• A.S. MONR51 mag mount antenna Q's

  • Discussion related to railroad radio frequencies, railroad communication practices, equipment, and more.
Discussion related to railroad radio frequencies, railroad communication practices, equipment, and more.

Moderator: Aa3rt

  by Agent at Clicquot
 
Hi all

I've got an Antenna Specialists MONR51 mag mount antenna. Bought it at least ten years ago. Finally retired it last summer when the mag mount was so deteriorated it couldn't hold at highway speeds.

I have the instruction sheet that came with the unit ... any sense in tracking down a replacement mag mount ... or should I just replace it?

Some questions for the techies:
- as the mag base fractured, wouldn't that cause a reduction in contact to my car's roof?
- would that contribute to decreases in sensitivity?
- does the ball at the tip play a role in the antenna's ability to receive, or is it a protective device?
- is there a downside to leaving the antenna mounted year around, subject to Boston, MA's weather?

Thanks!

* JB *

  by kr4bd
 
:-) :-)

I will try to respond to your questions about your antenna. I am sure you will get other input on this.


-as the mag base fractured, wouldn't that cause a reduction in contact to my car's roof?

Yes, but I don't think this would affect performance as long as it was still mounted against the roof. If tipped over, it definitely would not work well.


- would that contribute to decreases in sensitivity?

No. What I would be more concerned with is the condition of your coaxial cable after 10 years. As coax ages, and especially in magmount mobile situations, it is subject to wear-n-tear. If moisture gets inside, the cable and connectors will corrode and negatively affect performance. Ideally, you want to use well shielded, high quality cable. I generally find that after 10 years weathering in the elements, it is time to replace the cable.


- does the ball at the tip play a role in the antenna's ability to receive, or is it a protective device?

This is purely to prevent you from poking out your eyes.


- is there a downside to leaving the antenna mounted year around, subject to Boston, MA's weather?

Maybe. If the magnet is not holding well, the antenna will wander around your car's roof as you drive. Dirt, salt, etc., will get under it and scratch the paint on your car. I use magmounts all the time, but put adhesive, protective mounting pads on the roof of the car where the antennas are mounted to prevent scratching. Some magmounts will come with these pads.

Overall, I would just pitch your antenna if you think it can't be easily fixed. Radio Shack sells antennas that can be tuned (cut) for the Railroad Band (160-161 mHz). I would think that such antennas could be secured for under $25. If you have ham radio flea markets or vendors in your area, you might try getting one there. Ham operators would be able to show you how to adjust it for the frequencies you want to monitor. For the railroad band, this should be somewhere around 17 to 18 inches for a quarter-wave, groundplane, magmount antenna.
  by Agent at Clicquot
 
Tom

I'm going to call the manufactuer to see if they'll sell me (or tell me where I can obtain) a replacement base. FWIW, this unit comes with a new wire.

If that doesn't pan out, I'll ponder a replacement.

Thanks for you reply. :-)

* JB *

  by Ken W2KB
 
You could also try www.hamradio.com - they carry replacement parts, as well as complete antenna assemblies.