For our purposes, the most suitable Micro-tel receiver is the MSR-904a. They show up on eBay quite regularly. They have the capability of sweeping the entire frequency range from 1 to 18 Ghz and with external extenders up to 40 Ghz. They will also operate on any set frequency within that range.
While these receivers are 1980's technology, they have the very distinct advantage of having front end YIG tracking filters that provide a fair amount of selectivity at the front end.
They come with a number of selectable IF bandwidths. One of my MSR 904's has 500KC, 2 Mhz, 10 Mhz and 20 Mhz filters in it. The other one has 5, 10, 22, and 36 Mhz filters in it.
The receivers have built in AM and FM detectors and an audio output stage. But for SETI use we use the 24.1 Mhz IF output to run to an external IF stage with sharper filters and a product detector. Some units also have a 70 Mhz If output as well.
These receivers were originally designed for surveillance work (CIA & NSA) and have the ability to stop scanning when a signal of preset strength is encountered. They also have a panoramic adapter that gives a nice frequency display similar to a spectrum analyzer and have outputs that can be connected to a storage display oscilloscope or pen recorder.
Their great utility is in the enormous frequency range they can cover. Their downside is the receiver noise figure of 20 dB and wide IF bandwidths. However, this can be offset by using low noise amplifiers at the front end and an external IF with suitable filters. The microwave tuner and first mixer portion of the receiver can be remotely located at the antenna and then the first IF piped down to the shack at around 900 Mhz thereby limiting feedline loses.
These receivers are best used with the FCS-904 Frequency Counter/Synthesizer which uses indirect digital synthesis to control the frequency of the receiver. (It phase locks a YIG oscillator in the MSR-904A to a 10 Mhz standard, thereby providing 1st and 2nd mixer local oscillator signals with extremely low phase noise) It consists of a phase lock processor which phase locks the first and second conversion YIG oscillators to either an internal 10 Mhz crystal in an oven in the FS904 or to an external standard (I use a GPS based 10 Mhz frequency standard which gives unprecedented frequency accuracy and stability). With the FS904, you can program sweeps from the front panel or set specific frequencies from the front panel, digitally. You can set sweep times, sweep ranges, dwell times and signal strength necessary to stop the sweep. When the sweep stops it automatically indicates the frequency and provides that information to the HP-1B interface.
The entire system can be programmed, operated, and results recorded using the HP-1B interface for totally automated operation.
The MSR-904A receiver/ FCS-904 Counter/synthesizer goes for around $2,000 on eBay. The receiver alone for about $1,500. You will see them at much higher prices than this but most sell at the above figures. The receiver runs around $3,500 to $6,000 from typical used test equipment dealers.
These receivers, when coupled with good front end LNA amplifiers and line amplifiers, and using the FS-904 synthesizer/counter make a very versatile and sensitive seti receiver with unprecedented frequency agility.
For doing conventional SETI monitoring, you would want to operate at a fixed frequency (either crystal controlled or with the FCS-904 in fixed frequency mode) and use an external IF/filter/product detector along with FFT software to achieve narrow bandwidths and allow for integrating signals for sub noise level detection of weak signals.
Of course, if your intention is to monitor around the "water hole frequencies", there are much cheaper ways to go. An Icom 7000, 7001, 8500, can be had for a lot less money, has much lower noise level and already has sharp IF filters and a product detector to boot. In fact, I would only recommend the Micro-tel receiver if you planned to do SETI work over a very wide range of frequencies where the inclusion of the front end YIG tracking filters will be of benefit. That's really its only advantage.
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this page last updated 15 January 2005
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