Tag Archives: Narda 4244-6

Micro-Tel MSR-904A: RF tuner block diagram and component specs

Just to learn a bit about the way Micro-Tel was doing their engineering, let’s have a quick look at the way in which it functions, at least for the RF front end. After some study and tracing, here is the block diagram:

msr-904a rf tuner block diagram
Some parts don’t have model numbers – because these are hidden, and I don’t want to take the thing apart.

Luckily quite a few of the parts are still available, and datasheets are available for most. The YIGs are Avantek, have a customer part number, but I assume, essentially, slightly modified line item parts, with some specific specications. The only really uncommon part, is a “TREK MICROWAVE” 0.48-2.01 GHz 3-stage YTF. Didn’t know that such low frequency YIG filters existed, this has serial #00003.

YIG filter 4021-104

Even more, TREK doesn’t ring a bell for me, and the filter really looks very much like Systron Donner technology, with the characteristic color, and square-cube shape.

As it turns out, TREK acquired the YIG division of Systron, some time around 1984… so, this mystery solved.

The only part where no data seems available is the 2-18 GHz mixer, Avantek SX83 series, but can’t find a -1612 model anywhere.

Some datasheets:
5B120-2330_25-O_OP – 5915011438953 _ chebyschev 2330 MHz 25 MHz bw

k&l 5L120-300-0 low pass 300 mhz

8L120-2050-0 low pass – 5915012428744 _K&L filter

narda 4244-6 082-Couplers

a34 datasheet

qbh 101 amplifier datasheet

narda 4203-10 coupler