My impression is that most 'talkback' implementations are tapped from somewhere in the audio stage in the radio rather than the RF stage. This will tell you what your mic input sounds like, but this may not necessarily be a true reflection of what you sound like on the air. If your radio has been too heavily "golden-screwdrivered," there may be distortion present due to over-modulation or excess drive power which won't be evident just by listening to the audio stages.
Some ham rigs have actual RF monitors in them, which give you a good impression of what you actually sound like on the air, but even these can fool you if you use an amp.
In my opinion, the detector circuit that 76Q suggested is probably your best bet. Using a separate receiver is a good approach too, but it has one drawback: what you hear will be limited by the receiver's frequency response, which will depend on the IF filters and audio amp design. On the one hand, most people you talk to will likely have similar receivers, so this will give you an indication of what they hear. On the other hand, if you decided to try improving your transmitter's frequency response (e.g. more bass or treble), you may not be able to hear too much difference unless you modify the receiver for better response as well. In other words, what you'll be hearing on the other receiver won't necessarily be an accurate representation of your actual transmitted signal.
The diode detector circuit approach removes all the filtering limitations so, assuming you use a good set of headphones, you'll be able to hear exactly what you sound like. I wasn't aware that Dosy meter systems had those, but if so that's a good way to do it. There's also this:
RF Sampler | RF Demodulator | AM Modulation Monitor | Products
The downside to this is that it only works for AM. For SSB, you'll need a receiver. Same for FM. So a combination of a good receiver and a simple diode detector circuit would probably be ideal.
It's obviously pretty easy to overload a nearby receiver though. Some suggestions to try and deal with that:
- Connect the receiving rig to a dummy load
- Find a rig with an RF gain control and crank it to minimum sensitivity
- Find a 'sacrificial lamb' receiver that you don't care about and add some padding resistors to the receive path somewhere to really dampen its sensitivity
If you want to go really nuts, you could try to find a receiver with an IF output tap and use a software-defined radio program to demodulate the signal with a computer. Some packages will give you a nice spectrum display and will allow you to set the receive bandwidth as wide as you like. This assumes you have some money to burn though.
-Bill
