The procedures outlined below have proven successful over the last 18 months or so. There are other ways and methods, but the steps outlined below have been proven and documented.
Due to the increase of confusion and lack of concise operational procedures concerning our equipment, we found it necessary to compose a â€œTip Sheetâ€ to help fellow HAMs clear any issues and/or problems they may have, with the setup, integration and operation of our amplifiers. I personally have been using an early model 1.5Kfx amplifier for over 1 Â½ years with absolutely no failures or problems.
This trouble free operation was a result of a proper setup and a thorough understanding in the operation and tuning of solid state amplifiers. One important concept I like to relay to all HAMs is: â€˜IT IS NOT A TUBE AMPâ€. Please do not compare the operation of our solid state amplifiers with tube amplifiers you may have had in the past. Solid State amplifiers are NOT TOLERATE for continual operation into antennas with HIGH SWRs! In addition it is extremely important to proper adjust the transformer taps for the proper idle voltage (Vd) to the finals
Begin by carefully unpacking the amplifier and/or auto tuner and remove the top cover. I always like to look inside for any loose connectors, screws or components that might have dislodged during transit. Please 1st discharge the power capacitor (large power capacitor) by touching each terminal to ground with an insulated wire (e.g. 14ga) or tool attached to ground. I also like to go around with a screwdriver and check that all the screws are tight. After completing the above inspections replace the cover, using for now, only a few screws.
IMPORTANTâ€”BEFORE POWERING ON THE AMPLIFIER – Please check the rear fan assembly to be certain that the fan guard or fan has not been damaged in transit. Fan blades should turn freely with no binding and no damage should be visible. Contact THP support if you discover any damage. DO NOT power the amplifier if the blades do not turn freely.
POWER CORD SETUP
It is highly recommended that the amplifier be wired for 240V. This voltage is mandatory for the 2.5Kfx. Operation with 240V will allow the amplifierâ€™s transformer to run more efficiently and cooler. Due to the extreme variances of line voltages (230Vac-254Vac) scattered throughout North America, itâ€™s important to properly adjust the primary and secondary TRANSFORMER TAP settings on the power transformer for your particular location. This will insure that the proper voltage is fed to the output finals. In either case 120V or 240V, the transformer tap settings must be properly adjusted.
WIRING THE POWER PLUG
There are three wires in a 240V plug. You have 2 legs of 120V and a ground. The ground wire is always green and is connected to the center prong on a typical 240V plug. The remaining wires, Black and White are connected to the outer prongs. It does not matter what side, though, following 120V practices, you can connect the black wire to the right prong when the center prong is pointing down.
You can check proper 240V wiring to your outlet by connecting one meter lead to the center prong (ground) and the other to an outer prong. Repeat with the opposite prong. You should read 120VAC at each reading. Then connecting each lead to the outer prongs should result in a 240VAC reading. You are now ready to check the amplifierâ€™s Idle Drain Voltage Vd.
POWER TRANSFORMER TAP SETTINGS / IDLE Vd ADJUSTMENT
CONTINUED LONG TERM OPERATION WITH THE IDLE Vd ABOVE THE GREEN RANGE WILL HAVE A DETREMENTAL EFFECT ON THE LIFE OF THE MOSFETS!
Vd is the voltage to the finals in a non-transmitting (standby/receive) state. Because line voltages vary so greatly in this country, it is very important to tweak the idle Vd. Measure your line voltage, using an accurate digital multi-meter. Typically, line voltages will increase a few volts in the late evening, as the demand on the power grid decreases. Once again, remove the top cover and confirm the power cord is not connected, and that the power capacitor has been grounded. Taking note of your line voltage, refer to the manual and confirm that the PPRIMARY TAP SETTING on the transformer is closest to your actual line voltage, ALWAYS use the next highest setting. Example – If your line voltage is 236V, use 240V tap setting. After the Primary Tap setting has been set, replace the top cover, secure with a couple of screws, and plug the amplifier into the outlet. Confirm that the amplifier is switch to STBY and that the meter switch is selected to Vd. Turn on the amplifier and note the Vd reading. It should be in the green arc, 45V-55V.
IF IT IS TOO LOW, off the left side of the green scale, (following the above safety procedures) remove the cover and re-adjust the Primary tap setting to the next LOWER voltage setting. Replace top cover and check Vd once again. If the Vd falls into the green range, install all cover screws. If it is now too high, (out of the green arc), once again remove the top cover. (Use all safety precautions). Please follow the procedures listed below.
IF IT IS TOO HIGH, off the right side of the green scale, (following the above safety procedures). Remove the cover.
