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SRT CR91

 

The SRT CR91, or in full "Standart Radio and Telephone",  is a professional 19" receiver made in Sweden.  The CR 91 was built, however, with Telefunken technology.  Some circuits and especially the bandwidth filter with 200 kHz IF point to this fact. This model was built between 1982 and 1992. It was mainly used in Scandinavia at embassies and listening posts for monitoring radio communication. However, some radios made their way to other countries and also to Switzerland. SRT even used to have an office in Switzerland.

Here are the most important features:
Frequency range: 10 kHz-30MHz
Tuning Steps:   1Hz - 10Hz - 100Hz
Tuning speeds:
Slow: 2.5 kHz/turn        MED: 25 kHz/turn             Fast: 250 kHz/turn
Rotary knob with flywheel effect
Bandwidth filters: 0.3 - 0.6 - 1.5 - 6.8 3(USB) - 3kHz(LSB)
AGC: Short - Med - Long - and manual control for all modes
100 Memories
Remotely controllable
Excellent large signal rejection
Very good frequency stability
Weight: 12Kg
19" rack-mounting unit

As is often the case with such radios, it had to be repaired before the test. The colleague, who loaned me the CR91, had forgotten to test the unit before he gave it to me. Therefore, it happened what was bound to happen. The CR91 could not be switched on. Therefore, I had to use my contacts to specialists to find someone, who could bring back the CR 91 to life.  After only two weeks I could finally switch the CR 91 on.

After some time of familiarization, the CR 91 could be operated easily and speedily.  However, I had to use the manual because some functions were not immediately obvious.

The reception was really good when the radio was connected to normal SWL antennas.  Because of its excellent 200 kHz IF Telefunken filters , which offer an excellent selectivity, the CR 91 is a good receiver for SSB as well as AM.  DSP radios were not more selective. The CR 91  was on par with modern SDR-radios, up to a point! If you had to suppress a secondary carrier, its options were very limited. There are no noise blankers or other features.  The CR91 cannot offer the flexibility,  which is expected today.  What I noticed negatively,  was the extremely fast start of the flywheel effect.  Practically, I could only work with 1Hz tuning steps. Unfortunately, I could not find out,  if this effect could be switched off.  The socket for the headphones was not  typical, either. It is a DIN 5 - pole jack with 240. Fortunately, I found such a plug at the Hamradio 2014 to build an adapter.

Basically, it is a good receiver in "Telefunken quality", so to speak.

A radio for specialists. Not practical for short wave listeners.

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