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© 1995-2010, TelePost, Inc. All rights reserved.
Pricing and specifications subject to change without notice.
Detailed Specs & Performance
is a software defined IQ direct conversion receiver with integrated SDR
application to provide a high quality panadapter to rigs with IF output
jacks. The unit uses a combination of SMT and through-hole technology,
a custom aluminum case with powder
coated finish and silk-screening. Pricing for an assembled and tested
unit is $225 plus shipping, and a kit is available for $175 with SMT
parts pre-installed. The kit takes an average builder about 2 hours to
complete, plus another few minutes to adjust the front end filter.
LP-PAN is aimed at the Elecraft K3, but can also be used with many
earlier Kenwoods with IF output jacks, Yaesu FT950/2000/5000, as well
as TenTec Orion and
Elecraft K2 when modified to bring out the IF signal.
a list of current features...
* Crystal controlled local
oscillator for low phase noise.
Up to 192 kHz display on PC,
* Switching quadrature detector for
high dynamic range
* Strong buffer amp with very
isolation to protect K3.
* Ground isolated inputs / outputs
with mil spec audio output xfmrs
* Fully balanced architecture
with balanced and unbalanced outputs
* Jumperable ground lift on
RF input and audio outputs
* Point and click frequency
with PowerSDR / IF Stage. In addition, LP-Bridge
allows sharing of
K3/LP-PAN with up to five loggers, PSK programs, CW-Skimmer, etc.
* Usable with many other SDR
programs for basic panadapter display.
* Powder coated aluminum enclosure
silk screened graphics.
* Hardware or software mute
* Available for the following
8.215 MHz (Elecraft K3)
(most older Kenwoods)
9.00 MHz (Yaesu FTdx5000, TenTec Orion)
10.7 MHz (IC-R8500/9500 and others)
Orion & K2 require hardware modification to add an IF output port.
IC-R8500/9500 require the addition of a blocking cap in the RF cable to
LP-PAN. FT-950/2000 require IF-2000 interface board (see link above).
Here are current specifications (sound card dependent). Note:
Measurements represent the composite
results of K3 / LP-PAN. Standalone LP-PAN performance is even better.
* Approx. -125dBm MDS with K3 preamp on (about 8dB better with K3
buffer mod installed).
* +2dBm maximum input with K3 attenuator on
* ~105 to 115dBm dynamic range, depending on sound card
* 80-90dB image rejection with PowerSDR-IF
* Greater than +20dBm IP3 @ -15dBm, 2kHz to 20kHz spacing (composite
for K3/LP-PAN combo)
* ~90dB IMD DR @ -35dBm, 2kHz to 20kHz spacing (composite
for K3/LP-PAN combo)
* THD ~ 0.005%
* 600 ohm output Z, balanced
* +2dBV (1.27 Vrms, 3.6V p-p) nominal output level at
recommended maximum RF input
* Adjustable gain to interface almost any sound card
* L.O. offset to allow use with
older sound cards
* 11-16 VDC @ 55 mA
Note: Specifications dependent on
sound card, and subject to change.
Cited values were taken with an E-MU 0202 USB sound card. All
measurements also apply to M-Audio Audiophile 2496 PCI or FW cards
(limited only by 96 kHz display width), the Infrasonic Quartet and E-MU
1212m PCI sound card.
are included in the Performance section below. PowerSDRTM
open source application for use with IQ based software defined radios,
and is a
trademark of FlexRadio Systems.
LP-PAN consists of a multipole bandpass filter, followed by a
buffer amplifier with high isolation, followed by a balanced switching
mixer. The output of the mixer is fed to two pairs of balanced low
noise op-amps with ultra wideband 600 ohm output transformers for
in sound card interfacing. I have also tried to maximize interfacing
flexibility with the
card, to minimize hum and noise issues there. The devil is in
the details, and that is where I have concentrated my efforts to make
LP-PAN the best integrated panadapter solution for use with K3.
