[Milsurplus] Command Set Coffee-Grinder Saga Continues

[B. Smith]

Yes folks, just went you thought the Command Set Coffee-Grinder, Range Saga
was over.

Some more comments are below, A link is give at the end of this email  to a
couple of charts with fixes and  some other diagrams that I have temporarly
put on my web site.

BTW and this is very, very  important:   I gave a long and interesting and
comprehensive presentation at the MRCA meet in 2005 on Radio Ranges and
Procedures. Only 7 people fell asleep.  65 percent of the class flunked the
famous 4 color card K4CHE quiz given at the end of the presentation. This 
years
presentation on the R1155 produced about the same results.


First:
Looks like I did not read the complete previous postings, what I was talking
about was Coffee-Grinder tuning in general as used on receivers.  I believe
the term Coffee-Grinder was introduced after other low frequency receivers
became popular. I am afraid I read the term "Command Set" in a different
context and confused the term with previous radio nav installations that I
have become  familiar with.

Ask any of the troops that attended the MRCA meet at Gilbert this September-
they will  attest to the fact that I confuse nomenclatures.    :-)
Recommend:
Rob Flory or Al Klase or Dale or perhaps the Gilbert Fair Grounds Security 
guard.

However the coffee-grinder tuning was  utilized on the SCR-274 series for
the  same reasons that I stated earlier i.e.

1.   "The coffee-grinder" tuning was necessary during the en route
navigation and or approach phase where two or three different Low Freq Nav
Aids were
utilized. Often a fix was acquired using two Range Stations. Crank fast .
See my link at the end for scans of actual charts.

2.The Coffee-grinder tuning  could be useful  during the approach phase
where communications with tower was necessary while  flying the range. The 
Coffee
Grinder allowed quick QSY between the  Range and Tower. If you were lucky
and you had two working low frequency receivers. . .  if not you cranked 
fast. In crowded areas two ranges may have been used for a fix during the 
initial approach phase.

3. The most obvious reason for the Coffee-Grinder knob was  that the pilot 
"in those days" was  turning a long
flexible tuning shaft that was snaking back through the cockpit and
fuselage  to the radio bay.

It would be very hard to just turn this long shaft using a small knob during 
frequency changes.

To tune in a station you  tuned past it and usually  retuned and retuned. 
Anyway the Coffee-Grinder made tuning a lot easier.



What's the longest flexible tuning shaft  that anyone has run across?


4.  Navigation to a Range station was often accomplished without being
established on an outbound leg of another station. For instance  arriving in
the New York area  after cross the  Atlantic  direct from the Azores. The 
navigator
would take his last fix and then the crew would DR to hit a leg of the
range .
Upon arrival this would often require an "orientation" to ensure  the
correct range leg was chosen.

There were scores of "orientation procedures published" , some were simple ,
some used two or three different Range stations which required some fast
cranking and re-cranking to recheck and double check, some of the
orientation procedures were  arduous and
could make a grown man cry.  See the link at the end of this email for a
chart depicting a fairly simple three range station orientation procedure 
which required a lot of cranking.

5. The object of the navigating the range  was to listen for the on course
tone created by the combining  of the A and N letters  but  often in the
early days the tone   and A and N were  slight ragged as in the early days
when the ranges used actual  Loop wire antennas strung between  poles. It
was often reported that the signals would vary and modulate as the wind blew
the wires. . .Later they installed towers in different configurations such
as the Babcock range.  See link at the end for a depictions of the first 
loop
system with an excellent sketch by Clete, WB2CPN.

6. The cone of silence was very important as it  told  you where you
actually were for about 15 seconds. Your alitude determined the size of the
"cone".
IF you fly today  and fly precisely over the VOR station you can hear a
brief  loss of signal   but you gotta go  right over the station. A
depiction of the cone of silence is given on the page link at the end.

6.When flying a range leg it was published as a technique that it was
usually easier to off set to "the right"  of center  so that you
would pick up the solid tone and either the    A or the N  right zone
signal.
This made it easier to tell if you were drifting off course and this
technique produced a much narrower  path to follow. It was  easier to
tell if you were drifting off course because you were actually listening to
two signals at the same time the solid tone and just barely hearing the
right zone letter. Much easier than listening to the solid tone.

This procedure of flying to the right was also safer if everyone followed
it.      :-)

But I guess there were those that liked "flying to the left".

This  flying the range leg offset to the edge was often called"twilight".
Sometimes this was a much better technique  than wallering  around
in the solid tone zone. Reference: "U.S. Navy Instrument Flight" Part two.
Published 1943.
In addition  Bendix Radio published this procedure in their "For Wider
Horizons" pamphlet.

7. You always rechecked  your tuning of the Range because
with the flexible   cable sets, it seems that the
cable would flex kind of like a rubber band and detune the receiver slightly
and perhaps  there were other mechanical/electrical causes.

8. While discussing Ranges we might as well mention the VHF "Visual Aural
Range" that was introduced after WWII  that utilized  frequencies  in the
low VHF band around 108- 109 Mcs. These ranges were kind  of interesting as
they produced two "Aural legs" and two Visual legs.
The Aural legs you used your ears for the A and N signal and overlap, the
Visual you looked at an indicator in the cockpit. See link at the end.
-----------------------------


Here in my flight deck **  See the link below. I  presently have  8 feet of
flexible tuning  cable on a single low frequency receiver and the frequency 
tuning cable can be slightly difficult to turn. When I am finished with 
adding the additional navigation rack I will not have to tune back and forth 
for fixes  and tower  as I will have multiple receivers installed. I 
consider the Coffee Grinder knob an essential part of any of my navigational 
installations including my "Flak Bait" display. But   I
only have one  low frequency receiver installed  at present  in the "Flight 
Deck" so I am probably  lost but I keep my seat belt fastened at all times.

**(The term "Flight Deck" was coined by Mike Hanz)
------------------------
See this link for chart examples and other Range slides and my "Flight 
Deck".

      http://solo11.abac.com/zorroab1/Range/Rngpg1.htm