14oct16: 5/8MHz testing
What we did:
- tx 4 broad band amp was replaced (after 12oct14, before start
of this run).
- looking offline, alfredo said it was drifting around.
- Setup 5.125 Mhz, mesh 15 feet below reference.
- Look to see reverse power when mesh this low (8 mhz likes this
- saw large reverse power
- fwd pwr: 20-30 KW
- rvs pwr : 0 to 5.5
- move to 8.175 MHz. mesh 15 feet low.
- tx 4, 6 forward power computer readout was saturating
- Also saw large 2nd harmonics.
- Measured drive level at broad band input.
- values linear to 0 dbfs drive.
- Found the hittite 6 port rf switch for tx4,6
- So previous values tx 4,6 may be inaccurate.
- replaced 6 port rf switch
- calibrated the loss (with cables).
- tx1: 10.5 db
- tx2: 10.6 db
- tx3: 10.4 db
- tx4: 10.4 db
- tx5: 10.7 db
- tx6: 10.4 db
- Continued to use 10.5 db offset in anritsu spectrum
- Saw tx 4 monitored output continuing to drift with time.
- put tx4 front panel broad band output on spectrum analyzer
(with 10db pad).
- ran 0 span 600 secs, 100KHz rbw, .1 db/division.
- saw .03 db drift down in 600 secs. so broadband output is
- measured gain of tx4 broad band:
- -1dbfs = +1.2 dbm at input to broadband.
- broadband meter read 140 Watts into 50 ohms.
- 140 watts=51.5 dbm. so 50 db gain.
Summary plots of the day
- Page 1: morning, 5 MHz, mesh 15 ft low
- Page 2: morning, 8 Mhz. mesh 15 ft low
- tx3 (green trace) tripping on reverse power 10.95 with 50KW
- tx4,tx6 low.. probably because of bad 6port monitor switch.
- Page 3: afternoon, 8 MHz, mesh 15 ft low, new 6port switch
- tx4 power level moving around.
- output of broadband looked stable (to .03 db over 10
- tx3 trips (15.02 ) on rvs power with fwd pwr=70 KW.
- 14.25thunder, lightning, rain.
- put monitor cable loss through switch in table.
- plot rvs/fwrPwr for 5 Mhz at 15 ft low.
Problems we found:
- Hittite 6 port rf switch (ports tx4, tx6) were bad.
- replaced the switch
- showed large 2nd harmonic, saturation of fundamental.
- Forward power meter tx 6 reads higher than the value from
the coupler by up to 30 KW.
- This could be a calibration problem.. But we also saw large
harmonics on tx6 ...
- 5MHz will not work with mesh 15 feet low.
- Tx4 output power still drifting.
- saw arcing on . turning of tx 4 (or maybe it was tx3) caused
it to go away.
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