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Radio Equipment Installation Forum - Forum for discussing how to install radio communications equipment in Mobile, Base, Command Post, EOC, etc configurations.

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Old 06-26-2018, 9:20 PM
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Default Looking for mount

Hello!

I am looking for a nmo mount that would be able to get mounted on this easily.
https://www.rei.com/product/789675/p...CABEgL1TfD_BwE

Let me know if you have any ideas for a nmo mount I should buy.
Thanks, kjl
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Old 06-26-2018, 9:53 PM
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I take it you don't want to drill a 3/4" hole in that and just install the NMO mount in the center?

Try mounting this on there:
https://www.theantennafarm.com/catal...s-sbt3400-3857

Keep in mind that if you are going to transmit, you'll likely want to use a half wave antenna since this sort of mount will provide a pretty lousy ground plane.
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Old 06-27-2018, 10:07 AM
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I checked out that mount, I think it would work. Do you know if it is on amazon?

Also, question:
Would there be a better way ground it?


Best Regards,
Kyle Lucas

Last edited by kjl13; 06-27-2018 at 10:13 AM..
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Old 06-27-2018, 10:47 AM
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Yes, a similar one is on Amazon, but you'll pay a lot more for it:
https://www.amazon.com/Bracket-Truck...ds=NMO+BRACKET

Grounding it to the rack with the screws and some star washers should do the trick.
The issue is that a DC ground and an RF ground plane are different things. While the mount would likely be grounded to the frame of the bike, it's not going to be a good ground plane under the antenna. To get that you'll need radials extending one quarter wavelength around the base of the antenna.
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Old 06-27-2018, 11:11 AM
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How much would not grounding it effect rx and tx.
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Old 06-27-2018, 11:20 AM
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Not having enough ground plane will have a noticeable effect on tx and rx.


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How much would not grounding it effect rx and tx.
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Old 06-27-2018, 11:21 AM
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Ok, thanks.
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Old 06-27-2018, 1:06 PM
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Tell us more about what you plan to use this mount for, then we can probably help you out a bit better.

Many antenna designs require a ground plane to work correctly. There are some that don't.

Since the size of the required ground plane will depend on which frequencies you plan on using, it's hard to give you much of a detailed answer.

Half wave antennas will work without a ground plane (although they work better with one), so that might be an option. You can also find these antennas listed by amateur radio dealers as "NGP" (No Ground Plane), and "Ground Independent". Also, be aware that having the antenna down low behind the rider will not only have some impact on performance, but if you are running more than a few watts, can expose the rider to a fair amount of RF energy.
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Old 06-27-2018, 4:02 PM
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I am going to be mounting an antenna to the mount for radio communications, I am looking for a mount that would easily mount to that bike rack above. Any other information you need specifically?
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Old 06-27-2018, 4:17 PM
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Quote:
Originally Posted by kjl13 View Post
I am going to be mounting an antenna to the mount for radio communications, I am looking for a mount that would easily mount to that bike rack above. Any other information you need specifically?
Frequencies/band, power level, radio type, budget… Those would be a few questions I'd ask.
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Old 06-27-2018, 7:08 PM
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Frequeny is 453.975, the power is 25W, the radio type is a mobile radio, if your talking about the budget for the whole project includinf radio, it is a few hundred.
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Old 06-27-2018, 7:17 PM
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OK, that helps.

So, getting a single band half wave antenna isn't a problem.
These are all suitable:
https://www.theantennafarm.com/catal...-muf4502s-8347
https://www.theantennafarm.com/catal...-nmo450chw-833
https://www.theantennafarm.com/catal...s-b4502ns-3235
https://www.theantennafarm.com/catal...es-b4502n-3231

My concern is that transmitting at 25 watts that close to a human body isn't a good thing. Ideally you'd either want to lower the power to something below 10 or 15 watts, or put the antenna up higher than the rider.
Even police motorcycles usually run 15 watts or less.
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Old 06-27-2018, 9:40 PM
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Ok, thanks for your concern. What can happen if you transmit that close to the human body with 25 watts?

Also, I am looking for a longer antenna than those, know of any?

--
Best Regards,
kjl
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Old 06-27-2018, 10:21 PM
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Quote:
Originally Posted by kjl13 View Post
Ok, thanks for your concern. What can happen if you transmit that close to the human body with 25 watts?
High doses of RF energy heats the tissue. The FCC has exposure limits to reduce the chances of this happening. Even working in the industry I try to avoid getting too much exposure, but ultimately it's up to you.

Quote:
Originally Posted by kjl13 View Post
Also, I am looking for a longer antenna than those, know of any?
Here's 20 different models to choose from, just from this dealer.
Antenna Farm is pretty good for small quantities. I've purchased from them when my quantity is below the limits with the larger dealers.
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Old 06-27-2018, 10:35 PM
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I don’t see the 20 different models, not exactly sure what your talking about,

Quote:
Originally Posted by mmckenna View Post
High doses of RF energy heats the tissue. The FCC has exposure limits to reduce the chances of this happening. Even working in the industry I try to avoid getting too much exposure, but ultimately it's up to you.



Here's 20 different models to choose from, just from this dealer.
Antenna Farm is pretty good for small quantities. I've purchased from them when my quantity is below the limits with the larger dealers.
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Old 06-27-2018, 11:59 PM
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Whoops.
Did the cut, but not the paste…

Here's what I should have added:
https://www.theantennafarm.com/catal...-antennas-215/
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Old 06-28-2018, 12:31 AM
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Quote:
Originally Posted by kjl13 View Post
Ok, thanks for your concern. What can happen if you transmit that close to the human body with 25 watts?

Also, I am looking for a longer antenna than those, know of any?

--
Best Regards,
kjl
Warming/heating of body tissues. Damage to eyes, kidneys, and gonads, are most likely. It can affect electronics, too.

Here is a publicly accessible page, from the US Navy, on the topic.

https://www.public.navy.mil/NAVSAFEC...radiation.aspx

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Old 06-28-2018, 11:08 AM
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Thanks for the info.

Quote:
Originally Posted by krokus View Post
Warming/heating of body tissues. Damage to eyes, kidneys, and gonads, are most likely. It can affect electronics, too.

Here is a publicly accessible page, from the US Navy, on the topic.

https://www.public.navy.mil/NAVSAFEC...radiation.aspx

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Old 06-28-2018, 11:39 AM
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I took a look at the options the antenna farm has, and I have come down to these two:
https://www.theantennafarm.com/catal...en-om450ck-841
https://www.theantennafarm.com/catal...-nmo450chw-833


Would you recommend either one of those in particular?

--
Best Regards,
kjl



EDIT:

Disregard that.
One of those antennas does not support a nmo mount. I will be getting the (Larsen NMO450CHW: https://www.theantennafarm.com/catal...-nmo450chw-833)
Thanks for your help.

Last edited by kjl13; 06-28-2018 at 11:42 AM.. Reason: EDIT
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Old 06-28-2018, 12:01 PM
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I've always been happy with the Larsen products. 30 years and I've never had one let me down.


The OM style mount would work, even though it's not an NMO mount. It's designed to just bolt down on a surface. So you could use it with just a length of aluminum stock and screw it down.
But I agree, go with the NMO, wider selection of antennas to choose from.
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