Station Log of WC2XSR/13
July, 2002 - September, 2002
This is a copy of the Official Station Operating Log of Part 5 Experimental Radio Station WC2XSR/13.
It is presented here in reverse order, so that the latest log entry will appear at the top of this page. That way, you don't have to scroll through the whole thing to get to the new log entries. Since this log is transcribed from my notes, the wording tends to be a bit clipped at times, but, hopefully, the meaning will be clear.
30 SEP 2002- Transmitter off the air at 1431 CDT for antenna measurements. Transmitter returned to the air at 1510 CDT.
Frequency is 166.500 KC @ 400 watts. Modulation is QRSS30, signing XSR, followed by a 10 WPM CW ID.
29 SEP 2002 - Transmitter off the air at 1145 CDT for antenna measurements. Transmitter returned to the air at 1541 CDT.
Frequency is 166.500 KC @ 400 watts. Modulation is QRSS30, signing XSR, followed by a 10 WPM CW ID.
The changes recently made to the antenna system has caused the system resistance to decrease slightly, and the transmitter is running excessive drain current. The reflected power was running excessively high, measuring nearly 100 watts reflected with 500 watts forward power. It was necessary to add a ferrite core step-down auto-transformer between the 50 Ohm transmission line and the input to the antenna tuner.
The transformer consists of a single FT-193A-J core with a total of 21 turns of #14 THHN wire. The transmission line connects across the entire winding, and the input to the antenna tuner is connected to a tap on the auto-transformer at 16 turns from the ground end of the transformer winding.
The addition of this auto-transformer has brought the drain current back down to the design value of 20 amperes @ 26 volts DC input. There is very little heating noted in the auto-transformer core at the 400 watt power level under continuous operation. The reflected power has been reduced to 20 watts with 420 watts forward power, for a VSWR of 1.7:1, which is within acceptable limits.
RF power is measured with a Bird model 43 wattmeter using a slug which has been calibrated at 166.5 KC.
The antenna current reads approximately 2.6 amperes, but this may be in error; I will have to recalibrate the meter and verify this value.
A frequency span table was derived for the antenna system and tuner showing the tuner switch positions and the frequency coverage for each switch position. The LF Coil is the external 5-gallon bucket coil which is mounted on top of the antenna tuning unit. The Min and Max frequencies are determined by the tuning range of the variometer coil.
|COIL TAP POSITION||LF COIL IN CIRCUIT||MIN FREQ, KC||MAX FREQ, KC|
Note that there is a small frequency span between 208 - 224 KC which the tuner cannot reach without modification. Whenever two switch positions cover the same frequency, it is better to use the higher numbered switch position because this uses less of the main coil and reduces tuner losses slightly.
28 SEP 2002 - The transmitter went off the air sometime between 0500 CDT and 1000 CDT.
The computer controlling the transmitter crashed and shut off the carrier. Back on the air at about 1012 CDT.
At 1120 CDT I shut off the transmitter and began the modifications to the top loading wire. I managed to raise the main tower end about 5 feet. Due to clearance problems I could not manage to get it up any higher on the tower. Nevertheless, this did decrease the coupling between the antenna and the HF dipole. The separation runs between 8 to 10 feet along the length of the antenna top loading wire.
The VSWR increased slightly, and I will have to measure the antennas impedance and modify the tuning system to bring the VSWR back down again.
Transmitter back on the air again at 1250 CDT. Power output is 400 watts, modulation is 10 minutes on / 10 minutes off / 10 minutes on / 10 minutes off / 10 minutes on / 10 minutes off / 10 WPM CW ID, then the cycle repeats.
27 SEP 2002 - In an effort to assist Alan Melia, G3NYK, in confirming reception of WC2XSR/13, I have shifted frequency slightly off of 166.500 KHz.
This evening starting at 0400 z (2300 CDT here) WC2XSR/13 began transmitting 2 Hz higher in frequency, at 166.502 KHz.
