You now have plate voltage, nothing burning but the filaments and no plate current. With the next test you should have on hand an RCA phono cable, one end will plug into the socket in the rear of the amp marked Send/ or T/R. In the more modern amps this is a low voltage logic circuit about 5 volts across the terminals of the phono cable.
Take the other end in your hand and with a shorting device such as the metal end of a screwdriver short the positive and negative sides of the phono cable. You should hear the click of a relay and an indication of idle plate current. Consult your instruction manual about how much idle current, on some tubes it will be around 65 ma and with a pair of 3-500Z tubes it will be about 60 to 100 ma. If the meter pins, or is much higher then the value in the book, stop, consult the manufacture since it is possible you may have a defective tube. Different tubes have different readings, so do consult the manual and follow it to the letter.
After trying this test several times, shut off the amp, unplug it and you are now ready to place it into your operating position if you have not already done so at this time.
If you are not used to lifting heavy objects I would suggest you recruit another person to help you lift your amp in to the place you want it, once you have the power transformer mounted the tubes and all the hardware most amps weigh about 75 pounds. If you do not want to hurt your back, get a hernia, or change your voice an octave get some help to raise it from the floor, or your work bench to the operating position.
From this point let’s get that amp hooked up and on the air. If you have not done so construct a coax link that will reach from your transceiver to the input of the amp. I prefer using RG8, but you can use the smaller RG 58 since you will be transferring a maximum of 100 watts for drive power to the amp. You will also need two lines one for ALC and the other for TR/ switching. Now, remove your antenna from the transceiver and insert it into the out put coax connector of the amp. But, let’s take a moment, if you have a dummy load hook that up instead by doing this you can acquaint yourself with the adjustments, loading and tuning and become familiar with the amp without causing unnecessary interference to others.
For that Tr/line you can use a pre made audio line with a phono plug on one end and bare wires on the other, or phono plugs on both ends depending upon your transceiver and the method used for installing the cables.
However, before we go any further let’s make sure your antenna system will handle the power generated by a linear amp. Ask yourself some questions, is my antenna resonant on the band, or bands where I plan to use the amp? Do I have to use an antenna tuner to tune my rig to the mismatched antenna? In this case a good yagi, or a resonant dipole, vertical, or delta loop should provide a resonant length. Those mismatched long wires; makeshift antennas thrown out the window of an apartment building just do not cut the idea of proper matching. Let’s assume you have done this requirement and your antenna is ready to go, good match, low SWR and we mean less then 1.5 over all.
If you do not own a dummy load, I would suggest you obtain one and I would suggest using one that is oil filled since it will allow you much longer periods of large amounts of RF with out burning it up with rf applied for more then ten seconds. Now comes this last part of the hook up, depending on your rig and how you access the required terminals you will have to consult the manual. With many rigs you have an 8-pin din connector containing a contact of a relay to ground when activated that is used for the T/R line. Others may use the phono jacks, personally this one I prefer. I really do not like the DIN connectors since they are small numbers, hard to read and even harder to solder. Since there are various DIN connectors made and varying keyways, I have only found blank stares when asking for a DIN connector at your local Radio Shack.
Some manufacturers ship at least two DIN connectors in the accessory pouch, others do not, but let’s assume they did and you have one in your hand. Consult your manual as to the function of the DIN connectors and the pin numbers you want. Normally, you will have two grounds, one for the ALC and one from the TR line; you tie them together and use the center conductors for the appropriate pins. Now this is where you must be careful about soldering these DIN connectors, do not get the pins too hot, since the cheap plastic they are made of will melt. Plus the pins are small and only allow a small gauge of wire inside the hollow metal pins. In other words these connectors are a real pain and I wish they would lose them somewhere, but I fear they are here to stay. So if your rigs connections are via a DIN connector I would suggest you find a spare one just in case you mess up and melt it. With the dummy load connected let us now get acquainted with the amp, turn it on and warm it up. If you have 3-500zs in the finals you will be ready to go in a few seconds, if you have a ceramic tube you wait about three minutes before plate voltage is applied.
I would suggest at this time you do one test, hit your mic button and key the rig, if you got the DIN plug wired correctly the linear relay should click and the idle current should show up at this time. Failure for this to happen may mean you have the contacts on the Din plug wired incorrectly. Or you have not set the menu selection on the transceiver for the proper contacts, this is done in the menu with some rigs, you are looking for the normally open set of contacts. On some rigs it is not a menu item, but most of the recent models it is, keep in mind if your keying line does not work your amp will not work. Do not speak into the mic at this time just key the transmitter, there will be no output since we are in the ssb mode, or even if you can key up while in the cw mode with the mic keyed you still will not have any output until you hit the old Morse key. At this time you do not want to excite the amp since you are not tuned properly.
