Whistle for your frequency?

-b- wrote:

Thumbing through a 1962 FLYING magazine, I came across an
advertisement for the all-new Motorola M-400 NAV/COM. Among other
quaint features, such as the 100KHz spacing, later upgradeable to
50KHz, and the COM transmit frequency that automatically switches to
122.1 any time you select a NAV frequency "so you don't have to be
continually switching back and forth between your Com and Nav
frequencies!" I am puzzled by the all-new feature; Crystal Tuning so
you can dial-in your frequency. "No more whistling for a channel;
just dial your frequency and you're on!"

A cursory web search didn't reveal anything about this.
Who can enlighten me about this "whistling for a channel" business?


It's referring to "whistle stop tuning", introduced by NARCO, I believe, in
the late forties or early fifties. Back then you'd transmit on one of
four(?) crystal-selected frequencies but select the receiver frequency on a
tuner that covered both nav and voice bands. Activating "whistle-stop
tuning" turned the transmitter on at very low power, when the tuner reached
the transmitter frequency you heard a whistle and knew you were on the right
frequency.

"Steven P. McNicoll"
It's referring to "whistle stop tuning", introduced by NARCO, I
believe, in the late forties or early fifties. Back then you'd
transmit on one of four(?) crystal-selected frequencies but select the
receiver frequency on a tuner that covered both nav and voice bands.
Activating "whistle-stop tuning" turned the transmitter on at very low
power, when the tuner reached the transmitter frequency you heard a
whistle and knew you were on the right frequency.

Steven, I thought that the heterodyne whistle "stopped" when tuned to
the exact frequency. Been a long time ago though.

Bob Moore

In article 0,
says...


"Steven P. McNicoll"
It's referring to "whistle stop tuning", introduced by NARCO, I
believe, in the late forties or early fifties. Back then you'd
transmit on one of four(?) crystal-selected frequencies but select the
receiver frequency on a tuner that covered both nav and voice bands.
Activating "whistle-stop tuning" turned the transmitter on at very low
power, when the tuner reached the transmitter frequency you heard a
whistle and knew you were on the right frequency.

Steven, I thought that the heterodyne whistle "stopped" when tuned to
the exact frequency. Been a long time ago though.

Bob Moore



Great! Thanks for that piece of information. With that I was able to look
it up and find a wealth of information on the subject.

Sounds right to me that the whistle would "start" and not stop at the
right frequency, because that's where you'd get the feedback tone. Not to
be confused, of course, with the four-course range approach, where the
tone would become steady on the correct course.

The Motorola, by the way, unit does boast 180 transmit and 280 receive
channels at 100MHz (double those for the upcoming 50MHz), though they
indicate 122.1 is the "primary" enroute communications channel. Not
exactly 8.33 spacing, but now that we've bettered the "whistle-stop" the
path is direct to what we know today.

The unit featured "all-transistor power supply" and partially
transistorized transceiver, with only the power supply requiring remote
mounting... 9 pounds total.

Robert Moore wrote:

Steven, I thought that the heterodyne whistle "stopped" when tuned to
the exact frequency. Been a long time ago though.


No, the whistle was only heard when the receiver was tuned to the
transmitting frequency.

Hear the whistle? STOP! Youve found the correct frequency.

In article ,
says...


Robert Moore wrote:

Steven, I thought that the heterodyne whistle "stopped" when tuned to
the exact frequency. Been a long time ago though.


No, the whistle was only heard when the receiver was tuned to the
transmitting frequency.

Hear the whistle? STOP! Youve found the correct frequency.


It's pretty cool in a way, because it's a head's up process, and you
don't have to be looking at a display or counting clicks. If well
implemented (and I don't know if it was), maybe you could spin quickly
past the point, hear a blip as you cross it, then work back slowly to
ahere the blip was.

BTW - try to imagine all the spurious stuff a web search using the word
"Narco" brings up today ! I doubt they would name their company that
today - although given some of the stupid names people do come up with
I sometimes wonder. Just this past week I saw "AirExces" for a corporate
shares company and "RectAir" for another.

On May 18, 10:45*am, -b- wrote:

BTW - try to imagine all the spurious stuff a web search using the word
"Narco" brings up today ! I doubt they would name their company that
today *- *although given some of the stupid names people do come up with
I sometimes wonder. Just this past week I saw "AirExces" for a corporate
shares company and "RectAir" for another.

Back in the 80's we had the "Ayds Diet plan". Apparently, with Ayds
you could lose a lot of weight!!! Search youtube for some of the old
commercials; its pretty funny looking back!!!

-Robert