13sep16: hf rogowski coil then 8.175 MHz
What we did:
- 10:00 - 11:30: measured the currents in td8 cable with
the rogowski coil while transmitting at 5.129 MHz
- 11:30 - 11:50 : bring up all tx using 8.175 MHz.. but we were
transmitting out an open port (unconnected dummy load) rather
than the antenna
- 12:06 - 13:00 : bring up tx 1,2 using 8.175 MHz
(after switching to antenna port).
The plots show the transmitted power during the
testing (.ps) (.pdf):
- Page 1: entire test.
- Top: dbm read back from the rf coupler
- bottom: power converted to dbm.
- 10:10 to 11:30 we were cycling the tx on 5 secs, off 5
- Page 2: drive level (exciter) from signal generator.
- top: signal generator as set by hfsynth program. Y axis is
db below max drive
- bottom: measured output power (KWatts) for the given drive
- Page 3: drive level, power during rogowski test
- Top drive level.
- bottom output power (KWatts). peak hold values
- We were cycling tx on,off every 5 seconds.
- The estimated drive power during the rogoski test:
- tx1:25KW, tx2:21KW, tx3: 27KW, tx4:30KW, tx5:20KW, tx6:18
KW (radial pointing at td8).
- total tx power: 141KW
- Page 4: 8.175 MHz. drive level, measured power went
transmitting into open port
- tx 2 and 4 were connected to dummy loads. They started to
smoke (since the water wasn't circulating)
- tx 4 tripped (probably at 11.83 hrs).
Rogowski coil at 5.129
- 5.129 MHz was transmitted
- We toggled the rf 5 sec on, 5 sec off.
- Measurements were done on the td8 cable
- all 6 tx transmitting
- only tx 6 transmitting (radial pointing at td 8)
- We also measured the current in the ground cable (from td8
cable to ground).
- The coil was mounted on rightmost td 8 cable (with back
to center of dish) above the ground cable connection
- we wrapped thin foam around cable to the thickness of the
coil, then taped things closed.
- The preamp box sat on top of the limit switch box (next to
- a 15' cable ran from the preamp box to the tek 5ghz scope.
- We put 2 chokes on each end of the 15' cable (multiple loops
through the choke) to cut down the scope from
overloading at the transitions.
- The scope setup was:
- 20 mv/division,5ksmp sampling, 100000 points
- scope sample aliasing.
- The sine wave was 5.129 MHz. the sampling rate was .0002
- each .0002 sec sample moved 1025.8 5.192 MHz cycles, so 5
samples covered 1 sinewave cycle.
- We acuired a single traces on the scope and then stored them
on a memory stick.
Voltage output by rogowski coil
The plots show the scope trace
for each measurement (.ps) (.pdf)
- page 1: 20 seconds of data (full trace)
- top frame:td8 main cable, all 6 tx cycling
- You see the 5 second on, off cycle
- 2nd frame: td8 main cable, only tx6 (radial) cycling
- The peak went from 30 to 20 mv. About 70% of all tx on
- bottom frame: td 8 ground cable, all tx cycling
- peak value of 20 mv. 70% of td main cable with all tx
- Page 2: blowup showing individual scope samples at turn on.
- The under sampling take 5 samples to cover a cycle (actually
- The + show the scope samples
Currents in cables
Using the rogowski coil calibration sheet, dana
- main cable all tx: 30mv -> .85 Amps rms.
- main cable tx 6 : 20mv -> .57 amps rms
- If we assume the currents are linear with power, the
currents expected during a heating r
|power Out (KW)
|current (Amps rms)
| 3 A
- So we might see 3 + amps coming down a tiedown cable.
- about 2/3 of that goes down the grounding cable.
11:30 to 11:50 we started to bring up the tx at 8.175
MHz. The output rf switch had been plumbed incorrectly.
- the heliax was connected to the output port that normally goes
to the dummy load
- The output port that goes to the antenna was left open
- except that tx 2 and tx 4 actually had dummy loads connected
to these ports.
- water was in the dummy load, but it was not circulating.
- The tx's were then switched to filter B (8 mhz) antenna.
- This routed the output power to the open output port
of the rf switch.
- The tx were brought up slowly. There was pretty high reflected
power on the transmitters.
- Page 4 of the tx output power (see above) shows the output
power (measured before the output rf switch) starting to go up
around 11.75 hours.
- tx 4 tripped about 11.82 hours.
- the other tx got up to about 5 kw before we shut them
down (dummy loads started to smoke..)
We then switched tx1 and tx 2 to antenna. They
were brought up to about 20 KW and left there for about 20 minu
processing: x101/160913/process_day.pro, getrogowski.pro
- Rogowski coil
- need chokes on line from rogowski preamp to scope.
- .85 amps rms at 140 KW 6 transmitters
- .57 amps rms at 18KW, tx6 by itself
- This was measured in 1 td cable.. there are 2
cables/tiedown and 6 cables in total.
- For an hf run we would have around 3 amps/td cable at 500KW
- The dummy loads had smoke coming out of them (with no
circulating water). Not sure whether their calibration has been
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