In an attempt to help his weak signal detection efforts, I have also changed the modulation cycle to a repeating sequence of 10 minutes ON and 10 minutes OFF. Following three repetitions of this sequence, there is a 10 WPM CW ID which says "DE WC2XSR/13 DE WC2XSR/13". This ID occupies about 55 seconds. Four seconds after the ID ends, the 10 minute ON cycle starts once again.
Since you will probably not be able to copy the CW ID, you will likely see that as an OFF period. This, combined with the preceding 10 minutes of OFF time, will show up as an 11 minute OFF cycle. So, the sequence will be: 10 min carrier ON 10 min carrier OFF 10 min carrier ON 10 min carrier OFF 10 min carrier ON 11 min carrier OFF (repeat) I will stay on this modulation cycle for the next few days.
Later today, I will shut down in order to move one end of the top wire away from my HF dipole. I'll return the transmitter to the air as soon as possible. Most likely the down time will be will be an hour or so.
27 SEP 2002 - Noticed that the antenna current was a bit low and somewhat erratic.
I discovered that one of the open wire feeders running to my multi-band HF dipole antenna was broken off, apparently as a result of the recent tropical storm. I lowered the HF dipole antenna and repaired the feeder. After repairs, it was necessary to retune the LF antenna tuner for maximum antenna current. I had to reduce the final PA drain voltage slightly to bring the DC power input back to its normal value. Apparently the antenna impedance has changed slightly what with the slight reconfiguration of the multi-band dipole in relation to the LF antenna.
Operation back to normal at 400 watts output. Modulation the same as before.
When time permits, I will climb the rear tower and raise the mid section of the LF antenna where it connects to the top loading wire. That will increase the separation of the LF antenna to the dipole by about 5 feet and hopefully reduce the interaction of the two antennas. This interaction is not all bad, as calculations indicate that the increased top loading caused by the HF dipole increases the radiated power of the LF antenna by a slight amount compared to not having the HF dipole present.
26 SEP 2002 - Tropical Storm Isidore has passed; minimal wind damage; all antennas still up; WC2XSR/13 transmitter power is back to 400+ watts; 20" of rain; barometer made it down to 29.13"; not enough sleep; a very long day at work; life is good!
25 SEP 2002 - The power level of WC2XSR/13 is down to about 350 watts due to antenna detuning and increased local environmental losses caused by the wind and rain from tropical storm Isidore, which is slowly approaching New Orleans this evening.
Right now, the winds here are running about 30 M.P.H., with higher gusts. Moderate to heavy rain is falling, and about 9" of rain have fallen within the past 30 hours. Between 6 and 15 additional inches is expected during the next 24 hours. It is quite possible that this QTH may be flooded.
Transmission will continue until the antenna is blown down or the power fails completely. Although the emergency generator will easily handle the WC2XSR/13 transmitter, if the water gets too high, the generator will have to be shut down for safety reasons.
23 SEP 2002 - WC2XSR returned to the air this evening at about 1825 CDT.
Frequency is 166.500 KC @ 400 watts. Modulation is QRSS30, signing XSR, followed by a 10 WPM CW ID.
Most of the antenna structure modifications have been completed, and the top loading wire of the antennas has been temporarily rigged in place. I'll have to lower it again to re-rig the lines permanently. The modifications have allowed me to raise the outer end of the loading wire another ten feet, which increases the effective height of the antenna slightly. This is reflected in a slight increase in antenna current of about 0.05 amperes, for a total of 2.25 amperes as measured on my new RF ammeter.
When I get the time I will shut down and remeasure the antenna impedance again and correlate the readings of the two RF ammeters to ensure accuracy in the readings. I also plan to raise the end of the top loading wire which is connected to the vertical radiating wire by about 6-10 feet. This will give another small increase in the effective antenna height and will increase the separation of the top loading wire from my HF ham dipole system.
21 SEP 2001 - After almost a month of trouble-free operation, at 0830 CDT this morning, WC2XSR/13 went off the air for repairs and modifications to the roof top tower which holds the outer end of the top loading wire for the antenna.
