Cryptic letters on the right side are codes for
Japanese/Chinese characters.
| You want to turn the
variable capacitor of the antenna tuner near the antenna
from the inside of your shack. You might then use a
stepping motor attached to the variable capacitor and
turn it with a digital controller. I actually did the
same with a PIC micro controller before. It worked fine
and had no problem, but what can one do with an analog
circuit with a DC motor? Oh yes, I like the analog better
than the digital circuits. First of all, the motor needs
to be equipped with a gear box to cope with the critical
tuning of the capacitor. Then a DPDT switch can do the job as is shown in the next figure, but.... |
アンテナ直下のアンテナチューナー（もちろん手動式です）のバリコンを部屋の中から遠隔操作で動かしたいときには、ステッピングモーターを使えばよいのはわかります。当局もPICマイクロコントローラでそのようなコントローラを作って使っていました。でも、DCモーター（微調のために減速ギヤが必要）とアナログ回路でやりたい。どうしたらよいでしょうか？ 切り替えスイッチを使って次の図のようにすればできますが・・・・・。 |
| You easily run past the
optimum point and have to go back and forth many times
until you finally get the antenna tuned. You would be
irritated with such an iteration. Here is a good idea to do better with a remote turning knob attached on the axle of another DC motor (a common toy motor is OK). Remember that a DC motor generates DC current when its axle is turned. The polarity of the current is reversed if the turning direction of the knob is reversed. If you turn the knob the faster, then the higher the generated voltage is. Therefore, It could control the geared motor directly if they are mutually connected as is shown in the following figure. |
でも、微妙な調整は難しいでしょう。行き過ぎたり戻ったりを何度も繰り返してイライラすることになります。 そこで、もうひとつ別のおもちゃ用のDCモーターを持ってきて下の図のようにつないだらどうでしょうか？一般にDCモーターの軸を回してやると直流発電機になります。回す向きに従って発電される電流の極性も変わるし、回す速さによって電圧の強弱も変わります。ですから、このモーターの軸につまみをつけて手で回してやれば別のギヤ付モーターを制御できると思いませんか？ |
| OK, the generated current is
too feeble to turn the other motor. Then, follow the
standard practice. A DC amplifier can make it stronger.
In the next figure, an NJM2073
from New Japan Radio Co., Ltd. is used for this purpose.
It is a dual audio power amplifier IC for BTL output. This simple circuit works very comfortablly and is best for the tuner of a common wire antenna as well as for a magnetic loop antenna, of which tuning is especially critical. If this Japanese IC is hard to find out there, then you could also try it with an MC34119P or two LM386's. In those cases, the connection of the controling motor may be somewhat different from the following diagram. I leave you to think it over for your fun. Refer to the data sheet of NJM2073 for the hint. |
実際はちょっと電流が弱すぎますね。そんなときは定石通りアンプで増幅しましょう。新日本無線の2チャンネルオーディオアンプICのNJM2073をBTL出力として使って次の図のようにします。 こんな簡単な回路ですが、微妙な調整もうまく出来ます。手ごたえもなかなか感じいいです。マグネティック・ループアンテナはとくに微妙な調整が必要なのでこういうのがよいのではないでしょうか？ |
