Fw: Re: [HBR] what is the BEST receiver

[windy10605 at juno.com]

I have to agree with Bob on "today's best receiver". Gerald Youngblood,
from Flex Radio lives right down the street and many of the local guys
have spent much time at the Denny's figuring out solutions. We also have
Dan Taloe coming to the QRP session at Austin Summerfest next week
in addition to the usual Flex Radio presentation. The military is also
very interested because you don't require several radios, just one and
change the software. He's way behind on production. And the "biggie", you
have FREE software development from a worldwide software expertise pool
(because of the Internet). Talk about FRU "Full/FREE Resource
Utilization".  

But I sure to like the radios that light up. On another subject, I
finally got my B&K 747 tube checker working again after it fell onto the
floor. This is a solid state (kinda funny) mutual transconductance tube
tester. Now, I was figuring mechanical impact, mechanical problem and
went over it looking for something broken time and time again. I
remembered it was "ON" when it fell .......took out the FET. Apparently
something electrical happened on impact which the FET didn't like.

73 Kees K5BCQ


--------- Forwarded message ----------
From: Bob AH7I <bob at atl.org>
To: hbr at mailman.qth.net
Date: Thu, 28 Jul 2005 22:58:35 -0400 (EDT)
Subject: Re: [HBR] what is the BEST receiver
Message-ID: <Pine.LNX.4.58.0507282246030.6916 at arthur.atl.org>
References: <d.4923b874.301aeb94 at aol.com>



IMO the best HF receiver for the money, if you already have a computer,
is
a quadrature mixer based direct conversion utilizing a CMOS solid state
switch matrix and driven by as stable (in terms of frequency and jitter)
a
source as you can find. Put an good passive tuned RF filter in front of
this and a good passive bandpass filter behind it. Add your gain, if
required, after the bandpass filter. Lots of feedback to make it as
linear
as you can with the caveat of watching the contributed noise.Follow with
a
good (low jitter, enough bits, 2 channel A/D converter. There are some
excellent 24bit 96kHz sound cards in the $200 to $300 range that will do
th trick. Then do the rest in software. Linrad is good and free.

The switch matrix adds no noise and is extremely linear. The passive
filters add no noise, not much loss, and by amplifying after the filters
you have less stuff to mix as a result of any non-linearities in your
amplifier. Lots of bits and low jitter make for minimal noise
introduction
in going to digital and once there you don't have to worry abotu noise
any
more.

More antenna means more signal at the beginning and less
noise(distortion)
adding amplification later.

I'm not a radio engineer or EE, but it just makes sense that minimizing
noise will make a better receiver.

-Bob
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