I am removing a 6-meter beam and adding another 10 feet to the height of the tower. All the guy wires and roof anchor points are being replaced. Weather permitting, I will have the job finished tomorrow. I was hoping to complete it today, but even though I worked through three rain showers, the afternoon thunderstorms command my instant respect, and I retired from the roof, posthaste! I had managed to replace the roof anchors and the lower two sets of guy lines earlier during the past two weeks without shutting WC2XSR/13 down, but the remainder of the construction work requires that I drop the far end of the top loading wire. I'll be back on the air as soon as possible.
29 AUG 2002 - Transmitter off the air between approx. 1945 CDT and 2054 CDT.
The failure was due to an electrical fire. The 1450 KVA UPS unit malfunctioned due to reasons as yet unknown, and went online, producing an abnormally high output voltage. This excessive voltage fried four surge strips which were plugged into the UPS, resulting in flames from two of the power strips. Luckily, the flaming power strips caused no serious problems, and the fire was quickly extinguished as soon as the power was removed.
The UPS also suffered a smoke-releasing internal failure and died. (The shack still smells like a charred circuit board.)
The power failure shut down the control system for the transmitter and my entire computer network as well.
After determining what had happened, a quick rewiring with heavy-duty extension cords got the computer network and transmitter back online.
24 AUGUST 2002 - Transmission continues unchanged with a transmitter output power of 400 watts, modulation QRSS30, ID is Loop 5, "XSR" followed by CW ID at 10 WPM.
20 AUG 2002 - I determined that most of the antenna current change during rainstorms is caused by water filming on the outside of the upper loading coil cover. Droplets on the cover cause little problem, but a continuous film of water is conductive enough to cause trouble. I applied a coating of water repellent (Armor-All) to the exterior of the cover, and water now beads up and runs off before the detuning becomes severe. The remainder of the detuning is apparently caused by the tree leaves in the vicinity of the antenna system getting wet during the rain.
Transmission continues unchanged with a transmitter output power of 400 watts, modulation QRSS30, ID is Loop 5, "XSR" followed by CW ID at 10 WPM.
17 AUG 2002 - Transmitter back on the air at 1430 CDT.
Transmitter output power of 400 watts, modulation QRSS30, ID is Loop 5, "XSR" followed by CW ID at 10 WPM.
I replaced the shorted PA MOSFET, it was the #2 transistor, the same one which failed the first time when I accidentally shorted out the PA tank circuit, drain to drain.
I also changed the voltage regulator system for the frequency control pot to eliminate the slight frequency shift which happened when the transmitter was unkeyed. Before the change, there was a +5 Hz shift of the carrier oscillator from 2.664000 MHz to 2.664005 MHz. This equaled a carrier frequency shift of 0.3125 Hz. Normally, this shift was invisible, because as soon as the transmitter went on the air, the frequency returned to normal. However, during the CW ID keying, the shift was evident if you looked at the ARGO screen in QRSS30 mode. In effect, there was a very slight downward frequency chirp every time the transmitter went on the air. Replacing the 3-terminal + 12 volt regulator and replacing it with a 10.6 volt Zener diode eliminated the frequency shift.
I also reworked the frequency calibration pot and resistors to limit the maximum frequency variation of the 2664 KC oscillator to +/- 50 Hz, which equals a 166.5 KC carrier frequency shift of +/- 3.125 Hz.
I also added a new coaxial input jack to allow varying the DC oscillator frequency control voltage by an external source.
These changes have been reflected in the schematic diagrams which will be posted on the web site.
The modified RF current sample transformer appears to work, but the reading is a bit lower than it was before. This may be due to the fact that everything is soaking wet. There was a thunderstorm and several inches of rain about an hour ago. I expect the antenna current to increase slightly after a day or so of dry weather.
16 AUG 2002 - Modified the RF current sample transformer so that the primary is a single pass of 3/8" copper tube passing straight through the center of the transformer core.
