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Author Topic: RF Amplifiers  (Read 198 times)
KI4JIJ
Member

Posts: 7




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« on: January 02, 2007, 01:54:19 AM »

can I 'box' and use an amplifier board built for the CB band with my 2M HT or are amplifier circuits frequency specific?
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W6TH
Member

Posts: 1




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« Reply #1 on: January 02, 2007, 02:35:42 AM »

,
Can't be sure, but the FCC would not like the idea. If designed for cb it may not be up to the FCC principles.
.:
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W5RB
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Posts: 565




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« Reply #2 on: January 02, 2007, 02:59:56 AM »

I presume you're talking about amplifying the transmit side . Yes , amps are "frequency specific " to some degree .While modern amps are fairly broadbanded , there's a big difference in the requirements between 27MHz and 144 MHz .You can find a bevy of 2m amps  designed to work with your HT at the Mirage website , www.mirageamp.com  , or check the AES , HRO , or other ham store websites .Check the ARRL bookstore or your local club for reading material that'll give you a deeper understanding of the technical stuff . The more you learn , the more fun you can have .

Russ , W5RB
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K0ZN
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Posts: 1531




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« Reply #3 on: January 02, 2007, 07:04:45 AM »

 
Most equipment and antennas are "frequency specific" to a great degree. Equipment, amplifiers and antennas will only operate on the frequencies for which they were DESIGNED to operate. The main reason is there is a large physical difference in the wave length and physical properties of various wave lengths.

As an example to show the differences in frequencies antennas are excellent examples: a 1/4 wave vertical antenna on the CB band is about 9 ft. tall. A 1/4 wave vertical on 80 M is 67 ft. tall and on 2 M it would be 19 INCHES tall. The size and value of electrical components in the radios changes accordingly. Radio design must allow for these variables.

73,  K0ZN
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KI4JIJ
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Posts: 7




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« Reply #4 on: January 02, 2007, 02:44:36 PM »

Thank you all for the great information.  I did know about the Mirage amps, but being a 'tinkerer',  I was hoping to be able to use the CB board.  I guess I can always 'cannabalize' it for parts.  Thanks again for all the help; I learn alot on these forums.
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W9SZ
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Posts: 66


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« Reply #5 on: January 04, 2007, 08:30:46 AM »

A couple of points here -

1 - As already noted, a device that works as an amp at 27 MHz is not likely to work at 144 MHz.  

2 - Many of the cheaper CB amps are not very good, even at 27 MHz. You can always build your own. My favorites are the amp circuits designed by Helge Granberg K7ES when he worked for Motorola.  His designs are available as Motorola application notes. You could do a Google search for amp designs for 144 MHz, too.

3 - I own several Mirage amps and they have been doing a fine job. Just a little more expensive than building your own, but don't require the technical know-how (or patience) needed when building your own equipment.

73, Zack W9SZ
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