Vehicle Antenna & NMO Magnetic Mounts Recommendations for BC125AT

[pcgeek]

Hi all,

I know the Diamond RH77CA antenna is the gold standard for the BC125AT scanner but I'm looking for an antenna and a NMO magnetic mount that can be easily attached to and removed from the roof of a rental car.
My frequency range of interest is 150-174 MHz and 410-470 MHz.

By the way, for those who have used vehicle antennas/magnetic mounts in the past, did you have any problems running the cables through the door seal? Will heavy rain cause leaks?

Thanks in advance!

 

[Kiniutech]

Good place for you to start here
https://www.theantennafarm.com/catalog/index.php?main_page=index&cPath=191_192
https://www.theantennafarm.com/catalog/index.php?main_page=index&cPath=264

I am using Lasen and Laird NMO Tri-band antennas on my vehicles,

 

[vagrant]

The Larsen NMO150/450/758 is a good choice to use with an NMO magnet mount base and the frequencies you wish to monitor. As to coax and door seals, I have never had an issue but there are vehicle differences. I have that antenna and it works well. Put it on the top middle of the roof and it should work for you too. You may want to consider an inline filter to block broadcast stations as well. It is not that you may hear the station audio/music while using your scanner, but they can increase the noise floor ( hiss ). Still, if you can hear what you want without the filter, you're set.

As for a rubber duck on the BC125AT, I use a Diamond RH951S as it has improved resonance on VHF and other frequencies over the RH77CA. It notes 2m, 70cm, and 23cm, but it also plays well around 1.25 meters. It uses a BNC connector which is what the BC125AT has.

 

[n5ims]

The Larsen NMO150/450C is the commercial version of the ham NMO 2/70. You will need the NMO mag mount that is in two styles. The NMOMMRxxxx (xxxx indicates the connector type) that is round and has the newer style "HF" NMO mount that will work with the older tab style NMO antennas or the newer pin type antennas. The older NMOMMxxxx (as above xxxx indicates the connector type) is rectangular and has the older style NMO mount that only works with the older tab style NMO antennas. It would be best to get the "HF" style so your mount will work with either style antenna. Please note that "HF" in this instance doesn't mean the ham HF bands, but is Motorola's way of indicating antennas that work on the higher frequency bands. Initially this was the 800 MHz and higher antennas but now is any antenna using the NMO mount with the pin type connection (vs the older tab mount style).

The cable are generally some quality RG-58 that will work fine in most cases. Just be careful when closing the door that the cable goes through or you can pinch it and cause damage. Also place it on a door that will not be opened except when routing the cable as each time you close the door with the cable there will pinch it a bit and eventually will damage it. Note that there are some special order versions that use dual shield coax or LMR-200 coax but these are hard to find and much more costly. Unless you are on 800 MHz or higher, you won't notice any difference over the 15' coax length with the pricier and hard to find coax versions.

If you are careful when closing the door with the cable routed through it, you shouldn't have any serious issues. The rubber door seal should seal the weather out and other than the issue stated above shouldn't cause any real issues. Just be aware that a mag mount is designed for temporary use only and extended use can cause damage to the paint and coax. Also note that a mag mount will only work on steal vehicles and will not work on aluminum (think Ford Trucks for starters) or fiberglass panels that you may find on some less common vehicles (like campers or sports cars).

Please note that there may be different versions of the NMO150/450C sold. You will want the commercial version due to the commercial band frequency range indicated. Some may try to sell you the ham version instead. They will work on receive but not quite as well and there are 3 different models available with different specs (short, open coil, and closed coil). The short has little or no gain (similar to the 150/450/800 (the 800 may be 758 for the newer HF style while the 800 is generally the NMO tab mount) so unless length is a real issue, I'd go for the gain of the 150/450C.

 

[a417]

If you are careful when closing the door with the cable routed through it, you shouldn't have any serious issues. The rubber door seal should seal the weather out and other than the issue stated above shouldn't cause any real issues. <snip>

pick a door that you are most unlikely to open and route it thru that. Drivers door = bad, passenger rear door if you're the only one in it = good. Ya know?

