396XT 12v boosted antenna

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TDD326

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Would any one know off hand if a 12v power injected antenna would damage my 396, and if so is there any sort of connector that i can add inline to lower the voltage to something that wouldn't damage it ?

Also is there a known threshold voltage that would damage the scanner?

Thanks in advance.
 

SCPD

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Its just an signal amplifier nothing major. You will most likely need a bunch of F to BNC adapters. I would not even bother with it.
 

krokus

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You could build or purchase a DC block. (They are available through places that carry TV antenna accessories.)

Building one is fairly easy, with a little skill. You would just need something with a male and a female connector, and install a capacitor inline with the center pins of the two connectors.
 

TDD326

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I guess im more concerned with what the limit i can put into the 396 before i risk damaging it is.

i.e. if i can put in 2v then i dont need to take all 12 away which would give me + 2 v and by the spec on the antenna 9db strength.

what im thinking if i throw something inline just before the scanner it self then i will still get the gain but not the voltage?
 

jackj

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Without knowing exactly how the front-end of the 396 is designed, I'll error on the side of caution and say no voltage into the antenna input is safe.

Are you talking about using a preamp on your scanner that is powered by an external, 12v source? If so then you don't need to worry, the voltage is used to power the amp and is not applied to the scanner. Both the input and output of the amp are isolated from the power supply.

If you think that applying voltage to the coax will give you gain then you are wrong. You need an active component, like a transistor, to do the actual amplification and neither coax nor antennas have active components.

I hope this helps.
 

TDD326

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Without knowing exactly how the front-end of the 396 is designed, I'll error on the side of caution and say no voltage into the antenna input is safe.

Are you talking about using a preamp on your scanner that is powered by an external, 12v source? If so then you don't need to worry, the voltage is used to power the amp and is not applied to the scanner. Both the input and output of the amp are isolated from the power supply.

If you think that applying voltage to the coax will give you gain then you are wrong. You need an active component, like a transistor, to do the actual amplification and neither coax nor antennas have active components.

I hope this helps.
I some what think the preamp thing might be right, its a 12v lead that goes to the antenna it self, what i might do is whack it on a 12v source and take my multimeter to the end of the coax lead and see if there is any voltage there.
 

RadioDaze

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If you can tell the folks here more about the device, such as a name, model # and any other markings, they might be able to help you. But it doesn't sound like you know completely what you have there or what it's for, and we would all hate to see you damage your nice radio by using an inappropriate piece of equipment.

Can you take a photo? We will help you get it uploaded so that we can view it.
 

TDD326

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If you can tell the folks here more about the device, such as a name, model # and any other markings, they might be able to help you. But it doesn't sound like you know completely what you have there or what it's for, and we would all hate to see you damage your nice radio by using an inappropriate piece of equipment.

Can you take a photo? We will help you get it uploaded so that we can view it.
What i have and would "like" to use is an Aerpro AP104.

Does that help?
 

buddrousa

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What you have is a FM radio preamp 88 meg to 107 meg for car fm radios it should come with a DC block and power injection point but the gain is going to be in a narrow area and could cause frontend overload from music radio stations on your scanner meaning it will hear worse not better.
 

TDD326

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What you have is a FM radio preamp 88 meg to 107 meg for car fm radios it should come with a DC block and power injection point but the gain is going to be in a narrow area and could cause frontend overload from music radio stations on your scanner meaning it will hear worse not better.
So then just run it non injected?

I can not use any thing other than the glass mount antenna style.

Edit,

Or can that block be modded for a uhf set up?
 

TDD326

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On another note, just brain storming.

With a SWR meter can i test the antenna on 470-520mhz (same range i want to receive)?

Maybe see how it goes?
 

RadioDaze

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So then just run it non injected?

I can not use any thing other than the glass mount antenna style.

Edit,

Or can that block be modded for a uhf set up?

Your additional info was helpful, as we now know what you want to accomplish.

I was considering one of these at one time, but never followed up on it:
Transel - T64 - AM/FM to Scanner Splitter
Maybe someone else on the forum has some experience with it? Would it outperform a glass mount?
 

sjlamb

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On another note, just brain storming.

With a SWR meter can i test the antenna on 470-520mhz (same range i want to receive)?

Maybe see how it goes?
An SWR meter is for matching (tuning) an antenna designed for a specific band to a TRANSMITTER that operates on the same band for maximum (and most efficient) transmit performance. An SWR meter would have virtually no value in a receiver only application.

Likewise.... a FM broadcast pre-amp would be useless for improving UHF performance (and would most likely decrease performance across all but the FM broadcast band). You're giving me chills when you start talking about inputting voltage to your antenna line. When you see and smell blue smoke... you'll understand better.
 
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jackj

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You have gotten good advice, TDD326. This is a through-the-glass antenna designed to couple the signal across the glass insulator. There will be quite a bit of loss in the coupler plus the antenna is very inefficient. The amp is intended to make up some or all of the signal loss. As I stated in my first post, you won't hurt your radio by hooking it to this antenna but you won't receive much either. You will be a lot better off to buy an antenna designed for the frequency(s) you want to monitor. I know you said you can't use anything except a glass-mount antenna but I'm afraid that one isn't going to work very well.

Another point of information. An SWR bridge needs an external source of RF to work. It is used to measure reflected power so it needs to have some power to measure and a receiver does not furnish any RF energy.
 

jkahn

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As much as I dislike promoting Radio Shack anymore, they do carry a glass mount tri-band scanner antenna, and the one I have been using on the rear, side window of my van has worked extremely well for more than 5 years. I use it for either the 996, 396 or HP-1 equally well. Actually pulls some aero traffic on the EMS helo freqs and unicom from the far side of the next county.

JK :)
 
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