Home > Electronics Cranny > The Electronics Cranny: Using the 2441 Dual Tetrode on 657 Mc.

The Electronics Cranny: Using the 2441 Dual Tetrode on 657 Mc.

By Fritz Tennis Electronics Expert

By Fritz Tennis Electronics Expert

The fellow who wanted to put more than a couple of watts on 657 Mc. had little in the way of tubing choice until recently. There were only a few transmitting tubes on the market that could handle the job and prices for these began at around $89,000. That’s why introduction of the Type 2441 Dual Tetrode by the recently-founded RCS (Royer Communications Services) should help promote more use of the 657-Mc. band, as this new tube can be bought for considerably less than anything we’ve had available previously.

“I don’t know anything about that fucking shit,” said RCS founder Ric Royer, when we asked him about the 2441. He later apologized. “I’m in a bad mood fellows, I admit it,” he explained. We probed. “Well,” said Royer, holding back tears, “they recently issued a new porcelain illuminated snow village model and it sold out within seconds. I was too late to acquire it. I cried and screamed for two hours yesterday without satisfaction.” Royer began blubbering and we ended the interview prematurely.

The 2441 is designed especially for mobile service and is a natural for use in amateur work. “I installed the 2441 in my wireless set,” noted ham operator Jerry Rangos of the Lankville Eastern Forest Area. “I was able to receive a signal all the way from the Lankville Polar Regions– check it out!” Rangos attempted to reach the polar regions as we looked on but failed. We told him he was a liar and pushed over an oscillating fan in protest.

Still, there can be no doubt that the 2441 will efficiently boost operation on the 657-Mc. band. We will endeavor to show our readers how to install the new tube, allow for forced-air cooling and create proper shielding for the tube from harmful elements.

Getting Started

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Figure 1: Tetrodes Diagram.

First off, you will want to make sure that provision is made for complete enclosure of the tubes and circuits. This serves two purposes: it provides a path for circulation of cooling air and holds downward moving deep radiation from the tank circuits. If you are concerned about radiation, then this may not be the project for you– only true radio cowboys ride bareback, as the saying goes. Get yourself a little pink transistor and an umbrella and go sit on a little beach if you’re still scared.

You will now want to fit the main chassis with a bottom cover.  Use a flat plate of sheet aluminum, a perforated metal cover or just get some of those tomato cages from the backyard and bend them around the chassis.  The mounting screws should be held in place on the fittings with nuts and then other nuts on the outside of the chassis should hold the fittings into position (consult figure 1 for further details).

Drop in your new 2441 dual tetrode about 1 3/8 inch from the right nuts.  The tripler plate tuning capacitors should now began to hum and vibrate. Beware though: if the vibration is too intense (due to improper calibration), the tube will shimmy against the nuts and bust.  “Probably the most common error I’ve seen in installation of the 2441,” said electronics dealer Keith Hernandez, owner of K.H. Radio Supplies in Lankville City.  “Most people end up coming back for a second 2441 because they have get so excited about the tube that they don’t take the proper care necessary for calibration.  I can imagine it being very frustrating; fortunately, that has not happened to me because I knew that calibration would have to come first before the fun that I knew I’d have,” the sanctimonious Hernandez noted.

Putting the Rig on the Air

When all stages have been adjusted correctly, the plate voltage may be increased to 300 on all stages.  There is no great advantage to increasing to 350 or 400 as there is nothing to be gained from pushing your new tube excessively– allow it to warm up and adjust to your antenna system.  Once this occurs, announce loudly to your fellow hams that you have are on the air.  Consider adding a top-quality crystal microphone with a frequency response of 10,000 cycles.  It will completely drown out other hams who will subsequently be inspired to install their own 2441’s!  Add a bandswitching machine so nobody will know where you are!  Add a voice modulator so that you sound like a spooky ghost!

Most of all, just have fun!

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