EMRFD Message Archive 7813
Message Date From Subject 7813 2012-09-25 07:18:49 ha5rxz SSB Generation - Opinions Please When generating an SSB signal from audio and a 9 MHz carrier which would be the best mixer to use?
a) A high-level ring bridge mixer such as the SRA-1H
b) An H-Mode mixer using an FST3125 chip
c) An H-Mode mixer using a 74HC4016
d) Something else
Note that this mixer will not be used to demodulate.
7814 2012-09-25 07:50:24 Ashhar Farhan Re: SSB Generation - Opinions Please In my experience, if you keep the audio level low enough, it is
difficult to beat a simple two diode mixer.with a 10 db attenuator in
the output. Having just two diodes makes balancing of reactive as well
as resistive differences of the two diodes quite trivial. Schottky
diodes are best.
One thing, I did discover though is that the balance should be to
minimize the harmonic distortion, rather than just the carrier
What we are shooting for is to keep the In-band IMD down. Carrier
suppression is just hygiene. So, you will want to tune in to the
signal, modulating it with two tones and see it on a audio spectrum
analyzer (freely downloadable from the net) and try getting the third
Though the 'packaged' mixers don't give you the needed control for
hi-fidelity, for trivial usage, NE602 is pretty good. Just drop it
into the rig and live with what you get (which is not bad at all).
The best resource is the chapter on phasing receivers and transmitters
in emrfd. Rick is the guru. I hope joins this thread.
On 9/25/12, ha5rxz <email@example.com> wrote:
> When generating an SSB signal from audio and a 9 MHz carrier which would be
> the best mixer to use?
> a) A high-level ring bridge mixer such as the SRA-1H
> b) An H-Mode mixer using an FST3125 chip
> c) An H-Mode mixer using a 74HC4016
> d) Something else
> Note that this mixer will not be used to demodulate.
> Peter HA5RXZ
Sent from my mobile device
7815 2012-09-25 16:32:50 kb1gmx Re: SSB Generation - Opinions Please I'll weigh in..
Yes, they all work. You need a provision for adjusting carrier balance on some but anything over 40db will be good.
I've used 602/612s, SBL-1, SBL-1H, diode rings, and even varicap
diodes (there is a design using them in capacitively balanced
a modulator from many years ago. They all work if the levels are correct.
These days I use the sa612 for simple designs, SBL-1 with a 50ohm
pot added for balance for better radios and the 4 diode ring I've
used many times as its uncritical, needs only one untapped
transformer and easy to make. Most of those are listed in the
older 1975 through current handbooks and EMDRFD.
If needed I can post to the files section a few designs but
they are all textbook and all are capable of good results.
In just about all the diode modulator cases a fairly strong
carrier (5mW or more) is needed and the audio will be about
10db lower for very good result. The active devices like the
ca3028(and friends), SA612, MC1496 the levels for the carrier
and audio must be matched accordingly for the device. You can
look at the output with a scope and get a first order eyeball