[MRCA] Reading Airshow AAR

[Mark K3MSB]

Here's my attempt at a somewhat decent AAR.....

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I spent 4 days at the Mid Atlantic Air Museum's World War II weekend as
part of a regional reenactor group. Setup was Thursday June 4th with the
event running Friday June 5th through Sunday June 7th.

This was my second time at Reading as part of the reenactor group, and the
start of my second year of reenacting in general.  Weather was hot and
somewhat humid, but I had a nice breeze through the Comms Tent on all three
days.

It was great to see the B-17 “Sentimental Journey” in the skies over
Reading, as well as the A-26 Invader “Silver Dragon”.

Overall, I had a steady stream of visitors in the Comms Tent all  three
days, and did numerous demos each day.

Objectives:
Educate people on the HF / VHF radios used on Allied Aircraft in WW II.
Describe the differences between the SCR-274N Command Radios and SCR-287
Liaison radios.
Demonstrate how a DF unit works.
Demonstrate a BC-611.
Explain that during the Battle of Britain, the British not only had to
determine the position and speed of the German aircraft, but also of the
British aircraft in order to formulate a least time / least fuel intercept
solution.


Equipment used:
SCR-274N system.  Working on 40 & 75M AM.  40/80 TX,  40/80/LF RX.  New
this year were two remote tuning cables and a new Pilots Control box that
was in better shape than my old one.  Powered by a pair of 12V 100 AH
Lifepo4 batteries in series.   Dynamotors used for the transmitter and
receivers.

SCR-287 System.  The BC-375 and 2 additional tuning units were static
display only. The BC-348Q was working and has it's original dynamotor.
Powered by a pair of 12V lawn tractor batteries in series.

DF Setup consisting of a DU-1 and an ATA CBY-46145 Broadcast Band
Navigation Receiver.  Due to the lack of NDBs in the area, I did not
attempt to use my BC-453 Beacon Band Navigation Receiver this year.  The
BC-453 was in the SCR-274N rack.  The ATA receiver used a dynamotor.  It
was powered by a pair of 12V lawn tractor batteries in series (the same
ones used for the BC-348Q).  HV for the DU-1 was obtained from the center
connector of the ATA receiver.

BC-611.  Working on 75M AM.   Used 4 D batteries and the DC-DC converter
that used to be made by the Italian fellow.   Worked well!

SCR-522 VHF system with BC-608 Pipsqueak unit – Display only.

Setchell Carlson BC-1206 LF Receiver.  Display only.

MN-36 Loop Antenna.  Display only.

BC-221 Frequency Meter.  Display only.


What did I expect to happen:
Use the HF radios to talk to others at the event;
Use the DU-1 and associated receiver to illustrate how an aircraft found
it's position by the DF process.
Use the HF radios to “talk to each other” during demos.

What Happened:
I made two BC-611 to BC-611 contacts with Mark WW2RDO who was also at the
event.
I made one contact with Don K3OP with my SCR-274N.  He was in the parking
lot with a TS-480.
All three contacts were on 75M AM.

Demos of the DF setup, BC-611, and SCR-274N worked extremely well and was
well received.


What went well and why:

The DF demo went well.  I had the ATA receiver tuned to an AM broadcast
station about 50 miles away.   I explained how the operator would manually
turn the DU-1 loop to find the maximum signal then report the bearing to
the pilot (yes, I know they went for the null, but I didn't think that
detail was relevant for my purposes).  I explained that the DU-1 loop was
normally mounted on the fuselage with an extension shaft to the operator's
table, and I showed them the scales the radio operator used to determine
the bearing to the station.   I had an MN-36 Football next to the DU-1 for
static display, and I explained that there was a loop inside the MN-36 that
was motorized and worked the same way as the manual DU-1.

I then mentioned that our equipment tent has a Gibson Girl and explained
what it did, how it was used, and that downed crews were found using the
same DF process from land bases or flying boats.  I explained these were
examples of “Passive DF”.   I then explained how the SCR-247N could be used
by a lost pilot to get a bearing to a known ground station by pushing the
transmit button on the Transmitter Control Box in order for a ground
station to give a pilot a bearing to the station.

I explained the function of the Command sets (short range air to ground /
air to air)  and contrasted that to the function of the Liaison radios
(long distance).  I showed them the inside of a command receiver as many of
the younger people had never seen a vacuum tube.   I explained what each
box did and how they could be located in different parts of the airplane,
and what the pilot's receiver and transmitter control boxes did.

Demos were varied.
Transmit on the 274N and listen to the signal on the 274N receiver or the
BC-348Q.
Transmit on the BC-611 and listen to the signal on the 274N receiver or the
BC-348Q.
Feedback considerations aside, these demos worked fine and were well
received by the visitors.

