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Author Topic: Looking for advice on portable kit  (Read 2592 times)
JSW31
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Posts: 1




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« on: February 23, 2012, 01:12:16 AM »

First off, I must apologize because this will not be for amateur radio use. I am not a ham (yet!) because the day my test was scheduled (back when there was a technician plus) my grandpa died. I never scheduled another test and forgot a lot of the exam material. One day... I currently work in an emergency communications center and am trying to put together a proposal for a kit we can use both for emergency outages and building evacuation scenarios. The box would be plugged in to both roof mounted antennas and line power while in the communications center, but able to be packed up and taken mobile fairly quickly. I have been doing some research and checking out a lot of ham operators' wonderful boxes for ideas and I think I have a good inkling of what I want to do.

I'm quite interested in the Gator boxes, probably a 6U. I'm pulling a lot of design ideas from KA5CVH's photo.
I'd put a 1U power strip on top.
Currently I'm thinking two universal shelves, one at the bottom to mount three radios, an aviation band, a vhf, and a uhf. The aviation band we have in use already, the vhf and uhf would be new purchases. I don't want to use a dual band based on price for a type accepted dual band for public safety. There should be room to mount three mobile style radios side by side. I may have a blank cover with cutouts for the radios installed here as well. Above the radios would be another shelf with a ~28Ah SLA battery, and a Super Powergate 40S and a 12v power supply of some type. I'd have a blank cover in front of this to make everything look nice.
On the back I'd have a blank cover with some panel mounted SO-239 jacks for antennas. I'd also have 120v power connector and 12v power connectors or cigarette lighter jack here.

My two big questions to the experts here are 1) Is it reasonable and possible to either use a dual band antenna for all three radios? We would be transmitting around 123mhz, 155mhz, 461mhz frequency bands. When we pull the box to go mobile I'd prefer to have a single mag mount antenna we can use. On the flip side, how could I set it up so that we could have 2 or 3 antennas (we already have the aviation band antenna and anywhere I can cut costs is a plus) when at base and just a single antenna when mobile? Are there antenna switches or triplexers or something similar that would be easy for a layman to follow simple instructions to switch over?
2) Regarding the 12v power, would it be feasible to run 120v to the power supply, the power supply to a aux battery isolator, along with 12v power from say, cigarette lighter or external battery pack, and run from that into the powergate? Or would it be better to have a dedicated toggle switch to switch between 120v and 12v power supply?

Thanks for your time and any help you can provide would be greatly appreciated.
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NA4IT
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« Reply #1 on: February 23, 2012, 01:27:28 PM »

OK I'll try to help you, although we are talking about commercial bands...

"1) Is it reasonable and possible to either use a dual band antenna for all three radios? We would be transmitting around 123mhz, 155mhz, 461mhz frequency bands."

This is dependent on two things. 1) Is such an antenna available? In the amateur realm, we can get antennas that do multiple bands. Not sure if such an antenna would be available for what you are wanting to do because the 123 and 155 Mhz are close to each other, and it would be hard to "multi-band" and antenna for that. The 155 and 461 Mhz is doable, just depends on what is available. 2) As for diplexer or triplexer, same thing, a) is it available and b) how cost effective is that solution?

"2) Regarding the 12v power, would it be feasible to run 120v to the power supply, the power supply to a aux battery isolator, along with 12v power from say, cigarette lighter or external battery pack, and run from that into the powergate? Or would it be better to have a dedicated toggle switch to switch between 120v and 12v power supply? "

If you have rechargeable 12V supply available, by all means, use it. Setting up a jumper cable to go from the battery terminals to a distribution box wouldn't be hard. If it would always be used in the same vehicle, that could be made permanent to the battery.

As for the powergate / 120V supply arrangement, I prefer the RV type power supply chargers. I use one to float a UPS type battery in my shack for emergency power. (See http://www.qsl.net/na4it/ and scroll about halfway down the page.) That gives you a good power supply, and charging for the battery with automatic changeover from 120V supply to battery without the additional hardware. (And a note to the HF users, these supplies have very good RF filtering, I get NO noise from mine.)

Hope that helps you some. If you want some more ideas on the kit building, go to http://www.qsl.net/na4it/portable/portable.html. That page is geared towards amateur radio, but the hardware end will apply to what you are doing.

de NA4IT
« Last Edit: February 23, 2012, 01:30:04 PM by NA4IT » Logged
KC0UKR
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Posts: 38




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« Reply #2 on: February 26, 2012, 03:23:30 PM »

I think you may be in trouble right off the bat if you are trying to get 3 radios side by side in a 19" rack space?
I have done this type of setup several times and 2 on a shelf is really all that is practical.

Maybe if you have radios with remote control heads and mount them touching they will fit but I don't think so.

Also it would be tough to operate them being so close together.

As for the Powergate question,This is exactly what they are designed for so of course it will work?
Whether you do it this way using diodes(Powergate) or with a relay to switch power when the AC supply drops out really should not matter too much.
Getting the switchover is what counts and either would work fine.

I would provide for different antennas designed for use on each band,keep it simple.

Ed
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K1CJS
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Posts: 5875




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« Reply #3 on: March 09, 2012, 07:53:16 AM »

You may be OK with the three radios side by side, but I'll agree with the other two posters.  That seems a little too compact.

What I really wanted to offer is this--you're going to have a hard time with the antenna if you try to get it working on both 123 AND 155 mhz.  The match would have to be off to the middle of the two frequencies--that is with antenna being resonant around 140 mhz, and that would prevent good transfer of power from the transmitters to the antenna.  That will cut the range of all three radios down--drastically.

Better that you get an antenna for the 123 mhz radio and run it separately, and get a dual band antenna for the 155 and 461 mhz frequencies. 
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VK2ACM
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« Reply #4 on: March 19, 2012, 09:26:20 PM »

Hi,
Not sure if you have come up with any idea's as yet but Rick K5VXT and I had come up with a solution for our emergency kit for field use, attached is the link to my web site look under Porta- shack....73 de Clint W5/VK2ACM

http://vk2acm.tripod.com/
« Last Edit: March 19, 2012, 09:27:53 PM by VK2ACM » Logged
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