I just checked on my 1500 and what I notice is that when I change frequency from 481 kHz to 480kHz whatever filter is currently in the front end is removed/bypassed because and the receiver front end is wide open to everything from mediumwave stations to hams participating in the ARRL DX contest this weekend. It becomes a total mess.
I designed a lowpass filter that rolls off at 400 kHz. I chose 400 kHz because then there's sufficient attenuation at the lower mediumwave band. If I designed it to roll off at 500 kHz then some strong locals on 530 and 590 would bleed through. One or two people have asked me to share the design I came up with. I'm happy to do that and as soon as I put it in readable form I'll let everybody know and they can roll their own. 73 - Ken ________________________________ From: Jerry Flanders <jefland...@comcast.net> To: Jeff Singer <jsin...@i1.net>; 'Ken Alexander' <k.alexan...@rogers.com>; flexradio@flex-radio.biz Sent: Sunday, February 19, 2012 12:58:40 PM Subject: Re: [Flexradio] The new 472-479 kHz band - REAL DX At 11:41 AM 2/19/2012, Jeff Singer wrote: >Ken, I was likewise surprised by your statement about successfully using the >Flex-1500 to receive 600 meter ham beacons. I've read Flex discussion >boards for several years. To the very limited degree that users comment on >the lowfer receive performance of Flex radios, posts have always suggested >the 3000 and 5000 are worthless below the BCB (and perhaps not great even on >the AM BCB). I wonder what's so different about the 1500 in that regard. > > Flex has similar frequency coverage specs for all radios, but mentions that additional preselectors or filters are required below 1.8 MHz, even for the 1500. I remember reading that the 5000 has a superior set of filters, so it may appear "deader" below 1.8 MHz than the other radios. http://www.flexradio.com/Products.aspx?topic=SDR_Feature_Matrix#notes Seems to me this is an opportunity for a third party kitter/manufacturer to supply an outboard preamp+filter product. Jerry W4UK _______________________________________________ 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/
