Re: Differences between ULRs and SDRs

seta <michael.setaazul@...>

A very helpful overview of the difference between software and
hardware versions, Rick.

I, for one, would be most interested in your report on the Elektor
in due course. Maybe true SDR could become a new thread
because of its relevance in comparison with uldx receiver technology.

Michael, UK

----- Original Message -----

From: "Rick Robinson" <w4dst@...>
To: <ultralightdx@...>
Sent: Friday, January 07, 2011 2:39 PM
Subject: [ultralightdx] Differences between ULRs and SDRs

The Si473X based ULR radios are not software designed radios, they are
hardware based. The Si473X family use an external enbedded code
microprocessor to send the commands to the Si chip to control frequency,
bandwidth, etc. This is the same as any digital radio be it a CCrane
SWP or an Eton E10. There is software, or firmware, in the
microprocessor that gives the Si4734 its commands, but this is not
"software designed radio".

A true SDR, see the Elektor SDR receiver or RFSpace receivers, have no
RF components other than front end bandpass filters. All the functions
of the Si4734 hardware are done in software with an SDR design. An SDR
relies on the sound card of a computer along with special software to
perform all the functions the Si4734 receivers perform with hardware.
The DSP functions of the ULRs are performed with hardware designed into
the IC while the DSP of an SDR is performed by the control software.

SDR receivers use what is called an I/Q mixer and output 2 signals, the
I and Q outputs, to the sound card. The Si4734 based chips and no I/Q
output. ULRs are "stand alone" receivers, SDRs are not. SDRs must
have a sound card to operate and SDRs have no problem with AM, FM, CW,
SSB, and multiple bandwidths since all of this is done with software.
This is why the ULRs would have a problem with adding a BFO while SDRs
have no problem with multiple modes.

For $1.80, you can download the Elektor article on the Elektor SDR
radio. This is a very informative article on the basics of SDR radio.
For about $160 including shipping to the US, you can buy an assemble and
tested Elektor SDR and a nice selection of free SDR software to
explore. My Elektor SDR is on the way and if anyone is interested, I'll
post a report to the ULR list even though it is off topic.

Good DXing,

Rick W4DST

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