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Author Topic: 2M Mobile Antenna  (Read 2331 times)
KD8TFG
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« on: April 06, 2014, 05:57:15 PM »

I am currently using a 1/4 wave mag mount 2m antenna and looking to replace it, I am looking at either a 1/4 wave nmo mount roof top installation or an Antenna Specialists ASP-1450 nmo to be roof mounted and has 3db gain. I realize there will be no difference between the 2 hitting local repeaters, but we have a large group that run 146.520 and am curious if the 3db gain antenna will make a difference there. Both antennas would be in the center of my Chevy work van.
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W8JX
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« Reply #1 on: April 06, 2014, 06:10:17 PM »

I am currently using a 1/4 wave mag mount 2m antenna and looking to replace it, I am looking at either a 1/4 wave nmo mount roof top installation or an Antenna Specialists ASP-1450 nmo to be roof mounted and has 3db gain. I realize there will be no difference between the 2 hitting local repeaters, but we have a large group that run 146.520 and am curious if the 3db gain antenna will make a difference there. Both antennas would be in the center of my Chevy work van.

It is more than just the gain. When you get on fringes you will get less "picket fencing" of signal vs a 1/4 wave. This is because when mobile when you get to fringes the signal can have small lapses in coverage that the longer antenna will span better. It is a real phenomenon.
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KD8TFG
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« Reply #2 on: April 06, 2014, 07:20:14 PM »

Thanks for the reply that makes sense, but I have also read there would be very little difference between the 2 @ 55w 
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K5LXP
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« Reply #3 on: April 07, 2014, 06:23:43 AM »

In practice I've found the performance difference to be minimal, so maybe you could decide based on the physical differences.  A quarter wave is very inexpensive, virtually nothing to break or fail, isn't going to bang into stuff all the time and less likely to get sucked off in the car wash.  If those issues don't matter than you can run a 5/8 and get whatever incremental increase it might afford.


Mark K5LXP
Albuquerque, NM
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W8JX
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« Reply #4 on: April 07, 2014, 08:22:55 AM »

Thanks for the reply that makes sense, but I have also read there would be very little difference between the 2 @ 55w  

I used to do a LOT of 2m mobile local and cross country driving for many years. In town and shorter range a 1/4 wave is fine but on fringes and traveling a roof mounted 5/8 wave will do noticeable better. Also high power helps a LOT on fringes.
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KD8TFG
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« Reply #5 on: April 09, 2014, 05:38:24 PM »

I do alot of driving for work and many times am on fringes of repeaters and am going to go with the 3db gain antenna and see how it goes, worst case scenario it will be $50 or so wasted, heck have wasted $$ on other things in the past
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M6GOM
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« Reply #6 on: April 12, 2014, 06:36:55 AM »

Up to about 50-60 miles I've not noticed a difference between a 1/4 wave and a 5/8 wave, certainly not one that makes it worth spending money.

When it comes to repeaters, they're usually a lot higher than you so the lower take off angle of the 5/8 wave is actually a disadvantage over a 1/4 wave.

A friend of mine runs an amateur repeater and a commercial trunked system. He replaced the folded dipole he was using for a custom built 18ft long co-linear from Amphenol Jaybeam which had a 3dB gain over the folded dipole and which sits on the top of a 150ft tower which itself is 500ft ASL. Couldn't tell any difference both on RX and TX. Even on the fringe areas there was no noticeable difference.

The other thing you need to remember and which most people forget is the RADIO HORIZON. You're not going to get past that on VHF no matter how much power you throw out and around 50-60 miles is the radio horizon for most people.
« Last Edit: April 12, 2014, 06:46:38 AM by M6GOM » Logged
KD8TFG
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« Reply #7 on: April 12, 2014, 05:54:28 PM »

Up to about 50-60 miles I've not noticed a difference between a 1/4 wave and a 5/8 wave, certainly not one that makes it worth spending money.

When it comes to repeaters, they're usually a lot higher than you so the lower take off angle of the 5/8 wave is actually a disadvantage over a 1/4 wave.

A friend of mine runs an amateur repeater and a commercial trunked system. He replaced the folded dipole he was using for a custom built 18ft long co-linear from Amphenol Jaybeam which had a 3dB gain over the folded dipole and which sits on the top of a 150ft tower which itself is 500ft ASL. Couldn't tell any difference both on RX and TX. Even on the fringe areas there was no noticeable difference.

The other thing you need to remember and which most people forget is the RADIO HORIZON. You're not going to get past that on VHF no matter how much power you throw out and around 50-60 miles is the radio horizon for most people.

Thanks for the reply and I understand the radio horizon on vhf, while I do realize the 5/8 wave probably won't make a difference into repeaters, but what about simplex operation there is a large amount of Hams in my area that run simplex only will there be a difference there?  If there is even a slight difference I may try the 5/8 R and L has the Antenna Specialist ASP1450 for $42.95 with NMO and coax and work has me close to them all the time.  Any more input will be greatly appreciated especially since I am having a blast on simplex, it is great having a large simplex crowd in the area
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W8JX
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« Reply #8 on: April 13, 2014, 04:42:51 AM »

Thanks for the reply and I understand the radio horizon on vhf, while I do realize the 5/8 wave probably won't make a difference into repeaters, but what about simplex operation there is a large amount of Hams in my area that run simplex only will there be a difference there?  If there is even a slight difference I may try the 5/8 R and L has the Antenna Specialist ASP1450 for $42.95 with NMO and coax and work has me close to them all the time.  Any more input will be greatly appreciated especially since I am having a blast on simplex, it is great having a large simplex crowd in the area

I used to do a lot of simplex and 5/8 is better on fringes and better resistance to picket fencing of signal on fringes. (a 5/8 over 1/4 wave collinear is even better) Also there is a phenomenon on 2m where signal goes a bit beyond line of sight regularly but higher power on both ends is needed to exploit this. (50+ watts)
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KD8TFG
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« Reply #9 on: April 13, 2014, 09:13:48 AM »

Thanks for the answer on simplex operation, it is what I was hoping to hear

73 Gary
KD8TFG
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KD8TFG
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« Reply #10 on: April 17, 2014, 07:43:59 PM »

OK have decided on a 5/8 NMO roof mount for sure, and have narrowed down to the antenna specialist asp-1450 and the hustler bbg-144. Why those 2 you may ask ? They were both companies that started in Cleveland Ohio (am an ohioan) and at one time were very prominent in not only amateur radio antennas but commercial radio, public service mobile antennas, and both have a presence in both markets today. My choice of the 2 models listed is because they have the same ratings gain wise as well each has a spring between the coil and whip and since the antenna will be mounted in the center of a ladder rack of my work van I feel that is needed.  The cost difference is minimal I am just curious if any one has any thoughts or experience with the either antenna.

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W8JX
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« Reply #11 on: April 18, 2014, 05:15:59 AM »

OK have decided on a 5/8 NMO roof mount for sure, and have narrowed down to the antenna specialist asp-1450 and the hustler bbg-144. Why those 2 you may ask ? They were both companies that started in Cleveland Ohio (am an ohioan) and at one time were very prominent in not only amateur radio antennas but commercial radio, public service mobile antennas, and both have a presence in both markets today. My choice of the 2 models listed is because they have the same ratings gain wise as well each has a spring between the coil and whip and since the antenna will be mounted in the center of a ladder rack of my work van I feel that is needed.  The cost difference is minimal I am just curious if any one has any thoughts or experience with the either antenna.

I would pick to one with the stiffest radiator and spring. In theory you want antenna to stay as vertical as possible when driving for most consistent performance.
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