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.