[Lowfer] Ultimate LOWFER Transmitter?

[Don Davis]

Not quite.  It would be equivalent to exactly what you have, 4 one watt
trasmitters = 4 watts.

BUT, if they are not exactly sychronous (ie in perfect phase) the output
will be quite a bit less.  If I remember my physics correctly, random
radiators add their power to the square of the number of radiators.  So if
you have 4 one watt random radiators, it will look like a 2 watt radiator at
infinity.  Same thing holds true for light bulbs.  One 200 watt bulb puts
out more light than 2 100 watt bulbs

That is... if I remember my physics right...

Don  AD6PB

----- Original Message -----
From: "Stewart Nelson" <sn@scgroup.com>
To: <lowfer@mailman.qth.net>
Sent: Tuesday, March 12, 2002 9:04 PM
Subject: Re: [Lowfer] Ultimate LOWFER Transmitter?


> Hi all,
>
> Some good/bad news about an "array" of lowfer transmitters:
>
> The good news is that performance could be outstanding.  If you have four
> synchronous one-watt transmitters, and the antennas are sufficiently
> spaced so that their ground and other loss resistances are effectively
> independent, the combined far field strength will be four times greater,
> the equivalent of one 16-watt Tx!  IMO, 50 to 100 foot spacing is
> adequate.
>
> The bad news is that it could be very tough to make legal.  If multiple
> devices are "connected by wire or cable", they are considered to be a
> "composite system" and in our case would limit the total power input to
> one watt.  There are several mentions of this concept in Part 15.
> As a start, look at 15.29 (h) and (k).
> See http://www.lwca.org/sitepage/part15/index.htm or a complete edition.
> You might get around this limitation by coupling the carrier optically,
> inductively, or by radio on another frequency.  I don't know whether
> the units would be considered to be "connected by wire or cable", if
> they were merely connected to the same mains.  If so, the transmitters
> might also need to be solar/battery powered.
>
> 73,
>
> Stewart KK7KA
>
> > >As for the multiple amplifier concept, I also call your attention to
Section
> > >15.204, External radio frequency power amplifiers and antenna
modifications,
> > >paragraph (b):
> > >
> > >"A transmission system consisting of an intentional radiator, an
external
> > >radio frequency power amplifier, and an antenna, may be authorized,
marketed
> > >and used under this part. However, when a transmission system is
authorized
> > >as a system, IT MUST ALWAYS BE MARKETED AS A COMPLETE SYSTEM AND MUST
ALWAYS
> > >BE USED IN THE CONFIGURATION IN WHICH IT WAS AUTHORIZED.  An external
radio
> > >frequency power amplifier shall be marketed ONLY IN THE SYSTEM
CONFIGURATION
> > >with which the amplifier is authorized and shall not be marketed as a
> > >separate product."  (emphasis mine)
> > >
> > >In other words, if he wants to market it various such versions, he will
have
> > >to test it in EACH such a configuration, and sell it in exactly the
> > >configurations as tested.  Sell a two-output version, get Type
Acceptance
> > >for a two-output version; sell a four-output version, get Type
Acceptance on
> > >the four-output version; etc.
> >
> > I think you misunderstood although this is good information cogent to an
> > ongoing argument we've been having on another forum, so thanks! :-)
> > The system as-is is Certified to be used in the manner I described but
each
> > unit has only one output, and each is a standalone unit not just an RF
> > power amp. They can share carrier from a master unit (or not, each can
have
> > it's own xtal and can be trimmed to exact freq.) but that master when
used
> > as such is also a standalone unit not just an oscillator. These things
are
> > whole transmitters in other words, not piece parts of a system.
> > I assumed that most Lowfers wouldn't want this option but only mentioned
it
> > anyway just-in-case.
>
>
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