[Boatanchors] [BoatAnchors] LF Aircraft Ground-to-Air Coms

Fri Feb 15 23:39:53 EST 2013

Nick and others,

I remember way back in the late 40's and early 50's when I hung around New 
Orleans lakefront airport (NEW), there were a lot of tandem two seaters like 
the Piper J-3, Taylorcrafts, Aeronca Champions, most of which had NO 
auxiliary electrical system (Usual powerplant was the Continental A-65). 
There was one exception I knew about with a Motorola SKYBOY Sr.  which used 
same tube lineup you mentioned and internal dry batteries and a very poor 
and short antenna back to the vertical fin.  I did see some photos later of 
the same kinds of aircraft but with antennas strung to the vertical fin and 
then two runs of wire from that point to the trailing edge of the wingtips 
which seemsed to "Load up" much better .  At other times you had to observe 
which runway was being used or look at the windsock to get the wind 
direction.  You taxied to say the threshold of runway 36 and stopped, looked 
downwind to see if someone was on final and if not, turn around slightly to 
see the tower better and rotate the stick to make the ailerons and elevator 
"flop" up and down and wait for the green light from the tower.  After the 
green light you taxied towards the runway after making last minute check and 
runup magneto checks then entering the runway and taking off.  At NEW the 
usual first turn was left after you got to 400 ft or more and followed the 
left hand pattern before turning to your final course and climbing to 
whatever was your cruising altitude.  Landing, one just reversed the 
procedure, keep an eye on the pattern the aircraft in the pattern were using 
and enter the downwind leg following the last bird in the "chain" all the 
while keeping an eye on the tower in case you got a red or red/green 
alternating light to let you know you were "breaking into" the pattern at 
the wrong place or doing something the controller didn't like!  It was a 
head on a swivel/rubber neck situation until you settled into the pattern 
and finally got a green light on final to land or a red one as a "go around" 
or wave off signal.
Radios kind of actually created a "could be" hazard by allowing pilots to 
somewhat relax in the pattern and let the tower man let you know when there 
was a problem!  I do also remember NEW tower was on 382 Khz.  I do also 
remember a 278 marking for MSY tower instead of 349 khz.  We had a few NBD's 
but not many and then the Adcock "Range" was operational on 338 Khz. which 
was lined up with runway 10 at Moisant field  (MSY) where most of the 
airliners took off and landed at.

Ultimately the 3105 spot was changed to 3023.5 and later all the 3 mhz 
channels went silent for the most part as aircraft were getting a small 
1-1.5 watt VHF transmitter module added that operated much better tan the 
old 3 mhz transmitter, the existing LF receiver was still used or sort of 
"Ganged" to the VHF tower frequency and the operator talked on both channels 
at the same time.  Eventually the LF stuff went silent and VOR's took over 
and made the 4 beam "radio range" obsolete.  The old stuff WAS simple and 
you just needed a receiver to fly the range!

Them was the days.  Surplus aircraft were cheap.  One fellow bought an 
almost new P-51 mustang for $600 and complained his fuel bill was high as he 
burned about 80 gallons and hour flying it!  (But AVGAS was not 5-6 buck a 
gallon then!)

73,

Sandy Blaize W5TVW

-----Original Message----- 
From: Nick Broline
Sent: Friday, February 15, 2013 3:25 PM
To: boatanchors at theporch.com
Subject: [BoatAnchors] LF Aircraft Ground-to-Air Coms

Dave,
I believe the use of LF transmissions to early aircraft, particularly near
the war, were closely tied to the use of LF NDB's.  I remember as a kid in
San Antonio, Texas, I heard NDB's carrying flight service station responses
to aircraft, except this was in the early 50's and the aircraft transmitted
on VHF to the FSS.  I remember hearing aircraft tell the FSS on initial
contact they were listening on the beacon.  I also recall they ran weather
products on the NDB that were interrupted by ground-to-air transmissions.
(This was, of course, long before the advent of ATIS.)  Their practice was
also to provide the same voice services on VOR's.  They may have also put
voice info on the A-N Range stations, but I don't remember ever being glued
for hours to the radio listening to the range stations!  This appears to be
the practice in the 50's based on my listening experience and faded memory.
Someone please correct me if I'm all wet!

I have a benchmark in my hands...an Air Associates Inc. BR3T......a dry
battery transceiver using a 3105 kc transmitter and a 180-410 kc receiver.
It clearly has no ability to use the LF band in a navigation function, so
all that is left is com.  In fact, a mark on the receiver tuning dial shows
the "tower frequency" (note there is only one shown) to be ~249 kc....or
perhaps 249.5 kc??   This suggests the 249 ground-to-air frequency was
paired with the 3105 kc air-to-ground channel as a convention at this point
in time.  The registration slip tucked between a couple of tubes showed the
radio was FCC registered 3/27/43 to Globe Aircraft of Ft. Worth and the
manufacturer was Air Associates of Ft. Worth.  SN is 498. The registration
is on safety paper (as in check paper). One can't be too careful about these
things!

For anyone who cares, the receiver is a 4-tube superhet that is a 1.5V tube
analog to the all-American Five AC-DC broadcast receiver.  The transmitter
features a 1T4 oscillator driving a 3Q4 final, modulated with a pair of
paralleled 3Q4's through a real modulation transformer.  Tx power indicator
was a type 49 lamp paralleled by a resistor in series with the Tx antenna
lead.  Rx and Tx audio functions are on separate, but bolted together
chassis.  PA tuning was accessible without removing the case, so was
probably done in place.

The only other recollection of aviation linked LF transmitters was the
popular use of the 4D32 as the final in LF beacon applications.  It showed
itself in the Viking I and Collins 32V series. However, the 4D32 is probably
way too new to be relevant in your pre-40's search.

One concrete thing here is the apparent pairing of 249 and 3105 kc.  I
suspect this may have been a hold-over from the pre-war aircraft com
conventions.  Registration date is mid-WW2, and I doubt there was much focus
on civil aviation breakthroughs in that period because folks had other
things on their minds.  Please look at your old sectionals to see if there
are any "standard" frequency assignments.

NDBs and beacons have always been a problem with antennas.  The NDB, to be
maximally useful, would be very near the airport.  That implied the antenna
should be low.  I personally have never seen a LF beacon antenna that was
not T fed in the middle with the vertical radiator.  Of course, the more "C"
they can put on the top of the radiator the less loading coil needed in the
antenna tuner, so they probably did the best they could with capacitive
loading while keeping it low.
73,
Nick Broline
W5FUA
512 327 7425

We shall not cease from exploration
And at the end of exploring
Will be to arrive where we started
And know the place for the first time.
      T.S. Eliot--"Little Gidding"
-----Original Message-----
From: BoatAnchors [mailto:boatanchors-bounces at theporch.com] On Behalf Of
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Sent: Friday, February 15, 2013 12:00 PM
To: boatanchors at theporch.com
Subject: BoatAnchors Digest, Vol 105, Issue 6

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