Stryker SR-447HPC2 receive issue

[TnCbradio]

I am working on a friends Stryker SR-447HPC2 which is talking out just fine but when receiving the radio is very staticy and can barely be made out. The radio has been hooked up to an external speaker and has the same issue. It has been ran on his mobile setup which works with different radios and my bench setup and still has the same issue. I checked for static on the 4th prong of the audio receiver and there is plenty of static. I also check the frequency of channels 1-40 on a dosy meter and all channels are where they need to be. Any info on what might be causing the issue would be greatly appreciated.

 

[WA0CBW]

Is the receiver "on frequency"? If you input a 5uV signal does it still sound staticy? If it sounds bad on the bench then you have eliminated all external causes. Input a signal and follow it through the receiver stages. Try doing an alignment especially the IF stages.

 

[TnCbradio]

You’ll have to forgive my limited knowledge but when I check receive on my dosy FC50 frequency counter from my bench radio to the Stryker the frequency is correct from channels 1-40. I have eliminated everything that could be externally wrong with the radio. As far as inputting a 5uv signal I would need more of an explanation on how to do so.

 

[WA0CBW]

Do you have a signal generator, oscilloscope, test equipment?

 

[TnCbradio]

No sir I do not. I have basic equipment to work with. I have a sauter station, frequency counter, dosy swr/watt meter, 12v power supply’s, multimeter, and a test radio. I do not intend to do work like alignments without investing in oscilloscopes and signal generators. I just basically was wondering if with my limited tools was there a possibly way for me to test for the problem in the hardware. If not the radio will be sent off to be aligned.

 

[WA0CBW]

If your test radio works ok using the same antenna and power source then there isn't much you can do with the test equipment you have. Maybe someone else will jump in with more ideas.

 

[TnCbradio]

I appreciate the wisdom. I am new to trying to understand working on radios and am trying to learn as much as I can. If I was to invest in test equipment where should I start with a limited budget?

 

[WA0CBW]

The test equipment you need depends on the type of equipment you will be working on. Let's start with basic equipment.

Power supply; to power the equipment with the correct voltage and current. Should be variable above and below the equipment needs.
Digital volt meter; measure volts, amps resistance. Helpful if it has RMS measurement.
Oscilloscope, dual trace; 50 to 100 MHz depending on the frequency of the equipment being serviced with x1 and x10 probes.
Soldering equipment; both thru-hole and surface mount capabilities.

The following equipment depends on the type of equipment being serviced.
Signal generator; with a calibrated shielded output. Capable of CW, AM, FM etc. Modulation.
Service monitor; capable of monitoring/measuring the output of RF transmitters to .1ppm (parts per million).
Frequency counter; capable of measuring the frequencies of the equipment being serviced.

Most important is a thorough understanding the theory. Know the following: DC, AC, Semiconductors,, Digital, Circuits, Components, Receivers, Transmitters, Antennas, Transmission Lines and Test Equipment. No amount of test equipment will help if you don't know the theory and how to use the test equipment.

The above is focused on servicing 2-way radios. There are many other pieces of equipment that are handy to have like devices to test components (semiconductors, capacitors, inductors etc.). Hope this helps.
Bill

 

[GrayJeep]

I've had surprising luck just using my bare fingers touching on the receive path to see if my fingers add antenna area downstream from the signal input where the problem is. If the radio doesn't have 110 VAC you're pretty safe doing this. I've found bad solder joint in a coax connector on a CB, a blown diode in sw receiver, and a failing xtal in a scanner.
In this case it might be that the transmit-receive relay or switching transistor performing the same function is the problem.
Or not. But like I said, I've had surprising luck over the years just touching around inside if I know there aren't lethal voltages.