Geoff,
I have both the SDR-IQ and LP-Pan (but not the P3). Essentially, all
are SDR's and convert the RF signal into two signals which are
90-degrees out of phase with each other, thus the I and Q
designations. Difference is that the SDR-IQ is a stand-alone
receiver covering 500-Hz to 30-MHz and connects directly to a
computer using USB (so the I-Q signals are data streams). The LP-Pan
is dedicated SDR set on the IF of the K3 (or other radios, if
desired) and produces I-Q audio signals sent to a soundcard for
conversion to data in your computer. The P3 is a stand-alone
panadaptor with built-in SDR for processing the IF from the K3.
I bought my LP-Pan for about $150 used. SDR-IQ runs about $500 and
P3 even more.
You can run a SDR-IQ connected to the K3 IF by tuning it to 8.215 MHz
or run it separately.
But for your money (if you already have a K3) the LP-Pan is best and
will do everything the SDR-IQ does (within the restrictions of the K3).
I bought the LP preamps for my LP-Pan as I wanted maximum sensitivity.
I recently figured out how to slave two LP-Pan to a single xtal LO so
they would be phase-locked and do dual-Rx diversity reception. Info
on my website under "LINRAD".
I only take exception with one paragraph George makes: "The K3 takes
an RF signal from an antenna, filters and modulates it." The
received signal is not "modulated". It is filtered, amplified and
converted to the first IF for use by external SDR's. The roofing
filters do not come into play or the 2nd IF/SDR of the K3,
itself. There is no modulation or demodulation by the
K3. Demodulation is done by the DSP sw in the computer.
LP-Pan is a great little Rx to get acquainted with SDR.
73, Ed - KL7UW
------------------------------
Message: 51
Date: Wed, 6 Apr 2011 13:52:53 -0700
From: "George A. Thornton" <gthorn...@thorntonmostullaw.com>
Subject: [Elecraft] (phase signals RE: SDR IQ/IF Questions
To: "Geoffrey Wolf" <liltechdud...@gmail.com>,
<elecraft@mailman.qth.net>
Message-ID:
<c1a98f53a996d24fb5c20d436c5833049...@nwrrlaw.nwrrlawserver.offsitedataspace.com>
Content-Type: text/plain; charset="us-ascii"
IQ data is a method for describing the characteristics of a wave. IQ
uses amplitude and phase angle to describe the wave, see for example
http://zone.ni.com/devzone/cda/tut/p/id/3013
The K3 takes an RF signal from an antenna, filters and modulates it. At
some point the filtered, modulated signal is made available to an IF out
port where it can be used conveniently by various testing and measuring
devices.
A panadapter takes the IF signal and converts it into IQ signals. These
IQ signals can then be used to visually represent characteristics of the
signal on a chart or screen. The LP-pan converts the I and Q signals to
audio for input into a computer using a sound card. The P3 panadapter
directly charts the IQ data onto the built in screen.
The SDR-IQ is a standalone software designed receiver. It is designed
to hook directly into an antenna source and can be used with software to
directly display data about the signal. I do not believe it is designed
to work with modulated IF output from a quality receiver, but I could be
wrong.
The SDR-IQ can be used as a standalone panadapter through a computer,
getting its signal direct from the antenna, completely bypassing the
transceiver altogether. According to its own manual it does not have
much filtering and it can get overwhelmed by other RF sources.
The price for the LP-Pan and sound card is less than the price for the
SDR-IQ. The P3 costs only a small amount more than the SDR-IQ.
The P3 and LP-Pan were compared in a recent QST article. According to
the testers, the two approaches are roughly equal in their ability to
decode and display weak signals.
The LP-Pan has the advantage of allowing the use of a large computer
screen for a panadapter. The disadvantage is that it is complex to set
up, requires use of buggy computers and software with driver
compatibility issues and has a lot of loose wiring.
The P3 is a plug and play solution that is reliable and easy to use. The
P3 is more closely integrated with the K3. IN the future the P3 is
going to allow direct connection to a computer monitor and keyboard.
Given all the factors, I do not think the SDR-IQ solution is the best
choice here.
73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ 500 KHz - 10-GHz www.kl7uw.com
EME: 144-1.4kw, 432-100w, 1296-testing*, 3400-winter?
DUBUS Magazine USA Rep dubus...@hotmail.com
======================================
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