Typical carrier and sideband suppression in SSB system
I consider the design of an ssb exciter using either the 7360 tube or transistor based circuits and I need to take some decisions of which technology to use.
The 7360 tube is capable of 60db carrier suppression, so I need to know if this is good performance or if transistorized circuits or chips can provide a better carrier suppression.
I know that the MC1496 can provide 65db carrier suppression at the interested frequency of 500KHz, but is there any better way to do it, to achieve a better carrier suppression?
Generally 40dB rejection (for both carrier and sideband) is a good number.
40db can be achieved using the phasing method and a poor performance system I think... I wonder what is the carrier and sideband suppression on these commercial ssb CBs....?
40dB is relative easy to achieve, even at high frequencies using cheap components.
Now depends by applications or specs, if you need more.
The most expensive SSB transceiver on the market IC-7800 have 63dB carrier rejection, and 80dB sideband rejection. All of these rejections are done in the DSP.
Thank you, that was the information I needed for comparison.
The MC1496 has -65dB carrier suppression at 500KHz which can be heterodyned to any frequency. No DSPs and complex systems. By the addition of the ssb filter the carrier suppression is even greater, maybe 20db lower.
You know, even the deflection beam dube from the 60's can achieve -60dB carrier suppression... so this makes me wonder why are those expensive machines like the IC-7800 achieve so low performance at this point?
The carrier suppression will vary a lot with temperature and ageing with analogue parts.
Also, you will get a fair bit of passband group delay in the filter using an old school modulator + xtal filter (compared to modern DSP)
This will make the audio sound less natural.
Why do you want or need -65dB carrier suppression anyway? The IMD terms from a typical 100W SSB PA (eg class AB) will swamp this anyway?
Now this makes sense.
Well, the less the carrier and sideband suppression the less "AM power" will be radiated from a high wattage linear.
By the way, have you got any means of comparison between tube balanced modulators and transistor/chip ones?
I think the tube modulator will exibit greater noise (about 4-5db) but how about the "average" low cost solid state modulators? Just for comparison...