How much Digital in Digital Radios

How much Digital in Digital Radios

Post by anil110002.. » Tue, 02 Mar 2004 23:33:11

My own understanding of a digital radio - only the keypad and the
frequency display is digital and all the rest is analog . Pl. correct
me if I am wrong .

Cheers
Anil

 
 
 

How much Digital in Digital Radios

Post by Doug Smith W9W » Wed, 03 Mar 2004 03:05:37



> My own understanding of a digital radio - only the keypad and the
> frequency display is digital and all the rest is analog . Pl. correct
> me if I am wrong .

In general, true.

There is usually also a digital processor which handles selection of
modes (AM, FM, SSB, etc.) and often allows remote control from a computer.

Some radios do now have digital signal processing circuits, which accept
an intermediate frequency signal and filter out unwanted noises and
stations.

I suppose it would be possible to build an almost-all-digital radio.
The audio output circuits are inherently analog (though with a power D/A
converter you could have just a few resistors on the analog side).
You'd also need an analog amplifier to bring signals from the antenna up
to the point where an A/D converter could operate on them.

With current technology it's not economically practical to do it that way.
--
Doug Smith W9WI
Pleasant View (Nashville), TN  EM66
http://www.w9wi.com

 
 
 

How much Digital in Digital Radios

Post by Stephan Grossklas » Wed, 03 Mar 2004 05:29:35


Quote:

> My own understanding of a digital radio - only the keypad and the
> frequency display is digital and all the rest is analog . Pl. correct
> me if I am wrong .

Add the digitally controlled frequency synthesis via PLL to that. (Only
simple receivers use analog synthesis plus a frequency counter these
days.) But apart from that, the signal path from the front end over the
mixing, filtering, demodulation and output is indeed completely analog.
This is why a 40..50 year old tube equipped Collins boatanchor like the
R-390A can still keep up with good receivers today - it was built to the
highest standards of the time, and that is still pretty good even today.
(Though of course a tube rig will usually require - but also handle -
more antenna.) Solid-state equipment only caught up with tube gear in
the late 70s. It has been possible to build excellent short wave
receivers for a pretty long time, with the cost for a given level of
performance usually declining. Not extremely so, however - a Drake R7
would still be a far better choice for DXing than, say, the little Degen
DE1102.
It is in the "value" segment where you notice advances the most -
looking at Sony's "7600s", for example, you can see how at a rather
constant price point the SW reception and features got better and better
in the course of more than 20 years (due to higher integration and
general advances): The first set was a single conversion analog, the
second one was a dual conversion set and featured more bands, the third
one (more expensive at first) featured PLL synthesized tuning and
continuous shortwave coverage with 5 kHz steps and SSB along with
memories and other digital niceties (while neglecting speaker sound),
the sixth one added selectable sideband SSB and a better SW IF filter
along with much reduced PLL noise (though it lost a bit in terms of FM
reception), the seventh one featured 1 kHz steps and selectable sideband
synch detection along with some more memories, the 8th one added
significantly more memories and other minor improvements. Something that
the radio designers of years gone by were apparently better in was
building a well sounding radio...
At the moment, no real revolutions are to be expected. Some impulses on
the low-end market are coming from China, but that's more a matter of
labor costs. On the higher end, things have been slowing down for a
while, with no further "consumer level" IF DSP rigs in sight. (The
market for ham radio gear is a lot more active in this respect.)

Stephan
--
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How much Digital in Digital Radios

Post by saki » Wed, 03 Mar 2004 05:54:17



>> My own understanding of a digital radio - only the keypad and the
>> frequency display is digital and all the rest is analog . Pl. correct
>> me if I am wrong .

> Add the digitally controlled frequency synthesis via PLL to that. (Only
> simple receivers use analog synthesis plus a frequency counter these
> days.) But apart from that, the signal path from the front end over the
> mixing, filtering, demodulation and output is indeed completely analog.
> This is why a 40..50 year old tube equipped Collins boatanchor like the
> R-390A can still keep up with good receivers today - it was built to
> the highest standards of the time, and that is still pretty good even
> today.

I have several modern-era tabletops that I'm happy with at the moment but
came across a real delight this weekend (all right, not a Collins, but
someday, perhaps....)

A local pawn shop that specializes in restored vintage radios had a very
nice Blaupunkt from the fifties, the Paris model (type 22153), in a
beautiful wooden case. Other than needing a new dial lamp it's working
perfectly.

AM and FM sound great but the real treat is the SW band (5 - 13 mhz).
This thing has a huge speaker (compared to what I'm used to) and a
deliciously mellow tone courtesy of the tubes. Radio Sweden on 9495
Saturday evening sounded like a strong, local AM broadcast; the BBC and
Radio Netherlands were an audio delight. What surprised me was how little
drift there was (none that I could tell) and how little propagation
flutter there seemed to be. This is with only about 25 feet of magnet
wire about ten feet in the air hooked to the antenna outlet.

Old technology has its surprises, all right.

----