Next if you have a manual tune amp then set the plate tuning control on the band markings you have selected in your transceiver most amps have the plate tuning marked in bands so let me clarify this a little. If your amp is not marked in bands and some are not, then use the guideline in the manual for an approximate resonant tuning. By doing this once you key the amp you will not be in totally non-resonant condition.
Next reduce the loading control to zero, some amps will give you a starting point with the loading based on your band selection you can find this in the manual if published. . If no suggestion then start at Zero and will go from that point and work our way to full output.
Next reduce the drive to the minimum this should reduce your transceivers out put to less then 10 watts, or somewhere close to it. Make sure you have oil in the dummy load, I assume you have at this point checked your antennas for resonance on the band you intend to operate and I assume you have determined all is well in your station.
Now for the big test, with the drive at minimum key the transmitter some rigs will have a tune position, others do not, so in case you do not have a tune position use the cw mode on your rig. With no key plugged into the key jack the contacts are normally closed, so once you go to the cw mode your rig should key. If it does not, then a 1/4 inch jack and a shorting cable might be in order, just depends on your rig.
Once keyed observe the wattmeter on the amp, or relative power meter, if you have neither then install a wattmeter between the amp and dummy load. Set the wattmeter at the highest scale, now be sure your wattmeter will handle 2 kW or more.
Once keyed, you should see some indication of power, rock the plate tuning for maximum indication then let up keying. You do not want to burn up your dummy load, so limit your tuning to about ten seconds at a time with some off time in between checks.
Note plate current and grid current at this time, it is VERY IMPORTANT that you stay within the specs of the grid current for the tubes you have in your amp. Key up again and advance the drive a little retune the plate your power level should increase. Repeat these steps until you reach the recommended plate current and the power output is indicating around 1500 watts. You add more drive, loading and retune the plate tuning until you reach the required power output of the amp. You will note that advancing the loading will not have much effect until you increase the drive a little more. Once you see the effects of the loading and drive, you will see how they work together, plus the plate tuning.
You may want to try other bands in this process just to get the feel of the amp and the tuning, now we are ready to UN hook the dummy and install the station antenna. Find a frequency with no activity, key up and check your tuning again, if you have a resonant antenna system then only a slight touch on the plate tuning may be necessary. Peak it for maximum, and then make some notations of the setting of your loading control for the bands where you plan to operate. By doing this you have an indication of where the settings are and thus this eliminates off resonance conditions and prolong tuning.
Once you have the legal limit out put with the drive coming from your rig, do not advance the drive any further, you may find your amp drives fine with 30 watts, or 50 watts, it requires no more. Driving too hard produces splatter and distortion you will make enemies.
A word on antenna tuners, some amps insist on no antenna tuner between the amp and antenna, here is why… You have an inductive capacitive system with an antenna tuner, so you have to tune it for a resonant condition. You can although well meaning cause damage to your amp due to a Non resonant condition existing with prolonged tuning.
I do not use an antenna tuner after my amp, I do not need it, my beam has about 1.4 swr in the cw band, this adds up with one kw going to the antenna to a loss of 30 watts or slightly more. From a practical stand point gaining 30 or more watts with an antenna tuner that has an inductive loss of more then I would gain is pointless. Those lost 30 to 50 watts will not make one difference in working that rare dx. The choice is yours and if you feel you can tune both the amp and the tuner and you really need a tuner then go for it.
One more comment as to the antenna tuner in your rig, do you need it on when driving your amp? Well, here is the answer, while keying the amp check the swr without the tuner on, if it is one to one, you will gain nothing with it on, you can turn it off. You should have a 1 to 1 match, if you do not find out why and not rely upon the tuner to mask a problem. You may find the tuner tries to hunt during transmit times and thus affects your power output. Personally, I have found this to be true and turn mine off.
Now switch over to SSB adjust the rig audio for proper ALC and if you use a processor adjust it per your manual. Follow the guidelines. Oh, on adjustment of the ALC from the amp, use this method.. Some have an adjustment in the rear of the amp, set the power level to 1500 watts, adjust the ALC on the AMP so the power reduces slightly, set and forget. Use the manual guidelines for set up of audio level and processor for your transceiver follows them, you are ready to make that first contact.
Just one more thing, if you own a monitor scope and some of us do, you can check your amp with more precise tuning using a trapezoid pattern, plus you can check your audio for clipping and distortion. But, let’s face it most of the ops on the air do not have a monitor scope, but I would strongly suggest some air checks and have other hams check you for a wide signal. Good luck on that new purchase and hope this article was informative and helpful.
Comments, or suggestions are welcome and of course keep in mind that these comments are not set in stone, you may find another approach, or method that works better for you. Main thing is enjoy ham radio and be a good op..
