- We tested 8 MHz.This was to the first hf test with the
430MHz tx since the mar18 campaign.
What we did:
- The mesh was in the 8 MHz position
- we transmitted at 8.175 MHz rcp.
- 430 tx, single beam -> gr. za at za=1.06
- gr -> usrp
- ch -> echotek [4.5,8.5]]
- 12:00 start to bring up tx's
- tx5 pa cathode current 17Amps with only 40Kw output.
decided not to raise tx5 any more than 50KW. alfredo will look
into it later.
- 12:36 50KW each tx output.
- 12:48 had to restart synth gui, was 100% cpu cycles
- 13:40 disabled all tx but tx1. Measured rise time pulse
- siggen -> scope T (hiImp) ->synth driver
- coupler power tx 1 -> scope.
- Use rf on/off button to see the rise time.
- Tried hp siggen, but the button bounces. Ended up using hte
srs output and button.
- 14:07; all tx back online. the modulation was accidentally
left on the srs drive.
- 14:17 modulation of srs drive turned off
- 14:21 disable rf for 10 secs.
- 14:30 cycle mode 4sec on, 6 sec off. 407 KW.
- 14:39:09 cycle mode 2 on 8 off
- 14:43 stop auto toggle to get power level.. about 420 KW.
- 14:46 done
HF output power
Plots showing hf tx drive and
output power (.ps) (.pdf)
- page 1:
- Top: hf rf coupler output vs hour of day
- Each color is a different tx.
- the low purple level is when tx5 was offline.
- The rapid changes in power are during cycle modes.
- middle: output power in KW
- bottom: synth drive amplitude (in dbf)
- page 2: hf drive power vs hf output power
- the output power (in KW) vs input drive power (in dbf) is
plotted for each tx.
- values that lie below the trend, occur when an rf off occurs
during a spectrum analyzer power average. cycle mode points
have been removed.
dbf Drive for 50 KW output.. 8MHz
Generator power vs
The data from the 3 running generators was
used to measure how much generator power was needed to drive the 5
then 6 hf transmitters.
Generator output power vs hf
output power (.ps) (.pdf)
- Top: generator output power vs time.
- middle: total rf output from 5 then 6 hf tx
- bottom: gen power vs hftx output power
The rise time, delay through tx1 was measured.
The setup was:
- siggen output (8.175 MHzMhz sine wave)->
- T on oscilloscope chan1 (hi impedance) ->
- phase synth inputs
- rf Coupler tx 1 output -> control room front panel
-> oscilloscope chan2 input (50 ohms)
We set the oscilloscope to single trigger on
the rising edge of channel one. We then used the rf on/off button
on the srs siggen to turn the 8.175 MHz sine wave on.
The plots show the delay from
siggen output to tx1 rf coupler ouput (.ps) (.pdf)
- Top frame: delay measured using srs siggen.
- Black is the signal leaving the srs
- red is the tx1 rf coupler routed back to the control room.
- The difference is about 3 useconds.
- There may be a large fraction of a usecond in cable delay
going from the control to the tx and coming back.
- Bottom frame:
- this used the hp siggen for the test.
- The rf on/off button on the hp siggen bounces. Looks like it
takes up to 400 usecs to stabilize.
Plasma line movies
- Plasma line movies were made using the echotek and the usrp
data. They had 10 sec integrations.
- A higher resolution movie was made with the usrp data. It
blows up the freq and range showing the f-reqion line. The time
resolution is still 10 seconds.
to the movies
- Tx5 was not raised about 50KW because of the high PA
- The delay from siggen out to rf coupler output (back at the
control room is 3 usecs).
- we tried autotoggle 4on, 6 off, and 2 on , 8 off.
- There was a large enhanced plasma line after fof2 got above
- A hires movie showed that the plasma line peak was being
modified (smoke..) well before fof2 hit 8.175MHz.
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