[sci.electronics] Amplification of an RF signal from an antenna

woody@iear.arts.rpi.edu (Christopher Widmann) (12/13/90)

 I am attempting to build an amplifier for my FM antenna to improve
reception. Does anyone out there in netland know the maximum peak to
peak voltage and current that I can put into my antenna port? Also, any
suggestions on implementation? I am considering a push-pull amplifier.
Thanks.

					Chris Widmann
					woody@iear.arts.rpi.edu



Chris Widmann ---------------------------------------------------------------
 woody@iear.arts.rpi.edu - Rensselaer PolyTechniTortureTute 
"Life is like an ice cream cone, you lick it one day at a time"-Charlie Brown 
-----------------------------------------------------------------------------

myers@hpfcdj.HP.COM (Bob Myers) (12/16/90)

> I am attempting to build an amplifier for my FM antenna to improve
>reception. Does anyone out there in netland know the maximum peak to
>peak voltage and current that I can put into my antenna port? Also, any
>suggestions on implementation? I am considering a push-pull amplifier.
>Thanks.

There's no need for a "push-pull" amplifier; even if you were to build an
RF push-pull, it would have no voltage gain (being essentially two common-
collector amps back to back).  What you want is an amp with good voltage gain
and a wide bandwidth, and which can match to both the antenna and the
receiver's antenna input.  (By the way, there's no need to worry about
both the maximum voltage and current; the impedance of the antenna input is
fixed, so nail either of these down, and you've got the other.)  A common-base
stage, possible followed by a common-collector for impedance matching (although
there would be other ways to do this), sounds like the ticket here.  (Common
*emitter* stages aren't usually used for RF amplifiers, as the Miller effect
capacitance of this configuration limits the bandwidth over what could be
acheived with the same device in the CB configuration.)

So that we don't get into too much detail here, may I suggest getting a
copy of the latest ARRL Radio Amateur's Handbook?  It will describe a number
of suitable amplifiers and the theory behind them.  (Note that anything the
ARRL describes for use in the amateur 2-meter band should be easily
adaptable to broadcast FM.)


Bob Myers  KC0EW   HP Graphics Tech. Div.|  Opinions expressed here are not
                   Ft. Collins, Colorado |  those of my employer or any other
myers@fc.hp.com                          |  sentient life-form on this planet.

billn@hpcvaac.cv.hp.com (bill nelson) (01/01/91)

myers@hpfcdj.HP.COM (Bob Myers) /  4:01 pm  Dec 15, 1990 / writes:
>> I am attempting to build an amplifier for my FM antenna to improve
>>reception. Does anyone out there in netland know the maximum peak to
>>peak voltage and current that I can put into my antenna port? Also, any
>>suggestions on implementation? I am considering a push-pull amplifier.
>>Thanks.

..... deleted

>So that we don't get into too much detail here, may I suggest getting a
>copy of the latest ARRL Radio Amateur's Handbook?  It will describe a number
>of suitable amplifiers and the theory behind them.  (Note that anything the
>ARRL describes for use in the amateur 2-meter band should be easily
>adaptable to broadcast FM.)

Or, you could run down to your local Radio Shack and buy one.  The biggest
problem with amplifying FM signals is that you also multiply the multipath
error signals also. Your first choice should be the best FM antenna you
can find - then, if that is not sufficient, use an amplifier.

Bill