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Test unit for the Torn.Fu.b1 and f


Funksammler

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Another recent find is a "Empfängerprüfer für Torn.Fu. bf". This test unit was manufactured in relatively low numbers and allowed the Torn.Fu.b1 and f sets to be tested in the field. The test sets is a relatively small box that folds open to reveal a HF control, instrument, operating instructions and a storage compartment for the antenna cable. 

The unit itself plugs into the power and headphone socket of the Torn.fu.b1 and f transceiver, with the power supply cable coming from the battery box now plugged into the side of the test unit. An antenna cable with attached earthing wire is just long enough to reach the antenna socket and earthing boss of the transceiver. 

The unit provides a test signal at 3050 kHz, interestingly it does not use a quarz oscillator but a very stable RC circuit. The test unit allows the frequency scale of the receiver to the checked as well as the selectivity. Although it is called a "receiver tester", it also tests the power output of the transmitter and can be used to calibrate the frequency of the transmitter.

So with the "Empfängerprüfer für Torn.Fu. bf" the Torn.fu.b1 and f could be comprehensively tested and adjusted in the field. It would have been used by a "Funkwart", a trained radio maintenance specialist who would go around the field units to test and repair their radios. 


regards,

Funksammler

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Very rare accessory.  High quality construction, and performance characteristics.  LA6NCA has this also, and has taken it apart on his site.  

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Have you measured the frequency stability @Funksammler?

Normally those things are quality items that even now ~75 years

later keep their frequency amazingly accurately.

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2 hours ago, val said:

Have you measured the frequency stability @Funksammler?

Normally those things are quality items that even now ~75 years

later keep their frequency amazingly accurately.

No, I have not tested it yet. I would be very surprised if it was still at 3050 kHz after 76 years!

regards,

Funksammler

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3 minutes ago, val said:

Ah yes, my "Frequenzprüfer" quarz oscillators are bang on, but the "Empfängerprüfer für Torn.Fu. bf" purely relies purely on L's and C's (including the parasitic capacitance in the valve), so it would be a phenomenal achievement to be stable over 76 years!

regards,

Funksammler

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Here's my unit.   The cable needs to be restored, but otherwise, the set is in good condition.

https://kriegsfunker.com/accessories/test_equipment/tester_torn_fu_bf.html

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Serial Number 492 from 1942 and  520 and 689 from 1943, gives a rough idea of production period and numbers. Perhaps 1000 units were ordered... The cables are indeed a problem on these units, most I have seen have damaged cables due to dried out rubber. Mine has a small damage where it was pinched by the lock of the box but is otherwise soft and pliable.

regards,

Funksammler

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