2.5Kfx â€” Move the secondary tap from 0v to the adjacent 10V. The secondary tap is located on the same terminal strip as the primary.
1.5Kfx â€” Remove the (4 screws) aluminum top cross brace that partially covers the transformer and power capacitor. You will see the secondary taps on the power transformer. Move the secondary tap from 0 to the adjacent tap 2.7V.
1.2 Kfx â€” Move the top left black wire on the secondary tap to the next terminal with the brown wire.
Replace cover with a few screws and plug amplifier in to the outlet. Turn the amplifier on and confirm that the idle (non-transmitting) Vd is and stays within the green range. After confirming the Vd is within the green range, replace all the screws.
RADIO â€” AMPLIFIER CONNECTIONS-METERS
First and foremost, confirm that ALL EQUIPMENT IS PROPERLY GROUNDED. In my shack I also install a grounding strap from the negative post of my power supply to the grounding buss of the station. I try to eliminate as many floating grounds as possible. I cannot over emphasize the importance of proper grounding. For at low power levels of 100W or less, improper grounding might not be evident, but Increase the power 8-10 times, and then serious problems can rapidly develop.
It is highly recommended that you connect and use a good quality power meter with the amplifier. As a doctor would never think of operating without a monitor, you too should not consider operating into an antenna system without a SWR/Power monitor. At a glance, you can check on the health of your antenna system without any speculation or guessing! With the first transmission of the day, immediately you can tell if the antenna parameters have changed from your last operating session. My meter is the most used piece of equipment in my shack. I always glance at it numerous times during a QSO, to insure that the operational condition of my radios and antennas are in their â€œhealthy stateâ€! So many times I hear Amateurs stating, â€œIt was fine yesterday!â€, and only to find out, when itâ€™s too late, it is not fine today. Youâ€™ve spent thousands on your station, buy the cheap insurance and spend the extra few hundred dollars and purchase a good quality meter. You will not regret it.
Use good quality coax and fittings, insuring proper installation (no short, open, or high resistance soldered connections) and that all fittings are tight on their appropriate fittings.
METERS â€” PLEASE USE AND KEEP IN LINE A QUALITY POWER METER Most low cost meters do not accurately nor quickly enough, measure peak output power. Meters by Array Solutions Power Master, Digitronix, Wavenode, Bird, Coaxial Specialties, Alpha, etc, are very good products and are very accurate in the measurement of true peak wattage and the SWR of the antenna.
IMPORTANT: 1.5Kfx ONLY–Icom Radio Users Please Note: When using the Icom CI-V Interfaceâ€¦.Change the CI-V Address in your radioâ€™s setup menu to 5Ch. This insures that in the event of a trip fault on the amplifier and a reset is required, the amp will synchronize with the radio when the amplifier is turned back on.
Kenwood Users Please Note: Please confirm that you are operating with VFO A. The current firmware supports VFO A operation only! Operation with VFO B selected causes the amplifier not to track the correct band selected on the radio.
Iâ€™ll begin this paragraph with two words—USE IT! No matter what your feelings about using ALC is in the past, the use of a properly set ALC circuit is your ultimate protection for your finals! No matter how much you accidentally drive the amplifier, the ALC, when properly adjusted, will protect the finals. The use of ALC is strictly for ultimate overdrive protection. Please do not use the ALC to control your final output power, use the RF drive for that function. The use of ALC is especially important with 200Watt rigs such as the Icom 7800 or Yaesu 9000. Normally it should never come on except by accident! History has shown that in many failures, THE ALC WAS NOT CONNECTED OR PROPERLY SET.
Below is a detailed step by step method of properly adjusting the ALC. There are other methods, but the procedure outlined below has been documented and proven to protect the finals.
After connecting all the cables between the radio and the amplifier, connect the output of the amplifier to a load with a SWR of less than 1.5:1. This can be a non-resonant antenna with a tuner, a resonant antenna, or an appropriate dummy load. Please review all steps before beginning procedure.
ALC TUNING PROCEDURE
Turn on amplifier and radio.
Confirm amp is in STBY mode.
Place radio in CW mode. (You can also use RTTY mode w/transmit button)
Turn rear ALC Full Open clockwise (toward edge of case).
Confirm radio, amplifier and if necessary tuner are all synced and set properly.
With RF drive on radio turned up full, key down, and check each band. Select the band with highest output.
Turn RF Drive on radio full down, little or no output.
Confirm once again everything is in sync. Key down once again and slowly increase power to about 25 watts and confirm SWR is below 1.5:1.
Switch Amp to OPER and key down once more.
