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| To: | "LF-Group" <[email protected]> |
|---|---|
| Subject: | LF: Feld-Hell on the 136kHz band |
| From: | "Dick Rollema" <[email protected]> |
| Date: | Mon, 24 Jun 2002 16:37:19 +0200 |
| Cc: | "Bastiaan Edelman PA3FFZ" <[email protected]>, "Cas Caspers" <[email protected]>, "Cor Moerman, PA0VYL" <[email protected]>, "Gerrit Jan Huijsman" <[email protected]>, "Helmut Liebich, DL1OY" <[email protected]>, "Jaap Kroon, PA0IF" <[email protected]>, "Jan Harte" <[email protected]>, "Koos Fockens, PA0KDF" <[email protected]>, "Arthur Bauer, PA0AOB" <[email protected]>, [email protected] |
| Reply-to: | [email protected] |
| Sender: | <[email protected]> |
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As I found that the reflector had passed
only one of the attachments here the message again with the second
attachment. To All from PA0SE, Following my Feld-Hell transmissions on Saturday 22 June at 1300 UTC and Sunday 23 June at 0900 UTC I received reports by e-mail with screenshots of my transmissions from Alan, G3NYK; Ko, NL9222; Wolf, DL4YHF/DF0WD; Koos, PA0KDF; Geri, DK8KW, Mike, G3XDV and Jim, M0BMU. Many thanks to you all! My Saturday transmission was answered in Hell by Markus, DF6NM and Wolf, DF0WD. Unfortunately the signal/noise ratio was too poor for readable print on the paper tape. Using CW they reported good copy of my Hell signals ("UFB"). Their CW was perfectly readable which shows that Hell is not a weak signal system! Good reception was also reported in CW by Jim, M0BMU. The Sunday transmission was answered in Hell by DF6NM, DF0WD and DK8KW. Again their signals were too weak for a useable print. But then Wolf, DF0WD, switched to a large font (a useful feature of the IZ8BLY software!) and then I became readable text on the paper tape: see attachment. I also attach a screenshot of my signal, as sent in by Ko, NL9222. Geri also switched to the large font but it helped not enough for readable print. Koos, PA0KDF, had readable text on the screen of Geri's signal. But he lives near the German border in a rural area. So he is much nearer to Geri than me and probably has a lower local noise level as well. Now for some more detail on the 1944 Hellschreiber I use. It belongs to collector Arthur Bauer, PA0AOB and I have it on "permanent loan" since 1977, having used it for numerous QSO's on 20, 40 and 80 metres and now 2km. As you can see in the screenshots the machine produces the line of text twice, one above the other. That is done to avoid the requirement of perfect synchronous running of the sending and receiving machine. When their speed differs the lines of text become slanting on the paper tape (can be seen in the screenshot of NL9222) . But when the upper line disappears over the top the lower one is already coming up from the bottom. It took a genius like Dr. Rudolf Hell to devise such a simple way of avoiding the need of synchronism! The Hellschreiber has a speed control. In practice one simply turns the control until the lines of text become horizontal. The motor speed is controlled by a centrifugal speed regulator, like the one invented by James Watt for the steam engine. But in the Hellschreiber the rotating mass does not work against gravity but against a spring. When the motor speed exceeds the wanted value the mass moves outwards against the force of the spring and closes a contact. This causes an increase of the current through the field coils of the motor and the speed decreases until the contact opens again. The speed settles down at a value at which the contact periodically closes and opens. The small variations in speed are not noticeable. With the speed control knob the tension of the spring can be varied and with it the motor speed. The speed is controlled within very tight limits. The current through the field coils is not directly controlled by the regulator contact but via a thermionic valve so the contact is not loaded by the current and does not spark. The motor also is also a dynamotor producing130V HT for the valves from the 12V DC supply. It is not possible to send a photograph of "my" Hellscheiber via the Reflector. But I will send the picture by direct e-mail to those who have reported my signal and to anybody else who likes to receive it. Just drop me an e-mail. I also wanted to send this report to Hell-promotor Murray Greenman, ZL1BPU. But my server reports the message cannot be delivered. Perhaps his e-mail address has been changed and it is not on his web site. May I ask one of our New Zealand friends on the reflector to pass it on to Murray? Many thanks! 73, Dick, PA0SE JO22GD
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