[Milsurplus] Command Set Coffee-Grinder Saga Continues

jcoward5452 at aol.com jcoward5452 at aol.com
Wed Nov 15 18:54:03 EST 2006


220047576380

Test your skill! (read description).How much sweat was expended due to 
this thing?I would love to see a cadet's first plots!This is why Hot 
Air Ballooning is more fun.You never "know" where you are going to end 
up but you better know how to stay out of the ATC zone!
 Jay KE6PPF

-----Original Message-----
From: smithab11 at comcast.net
To: milsurplus at mailman.qth.net
Sent: Wed, 15 Nov 2006 7:34 AM
Subject: [Milsurplus] Command Set Coffee-Grinder Saga Continues

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 
 
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