RF power amplifier - RF Cafe Forums

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veerasamy
 Post subject: RF power amplifier
Posted: Wed Oct 07, 2009 6:29 am 
 
Captain

Joined: Wed Oct 07, 2009 6:27 am
Posts: 6
I am currently working on radio transmission and reception at the frequencies of around 200MHz. The range of transmission is not currently important.
It is enough if I could transmit for 10 meters or so. My question is, Is it necessary to have a power amplifier? Can an ordinary gain block can be used?
Will antenna be able to radiate without PA?

thanks & regards,
veerasamy
 
   
 
Kirt Blattenberger
 Post subject: Re: RF power amplifier
Posted: Wed Oct 07, 2009 11:06 am 
 
Site Admin
 

Joined: Sun Aug 03, 2003 2:02 pm
Posts: 308
Location: Erie, PA
Greetings veerasamy:

At 200 MHz, you should not need much power to reach 10 meters. Path loss over 10 m at 200 MHz is a little under 40 dB. So, depending on what the minimum signal level required at the receiver is (kTB + SNR), you can probably get away with an output power of under a watt and not need a high power amplifier. Of course, crappy antennas can really knock down the received power.

There is a path loss calculator on this page:

http://www.rfcafe.com/references/electrical/path-loss-1-way.htm

The Friis equation for path loss is here:

http://www.rfcafe.com/references/electrical/path-loss.htm

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RF Cafe Progenitor & Webmaster
 
   
 
veerasamy
 Post subject: Re: RF power amplifier
Posted: Thu Oct 08, 2009 12:26 am 
 
Captain

Joined: Wed Oct 07, 2009 6:27 am
Posts: 6
Thanks Blattenberger,

Calculator was useful. I thought I need more current to drive signal through antenna which my gain block cannot provide. It can provide output power upto 16 dBm but it has mostly voltage amplification. Is it not a problem? I have a good antenna too.
 
   
 
david1hitch
 Post subject: Re: RF power amplifier
Posted: Wed Jan 06, 2010 1:30 am 
 
Lieutenant

Joined: Mon Jan 04, 2010 1:12 am
Posts: 3
Hello just a technical note that most younger Engineers may not be aware of is that the Broadcast power can be developed either by high Voltage low gain as in Valve based circuits or low voltage high current as in Solid State designs , i have spent over 30 years working in the Broadcast and Military Communications Fields .
David




Posted  11/12/2012