Just to pass the time I used a wire to link across an unused filter position (with a series 0.1u DC blocking capacitor), adjusted the filter bandwidth to 8kHz, and listened to AM broadcast stations. Quite a respectable performance, much better than with a 2.7kHz filter.
Now I know that it is worth making even a fairly loose LC filter just for occasional AM reception. 73 Stewart G3RXQ On Mon, 05 May 2008 20:25:59 +0100, David Woolley (E.L) wrote: > Jerry Flanders wrote: >> for SWL. Only downside (a minor one, IMO) is that you might get response >> from images 30 KHz away. How much weaker is a signal when you tune to >> its image 30 KHz up/down? >> > Less than 30kHz. The whole point of the exercise is to use wide > filters, so, assuming that the interference is from a carrier and > appears in the demodulated audio, the image can be 25 (5kHz audio) to > 20kHz (10kHz audio) away from the carrier (20 and 10kHz from the > passband edge). If the interference is from an audio component at the > extreme of the bandwidth and the transmit is the same as the receive > bandwidth, the carrier can be 20 to 10kHz away (although in the latter > case would have other problems). In practice, I would expect the > carrier to get past a weak filter better than an extreme sideband frequency. > > Note this means that if the signals are trying to reproduce audio up to > 10kHz, the adjacent channel will be an issue. _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