LP-PAN can be used with
most SDR decoding applications, like PowerSDRTM,
Rocky, SpectraVue, Spectrum Lab, TRX-Pan, etc. With NaP3, TRX-Pan or
the /IF branch of PowerSDRTM and LP-Bridge,
click frequency tuning is available. LP-PAN
with other programs which will decode an audio IQ signal, like the
nifty CW Skimmer from
Alex, VE3NEA. The pictures in
the performance section
below are taken from various flavors of PowerSDRTM.
allows you to use your
PC / sound card as a second receiver with
lots of nice features if you use the PowerSDRTM app. Shown above is split
operation using the main and sub receivers in PowerSDR. VFO A (green)
K3 is linked to the main receiver in PowerSDR, and VFO B (blue) is
the sub receiver. The K3 doesn't need the KRX3 2nd receiver option.
PowerSDR provides both receivers. PowerSDRTM
has lots of flexibility in terms of
modes, bandwidths, interference reduction tools, etc. I find listening
to SW broadcasts with the synchronous AM detector very nice.
is version 0.9.9.76
of LP-Bridge program (reduced size image). It does several
1) It provides a
method of allowing several applications to
simultaneously share bidirectional
communications with the K3 by
creating up to 5 virtual ports for the other
applications to connect to. Communications are optimized to eliminate
collisions and minimize traffic to the K3.
2) It provides a means to obtain
offset data from the K3, and passes it along to WU2X's IF Stage version
of PowerSDR to keep the two IFs synced.
3) It provides a convenient
way to implement
point-and-click tuning from PowerSDR /IF Stage by providing an
extensive interface to PowerSDR.
4) It provides frequency linking to hardware such as SteppIR antennas,
AT-Auto tuner and amplifiers.
Setup allows you to add an
name to go with each virtual com port to keep things straight. The
ports can all be automatically created/connected when LP-Bridge
launches, and the associated applications can automatically be launched
as well, including up t two instances of PowerSDR-IF (for SO2R).
choices for applications would be loggers, a PSK application or
CW Skimmer... any application that requires serial communication with
the K3. To maximize throughput, all normal polling is handled by
LP-Bridge. Polling requests from the applications are responded to
directly by LP-Bridge, from a "virtual K3" mirror, preventing
collisions from multiple requests to the K3 from various programs.
Handskaking lines for CW and PTT keying are passed through to the K3 to
allow PTT or CW keying using DTR or RTS.
For more details or to download the
program, go to the LP-Bridge
Note: All test results were obtained
using an E-MU 0202 USB sound card. Similar results can also be obtained
with the E-MU 1212m or 1616m PCI cards, or the Infrasonic Quartet PCI
card. At up to 96 kHz, the M-Audio
Firewire Audiophile card (discontinued but available on eBay) or E-MU
2496 PCI card will also produce similar results. Except for the 1616m,
these cards are all priced in the $80-150 range.
Performance is a composite of LP-PAN / K3 system unless otherwise noted.
Usable Dynamic Range:
connected to the K3, LP-PAN provides up to 115dB dynamic range
noise floor and clipping, depending on sound card. Below is an example of LP-PAN
working with PowerSDRTM. There is no
higher order distortion visible at a level of -20dBm (~ S9 + 53dB) from
signal generator at this bandwidth setting. 2nd harmonic, not shown, is
about 80dB down. Increasing the
level to -10 dBm (~ S9 + 63dB), about 5 dB before clipping, a couple
about 10-15 dB above the noise floor. The average noise floor is
-120 dBm (~0.2uV for 10dB S/N)
in this setup. This test was run with the K3 preamp OFF.
Noise floor with the preamp ON is about 10dB better. The smaller blip
is the image, which is 70dB down (Image Rejection with PowerSDR-IF
v1.19.34 has improved to >80dB).
addition, there is a little mod
that I have developed for the K3 which improves the noise floor by
about 6dB. It requires changing two SMT resistors with either SMT or
standard 1/8W resistors to reduce the loss in the K3 buffer. Details of
the buffer mod can be found here, K3
Buffer Mod . Elecraft now
ships K3 with a similar mod, and provides a mod kit for older K3s.
