[R-390] DSP IF
Bryce Ringwood
BRingwoo at csir.co.za
Fri Apr 22 03:29:02 EDT 2005
Hi all,
There's quite a few DSP sofware packages out there - one has already
been mentioned. Another on my computer is "Spectrum Lab". You'll need to
convert the IF down to 25kc/s with an MC 1496 chip (or similar, or
better). - or a 7360 ;-)
I've got an old Analog Devices ADSP 2100 evaluation kit which I keep
meaning to play with, but never get around to it.
How about simply putting a hollow-state notch filter on the R390-A ? -
that seems more "in-keeping with the propriety of the radio".
- Bryce
(The mind boggles at the thought of doing DSP with tubes - we don't
even generate enough electricity in this country to power the thing).
>>> "Bill Levy" <levyfiles at att.net> 04/22/05 5:18 AM >>>
Golly Cecil and Mike
What a can of worms you have opened up.
Why not just buy a DSP radio and tune it to 455 and plug that into the
390a.
Wouldn't that accomplish the same darn thing.
Now no one say why go to the expense of another radio......thats what
we do
fellows. Any excuse to try something requires a new radio!
N2WL
----- Original Message -----
From: "Michael Murphy" <mjmurphy45 at comcast.net>
To: "Cecil Acuff" <chacuff at cableone.net>; "Bob Camp" <ham at cq.nu>; "Dave
Maples" <dsmaples at comcast.net>
Cc: "R-390 HF Receiver List" <r-390 at mailman.qth.net>
Sent: Thursday, April 21, 2005 10:26 PM
Subject: Re: [R-390] DSP IF
> Cecil,
>
> We built something like this at work (at a higher IF frequency 45
MHz!!).
> I'm no expert but..
>
> I think you have to sample the IF with an outboard A/D converter
first
> before sending it into the DSP to keep the costs down. If you want to
talk
> about a digital IF processor in an outboard box, the intermediate
> frequency
> spectrum (of the R390A) is first digitized by an analog-to-digital
> converter
> (ADC) into a slower digital data stream; this contains all of the
signals
> present in the IF. Nyquist says we need to sample at twice the
frequency
> of
> our 455 kHz IF and most converters can easily do this. Even low cost
Sigma
> Delta converters (like the one in your sound card) get close to being
able
> to do this. There may be some Sigma Deltas around which can do 1 MSPS
or
> better.
>
> The digitized IF signals are then translated to baseband by something
> called
> a Digital Drop Receiver or Digital Drop Converter (DDC). This could
be a
> chip or it more likely is code running in an FPGA or DSP core.
> Downconversion is accomplished by digitally mixing the intermediate
> spectrum
> of frequencies with a sinusoidal waveform generated by a synthesizer.
The
> baseband output can be thought of as the R390A receiver's 4th IF,
which is
> selected from the DDC's other output frequencies by a very efficient
> brick-wall digital filter. It is at this stage that the outboard
circuit
> can
> crank in some serious selectivity. Remember, we are talking about
> programmable gate arrays or pure software in a DSP for all of these
stages
> and functions.
>
> The DDC's baseband output is fed to a DSP (or into another section of
the
> DSP or FPGA which is actually acting as a DSP), which performs
signal
> demodulation. The DSP's output is then converted from the digital
domain
> back into the analog domain by a digital-to-analog converter,
amplified,
> and
> is made available to Cecil via a bigass tube amplifier and a
speaker.
>
> Mike Murphy WB2UID
>
>
> ----- Original Message -----
> From: "Cecil Acuff" <chacuff at cableone.net>
> To: "Bob Camp" <ham at cq.nu>; "Dave Maples" <dsmaples at comcast.net>
> Cc: "R-390 HF Receiver List" <r-390 at mailman.qth.net>
> Sent: Thursday, April 21, 2005 8:15 PM
> Subject: Re: [R-390] DSP IF
>
>
>> The thoughts of an 455 Khz IF based DSP filter system has been
rolling
>> around in the back of my head for quite some time. An outboard
accy. of
>> that type would be very popular considering the number of radios
that use
>> the 455 Khz IF. I might try sending the IF output from my R-390A to
the
>> antenna port on my Icom 756 Pro II and use the Pro as an
> IF/Processor/Demod
>> and see how things stack up...
>>
>> My understanding is that DSP processors that go up to 455 Khz are
quite
>> expensive and mostly smoke and mirrors at this point. You'd have to
down
>> convert to something lower....
>>
>> Cecil...
>> ----- Original Message -----
>> From: "Bob Camp" <ham at cq.nu>
>> To: "Dave Maples" <dsmaples at comcast.net>
>> Cc: "R-390 HF Receiver List" <r-390 at mailman.qth.net>
>> Sent: Thursday, April 21, 2005 6:32 PM
>> Subject: [R-390] DSP IF
>>
>>
>> > Hi
>> >
>> > The idea of putting a DSP IF processor on the IF output of an
R390
> sounds
>> > like an interesting project. The nice thing about the 390 is that
you
> can
>> > get at both the IF output *and* the AGC chain without modifying
the
> radio
>> > at all. Given the high performance RF section and the mechanical
>> > filters
>> > the result should be very competitive.
>> >
>> > Of course this gets into the general direction of witchcraft and
the
> like
>> > ....
>> >
>> > Enjoy!
>> >
>> > Bob Camp
>> > KB8TQ
>> >
>> >
>> >
>> > On Apr 21, 2005, at 5:22 PM, Dave Maples wrote:
>> >
>> >> All: Hmmm...why stop there? Get a large touch-screen display so
the
>> >> radio
>> >> can REALLY be "man-sized", and follow this with a hue-changing
routine
>> >> where
>> >> the panel, knobs, and display fade from color to color.
>> >>
>> >> Add DSP to correct distortion in the audio chain.
>> >>
>> >> Possibilities are endless...
>> >>
>> >> Dave WB4FUR
>> >>
>> >> -----Original Message-----
>> >> From: r-390-bounces at mailman.qth.net
>> >> [mailto:r-390-bounces at mailman.qth.net]On Behalf Of Barry
>> >> Sent: Wednesday, April 20, 2005 5:49 PM
>> >> To: r-390 at mailman.qth.net
>> >> Subject: Re: [R-390] Crayola front panels
>> >>
>> >>
>> >> Don't paint the front panel at all. Mount motor drives on all
front
>> >> panel
>> >> controls with the appropriate serial/parallel interface to a
computer
>> >> program that looks like the front panel. Put the R390x right up
next
> to
>> >> the
>> >> antenna to eliminate any feedline loss. Run the controlling
wires
>> >> from
>> >> there to the computer.
>> >>
>> >> Change the color any way you want, any time you want.
>> >>
>> >> Barry(III) - N4BUQ
>> >>
>> >> _____________________________________________________________
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