The insulation was changed from plastic to air, but the maximum RF voltage the unit will withstand has been lowered somewhat, However, the RF loss in the unit is considerable less than the plastic insulated unit.
I am unable to run tests on it until I get the transmitter back online.
15 AUG 2002 - Transmitter failure occurred at about 0440 CDT.
One of the output MOSFETs shorted out and shut down the transmitter. The probable cause was excessive drain-to-drain voltage caused by running the transmitter with a light load and elevated drain voltage. The transmitter will be off the air until I can repair the RF current transformer in the antenna tuner cabinet and replace the shorted transistor.
While the transmitter is on the bench, I will make some planned modifications to the front panel , oscillator circuit and the oscillator power supply.
It is unknown at this time as to when the transmitter will be back on the air, but hopefully within a week.
15 AUG 2002 - Transmitter back on the air again at 0415 CDT at 200 watts.
Will stay at reduced power until I can replace the RF current transformer insulator with a better one.
14 AUG 2002 - Transmitter off the air at 2100 CDT.
Power was falling from 400 watts to about 300 watts. Found that the center insulator in the new RF current transformer was overheating and becoming conductive. Turned off transmitter before it burned up and caused a fire in the antenna tuning cabinet.
14 AUG 2002 - Transmitter off the air at 1437 CDT for antenna tuner modifications.
I installed the new RF current sample transformer in the antenna tuner cabinet.
I also replaced all the steel hardware connecting the coil tap switch wires to the coil with brass hardware in an attempt to reduce the RF induction heating which was occurring with the steel hardware.
The coil switch setting is one tap higher than it was previously. I suspect this is because of the added capacity between the primary of the current sample transformer and the Faraday shield surrounding the primary. Measurements show the added capacity is about 12.5 PF.
Transmitter returned to the air at 1625 CDT.
13 AUG 2002 - Operation continues normally.
Transmitter output power of 400 watts, modulation QRSS30, ID is Loop 5, "XSR" followed by CW ID at 10 WPM.
Considerable showers and light rain today, so I cannot install new RF ammeter current transformer in antenna tuning network cabinet.
12 AUG 2002 - At about 1530 CDT the two "D" cells feeding the audio booster amplifier between the CD player and the transmitter began to fail.
This reduced the audio drive to the transmitter keying circuit so that the transmitter began to drop off the air during transmission of the long dashes. As the battery became weaker, the transmitter began trying to key on and off the air at the control audio frequency of 2 KHz. This resulted in a broad but weak signal on the air.
This battery failure mode continued until about 2100 CDT, at which point the battery failed completely. Shortly thereafter, I replaced the battery with a surplus cell phone car adapter connected to the auxiliary +15 Volt DC output connector on the transmitter. The adapter supplies 4.5 Volts DC to operate the amplifier.
The transmitter was restored to normal operation at 2110 CDT.
11-12 AUG 2002 - The transmitter went off the air at about 2250 CDT and was placed back on the air at 0410 CDT.
The cause of the downtime was the CD player - again. I had replaced the CD with a new copy, because I discovered that the CD player would not read some portions of the old disk. At first the new CD played OK, but later in the evening it too, was misread by the CD player.
I replaced the CD player with a different unit. I had to add a small audio amplifier between the CD player and the transmitter, since the audio out of the new CD player was not sufficient to drive the transmitter's keying circuit. Not having an AC power supply handy, I connected the amplifier to two "D" cells. These should power the amplifier for a few days.
11 AUG 2002 - Sometime between midnight and 0830 CDT, the transmitter went off the air.
This was due to the failure of the CD player which plays the ID loop for the transmitter. The CD player shut itself down several times yesterday evening for reasons unknown. Since the actual ID signal controls the RF output, any loss of the audio from the CD player will shut down the transmitter. This is the second one of the same model CD player that has failed in service. The previous unit failed when it would not recognize any CD's at all.