 

[mmckenna]

Also note that a mag mount will only work on steal vehicles….

I would highly discourage you from "stealing" a vehicle for this.

 

[n5ims]

I would highly discourage you from "stealing" a vehicle for this.

I don't want MY vehicle's paint to be ruined by the mag mount so I was thinking that stealing a steel auto might help.

 

[pcgeek]

The Larsen NMO150/450/758 is a good choice to use with an NMO magnet mount base and the frequencies you wish to monitor. As to coax and door seals, I have never had an issue but there are vehicle differences. I have that antenna and it works well. Put it on the top middle of the roof and it should work for you too. You may want to consider an inline filter to block broadcast stations as well. It is not that you may hear the station audio/music while using your scanner, but they can increase the noise floor ( hiss ). Still, if you can hear what you want without the filter, you're set.

As for a rubber duck on the BC125AT, I use a Diamond RH951S as it has improved resonance on VHF and other frequencies over the RH77CA. It notes 2m, 70cm, and 23cm, but it also plays well around 1.25 meters. It uses a BNC connector which is what the BC125AT has.

Thanks for the recommendations! Is there anything that I need to pay attention to when choosing a NMO magnet mount?
I'll also look into the RH951S handheld antenna.

 

[pcgeek]

The Larsen NMO150/450C is the commercial version of the ham NMO 2/70. You will need the NMO mag mount that is in two styles. The NMOMMRxxxx (xxxx indicates the connector type) that is round and has the newer style "HF" NMO mount that will work with the older tab style NMO antennas or the newer pin type antennas.

Thanks for the suggestions!
How about the Larsen NMO150/450/758 as recommended by another forum member? Is the commercial grade Larsen NMO150/450C any better?
I believe the Larsen NMOMMRBNC should be compatible with both the newer and older style NMO mounts.

Just be aware that a mag mount is designed for temporary use only and extended use can cause damage to the paint and coax. Also note that a mag mount will only work on steal vehicles and will not work on aluminum (think Ford Trucks for starters) or fiberglass panels that you may find on some less common vehicles (like campers or sports cars).

Thanks for the heads up! Yes, I intended to use them as a temporary solution for rental cars but still, I wouldn't want to damage the paint. I'll also look up the roof material of the rental cars. What are the other temporary mounting options if I get a rental car with an aluminum top?

 

[vagrant]

Thanks for the recommendations! Is there anything that I need to pay attention to when choosing a NMO magnet mount?

Avoid a lot of leftover coax. They often come with 10-15 feet of coax which should be fine for dropping a wire inside. As to different size NMO magnet bases, a 3 inch or more base should hold that antenna, but for a few extra dollars, a 5 inch size would be prudent. Also, that particular model antenna has a spring and would flex should it hit a branch or something. The larger magnet base also comes into play when that happens.

You will typically need an SO-239 to BNC male adapter as well that connects to the end of the coax. The BNC part connects to your scanner.

 

[GROL]

This antenna is pretty amazing. Browning BR-137. It needs a strong 4 inch or more magnetic mount. It looks weird and is quite heavy at the base, but being short there is not a tremendous amount of wind load. https://www.theantennafarm.com/cata...oduct_info&cPath=191_192_466&products_id=8937
Also available on Amazon. Amazon.com: Browning BR-137 Tri-Band High Gain Antenna 22 inch VHF 136-174 UHF 380-520 & 698-960 MHz 3/4 inch NMO Connector for all VHF UHF Mobile Radios: GPS & Navigation


I use it on my vehicle as a broadband scanner antenna. It is more broadband than I expected. In the advertised bands it is no more than 2:1 VSWR down to near 1.2:1. From 118 MHz through 870 MHz it is no more than 4:1 on the antenna analyzer, and reception is very good in the entire range. I get better than expected reception with 150-170 MHz, 700/800 Mhz plus the civilian and Mil Air bands.