K6MYK Repeater information.
Repeater operations by Burt, K6OQK.
The original repeater had rack panels that were all different colors with extra
holes from whatever they were before becoming a part of the repeater.
When the repeater was going to be brought to the San Fernando Valley
Radio Club's picnic, Art, Bill and I brought the repeater back to
Northridge to give it an overnight face lift. All of the equipment
was removed from the rack and all of the panels were removed. They
were painted the same color and all of the holes were filled With
screws or cover plates. We were up all night laughing, giggling and
probably cursing.
The telephone dial on the front was the local control of a stepper
relay used to access various functions of the repeater and was
probably a modification that happened in about 1968. The original
control system only had four basic functions using four supersonic
tones in the region of 15 to 20 kHz. The original functions as I
recall were:
1 Transmitter on
2 Transmitter off
3 Audio transfer
4 Squelch adjustment up and down
The 420 control receiver was a very modified ASB-7 receiver. It was
a wideband FM system, probably in the vicinity of 100 kHz deviation.
The 420 path from Northridge was not very good as it had to shoot
through Cahuenga pass, the higher peak just west of Mt. Lee. Later
Art added one or two pre-amplifier stages to the original ASB-7. The
pre-amp/s were built in to cavities from another piece of Military
Surplus equipment that originally used light house tubes. Instead,
Art used Nuvistors that had grid caps and plugged into the lines
inside the cavities.
In my memory the repeater was about the only thing that ran in that
part of the Mt. Lee building. It was located in a room within a room
about, maybe 8' by 8' that had a glass window looking into the outer
area room. When you walked into the repeater's room there was only
the sound of a few fans whirring. the receiver speaker was usually
left turned down. If the repeater was in use, and it usually was,
you could hear relays clicking from inside of it. When the ID would
start you would hear the 35mm mag-strip film pick up speed and move.
You could hear the film riding on the silver shoe and then the
contacts falling into the various holes that were punched in the
film for the MCW ID. There were three sets of parallel holes. One
was the K6MYK ID, another the K6ROC ID and the third was a single
hole to tell the loop to stop. There was a switch for switching
between the K6MYK ID and the K6ROC ID. The 35mm mag-stripe was about
a five foot loop. The Code consisted of holes punched using a
standard hand held paper punch. A dit was one hole, a dash was three
holes and a space between a dit and dah was three spaces. The space
between the DE and K6MYK was six spaces. Good phrasing actually.
The drive for the film loop was an old turntable motor assembly with
the shaft extended through the front panel to carry the 35mm drive
sprocket. There was also a Shure Bros. tape head that rode on one of
the mag-strip tracks that contained Millie's voice ID. When Art had
to make a new ID track he had to take a tape recorder to the repeater
and plug the ID tape head into the recorder in place of the
recorder's normal head. As I recall it was a Bell and Howell tape
machine. It was the same one he later used for the QST bulletins.
There was also one other unique sound that could be hear in the
room. That was the sound of the audio transfer relay when it would
move. It was a Ledex rotary selenoid. Every time it was pulsed it
would rotate a standard rotary switch one position - basically a SPST
as a result of every other contact wired causing control each pulse
to toggle the audio between the two-meter receiver and the 420
control link receiver.
The two-meter receiver (AM) could be switched between the normal input on 145.18 MHz and 145.22 MHz, the K6ROC LACD frequency.
I mention all of this because the memories the pictures brough back
to me. I still have a full set of schematics of the original
repeater and its control system K6OQK.
From Paul, W0rw:
i would go up to Mt. Lee (Mt. Hollywood) every Monday (1960's) to operate K6ROC, It was the second frequency of the K6MYK repeater, K6ROC was the LACD frequency, locally. This was in the 1960's.
Most of the users had Gonset Communicators and the city gave the crystals to the LACD members.
See the 'K6MYK' repeater article in QST, March 2004...p52, written by Bill Pasternak, WA6ITF.
The Mt Lee building operator/guard would 'buzz' the entrance gate open after you told him who you were.
(This building was the first TV studio/stage for the Don Lee Broadcasting Co.
W6XAD/ W6XAO. TV on 44.5 MHz. Having the studio up on Mt. Lee eliminated the need for a VHF transmission link down to the city.)
i am not sure he was an 'Officer' but he handled traffic to outlying PD's around the country.
i think his traffic was mostly stolen car info. He operated on 5140,5185/5195 kHz, CW, i watched him operate.
He was also called the "Link" operator. He also kept the Fire water Storage Facility (Swimming Pool) clean.
He sat in the same area where all the LAPD Receivers were located, There was a tall rack
of about 19 Motorola Unichannel VHF receivers for the sector car frequencies.
All those channels were microwaved down over the "Link" to LAPD HQ.
The Dispatchers listened to one or 2 of those channels and would all take turns transmitting over the Elysian Park MF Transmitter on 1730 kHz AM, (KMA367). Their "Transmit"
control took turns, when they pushed their PTT control they had to wait for their red light to come on, when it did they had the "Air".
Mt Lee also had lots of other transmitters, The LACD had about 10 different GE Base Progress Line Stations, one for Command (47.66) , and one for each City Department: Police, Fire, Public Works, Red Cross, DWP, etc, These were all remote controlled from the old lower office section (in cubicles) of the main Mt. Lee building.
They were hardly ever used.
The same layout of stations was also installed in the big LAPD Command Trailer. That trailer was taken to the Granada Hills HS for the San Fernando Earthquake communications.
The Valley LAPD station was KMA787 , Transmitting on 2366 kHz and the main VHF receivers for the Valley were up on top of the Van Nuys City hall. We (LACD) had a GE 450 Mhz base station there too.
The big 'TV Stages' at the rear of the building were empty and only other guy who had an office there was the RADEF Training guy, Skip Trigg.
This building has now been torn down because it really was indefensible in the high fire
risk area. The swimming pool was not enough to protect it. Now there are only communications shelters and the big 150? foot tower remaining.
Paul w0rw