I used this particular model because it has sufficient audio output to drive the transmitter audio input directly. I my have to add an audio amplifier stage to the transmitter so I can use other types of CD players. An alternative is to use the sound card output of a computer to drive the transmitter. I initially rejected this due to the undesirability of tying up a computer for this use, and the increased cost of electrical power required to operate the computer compared to the relatively minuscule cost of operating a CD player.
The transmitter was back on the air at about 0850 CDT.
10 AUG 2002 - Reception reports of WC2XSR/13 to date total four. Distances to the receiving stations are 35, 40, 117, and 278 miles.
This evening, I completed calibration and assembly of a new RF ammeter to be placed in the tuning unit cabinet. The ammeter pickup assembly is designed to handle the high RF voltages encountered in the antenna system. It is switchable, with full-scale ranges of 1.5, 3, 6, 15, and 30 amperes.
8 AUG 2002 - The transmitter unexpectedly went off the air at about 1325 CDT.
The cause was unrelated to the transmission equipment, but was instead caused by the failure of a backup UPS system which supplies power to the networked computers at this location. The CD player which was playing the ID loop was powered by that UPS, so when the UPS failed, the CD player also stopped, shutting down the transmitter automatically.
Primary AC power was temporarily restored at about 1453 CDT and the transmitter was returned to the air at that time.
7 AUG 2002 - Transmitter off the air between 1509 - 1544 CDT for equipment tests to perform initial range calibration on a newly fabricated RF antenna current transformer. Returned to the air with transmitter output power of 400 watts, modulation QRSS30, ID is Loop 5, "XSR" followed by CW ID at 10 WPM.
6 AUG 2002 - At about 1500 CDT today, the transmitter PA current began taking erratic dips for several seconds. Simultaneously, the RF forward power dropped from 400 watts to 100 watts, and the reflected power went up from 10 watts to 100 watts, a sure sign of either a shorted or an open feedline.
Since it had just begun to rain, I thought the cause of these current changes might be an arc condition in the antenna system. An inspection of the antenna showed nothing wrong, but the static gap at the output of the antenna tuner was intermittently flashing over. There was no lightning associated with this rain event.
After watching the static gap for a few minutes, I saw the cause of the arcs. As rainwater ran down over the grounded leg of the static gap, the water tended to collect and form hanging droplets on the underside of the flap portion of the horizontal leg of the gap. After a few moments, they would grow large enough and drop to the ground. If the droplet reached critical size, and just before it fell away from the gap leg, if the transmitter turned on at that moment, the high electric field would attract the water droplet into the narrow portion of the gap itself. This water intrusion in the gap would substantially reduce the effective gap spacing, triggering an RF power arc, which would remain there until the transmitter turned off again or the water drop evaporated due to the heat of the arc. I will install a plastic rain shield to prevent this in the future.
Another interesting thing was observed as well. After about 10 seconds of the transmitter turning on with the QRSS30 modulation, I observed what appeared to be smoke rising from the area of the static gap. Closer inspection showed that it was not smoke, but steam!
Apparently what was happening is that during the "off" periods of the QRSS30, the ceramic bowl insulator was becoming wet from the rain. When the transmitter turned back on, the RF is heating the bowl insulator and the water enough to create the steam cloud I saw. I will have to observe this in the dark so that I can determine how much of the heating is caused by dielectric loss in the ceramic and how much is caused by surface corona discharge. This is just another interesting item that I have noticed while working with high power LF energy.
4 AUG 2002 - Transmitter back on the air at 1622 CDT.
Power 400 watts, modulation QRSS30, ID is Loop 5, "XSR" followed by CW ID at 10 WPM.
While the transmitter was off the air, I cut back some of the tree branches which were close enough to the vertical feed pipe of the antenna to cause detuning of the antenna when the branches moved in the wind. I have not checked the antenna current after cutting the branches, but the tuning adjustment of the variometer indicates that more inductance is now required to resonate the antenna. This indicates that the tree branches were capacitively loading the lower portion of the antenna.
