Equipment "substitutions" for setting RX sensitivity?

[Cutlass327]

I know a freq generator with a certain output is the standard, but is there a way to do it if you do not have one? I remember reading people using audio thru the mic instead of a signal gen to set certain parts.

I do have a 'scope, and I know you adjust until you have the highest reading with the specified input. I had a radio that sounded like it was just barely picking up anything, meter barely moved even when you adjusted the meter full out. By turning the Rx adjustments, listening for the loudest static from the speaker, the meter moved better and RX sounded much stronger from those base units that sounded weak.

I'd like to set it better, as since I did that the SSB meter reading is S9+ instead of S1 a lot of the time, until the time comes that I find that impossible-to-pass-up deal on the proper generator, a substitution would be great.

 

[Robb]

I remember reading people using audio thru the mic instead of a signal gen to set certain parts.

Could you explain that with some detail please?

The problem with freq alignment is twofold. First, you have to get a STABLE freq of the actual freq itself before you can get an accurate result for tuning. Then the amplitude of that freq being fed in must also not vary either. Otherwise your freq peaking, squelch adjustment, and meter adjustments won't be credible.

 

[Cutlass327]

I don't remember the process they did, it was last year I read about it somewhere. See the "Useful Testing Apps" sticky for idea.

For mine, I just need the signal strength tuned. Frequency and such is still ok.

 

[loosecannon]

you can use anything that will put out a signal on the channel you are using if you just want to peak the receiver for maximum.

when you want to define what "maximum" is, like "maximum noise" or "maximum signal" then a SINAD meter is pretty much the only way to go.

if you just have a radio you want to peak the coils in, just use another radio keyed up into a a dummy load, and turn the power of that radio down to the point where it barely registers on the meter of the radio you are trying to tune up.

some go a step further, and put a 1K tone into the mic of the radio being used as a signal generator so they can tune for something better than static.

once you want to set your squelch and your S meter, you need a source with a calibrated output.

you can find the HP 8657 or similar units on ebay for a couple hundred bucks, but shipping can be a killer as they are big and heavy.
LC

 

[Handy Andy]

some go a step further, and put a 1K tone into the mic of the radio being used as a signal generator so they can tune for something better than static.

once you want to set your squelch and your S meter, you need a source with a calibrated output.

LC

While you're doing that... leave that mic on, open or enough of a gain on that "signal generator radio" opened and turn up the volume control on your radio you're tuning on up onto - that carrier of the other...

If you turn up the volume, you can get a squeal of feedback, you can use that to re-tune the IF strip chain further up the line as well as listen for distortion and loudness. Tune accordingly.

In reality - when you look at it - the "Setup" you read about, is nothing more than generation of a signal you tune the radio to. The extra features and jigs - wire and plugs, are all to keep it quiet so the boss doesn't come busting in saying something to the effect of "WHY DID YOU AWAKEN ME FROM MY SLUMBER?" - Only not necessarily using those words...

​

Adjust the volume of your radio to obtain a "barely" - squeal or thereabouts, if you do this right, to even reproduce the "Hiss" you are heating from this carrier from your bench radio. With that "Hiss" - you can also use it to "center" your tune-up radio to the center carrier of the "dummy loaded" radio.

For grins giggles and even a quality check of effort, play a radio tune to a music station within the room to check volume and sensitivity - of both your radio and the mic of the dummied radio - to obtain the best fidelity to noise ratios. Makes for an interesting effect as well as echo - neighbors will think you're weird but hey, they're not playing - you are.