Jfet RF preamp construction.

Taking a look at your .asc you have a 1kHz signal linearly added to a 384.259 Hz carrier. You better have a really long antenna for that puppy

If you are thinking of AM, then you should use a controlled voltage for the carrier, multiplying it by the value of the modulating signal, and taking a 50% DC offset. As a suggestion probe the signal source, I don't think it's what you expect.

I cheated and swiped the ideas from http://www.auldies.euweb.cz/me/Amf1.html
because I couldn't work out how to do AM either It looks OK at 100%, though aliasing makes it still a bit grotty. But AM it is.

The linked website indicates that this is an RF preamplifier for a range of 20kHz to 30MHz. 1 kHz is way too low a frequency.
Also, you do require to tune the input tank circuit to the input frequency.
And, run the DC bias operating point before doing a transient analysis. As mentioned in the article, you should adjust the bias resistors to have an idling VDS and VCE value of half the supply.
Lastly, simplify your circuit. You don’t require ancillary components like D1 to run your simulation.