Re: How to know there is a receiver or not when I am FM transmitter?

John Larkin wrote:
On Wed, 29 Mar 2006 19:05:32 -0800, "Joel Kolstad"
<JKolstad71HatesSpam@xxxxxxxxx> wrote:


"Boki" <bokiteam@xxxxxxxxxxxxxx> wrote in message news:1143683808.881098.25670@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

How to know there is a receiver or not when I am FM transmitter?

A common technique -- used by the RFID guys, and also pretty much the same technique used in some inventory control tags -- is to monitor "the load" on the transmitter. That is, you run your RF power amplifier off a constant voltage or current source and then monitor the resultant current or voltage; the receiver purposely places a changing load on its antenna (e.g., by shorting it!), and this causes the load seen at the transmitter to change.


Right. If you go to any big radio station, there's a big round
plate-current meter on a black wrinkle-finish panel. Every time a
listener turns on his radio, you can see the current jump up. Some
meters are even calibrated in kL, kilo-listeners.

Right.

John



Trouble is, it doesn't work any more, what with radio
over the internet. Now, one person can turn on his radio,
digitize the audio, and pipe it overthe internet to millions
of listeners, and that radio station plate-current meter
won't deflect any more than it does when one listener
turns on his radio.

In fact, if I remember right, there will be a lecture on this
problem 24 hours and 48 minutes from now at Yankee stadium, by
Dr. F. Newton Farnsworth, one of, if not *the* world's foremost
authorities. The theme of his lecture will be "The reverse
coriolus effect as applied to RF spectral emmissions due to and
stemming from the inception of radio over internet and the
correlative innaccuracies of kL calibrated plate currant meters".

Ed
.

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