The SCR-247N was on 3885.  Last year, my antenna was a 45 foot wire that
exited the CommsTent, went over the top and down the other side, then ran
parallel to ground around the perimeter of the tent at a height of just
over 6 feet.   This year, I used a Hustler 75M Mobile antenna attached to
one of my wife's biggest baking pan (yes, with prior approval....you don't
get to be married for 44 years without asking about something like this
first....).  The assembly was hidden behind a canvas partition in another
part of the tent.  A counterpoise was used.   Matching was accomplished by
my custom box of a 4:1 UNUN and series matching capacitor and MFJ Tuner.
Matching was not a problem

I explained the use of the BC-221 Frequency Meter and explained how all the
various radios were netted to the mission frequencies before a mission.

I explained the use of the SCR-522 and how it was used alongside the
SCR-274N and SCR-287 radios.  I had the BC-608 “Pipsqueak” unit running and
explained that this was used to aid the British in determining the position
of their own aircraft.   I explained that every minute for 14 seconds, the
Pipsqueak would cause the SCR-522 to send out a signal, and the ground
stations would DF (triangulate) on the signals to get an accurate position
of the Spitfires, Hurricanes, etc.   That position, combined with known
winds at altitude and the specific performance of the various aircraft
types,  the best intercept solution to intercept the German aircraft would
be determined.   Explained this was pre IFF.  Most visitors had no idea the
British had to do this.  My goal was to get the visitors to understand the
complexity of how the British got their planes to intercept the Germans;
 it was a LOT more complicated than “Go East young man”....... and the
computations were done without computers!

To tune and net the SCR-274N each morning,  I had an ICOM transceiver in a
plastic container under a canvas tarp on the bottom shelf of my big table.
Day to day tuning of the antenna was minimal, and surprisingly the radios
held frequency very well day to day.   Netting the SCR-247N TX to 3885 was
quick using the ICOMs band-scope.

What can be improved and how?

Antenna for the SCR-274N.   The mobile whip worked OK, but others not on
the field were unable to hear me at the appointed times.  And, since I was
making short transmissions during my demos (with proper FCC ID.....) that
may be a good thing.   I need to get a wire antenna vertically up through
the top of the tent then horizontally to another tent.  There are
non-technical reasons why this is a challenge, but I will try again next
time.   I enjoy POTA (Parks on the Air) and I use a 55 foot wire to a 9:1
balun for 40M.  No counterpoise, and it works very well.   I'm doing to try
that on 80M as well.    Try as I might, I've never gotten a 274N
transmitter to work directly to a wire regardless of using a counterpoise
or not.  This is why I  go from the 274N via a 4:1 UNUN and series matching
capacitor into the MFJ tuner;  I can get 50 ohms unbalanced into the tuner
and let the MFJ handle matching whatever I put on the other end.   The
visitors never see this stuff.

Build a DC-DC converter for the BC-221 so I can actually demo it.  It
currently runs off of 110 VAC and that doesn't do me any good in the field.

Get dud tubes for the BC-375 to display them.

Have a code practice oscillator available for the young kids to play with.

My mic for the SCR-274N went belly up on Sunday afternoon.  Bring a second
mic.

Conclusion / comments

Being able to demo the SCR-274N and BC-611 at will for people was a huge
success.  Most people assumed that radios were just replicas until I turned
on the SCR-274N and they heard the dynamotors spin up.    “You mean this
stuff works?”.....   “Yup, let me show you”....

My setup was well received by young people.  I had kids turn the DF loop if
they wanted to for a “hands on” experience.

A father and daughter came into the tent.   He said his father (her
grandfather) was a radio operator on a B-17 during the war.  I told them
the radios I had were the ones he would have used.   After I gave them a
demo, I noted some tears starting to form in the granddaughters eyes.
Encounters like this make all the time and aggravation of getting these
radios restored and working in the field worth it.   We talked for quite a
few minutes afterwards.

A young girl, maybe a teenager, came in and I gave her a demo.   She then
asked me “that's good, but how do you address the battery issue on the
BC-611?  They can't be good after so many years”.   I said that was a great
observation and told her about the DC-DC converter inside the unit.  We
talked a bit more about restoration and she then said she  enjoys restoring
first generation computers and runs into some of the same kinds of problems
I run into.   OK, she's not restoring radios, but she is restoring!  That's
a start!

Saturday night around sunset we had weather warnings about a severe squall
line that was approaching.  Heavy rain and strong winds, but the line was
pretty narrow.   Each night I cover my radios with a vinyl tarp, even
though the radios are in a zipped canvass tent.    The tent is old and
leaks a bit.....   So, I got the tarp over the radios and we secured the
tent, double checked the tie downs etc.    The squall line hit and the
winds were strong.   All of sudden people were yelling as one of the main
sleeping tents that housed about 10 cots and people's belongings went
airborne.   Apparently wind got under the tent.  So, it was all hands on
deck to get the tent back over people's belongings and we sat on the tent
getting drenched to the skin for several minutes.   We spent about an hour
afterwards helping to get the tent back up.... all was completely soaked.

Afterwards I realized that in the Comms tent,  under the vinyl tarp, in a
tight plastic box, in a small canvas bag.... was my poncho..... nice and
dry.....

73 Mark K3MSB
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