Lm1496

Hi there,

I feed in a carrier of 500kHz and modulating signal 125kHz but the output is not clear. Not really a DSB signal.

Is there a minimum requirement saying that the carrier frequency need to be at least how much higher than the modulating signal frequency in AM application?

BTW, i need a power amplifier for the 1496. So is the lm386 suitable? Construct it as shown in the datasheet?

Regards,
cwt

I suggest you give more details of what you're wanting to do?, but an LM386 isn't suitable as an RF power amplifer.

Certainly your modulating frequency seems far too high for anything I'd attempt, but without more details it just sounds very bizzare?.

Why modulate a radio wave with another radio wave?

What you have is a mixer. If the signals are sinewaves, the output will be 625 kHz, 500 kHz and 375 kHz of varying amplitude. If the signals are square waves, the output will be a real mess!

Actually i was using the lm1496 for amplitude modulation in my frequency hopping transmission. And another lm1496 is used to demodulate the message.
Previously i was using a 2khz message signal and 100khz carrier signal. I can get a DSB output. And when i connected the modulator and demodulator through wire, i can obtain the original message with a slight phase shift.

During one of my try out, i just wondering why a message signal of 125khz cannot be properly modulated with a 500khz carrier. Is there any requirement stating that the carrier frequency need to be at least how much greater than the message signal in order to modulate properly?

I would like to have RF power amplifiers to make the transmission wirelessly. The range need not to be far. Maybe around 1-2 meters. Any suggestion for the amplifier part?

Regards,
cwt

Your RF frequency is so low that either the antennas will need to be very long (100m?), or with shorter antennas the RF power will need to be very high (10W?) for a transmission to be received.

I think i'll go for the higher RF power for transmission because the antenna approach is not practical. I had set up almost everything, the only problem now that i face is how to transmit my signal wirelessly. To be frank, my carrier ranges from 120kHz - 500kHz.

Regards,
cwt

Why such a low frequency?, and why try and use DSB reduced carrier?, data links normally use UHF, on specific licence free frequencies - your device (as well as not working well) will be illegal.

Aerial size is also inversely proportional to frequency, at 433MHz it's a few cm's - at your frequency it's hundreds of meters.