I'm sorry.

In 'the trade' there is a very definite feel or concept
of what RF is - and is not.

The instrumentation, test and measurement equipment utilized
in classical RF is a far cry different from that which (until
only recently) was used in any other field.

Whereas Vector voltmeters, Vector Network analyzers and
Spectrum Analyzers and signal/sweep generators are/were the
maintays of RF electrical engineering the 'other' fields
employed oscilloscopes, pulse generators, logic analyzers
and the like.

Notice the contrast?

The field of RF typically (going back just a FEW years now)
concerned itself with narrow, Hi-Q silver plated cavities
for frond end filters, low noise GaAs FET amplifiers,
doubly-balanced (some people call them "double-balanced" mixer,
I do not!) mixers fed by PLL LOs. The IF output of the DBM
was routed to an IF chain employing a series of amplifiers
(perhaps log amps) and appropriately designed filter banks
which then led to either an FM discriminator, or a product
detector. Today a DSP sits at the end of the IF chain.

What does 'audio' or digital work generally employ? Op-amps,
uCs such as the PIC families and NOTHING milled or drilled
out of solid aluminum or copper stock connected up using
waveguide or a plethora of Type N connectors and double
shielded silver-plated coaxial cable, smei-rigid or Andrew
Corporation "Heliax".

Notice the contrast here too?

I still stand by my previous, albeit minor, dissertation.

Jim

PS. I too have been engaged in the 'practice' since the
    70's as well employed at such firms as diverse as TI and
    Heathkit - employed doing actual engineering work at
    frequencies from DC through Ku band ...



----- Original Message -----
From: "Bourdon, Bruce" <bbourdon@ZYDACRON.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Wednesday, February 13, 2002 8:59 AM
Subject: Re: [pic]: Can you amplify with a single 2n2222 ??


>     "Audio is ELF. An audio-frequency circuit still radiates
>      electromagnetic waves, just not very efficiently."
>
>  "Very incorrect in all but perhaps a very few ill-designed
>  products. Most of us responsible for actual RF design
>  don't call possible 'spuriuous emissions of AF energy' over
>  100 dB down from a 'box' "radiation of electromagnetic
>  waves". Leakage flux perhaps (as from a power xfmr) - but
>  not 'radiation'.
>
>  I realize I'm addressing a majority digi-head crowd - some
>  of this discussion is only underscoring that point.
>
>  No offense meant to any digi-head on the list. We couldn't
>  possibly do what we do in the field of RF today without uC's
>  or the talented programmers and designers who actually make
>  those devices 'sing' and 'dance' ...
>
>  Jim"
>
> Jim, others:
>
> I'm afraid your not quite correct here Jim; as stated by others, there is
no
> magic frequency where AF ends and RF begins - it is most definitely
blurred.
>
> What is important is Efficiency, as efficiency for each purpose varies
with
> frequency.
>
> But there definitely are audio frequency "RF" transmitters, and these are
> not "ill-designed products." For example, the U.S. Navy uses what most
would
> consider as "Audio Frequencies" in their equipment designed to communicate
> with submerged submarines. Though efficiency is horrendous, the importance
> of the task makes the inefficiencies acceptable.
>
> Also, you should not assume that the audience cannot rationally consider
the
> topic, as many have mixed disciplines. While I probably could not match
your
> level of expertise, I have been workinging with RF as an amateur (HAM)
since
> the '70s. I'm sure there are many readers that have even more experience
> than I.
>
> Bruce.
>

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