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Tune up procedure if your rig has tube finals

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va3ts
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Tune up procedure if your rig has tube finals

Post by va3ts » Sat May 20, 2017 2:50 pm

Tune-Up Procedure
ALWAYS Tune into a dummy load, do not QRM your fellow radio operators.

The Kenwood User's Manual has the "Kenwood Approved" procedure for tuning up the. In particular it has a nice chart of initial settings for ALL the controls, which is useful if you have never done this before. The procedure presented here differs in some respects.

1. First, fire up the rig and tune to the band you would like to transmit on. The rig needs a load that is fairly close to 50 ohms. Less than 2-1 SWR is good. If your antenna has been trimmed for the band you are going to transmit on, you're probably all set. If you are using an Antenna Tuner to load up a random wire or mis-matched dipole, the procedure is to connect a dummy load (rated 100 watts or better) to the 520 and tune the rig into THAT perfect 50 ohm load, THEN switch in your antenna tuner and adjust it for minimum SWR. You might want to use a dummy load to practice this tune-up procedure anyway, since part of it involves putting a signal on the air.

2. Make sure the H.SW is on. Warm up the tubes.

3. Make sure the FUNCTION switch is in the VFO position. Make sure RIT is OFF (out). Make sure RF ATT is OFF (out).

4. Plate idle current: Kenwood wants to be sure the idling current of the plate is at 60ma before you begin. Generally, you only have to check this once in a very long while. Set the METER switch to "IP" (current, plate), tune to the band of interest, set the MODE switch to USB or LSB. Flip the rec/send switch to "send." You should read 60ma on the top scale of the meter. If you get a different value, you need to open the little door on the left of the rig and turn the bias pot until you get it. See the manual.

5. Get the DRIVE control into the ballpark: If you have an antenna connected, you can turn the DRIVE knob until you hear the loudest static (with the MODE switch on USB or LSB). If you are working with a dummy load, or just want something easier to work with, flip the FUNCTION knob a click to the left to the Cal 25 Khz setting. Then tune to the nearest 25,000 HZ division (i.e. 7.125, 7.150) so you can hear the tone then turn the DRIVE knob until the tone is loudest. Be sure to set this switch back to VFO when you are done. (The marker is every 25khz, but, like CW, you have to offset to hear it -- or my radio is out of whack! -- for example, at 14.150 I use 14.152.5.)

6. ALC adjustment: Turn the CAR and Load controls fully counter-clockwise. Put METER switch in "ALC" position. Put the Mode switch in the "tune" position. (If you are not using a dummy load, find a quiet place on the band.) Flip the send/rec switch to "send." Turn the CAR control slowly clockwise until you get a half-scale deflection or so. (The original instructions and manual are unclear, I turn for a half of the ALC scale, or S5. I think this is right.)

7. Fine tune the DRIVE: With the rig still set to "send", turn the DRIVE control to peak the ALC meter reading. I wind up at S9 on the ALC scale. Put the send/rec switch back to "rec" and breathe. (Try keep the rig in "send" as little as possible -- less than 15 seconds at a stretch -- and let the tubes cool down between time.) Franky, I've been skipping this step lately (Oct02), since the right setting is good for both xmit and receive you can do either this step or the ballpark step above and be OK. I think this is harder, so I've been using the 25khz tone and peaking the receive side instead.

8. Dip the PLATE: This is my favorite step, if only because of the name! Put the Meter switch in the "IP" (current,plate) position. Set the PLATE for the middle of the band you are tuning on. With the MODE switch still in "Tun", flip the send/rec switch to "send." Quickly adjust the PLATE control for minimum meter reading. (I think the dip is bigger on the higher frequency bands.)

9. Peak the output: Everything is close now. Put the Mode switch to CW, the Meter switch to "RF" (or, if you have an antenna tuner, read the actual RF power there). Be sure you're on a dummy load or quiet place on the band. Put the send/rec switch in "send." Key down. Quickly turn the LOAD control for maximum RF output. Jump to the PLATE control and twiddle it for maximum RF output. Alternate back and forth between the two quickly and "walk" the meter up to the most RF you can get out of your rig. (Right now, I get around 100 watts on 40m, maybe 90 on 20m.) Key up between jumps. Don't do this for very long. When done, put the send/rec switch back to "rec." Breathe.

10. Final adjustment: send/rec to send, key down. Twiddle the DRIVE control to see if you can get anymore RF out of the thing. Probably not if you've done the previous steps properly. Leave DRIVE at the strongest meter reading. Adjust the CAR control to where the RF output just starts to drop. Again, you should already be close. Key up. Flip the METER switch to IP. Key down. The plate current should be about 240ma. Mine hits this exactly if I tuned into my dummy load properly. If the current is more, you need to reduce the loading -- turn LOAD to the left and re-dip the Plate control.

11. Congratulations, you are resonating! If you have an Antenna tuner, switch from your dummy load to it and make your final antenna tuner adjustments, if necessary. The rig has to be re-tuned if you change frequency by more than 1-2% or so, and want to transmit. This means 25-50 kHz on 80 meters, and progressively more on the higher bands.
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