- During the heating campaign the 8 MHz radial element on tower
1 had arcing problems when we were transmitting with the 5 MHz
- After the hf run, the 8 MHz radial balun was removed. holes
were found in the heliax (toward the top of the balun).
- The heliax going through the balun was replaced.
- On the 3rd day of the oct16 hf campaign, tx 5 failed. It
remained offline for the rest of the campaign.
- alfredo and victor have worked on the tx 5 since the
What we did:
- mesh at 5 MHz reference position.
- use 5.1 MHz, rcp
- we used the 430 MHz ch and the interim correlator to monitor
- bring all 6 tx up at lower power (25 to 45 KW)
- At 13.3 hrs tx5 was at 40KW. When we increased the
power, power went to 0.
- alfredo said that the tx did not trip, but that the output
of stage 2 was not working properly.
- We brought the other 5 tx up to 60 to 70 KW
- The ch spectra showed arcing.
- We then went down to the bowl.
- We could here an arcing coming from the 8 MHz radial tower 1
(though not very loud).
- At 13.48 hrs we brought the power of the the 5MHz radial
(tower 2) to 0. The arcing stopped.
- At 13.8 hrs - switch to 8 MHz check the reflected power (1 tx
at a time) to see if we damaged 8MHz radial tower1
- a tx was brought up to about 16 KW and then we measured the
reflected power (on the fieldfox).
||rvs power note
- Tx 1 reflected power was no larger than the others..
so it probably isn't damaged (at least we didn't see it
at low power).
- See page 2 of the plots..
- Carlo mentioned that the safety cable for tower 1 was passing
close to the ground cables of the two elements.
- He climbed the tower and removed the metal safety
- At 14.7 hours we switched back to 5MHz and brought the 5
transmitters up to 50 to 70 KW.
- We went down to the bowl to listen for arcing from tower 1..
we didn't hear anything
- Looking at the ch monitor, there was still some arcing seen
- see page 3 of the plots..
Summary plots of the day (.ps)
- Top frame: transmitted power measured from rf coupler in dbm.
- middle frame: transmitted power converted to KW.
- bottom frame:
- colored lines: synth drive level used for each transmitter
- red lines. Total power measured from carriage house monitor.
- 1 second dumps. Used to check for arcing.
- Page 1: 5 MHz 13:00 to 13:42
- this shows when tx 5 failed (13.3 hrs).
- The arcing is seen in the bottom panel (red lines).
- The arcing stopped when we brought tx3 down (13.47)
- Page2 : test 8MHz. 1 dipole element at a time
- We measured the reflected power for each forward power.
- Page 3: tx 5 MHz after tower 1 safety cable removed.
- We did not hear arcing down at the bowl.
- The ch monitor still showed some arcing .. but it could have
been coming from something else.
- The power level for the test with no safety cable was less
than the first test (that showed arcing)...
- So maybe we need to crank the power up next time..
- TX 5 at 5 MHz still has problems.
- The arcing on 8 MHz radial , tower 1 is still occurring when
we use the 5 MHz tx.
- the 5 MHz radial on tower 2 is causing the arcing (at least
turning it off stops the arcing).
- We did not see high reflected power from tx1 8MHz (twr1 radial
which had the arcing) when we used 16 KW.
- so hopefully it is not damaged.
- After removing the safety cable on tower 1 and then
transmitting with 5 MHz.
- we could no longer hear arcing from the tower
- There was still some arcing seen in the ch data.
- the power for this test was a little lower than the value
used to generate the initial arcing.
- initial: 5MHz tower3 radial - 65 KW,
- after : 5MHz tower3 radial - 60 KW.
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