Whistle for your frequency?

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?

Thanks

-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.

-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?

Thanks

This is a speculative, yet plausible response.
Transmitters without a crystal per channel might yet have a crystal
controlled comb generator, which when manual tuning, would null a beat
frequency whistle when on frequency.

Brian W

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.

Brian Whatcott wrote:
-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?

Thanks

This is a speculative, yet plausible response.
Transmitters without a crystal per channel might yet have a crystal
controlled comb generator, which when manual tuning, would null a beat
frequency whistle when on frequency.

Brian W

The Narco whistle-stop radios had a limited number of transmitter
crystals (9 for the SuperHomer and 27 for the Omnigator). The receiver
tuner was analog. So, if you pulled out the whistle-stop button as you
got close to the selected transmitter crystal the whistle-stop tone
activated.

Sam Spade wrote:
Brian Whatcott wrote:
-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?

Thanks

This is a speculative, yet plausible response.
Transmitters without a crystal per [rx] channel might yet have a crystal
controlled comb generator, which when manual tuning, would null a beat
frequency whistle when on frequency.

Brian W

The Narco whistle-stop radios had a limited number of transmitter
crystals (9 for the SuperHomer and 27 for the Omnigator). The receiver
tuner was analog. So, if you pulled out the whistle-stop button as you
got close to the selected transmitter crystal the whistle-stop tone
activated.

I found a little more on this topic - a note from Jim (the leading light
at RST) explaining the Superhomer when he was hunting for pix to
illustrate an article on the topic 3 or 4 years ago. [below]

And here's a URL for a picture (bottom right)
http://www.flightglobal.com/pdfarchive/view/1957/1957%20-%200495.html
or in tiny format:
http://tinyurl.com/o7xhl3

[Jim...]
For those of you who came into this game too late to "enjoy" this
little rascal, it gave you your choice of four (count 'em again, FOUR)
transmit channels and a slide-rule type tuner that would go all the way
from 108-126 MHz. in one continuous band. That little "transmit" light
was really neat -- it actually stole a little power directly from the
transmit antenna port so that you knew for a fact that the transmitter
was mitting. It also flickered in time with your voice so you knew that
the microphone was doing its job also -- so far as I know, this was the
last device to have both a positive RF and audio indication of transmit.

Those were the REAL days of voice-over-VOR, because once you dialed
the VOR in, there was no way to switch back and forth between the COM
and NAV bands. At some point, one of the smarter troops at Narco put in
a little switch called "whistle-stop tuning" that turned the transmitter
on at micropower and let you zero-beat the receiver to the crystal so
that you were on the correct channel.

I went from San Diego to Boston in a C-120 behind one of these boxes
and didn't know any better.

Jim



Brian W

Brian Whatcott wrote:
Sam Spade wrote:

Brian Whatcott wrote:

-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?

Thanks

This is a speculative, yet plausible response.
Transmitters without a crystal per [rx] channel might yet have a
crystal controlled comb generator, which when manual tuning, would
null a beat frequency whistle when on frequency.

Brian W


The Narco whistle-stop radios had a limited number of transmitter
crystals (9 for the SuperHomer and 27 for the Omnigator). The
receiver tuner was analog. So, if you pulled out the whistle-stop
button as you got close to the selected transmitter crystal the
whistle-stop tone activated.


I found a little more on this topic - a note from Jim (the leading light
at RST) explaining the Superhomer when he was hunting for pix to
illustrate an article on the topic 3 or 4 years ago. [below]

And here's a URL for a picture (bottom right)
http://www.flightglobal.com/pdfarchive/view/1957/1957%20-%200495.html
or in tiny format:
http://tinyurl.com/o7xhl3

[Jim...]
For those of you who came into this game too late to "enjoy" this
little rascal, it gave you your choice of four (count 'em again, FOUR)
transmit channels and a slide-rule type tuner that would go all the way
from 108-126 MHz. in one continuous band. That little "transmit" light
was really neat -- it actually stole a little power directly from the
transmit antenna port so that you knew for a fact that the transmitter
was mitting. It also flickered in time with your voice so you knew that
the microphone was doing its job also -- so far as I know, this was the
last device to have both a positive RF and audio indication of transmit.

Those were the REAL days of voice-over-VOR, because once you dialed
the VOR in, there was no way to switch back and forth between the COM
and NAV bands. At some point, one of the smarter troops at Narco put in
a little switch called "whistle-stop tuning" that turned the transmitter
on at micropower and let you zero-beat the receiver to the crystal so
that you were on the correct channel.

I went from San Diego to Boston in a C-120 behind one of these boxes
and didn't know any better.

Jim



Brian W

As I recall the SuperHomer wasn't legal for IFR.