29 JUL 2002 - The transmitter has been shut down at 1705 CDT. It will be off the air for a few days to do some listening around 165-185 KC.
Other tests will be made on the antenna system during this transmitter down time.
27 JUL 2002 - Transmitter off the air at 1335 CDT.
I was planning to make some minor changes on the lower feed connections to the antenna, but upon inspection, I discovered that the #1 PVC pipe support bar which holds the antenna wire away from the tower directly above the antenna tuner had been arcing and had burned back from the point where the antenna wire passes over the pipe to a distance of about 14 inches. The arcing did not quite make it all the way back to the antenna tower, so the antenna was still working.
I went to Home Depot and bought some copper pipe, fittings, and some more PVC pipe with which to make some modifications to the antenna feed connections.
I replaced the #14 copper wire feed between the antenna tuner and the bottom of the vertical antenna wire with an assembly of 1/2 inch diameter copper pipe. This is supported by two PVC pipe insulators, but these have #12 copper wire corona rings installed at the insulators. Hopefully this system will prove more resistant to high voltage RF corona failure.
The antenna impedance has changed somewhat after the modifications. I had to remove 12 turns (1 tap point) from the variometer loading coil to bring the antenna to back to resonance at 166.5 KC. This means that the antenna now has more self-capacitance after this afternoon's changes in the feed system. This will likely be bad for performance, since the added capacitance is directly above the output of the loading coil, and and extra capacitance there will serve to reduce the effective radiation height of the antenna.
Transmitter returned to the air at 1718 CDT.
26 JUL 2002 - Transmitter off the air at 2045 CDT.
Added plastic rain shield cover over the top external loading coil. I made the cover from a plastic trash basket from Wal-Mart. The item is a Sterilite 13 Gal / 42 Qt / 40 L swing-top trash basket, part # 1086, SKU = 0-73149-10868-5.
I used the bottom 16.25 " of the bucket and discarded the 4" cut off section from the upper portion of the bucket and the swing top assembly. This was a perfect slip fit over the Home Depot bucket wound with #14 THHN solid Copper wire. No retuning was necessary after adding the rain cover.
Transmitter back on the air at 2210 CDT.
I also found that the steel connection bolts on the lower variometer & loading coil are heating substantially die to RF induction heating. I will remove the bolts and solder the connections to the coil taps.
25 JUL 2002 - Transmitter off the air between 2223 and 2238 CDT.
The downtime was required to replace the burned #1 upper loading coil support tube, which was damaged when the PVC "T" insulator failed.
This support was a part of the "T" insulator, but a separate pair of insulators to prevent future failure will replace the "T" insulator assembly.
23 JUL 2002 - Transmitter off the air at about 2050 CDT.
This evening at about 2045 CDT the PA Drain current became erratic, and shortly thereafter dropped to a very low level.
After shutting down the transmitter, I inspected the antenna tuning system and determined that the plastic "T" standoff insulator, which supports the top lead of the loading coil, had failed. The failure apparently began at the point where the corona discharge damage had occurred during the previous antenna insulator flameout. I have not yet had a chance to repair the earlier damage. I guess this is the time to make the repair!
No damage was done to the loading coil or any other components, and I able to get the transmitter back on the air at about 2132 CDT after temporary repairs were made.
No change in power, frequency, or modulation.
21 JUL 2002 - Carrier frequency measurement performed at approx. 0100 CDT.
The station frequency was measured at 0.166.496.84. or about 3 Hz low, as expected.
The previous calibration was done using only the BC-221, which had had its 1 MHz calibration oscillator compared to the 10 MHz signal from WWV. Then, the 1 MHz oscillator was used to set the BC-221 VFO, and then the VFO was compared to the 166.5 KC carrier by zero beating it with the BC-221 VFO. This procedure resulted in less than 1 Hz error at the carrier frequency.
The station frequency was readjusted to exactly 0.166.500.00, for a VXO frequency of 2446.000 KC.
