[MOVED] shortwave converter for MW radios schematic needed
Discrete designs with BJT are preferred with the output connected to the MW receiver's loopstick, so as not to modify the receiver, but slight modifications could be acceptable.
Any thoughts?
I guess by MW you mean AM radio? 530 to 1700 kHz?
There are many projects for bringing in shortwave on an AM radio. The first hits of an internet search were discussions about it.
One project was mentioned that sounds easiest and simplest... wrapping a few turns of wire around the loopstick antenna. I don't know where it should be connected to.
This moves the frequency of response to a higher range.
You will need to experiment to find the proper position and number of windings, to hear the shortwave band you want.
My basic problem is the imgae signal. On the MW (AM) radio, the image is rejected by filtering on the front end that follows the oscillator.
I haven't seen such a converter that can filter the imge signal though?
Maybe I should try a static bandpass filter before the converter front end, would that be enough to reject the image, assumming a 455KHz below or above oscillator is used?
If that means it rejects signals above 1700 kHz, then a successful method will require more knowledge than I've got.
Example, this project appears to receive the shortwave band, then convert it to the band used by AM.
http://www.ramseyelectronics.com/dow...anuals/SC1.pdf