Comtek is a program that uses the line input of your sound card to see the SINAD.
From Wikipedia:
A typical example, quoted from a commercial hand held VHF or UHF radio, might be:
Receiver sensitivity: 0.25μV at 12dB SINAD
which is stating that the receiver will produce intelligible speech with a signal at its input as low as 0.25μV. Radio receiver designers will test the product in a laboratory following a procedure. A typical example procedure is as follows:
- With no signal present on the input, the noise and distortion of the receiver are measured at a convenient level
- A signal is applied to the input which causes the output to increase 12 dB
- The level of the signal needed to produce this is noted and is found to be 0.25 microVolts.
According to the radio designer, intelligible speech can be detected 12dB above the receiver's noise floor (noise and distortion). Regardless on how accurate this output power is regarding intelligible speech, having a standard output SINAD allows for easy comparison between radio receiver input sensitivities. This value is typical for VHF commercial radio while 0.35μV is probably more typical for UHF. In the real world lower SINAD values (more noise) can still result in intelligible speech but it is tiresome work to listen to a voice in that much noise.
Translated, this means that a SINAD meter is basically making sure that when a receiver is being peaked that it is not peaked too much and go into distortion and noise. These elements can make a receiver nasty sounding and hard to understand - in simplest terms. Doing a receiver is not exactly a 'piece of cake' for the beginner.
So, you see that SINAD is important to get the best signal to distortion ratio when doing a receiver alignment. You will also need a signal generator as well. But we are getting ahead of ourselves here.
Think the equipment you need at this point would be a dummy load, watt meter, DVM, O-scope, and perhaps a freq counter. Forget about doing receiver alignments until you can establish transmit alignments
first. Receiver alignments are a bit trickier and a bit more costly - equipment wise - as well as a bit tougher to grasp and perform if done well.
This link is for the Spectrum analyzer I talked about. Never used one of these units and I don't know if it will do the job as yet:
http://rover.ebay.com/rover/1/711-5...0001&campid=5336136228&icep_item=111805709667
If it does work as I hope, this could a very simple and inexpensive means to monitor a CB for spurious emissions/'harmonics'. Until now, lab grade analyzers are very expensive, but aren't really necessary to get the job needed for the CB.