03-06-2014, 08:41 PM
Yes, most likely the SG165's FM RF output is too low for a counter to read directly. Unfortunately, there may have been nothing wrong with the unit you sent back. Without an RF millivoltmeter, the only way to check would have been to connect it to a FM receiver and listen for the RF carrier.
If there is one downside to the ST 1000A its the lack of a 10.7 MHz output for aligning the IF. Personally I have never seen this as a problem as I typically use a standard signal generator to peak the IF at 10.7 and provide a marker. Then use the sweep output of the ST to optimize the response and adjust the FM detector for max linearity. The ST provides its sweep output as RF from 88 to 108 MHz, so it sweeps the entire receiver from front end to detector.
The ST's dual sweep function modulates the swept signal with an additional 10 kHz frequency. You feed the RF sweep into the ant input then pass the receiver's output through a filter in the ST, which removes the low freq sweep but passes the 10 kHz signal. When you look at the 10kHz on a scope, you should see a flat amplitude across the swept bandwidth. If there is any tilt or variation to the amplitude waveform then the IF or detector is nonlinear and needs tweaking.
The nice thing about the setup is that you can check the IF and detector alignment without even taking the cover off the receiver. Just feed in the sweep signal at the ant terminals and look at the demodulated output on the scope.
If there is one downside to the ST 1000A its the lack of a 10.7 MHz output for aligning the IF. Personally I have never seen this as a problem as I typically use a standard signal generator to peak the IF at 10.7 and provide a marker. Then use the sweep output of the ST to optimize the response and adjust the FM detector for max linearity. The ST provides its sweep output as RF from 88 to 108 MHz, so it sweeps the entire receiver from front end to detector.
The ST's dual sweep function modulates the swept signal with an additional 10 kHz frequency. You feed the RF sweep into the ant input then pass the receiver's output through a filter in the ST, which removes the low freq sweep but passes the 10 kHz signal. When you look at the 10kHz on a scope, you should see a flat amplitude across the swept bandwidth. If there is any tilt or variation to the amplitude waveform then the IF or detector is nonlinear and needs tweaking.
The nice thing about the setup is that you can check the IF and detector alignment without even taking the cover off the receiver. Just feed in the sweep signal at the ant terminals and look at the demodulated output on the scope.
