roof. One night I was coming down a dimly lit city street and hit the antenna a little more than half way up on a low hanging tree branch traveling roughly 15 MPH, which is frankly slow to me. By then, the damage was done. The antenna had actually pulled the NMO mount out of the roof of the vehicle. 

 

Notice now, Comet sells a spring for that antenna. I guarantee you I'm not the first one who has pointed out to them (out of first hand experience) that the antenna they market as a Search and Rescue antenna, is way too stiff to be useful in a real Search and Rescue environment. They may have also been looking like they were facing several lawsuits. 

 

Back to the antenna being on my Trailblazer. While it was on the roof, I actually took the time to hook the antenna up to an analyzer and the results I got, are what I quoted in my previous post. 

 

Now back to where that antenna happens to be on my Jeep. I'm not sure if you've ever spent a lot of time in heavily wooded areas, especially driving vehicles through them, but you're always gonna hit antennas on something. After witnessing what happened to the roof of my daily driver, I carefully picked a mounting location that would both be sturdy enough for that antenna (until I found a different antenna solution that would suit my bandwidth needs). So I chose to sacrifice some signal to mount the antenna on something much more sturdy than the roof. I might also add, the only current use for that VHF 1/4 wave antenna on the roof of that Jeep, is for an APRS tracker I have in that Jeep.

 

Here is another interesting little tit bit to look at. A quarter wave antenna (VHF or UHF) cost roughly $5-12 (or I can even get a Larsen NMO150WB for $30). My wideband UHF knobs, $30. The last CA2x4SR I bought cost roughly $75. However, if roof mounted, the CA2x4SR can cost you several hundred dollars at a body shop if one was to hit the antenna on something in the right spot. For the other options, you'd be worrying about dragging the roof before you ever even considered the antennas doing damage to the roof from snagging on something.

 

That is the primary difference between commercial antennas and amateur antennas. Commercial antennas are designed to take a beating through a parking garage, in the woods, over rough terrain, even survive a roll over. You break a base, you can usually buy a base without buying a new antenna. You snap a whip, you can generally get another for less than $10. You just don't get that kind of quality out of an amateur antenna, and you definitely don't get that out of the 2x4SR.

 

I live in the woods, but trim my trees when the antennas start clipping them.  I've also done a fair amount of four-wheeling, but take the antennas off for that.  If I'm upside down, I can then put them on the undercarriage and call for help. LOL.  I mainly use my radios for Storm Chasing and SkyWarn Spotting, hense I need a little bit of gain.

 

So where do you find a commercial equivlent to the 2x4SR?



#25 zap

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Posted 21 January 2015 - 11:44 AM

You don't. You either sacrifice the widebanded-ness for something like a Larsen nmo2/70 or go to something like a Larsen NMO150WB (wideband vhf 5/8 wave) and a wideband uhf antenna.

I live in an extremely flat area. Storm chasing, never needed an antenna with gain.

Our skyward guys have a decent uhf link system. Covers something like 10 counties.


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#26 PastorGary

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Posted 22 January 2015 - 01:03 PM

Just a reminder - The Tri-Band Larsen NMO150/450/800 is a very competent antenna for dual or tri-band radios. We have one of these on a Chaplain Responder vehicle in Alabama and it works as well or better than individual 1/4 wave antennas in each band.

 

Link >>>  http://www.theantenn...0-800-1050.html

 

And, of course, it is excellent to be used with a digital scanner in a mobile application.



#27 DoctorZ

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Posted 24 January 2015 - 12:09 PM

You guys and your Larsen antennas......I guess whatever other type of antenna I buy, it wouldn't be a Larsen.  Speaking of antennas, my new GMRS Repeater antenna came yesterday!  I won't be able to put it into operation until Spring though.  Too much snow on the ground right now.



#28 zap

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Posted 24 January 2015 - 12:10 PM

What antenna did you get for your repeater? I'm still working through a pile of surplused dB antennas so I haven't had to purchase one yet.


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#29 deputycrawford

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Posted 27 January 2015 - 04:02 PM

     I have been told by a radio specialist that the 1/4 wave antenna has the flatest radiation take off angle. The 5/8 wave might give you that extra mile or so at the edge but the take off angle is higher. I have run them both on NMO mounts. I have not seen a difference so the 1/4 wave stays on. A little 6in or so 1/4 wave on a magnate mount NMO with 6 in or so of ground plan will do you well. The center of the roof is best in my opinion. I have a clip on NMO on the trunk of my convertible and drilled a hole in the roof of my truck. What can I say, I'm a diehard. I've drilled holes in many of my cars.

 

Jerry






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