20 JUL 2002 - Calibrated station frequency.
Calibration Procedure traceable to NTIS / WWV for the precision VXO of the WC2XSR/13 Transmitter:
The example shown here is for a carrier frequency of 166.500 KC, with the transmitter VXO operating at a frequency of 2664.000 KC.
** Begin Calibration Procedure**
1) Set the calibration variable frequency oscillator ( BC-221 VFO ) to a frequency of 2500 KC.
2) Heterodyne the 2500 KC signal from the VFO with the 10,000 KC signal from WWV.
3) Achieve zero beat between the VFO signal and WWV by watching the S-meter on the receiver while simultaneously adjusting the VFO for an "S" meter swing of less than 1 cycle per second. Since we are comparing the fourth harmonic of the VFO to WWV, this indicates an accuracy of +/- 1/4 Hz of the 2500 KC VFO fundamental frequency.
4) If necessary, adjust the time base oscillator of the frequency counter to make the frequency counter indicate a frequency of 2500.000 KC. Since the counter's stated accuracy is +/- 1 count, we may assume that the indicated reading shown is accurate to +/- 1 Hz. In practice, a time-averaged series of readings will allow us to get the uncertainty down to about 1/2 Hz, by simply observing how often the indicated reading is over or under the expected frequency.
5) Measure the WC2XSR VXO carrier oscillator frequency with the frequency counter. Adjust the VXO to read 2664.000 KHz.
** End Calibration Procedure**
We know that the frequency counter is accurate to within +/- 1 Hz, therefore, we also know the VXO frequency to within +/- 1 HZ or better, depending on the accuracy of our time averaging measurements.
Since the 2664 KC VXO signal is divided by 16 to obtain the actual 166.5 KC carrier frequency, we can also conclude that we know the carrier frequency to within +/- 1/16 Hz, or better, depending on the accuracy of our time averaging measurements.
This places the carrier of WC2XSR between the upper and lower limits of 166.49994 to 166.50006 KC.
Since the VXO stability is generally within +/- 1 Hz over a 24 hour period, we can conclude that the carrier frequency will remain within 1/16 Hz of 166.500 KC.
18 JUL 2002 - Switched to QRSS30 mode at approx. 1736.
ID loop is "XSR" in QRSS30, followed by 10 WPM CW ID. Loop time is 17:24.
15 JUL 2002 - Transmitter intermittently off the air between 1738 - 1813 CDT.
Inspected the antenna tuner and found that the # 4 contact had become hot enough to melt itself into the plastic frame making up the switch assembly. Must repair the assembly now, before serious damage is done.
Fabricated and installed copper switch contacts for the load coil tap switch contact # 4 and the wiper contact. I did not install wiper arm copper shunt strip yet.
Test operation for 5 minutes shows no apparent heating of the contacts and little or no heating of the aluminum wiper arm assembly.
Added a temporary ground strap connection between the outside of the tuning cabinet (RF ground return) and the copper water pipe at the rear of the house. The connecting wire is about 15 feet of #12 stranded wire lying on the ground.
Measurement shows that for the same transmitter loading of 400 watts output, the antenna current has increased from 2.8 to 3.0 amperes, corresponding to an increase of antenna Rrad power from 2.98 watts to 3.42 watts, or about 15%.
The antenna efficiency has increased from 0.745% to 0.855%. This test indicates the desirability of installing a heavier, more direct connection to the water pipe system.
Transmitter off the air from again between 2005 to 2022 to add the rest of the copper contact points to the antenna tuner tap switch.
14 JUL 2002 - Noticed visible static flashes in local off-air TV signals.
Close inspection of the antenna tuner shows that the antenna tuner tap switch contacts beginning to exhibit micro-arcs at the contact surfaces.
I will try adding a section of copper sheet to the fixed and movable wiper contacts to see if that will reduce the heating. I will try modifying the wiper contact and fixed contact # 4, which is used at 166.5 KC. If that is successful, I will modify the remainder of the contacts as well.
