if you already have a DC receiver, all you need to do is add a simple
ladder filter to the input of the DC receiver, add a mixer to the
otherside and a VFO. You will have a pretty decent superhet. Don't
throw away the DC receiver, just build up a superhet around it.
As I wrote I have DC RX, but for 3.5 MHz. What I need is monoband for
14 MHz. My RX is very simple and I am not sure if its circuit,
especially the VFO will work well in the higher frequency.

You current VFO can be moved up to being the Local oscillator for the
superhet. Two or three crystal filter at the input of your current
product dectector should provide you with bright quality of filtering.
On the front-end just use a single FET with a post-mix amp. check my
transceiver for the idea at http://farhan.co.net.nr.

Thanks for the link.

jvereker