Hi All,
I'm not sure what kind of parameters you'd like to be able to adjust Brian. I think that if you put a good filter at the antenna jack and get rid of the AM broadcasters then your Flex can easily do the rest. I have already built a lowpass filter that cleans the longwave band of any AM broadcast interference. A bandpass filter is more difficult to do; it's not as forgiving of variations in component values so trimmer capacitors would have to be added to get it set up correctly, which makes it more expensive to build. It seems to me one only benefits from a bandpass filter if one lives in parts of the world where Loran-C is still operating, or where the longwave broadcast band is still active, i.e., not North America. Otherwise, the lowpass filter lets you hear EVERYTHING below 500 kHz. Anyway, I'm building a few lowpass filters as soon as I get the rest of the components I need; one for me and one for a list member I've been corresponding with who is going to give me some feedback. I'll be glad to make more if they work out well. The bandpass filter too, but that'll take a little longer. 73 - Ken, VE3HLS ________________________________ From: "Robert Costa, KB6QXM" <kb6...@yahoo.com> To: Brian Lloyd <brian-wb6...@lloyd.com> Cc: "Carol F. Milazzo, KP4MD/W6" <kp...@cfmilazzo.com>; flexradio@flex-radio.biz Sent: Tuesday, February 21, 2012 12:48:24 PM Subject: Re: [Flexradio] The new 472-479 kHz band - REAL DX Brian, Yes I agree about your assessment on the preselector, but who is going to take the time to design, test and market the preselector. We could talk all day what it should be in theory, but until someone takes the time to take their theory and make it a viable product all we have is " what if" 73, Robert KB6QXM "Ham Radio Open Conversation" Yahoo group owner/moderator ----- Reply message ----- From: "Brian Lloyd" <brian-wb6...@lloyd.com> To: "Robert Costa, KB6QXM" <kb6...@yahoo.com> Cc: "Carol F. Milazzo, KP4MD/W6" <kp...@cfmilazzo.com>, <flexradio@flex-radio.biz> Subject: [Flexradio] The new 472-479 kHz band - REAL DX Date: Tue, Feb 21, 2012 9:35 am On Tue, Feb 21, 2012 at 8:47 AM, Robert Costa, KB6QXM <kb6...@yahoo.com> wrote: What I want to see is someone design a tuneable preselector with many adjustable parameters. Anyone up to the task. I will even build your website to market it. Signal levels tend to be pretty strong unless using a small loop antenna, and then you need a preamp. No reason that the small, multi-turn, receiving loop antenna cannot itself be made tunable, followed by a preamp and a second tuned stage that is gang-tuned with the loop. (If Q is low enough the loop can be tuned with lumped constants.) But if one wants the preselector to be independent of the loop, I would use a link or tapped input to the first LC network, loosely-coupled to a FET gain stage, followed by a second, identical LC network, followed by a FET buffer to match a 50-ohm feedline to the RX. Just thinking aloud here. -- Brian Lloyd, WB6RQN/J79BPL 3191 Western Dr. Cameron Park, CA 95682 br...@lloyd.com +1.767.617.1365 (Dominica) +1.916.877.5067 (USA) _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/ _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/