13 JUL 2002 - On the air from 2030 - 2045 CDT at 400 watts for antenna testing.
The antenna has been repaired, and all four antenna insulators have been replaced with the new insulators which have anti-corona rings installed. They are made from 3/4" PVC pipe, and the gap between the rings is about 14". The rings are fabricated from 3/8" (10mm) soft drawn copper tube. The rings are 100 mm in diameter. The rings extend forward of the stainless connection bolts by about 2" to prevent corona from occurring on the connection bolts.
Installed copper anti-corona ring on the output terminal of the upper loading coil where arc tracking had occurred during the insulator failure time frame. The new ring is made from #14 wire, about 75 mm in diameter. It is made from bare wire.
Transmitter placed back on the air at 2115 CDT at 400 watts and QRSS3, using CD ID loop # 4.
8 JUL 2002 - WC2XSR is off the air until repairs and modifications are made to the antenna system.
At about 2155 CDT this evening, two of the four plastic insulators supporting the transmitting antenna literally burned up, causing the antenna wire to fall to the roof of the house. Luckily, this so detuned the antenna system that no further arcing occurred, and the roof of the building did not catch fire.
Preliminary investigation indicates that moisture from a late evening rainstorm allowed high voltage RF arc tracking to begin, which resulted in the eventual destruction of the insulators.
I suspect that the switch from 10 WPM CW to QRSS3 transmission aggravated the situation, since the full carrier power was applied to the insulators for a much longer period than with the 10 WPM CW transmissions.
07 JUL 2002 - Transmitter off the air between 1837 and 1842 for antenna tuner inspection.
I found that stainless steel contact bolt heads on the variometer loading coil are overheating enough to discolor, but not enough to melt the plastic panel. Removed the aluminum contact sheet from between the bolt heads to allow bolt head-to-bolt head contact. Will check later to see what the temperature rise is in that mode.
Transmitter off the air between 1905 and 1915 for antenna tuner inspection.
Heating still occurring, but not as bad. Placed new copper plated penny between bolt head connections. Will check again.
Transmitter off the air between 1936 and 1939 for antenna tuner inspection.
The heating was somewhat less than previous test, but still excessive. Noted heating at pivot joint, which has a better pressure connection, but apparently still not adequate. Will replace contact #3 with copper wire jumper and test that method. If successful, I will replace all bolt head tap switch connections the same way.
Transmitter off the air at 1950 for generation of a new QRSS3 / CW ID CD loop.
The new loop plays the following ID at QRSS 3: "XSR XSR XSR XSR XSR XSR" Then follows a CW ID at 10 WPM which plays" "DE WC2XSR/13 DE WC2XSR/13 QSL VIA W5JGV" The ID loop then repeats continuously by using a CD player a the audio source.
Transmitter back on the air with new ID loop at 2104.
05 JUL 2002 - Transmitter OFF at 1939 for antenna checks. T
he antenna current was measured at 2.8 amperes with 400 watts (unmodulated) carrier out of the Low Pass filter.
The antenna impedance was calculated and verified by measurement at approximately 0.3802 ohms, -j 4442 ohms.
The RF power lost in the resistance loss of the earth ground and the loading coil system having an equivalent resistance = 397.02 watts. The RF power consumed by the radiation resistance of the antenna = 2.98 watts. The calculated maximum antenna gain at +22 degrees elevation = -24.93 dBi.
The effective antenna efficiency = 0.745% Transmitter ON again at 400 Watts output at 2018 after completing the antenna system checks.
03 JUL 2002 - First RF!
Transmitter turned ON at 2150 at 400 watts output.
The station was intermittently on the air at varied power levels while tuning the antenna system during the following 60 minutes. Following antenna tuning, the station remained on the air at 400 watts.
Modulation is A1, sending the following loop at 10WPM: "eeeeeeeeee vvv vvv de wc2xsr/13 de wc2xsr/13 qsl via w5jgv". There follows 30 seconds of continuous carrier with no modulation.
73, Ralph W5JGV
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