2 or 3 antennas?

[Twhit]

Have a tri band scanner in my truck that I have a 800 MHZ antenna and a dual band 144 and 440 MHZ. Found a nice diplexer to use for the scanner. Question. My SAR radio broadcasts on 160. Should I diplex off the dual band antenna for the SAR radio or run a separate antenna? I have a supercab F150 so only so much room on the roof.

Lastly, my County radio is handheld and broadcasts on 868. Just in case that makes a difference. Shouldn't but you never know.

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[Voyager]

Run a separate antenna. If you have VHF passing to the scanner, and you connect a VHF radio into the system, you will damage your scanner and/or the radio.

 

[Project25_MASTR]

So how many mobile radios do you have? I think it's 2 but the way you described it you may have 3.

If two, I'd run a dual band antenna for the dual banded and a tri band for the scanner.

If 3 radios…I'd do something a little different.


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[Twhit]

One scanner for RX only. Use it for County 800 and DPS 400 band when I'm out "in the weeds". One radio for TX and RX on 160 band for SAR. Need to keep antennas fairly short so truck can still get in garage so looks like a dual band and 800 MHZ antenna with diplexer for the scannner. And a second dual band for the radio I TX on. Thanks guys. Appreciate the info.

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[K5MPH]

Run a separate antenna. If you have VHF passing to the scanner, and you connect a VHF radio into the system, you will damage your scanner and/or the radio.

Like Voyager is saying run a separate antenna for the scanner radio.......

 

[Twhit]

Thanks guys. Was going to change the dual bands to the Diamond AZ504FXH. These look to me like they may be for a handheld though. Would these be good for my truck? http://www.theantennafarm.com/catalog/diamond-az504fxh-4841.html

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[Voyager]

I would think that may bend in the wind and may not recover after time. It looks like a portable antenna that has a PL259 on the bottom.

 

[Project25_MASTR]

You might look at doing something like the Larsen NMO-150/450/800 for the scanner and an appropriate dual band antenna for the two-way. Moun the tri-band over the 3rd brake light and then 19" in front of it mount either a 1/4 vhf or dual band VHF antenna.

If low profile (less than 10" of clearance) is an absolute necessity, you could also look at using Sti-Co flexiwhips in the same configuration as stated above. 1/4 wave VHF is 3/4 wave on UHF (it's not ideal for transmitting but it's a match and works great for receiving) and it'll work well enough for 800 MHz (since it's primarily LOS).

 

[K5MPH]

I would stay with the NMO Mount it's a lot stronger......

 

[Project25_MASTR]

I would stay with the NMO Mount it's a lot stronger......

Not to mention there is a lack of seals.

N is stronger than NMO but only offers a single seal and requires more space to mount (also has to be done from the underside).

NMO is a standard and offers double seals when used with commercial grade antennas, only "requires" top side access to install (head liner does not have to be removed) but it is recommended to always check what you are about to drill into.

 

[Twhit]

Thanks for everyone's help. Got called out last night for a missing child. Talking with the command post and helo on my handheld SAR and county radio was hit and miss. Good motivation to install my mobile. Last question. Given I need an antenna under 20 inches I can do either the Larsen tri band or a dedicated 890mhz antenna with a dual band and diplexer. Which will give better reception?

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[n5ims]

Use the standard NMO mount and purchase multiple antennas, some short for normal use and others longer and with gain for use when you're in those remote and hard to reach areas. Takes less than a min to swap the antenna out and they generally can be kept in your trunk or other secure area when not in use. Just remember that when you have the long antenna attached that you need to stop and swap out for the smaller one prior to pulling into a garage.

For example, for your 160 MHz coverage, you can have a quarter wave vertical (zero gain, but good local coverage) for normal use and well within your 20" height limit. For remote areas, a 5/8 wave antenna (3 dB gain) will give you extended coverage and a 36" or so height. With a bit of planning (and small amount of effort swapping antennas) you can have the best of both worlds.

 

[Project25_MASTR]

Use the standard NMO mount and purchase multiple antennas, some short for normal use and others longer and with gain for use when you're in those remote and hard to reach areas. Takes less than a min to swap the antenna out and they generally can be kept in your trunk or other secure area when not in use. Just remember that when you have the long antenna attached that you need to stop and swap out for the smaller one prior to pulling into a garage.

For example, for your 160 MHz coverage, you can have a quarter wave vertical (zero gain, but good local coverage) for normal use and well within your 20" height limit. For remote areas, a 5/8 wave antenna (3 dB gain) will give you extended coverage and a 36" or so height. With a bit of planning (and small amount of effort swapping antennas) you can have the best of both worlds.

I've yet to see a 36" 5/8 wave VHF antenna. They are generally closer to 46".

For the most part, you'll never see a difference between a mobile antenna with some gain and one without unless you are doing a lot of simplex mobile to mobile or mobile to portable work. Mobile to air a 1/4 wave would be the best solution.


If only a single antenna is to be used, I'd go with the tri-band Larsen. If two antennas (one for UHF another for VHF) I'd go with with a Sti-Co Flexiwhip and and 800 MHz knob antenna.

Of course, everyone provides a diiferent opinion and as stated one of the major plusses to NMO, it's an industry standard.