The FLEX-1500's low frequency hardware band pass filter starts to roll
off @ 490 KHz very rapidly.
Tim Ellison, W4TME
Product Management, Sales & Support
FlexRadio Systems^(TM)
4616 W Howard Ln, Suite 1-150
Austin, TX 78728
Phone: 512-535-4713 Ext. 223
Email: t...@flexradio.com <mailto:t...@flexradio.com>
Web: www.flexradio.com <http://www.flexradio.com>
logo
On 2/19/2012 8:12 PM, Ken Alexander wrote:
One other thing that would be nice is to have an option to bypass the
built-in front-end filters thus allowing selection of an external
filter.
It's not an option, but that's what my 1500 does right out of the box. The
front end filters (appear to) cut out when I tune down from 481 kHz. All is
well on 481. It's a total mess on 480 kHz and below.
73 - Ken
________________________________
From: Brian Lloyd<brian-wb6...@lloyd.com>
To: Ken Alexander<k.alexan...@rogers.com>
Cc: Jerry Flanders<jefland...@comcast.net>; Jeff Singer<jsin...@i1.net>;
"flexradio@flex-radio.biz"<flexradio@flex-radio.biz>
Sent: Sunday, February 19, 2012 8:03:52 PM
Subject: Re: [Flexradio] The new 472-479 kHz band - REAL DX
On Sun, Feb 19, 2012 at 3:05 PM, Ken Alexander<k.alexan...@rogers.com> wrote:
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.
You might also want to consider a sharp, two stage, tunable, LC bandpass filter. We are only talking about a band that is 7kHz wide. I would think that a lowpass filter would be difficult to make and a simple tunable bandpass "preselector" would work better.
One other thing that would be nice is to have an option to bypass the built-in
front-end filters thus allowing selection of an external filter.
_______________________________________________
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/