SLOWLY INCREASE RF Drive until maximum power just peaks. While still keying, release the RF drive and THEN TURN THE ALC CONTROL COUNTERCLOCKWISE (towards center of case) TO DECREASE OUTPUT POWER 25-30 WATTS FROM MAXIMUM READING. This will be the final position of the ALC control knob, for it will never be touched again, unless you want/need to re-adjust the ALC. This next step is very important, for you do not want the ALC to operate during normal operation. Otherwise you will clip your audio on voice peaks. You will sound like you have a broken or loose microphone wire.
Key down a final time and TURN DOWN THE RF DRIVE ON THE RADIO ANOTHER 25- 30 WATTS.
DO NOT try to get all the bands to operate at the same maximum power levels. Modern transceivers today, all exhibit variations in output from band to band. In addition the conditions at the antenna are different from band to band. It is perfectly normal to have variations as large as 50-100 watts from your highest to your lowest reading.SWR
A quick word about SWR. The amplifier will fault/shut down with an SWR of more than 2:1. Try to achieve a 1:5 SWR or less at all times. Using a tuner does not change the SWR of the antenna! It does not improve the performance of a poor antenna; it only simply allows you to operate a radio and/or amplifier into it! The further away the antenna is to 1:1 SWR, the less output you will have from the antenna. 100 watts into a 1.2:1 antenna will have more radiated power than using 400 watts into an antenna with a SWR of 6:1, having the tuner reduce it to 1.2:1. Do not be fooled into thinking that a 1:1 SWR with a tuner is a perfect setup. Remember a dummy load will also give you a 1:1 SWR STRAY RF
This problem is probably the single most cause in the improper operation of our equipment. While users have been operating their stations for years with no problems, suddenly with the introduction of a solid state amplifier, problems arise. Erratic operation, random blinking or indication of warning lights, ODrive light illuminating with low RF drive levels, are all symptoms of excessive RF in the shack! Any microprocessor controlled device, including our amplifiers and tuner are extremely sensitive to environments with large amounts of STRAY RF. There are numerous ways to eliminate stray RF. Though this subject is quite involved, and is beyond the scope of this booklet. I will briefly touch upon a few areas to consider. UNDER NO CIRCUMSTANCES SHOULD YOU OPERATE THE AMPLIFIER FOR LONG PERIODS OF TIME, UNTIL THE EXCESSIVE RF IS ELIMINATED.
Grounding Once again, most important. There is an old electricianâ€™s wise tale..â€When in doubt, ground it!â€…Very good advice, ground everything ..There are two schools of thought on grounding. Daisy chain the connections (series), though some sources find this an incorrect way to connect grounds, or connect everything to a common buss bar (parallel). Experiment and see what works best for you. Try to use braided wire. The more surface area you have (braided wire, cooper strapping) the better the ground connection. PolyPhaser publishes an excellent book on grounding for around $20. It explains in detail the entire grounding system for a transmitting siteâ€¦
Poor Antenna Design/Baluns There are certain manufactured antennas with poor designs and/or badly designed baluns that are notorious for creating RF in the shack. The RF returns back down the coax. Many customers want a single multiband wire antenna. I have found that, Off Center Fed Dipoles with â€œquality high power balunsâ€ work extremely well for a single wire multi-band antenna. So does a Double Bazooka with a quality tuner. A double Bazooka cut for 160m or 80m along with a tuner for the other bands, seem to work the best. Changing your antenna to a more proven design might be your quickest and most effective solution to your RF problem.
Construct a choke on the coax. Simply wrap the coax around a coffee can or a liter sized soda bottle. Loop it 7-8 times and tie-wrap the loop into a neat circle. Attach this to the feed point of your antenna.
Install ferrite beads on the coax and control cables. When installing beads on the control lines and/or coax use a tight fitting diameter ferrite bead. A bead that easily slides up and down the cable will be less effective than one that firmly clips and is secured on to the cable. Make sure you install the ferrite beads on both ends of the cable, close to the connectors. Companies such as Palomar and Amidon specialize in the reduction of unwanted RF. They can supply the â€œknow howâ€ and the necessary parts, (ferrite beads, torrid cores, filters, etc.) for reducing and eliminating RF on the coax line.
Coaxial Line Filters are pre made ferrite bead assemblies that conveniently screw into the coax line.CONCLUSION
There is no one single cure for STRAY RF. Every situation and scenario is different and all cases must be treated individually. Eliminating stray RF is a tedious and time consuming process. Many possible solutions must be tried until you find the right combination that works for you. The ARRL Antenna Manual and other publications are great resources in obtaining information for the elimination of RF. Companies listed below can not only supply you with the proper supplies, but have the necessary expertise in helping you solve your problem. In addition, there are thousands of web sites on the internet that post tips and information in the cures of stray RF