ANTENNA TUNER CHOICES
There's a basic choice about antenna tuners. If you go to a "manual" tuner (I have an MFJ-945E), it's a bit more work. But you have a better idea of the "quality" of the tune, that is how far the tuner has to stretch to achieve proper tuning. An automatic tuner is very desirable to reduce workload during contesting.
If you use a manual tuner, do a bunch of measurements in the middle of each band and write these down with all the tuning knob positions. Keep that list right by the tuner since it helps you to quickly go to about the correct setting. You may still need a final small tweak. Remember that a tuner only makes the radio happy to see 50 Ohms non-reactive. The tuner does NOT magically fix a badly mistuned antenna.
Most manual tuners will adjust for a wider impedance range than an automatic tuner. However, wide impedance mis-match suggests that you may want a better antenna. My manual tuner is not supposed to work on 160M with my Windom dipole. However, I can actually achieve tuning on 160M with far settings of the knobs - enough to make a QSO. An automatic tuner usually cannot do that.
An automatic tuner (I have an LDG Z-11 Pro-II) is less work but it hides the quality of the tune. In the extreme case, it tries and tries but never tunes. You can sometimes tell marginal tuning by how long it takes to tune.
What is marginal tuning??? Your raw antenna (without tuner) is quite far from resonance on your desired ham bands. The result is higher losses on the feedline and possibly a lower output signal. That loss is made worse by coaxial cable with lower bandwidth at higher frequencies.
I suggest NOT leaving the automatic tuner always on "full automatic". Otherwise, if you QSY just a bit, you may get an unwelcome retuning right in the middle of a QSO. Or you may get an unfriendly retuning if the original tuning was on the hairy edge. Instead, I use the mode where I must press the button to do the tuning. See below.
Avoid Full Power Retuning
Also, automatic tuning with full power causes arcing with the relays as they rapidly switch different inductors in and out. This arcing may eventually make the relays fail. The alternative is to use a manual tuning mode, power down your transmitter, tune then power back up. That causes less arcing. Yes, it takes more time but it is still faster than a manual tuner. I believe the Z-11 Pro-II only needs about 5 Watts of RF for a retuning.
If you are already running a lower power (say 25 Watts as for some digital modes), you might not need to power down to retune. If you are running QRP low power, you might need to power UP to use an automatic tuner!!
Remember too that Single Sideband Mode produces NO RF power during tuning if there is no audio. You can say "Ahhhh" into the mic. but your voice may change a bit, causing the needles to wander. Instead, switch to AM or CW mode temporarily then switch back.
The Z-11 Pro-II is very cool because it can be battery powered. Once tuned, it uses very little current because the relays inside are the latching type.
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Another good idea is to use an Antenna Analyzer alone on your antenna (I have an MFJ-259B Analyzer). Test the raw antenna on all the ham bands WITHOUT the tuner. If you have a multi-band antenna, lowest SWR should be close to the center of each band. Write down all these settings.
For example, my Windom dipole gets the lowest SWR around 7.0 MHz for the 40M band without the tuner. That's not bad and it means that the tuner only has to compensate a short distance.
If you keep a handy list of these "raw" antenna SWR readings and periodically retest them, you can see changes in the SWR, possibly indicating antenna problems starting.
My manual tuner can see tiny SWR changes with the leaves on or off the nearby trees!!! Each leaf is a tiny capacitor plate absorbing RF. Even snow makes a difference!! You won't see that with an automatic tuner.
Finally, you may want to plan ahead a bit. These lower cost, smaller tuners are fine up to about 100-200 Watts (check your specs). If you will someday have a linear power amplifier, you will need a larger, heavier, more expensive tuner.
Just my 2 cents!!
73, Larry
KB1UMD
