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CDM1250 mobile used indoors in emergency <antenna> que

Posted: Sun Dec 25, 2005 6:42 am
by xxx2fan
Can I use a motorola HAE4001A mag mount antenna on UHF CDM1250 inside and just put the antenna on a large pizza pan and it be ok to transmitt on and not hurt the antenna. This question has come up with our Vol.Fire Dept. to use mobile in emergency.

Anyone have knowledge in this

Thanks in advance.

Saw something about mobile antenna's used in base app. but cant find it in search

Thanks again

Posted: Sun Dec 25, 2005 7:17 am
by VE9MP
You should be fine using a pizza pan, cookie sheet, fridge, filing cabinet.....you get the idea :)

I have a VHF mag mount sitting on a metal heater and it works with no problems.

Posted: Sun Dec 25, 2005 8:55 am
by wa2zdy
It won't hurt the antenna, not at all. But be sure wherever you put the antenna is relatively clear of other stuff. You don't want metal objects sticking up within a reasonable distance of the antenna. A quarter wave length away is considered the rule of thumb minimum distance for other metal objects, but farther is better. On UHF the 1/4 wave is only 6 inches, so that's not really an issue.

But don't put the thing on the floor a foot from a filing cabinet or right next to a metal window screen either. Those objects will really screw your coverage up.

Last step is to set the antenna up ahead of time in a situation as close to what you expect will be "normal" operating conditions. When it's set up have a tech check the SWR and make sure it's good. That way when you do need it, you have a fair idea it will be decent. SWR will depend on the immediate surroundings, but if you have it set carefully ahead of time, you stand a good chance it'll be ok later.

This last step is necessary to be sure you don't nuke your radio while using it.

Good luck.