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While I understand the interest in multiple, independent channels
(more than receivers; akin to additional ADCs on Angelia) I don't
think I'm interested in trying to solve all problems at once. I'm
definitely not interested in doing an amateur-banded approach again.
<br>
<br>
What I'm pondering is essentially a stepping 25 MHz wide block
up/down converter that can quickly go anywhere from 50 MHz to [6
GHz]. With this approach, if someone wants simultaneous different
amateur microwave bands, they would have to purchase additional
block converters.<br>
<br>
It would be possible, I suppose, to put hooks into the last fixed IF
(somewhere a bit above [6 GHz]) and sum independent bands up there
but that has the problem of broadband noise floors degrading things,
since narrow filtering probably isn't always practical at the higher
bands. Better to just do the whole thing again and go into a
different Angelia ADC.<br>
<br>
This architecture could solve the scope shortcoming but still
requires the purchase of additional hardware in order to get
simultaneous multple bands. But each band already requires
post(power) amplifier, LNA and filtering on a per-amateur-band
basis, no matter how it is done. Even the traditional approach has
this characteristic. The extra cost of two additional fixed
frequency conversions would likely only increment the per-band cost
a modest percentage of the amateur-band total, depending upon what
one chose for performance.<br>
<br>
My thought would be that this stepping block converter would leave
the user with, say +20 dBm and 10 dB NF, improvements to this would
be expected to take place however and wherever the user wanted it,
e.g. mast or near-mast mounted LNA and kW for EME.<br>
<br>
On receive, external gain will eat into dynamic range, but as has
been noted, microwave is a different context and super-high dynamic
range and IMD, and even superlative phase noise performance, are
probably not as crucial in practice.<br>
<br>
In my view, the trick is to come up with an architecture/scope that
is<br>
<ul>
<li>easily reproducible</li>
<li>attractive to the majority of SDR users as a means of
extending range</li>
<li>at a tolerable per-band price point</li>
<li>also able to act as broadband spectrum analyzer and vector
network analyzer </li>
</ul>
The per-band enhancements would be out of scope.<br>
<br>
I'm still considering if/when I would want to take on this limited
task. It looks like a several man-year project to me.<br>
<br>
Glenn n6gn<br>
<br>
<br>
<div class="moz-cite-prefix">On 04/22/2015 12:04 PM, Duane - N9DG
wrote:<br>
</div>
<blockquote
cite="mid:1429729463.52276.YahooMailBasic@web126203.mail.ne1.yahoo.com"
type="cite">
<pre wrap="">
If pursuing the traditional heterodyne mixer down converter approach, I would strongly suggest that they each be designed with different IF output frequency ranges. That way multiple bands can be fed into a single SDR IF radio that can then be watching and listening on multiple bands simultaneously. And therefore have multiple panadapter / waterfalls always running at all times. And at least 1 (preferably 2) RX per band for as many bands as the user can successfully listen to at one time.
The common DC - daylight radios that are out there all have MAJOR shortcomings when it comes to usability. These usability shortcomings are primarily in two key areas: 1) poor or non-existent scopes, 2) they can only be used on one band at a time.
Duane
N9DG
</pre>
</blockquote>
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