SA612 as a Balanced Modulator

SA612 as a Balanced Modulator

Post by Murray Lan » Thu, 23 Nov 2000 04:00:00

Has anyone used an SA612 as a balanced modulator?
I bought one thinking it was functionally equivalent to an AN612 but it's
not, quite.While they're both balanced mixers, the SA612 doesn't seem
intended for audio modulation. What concerns me is that it has no balance
adjustment. I tried it on a prototyping board and it seems happy to modulate
with audio signals. As far as I could measure, the carrier was  suppressed
about 30 dB. I'm not sure how much of this I can attribute to the high
capacitances around the prototyping board.

Any thoughts?

Regards
Murray - VK6HL

 
 
 

SA612 as a Balanced Modulator

Post by Mikae » Thu, 23 Nov 2000 04:00:00


Hi,
I have used the NE602, which is about the same device.

You can adjust the balance slightly,
 by adjusting the voltages on the audio input pins.
I think those are pin 1 and 2.
Connect a 10 Kohm trimmer between pins 1 and 2.
Then connect a 470 Kohm resistor from the middle trimmer pin, to Vcc.

Still,you wont get an extremely deep null.

The SSB filter should buy you 20 dB more carrier suppression.

Mikael, OH2AUN


Quote:> Has anyone used an SA612 as a balanced modulator?
> I bought one thinking it was functionally equivalent to an AN612 but it's
> not, quite.While they're both balanced mixers, the SA612 doesn't seem
> intended for audio modulation. What concerns me is that it has no balance
> adjustment. I tried it on a prototyping board and it seems happy to
modulate
> with audio signals. As far as I could measure, the carrier was  suppressed
> about 30 dB. I'm not sure how much of this I can attribute to the high
> capacitances around the prototyping board.

> Any thoughts?

> Regards
> Murray - VK6HL

 
 
 

SA612 as a Balanced Modulator

Post by Murray Lan » Fri, 24 Nov 2000 10:43:18

Thanks Mikael,

Yes, the NE/SA612 is just a 602 with somewhat better specs. I think it's
worth me spending the time to design a circuit board around it. The nice
thing is that the same chip and oscillator can be easily set up as an SSB
demodulator.
Regarding the biasing of the audio input, I'll give it a try. The datasheet
says that these pins should not be biased but if it works then so what!

Thanks again.
Murray


> Hi,
> I have used the NE602, which is about the same device.

> You can adjust the balance slightly,
>  by adjusting the voltages on the audio input pins.
> I think those are pin 1 and 2.
> Connect a 10 Kohm trimmer between pins 1 and 2.
> Then connect a 470 Kohm resistor from the middle trimmer pin, to Vcc.

> Still,you wont get an extremely deep null.

> The SSB filter should buy you 20 dB more carrier suppression.

> Mikael, OH2AUN



> > Has anyone used an SA612 as a balanced modulator?
> > I bought one thinking it was functionally equivalent to an AN612 but
it's
> > not, quite.While they're both balanced mixers, the SA612 doesn't seem
> > intended for audio modulation. What concerns me is that it has no
balance
> > adjustment. I tried it on a prototyping board and it seems happy to
> modulate
> > with audio signals. As far as I could measure, the carrier was
suppressed
> > about 30 dB. I'm not sure how much of this I can attribute to the high
> > capacitances around the prototyping board.

> > Any thoughts?

> > Regards
> > Murray - VK6HL