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Torn.Fu.b1/c/f - why receiving range different from transmitting range?
Old 01-04-2018, 12:05 AM   #1
Yuri D.
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Default Torn.Fu.b1/c/f - why receiving range different from transmitting range?

Does anyone know why the ranges on these transceivers don't completely overlap?
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Old 01-04-2018, 05:40 AM   #2
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During the development years of the Wehrmacht, frequency bands were not yet set in stone. As the different branches of the Wehrmacht developed, so did their communication needs resulting in changes and reassignments of frequency bands.

At the prototype stage the Torn.Fu.a covered the full band from 3 to 6.5 Mhz, with the Torn.Fu.b limited to 3 to 5 Mhz (probably one of the reasons it was not adopted by the Wehrmacht).

When the new generation of portable shortwave transceivers was designed in 1936, the army had split the shortwave band, with 3 to 4.5 Mhz assigned to the infantry and 4.5 to 6.5 Mhz assigned to the artillery. So the new shortwave transmitter was manufactured in two variations, the b1 for the infantry and the f for the artillery sharing the same receiver block but with a different transmitter.

At the same time the upper medium wave band (the Germans called these "Grenswellen") of 1.5 to 2.5 Mhz was assigned to the pioneers, specialised troops required to crack the Maginot and other defensive lines opposing the German armies, so a special veriation was created: the Torn.Fu.c. The design of the c seems almost improvised, they did not bother to design perfectly linear and overlapping oscillators for transmitter and receiver, it was a quick and dirty solution to a short term requirement.

From 1940 the command frequency band used by the Panzer divisions was extended to include the upper side of the medium wave band previously assigned to the pioneers, so the Torn.Fu.c was discontinued.

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Old 01-04-2018, 12:54 PM   #3
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Excellent explanation FS. May I please include it on my site? (with full attribution of course)
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Old 01-04-2018, 02:03 PM   #4
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Quote:
Originally Posted by Yuri D. View Post
Excellent explanation FS. May I please include it on my site? (with full attribution of course)
by all means, go ahead!

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Old 01-04-2018, 09:10 PM   #5
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I have also one question here.

To receive on CW you must actually be off the transmit frequency to hear the signal locally produced by the BFO. What was the official german funker's procedure to tuning transmitter and receiver to achive this? I'd very much like to see some official training manual where this is described. I know several methods, zero beat is one of them but i'd like to know what method german funkers used. Thanks.
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Old 01-05-2018, 06:39 AM   #6
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The Torn.Fu.b1 receiver was tuned by ear, the operator would simply tune to achieve the higher volume. The b1 transmitter uses A1 (Telegrafie Tonlos), so there is no modulation on CW. The b1 receiver does not use beat oscillation, it uses regeneration to create an audible tone. The output from the rectifier valve is fed back to the input (the amount of which is determined by the volume potentiometer acting on the screen grid voltage). At higher volumes the receiver will automatically start to "scream" when it detects a signal of sufficient strength. So there is no zero beat or tone variation, the operator will just experience a variation in volume of the "screaming" with the highest volume when the receiver is exactly tuned to the the transmitter's carrier wave frequency.

regards,

Funksammler

Last edited by Funksammler; 01-05-2018 at 06:46 AM.
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Old 01-06-2018, 01:58 PM   #7
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Quote:
Originally Posted by Val View Post
I have also one question here.

To receive on CW you must actually be off the transmit frequency to hear the signal locally produced by the BFO. What was the official german funker's procedure to tuning transmitter and receiver to achive this? I'd very much like to see some official training manual where this is described. I know several methods, zero beat is one of them but i'd like to know what method german funkers used. Thanks.
You can find the full answer to your question here: https://www.ebay.de/itm/Original-Die...4AAOSwgbhaR70p

regards,

Funksammler
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Old 01-06-2018, 08:53 PM   #8
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Thanks Funksammler.
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