From: gary@ke4zv.uucp (Gary Coffman)
Newsgroups: rec.radio.cb
Subject: Re: Linear Amplifiers
Date: 11 Oct 92 12:12:21 GMT
Reply-To: gary@ke4zv.UUCP (Gary Coffman)
Organization: Gannett Technologies Group

In article <1b5eu1INN92f@agate.berkeley.edu> odonnell@ocf.berkeley.edu (Shawn Christopher O'Donnell) writes:
>Date: Fri, 9 Oct 1992 18:57:58 -0700
>From: Shawn Christopher O'Donnell <odonnell>
>Message-Id: <199210100157.AA01801@tsunami.berkeley.edu>
>Subject: Re: Linear Amplifiers
>Organization: U.C. Berkeley Open Computing Facility
>
>I'm seriously thinking about building a linear amplifier. I have
>a good design, one that won't interfere with planes or televisions,
>its cheap, and it seems necessary to me. I'm not particularly interested
>in "skip", although at some point I might be, but for now, I would
>simply like it if people that I talk to locally don't constantly
>criticize me for running a "baby unit" that "only" runs 4W. The
>Los Angeles area, where I live, seems sufficiently noisy during the
>day that 4W just is not enough. Furthermore, I haven't seen or met anyone
>that ran the basic settup-- a 4W tranceiver. I am the only one.
>
>Obviously I'm not posting this simply to announce that I will build a
>linear for myself, I am writing because I want other opinions on
>how to accomplish what I want without having to spend a weekend
>buiding something that is illegal in the first place, and might not
>even work in the second: some people have said that increasing 
>the power from 4W to 60W will only make a small difference, if any
>at all. What's that all about? Why doesn't more power on a given
>settup translate into commensurately greater range on the same settup? 
>
>I feel that, being the only one who runs 4W I am unfairly handicapped
>by the rest of world. Proponents of NOT using a linear in the 9WATT
>war zone that is Los Angeles, what would YOU do?         
>
>Basically, I want to be heard clearly within a 30 mile radius under
>bad conditions. I was planning to build a Linear with variable
>output that would do from 4W on the low side to 150W on the high side.
>I figure, that will be enough for my purposes, and if its too much, I can
>always turn it down. On the other hand, I truly don't want to be
>an irresponsible person and if there is a "right" way to do the same thing
>that is somehow more sensitive to the insensitive people that surround me,
>I would definitely like to know what it is.

I can appreciate your desire to bark with the big dogs, but it's not
a good idea, and the performance improvement will be very minor. Unless
you are a very excellent designer and very experienced constructor, 
anything you can slap together on a weekend cheap isn't going to be clean. 
Designing and building a clean class AB1 amplifier for AM is not a
trivial task. An amplifier for SSB is somewhat easier to do, but you
won't build either in a weekend, and it's going to cost at least $200
to do it right for a 60 watter.

You'll be much better off spending the time and money improving your
antenna system and buying an SSB radio. Most CB antenna installations
suck, yet it's the most important part of your station. Spending some
money and time improving your antenna will make you a bigger dog than
a 60 watt amplifier. Groundwave range on CB is limited mostly by terrain 
and line of sight distance. You need an antenna that is high above
surrounding terrain and that concentrates as much energy as possible
directly at the radio horizon for best distance. Non line of sight
paths incur at least 100 db of additional path loss while your proposed
amplifier only offers 10 db of gain. It just won't extend your range
much if at all.

One major advantage of improving your antenna that most CBers seem
to ignore is that you'll be able to *hear* other stations much better
as well as having them hear you better. That's because the antenna
works in both directions while an amplifer only works in one. It
does no good to put out a bone crushing signal if you can't hear
the other guys you are clobbering complaining about you. :-)

Gary KE4ZV
Newsgroups: rec.radio.cb