The above display shows
typical image rejection with older version of PowerSDR-IF. The latest
version, v1.19.35, uses the new Wide Band Image rejection (WBIR)
of PowerSDR, and provides image rejection of 80-90dB or better over the
entire display, with no user adjustment. WBIR "learns" the correct
values and saves the parameters in a database file. This means that a
signal of S9 + 30dB to S9 + 40dB will have no visible images. More
information regarding image rejection can be found on the SOundcards
web page, http://www.telepostinc.com/soundcards.html
There are many reasons why a user might see spurious signals in his
Many of them, if not most of them, are stray signals from local noise
sources around the home and neighborhood. Some come from the shack in
the form of noise from a PC, serial or USB cables, switching power
supplies, etc. These signals can be picked up in the cabling between
LP-PAN and the rig, power supply or sound card. In general, if the
spurs don't change with band changes, they would fall into the category
of locally generated noise entering through connecting cables. Careful
grounding, selection of well filtered power supplies and use of high
quality shielded cables should eliminate these.
Some spurs may actually be radio signals that are unidentifiable. These
would change with bands and band conditions.
And some can be generated in the rig itself in the form of images
generated in the rig's front end and spurs generated by the rig's
synthesizer. Since LP-PAN is generally fed by a buffered output of the
rig's 1st mixer, any strong image signal getting through the rig's
front end filter can cause a spur. Also, unwanted signals from the
synthesizer chain can mix with desired or image signals, or just be
passed through to the mixer output. Note that you may see spurs from on
the rig's IF output port that you can't hear on the rigs audio output.
Since synthesizer spurs can be calulcated, manufacturers can use
digital wizardry to blank out the spurs in the DSP processor which is
downstream of the IF output.
The RBW (Resolution Band Width) setting in the SDR application can also
affect what you see. RBW is defined as the smallest frequency interval
that the software can display, and is determined by the total bandwidth
of the display and the number of samples (or FFT bins) that are used
across the display. In PowerSDR/IF the RBW is a fixed value dependent
only on the sound card sampling rate. The number of bins is 4K (4,096),
and the sampling rate is usually 192kHz, but can also be set to 48kHz
or 96kHz. At 192 kHz sampling rate, each bin represents a frequency
change of ~48Hz. Many spurs can fall between steps this large. In NaP3,
the user can select up to 64K FFT samples. Frequency changes are thus
16X smaller, or 3Hz. Clearly, it would be harder for a spur to hide
with this kind of resolution. The question is, how much RBW is enough.
Most users should find that 16K FFT samples would be more than enough
except possibly at the narrowest of displays spans (below 10kHz). Below
are pictures of the 6m band at N8LP with a span of 80kHz and various
conditions as captioned.
K3, no antenna, FFT setting of 4K. Note the absence of spurs.
K3, no antenna, FFT setting of 64K. Note many more spurs visible
because of the finer RBW and lower noise floor due to oversampling.
LP-PAN cable unplugged from K3 IF output jack. Note noticeable
reduction of spurs without any change in noise floor.
Blocking Dynamic range (BDR):
I wanted to make sure that the
K3 was the
limiting factor when used with LP-PAN, at least up to the maximum
signal level of LP-PAN,
which is +2dBm (S9+75dB). To
test the BDR
performance of the LP-PAN / PowerSDRTM combo, I set up the following test...
I fed a strong signal (S9+50dB) to the K3 using a homebrew xtal
oscillator which has very low phase noise. 2kHz away I mixed in a 3uV
signal from my HP-8640B signal generator using a hybrid
combiner. The widening of the
base of the signal from the xtal oscillator is due to the phase noise
of the K3. I purposely used a xtal local oscillator for LP-PAN to
minimize phase noise degradation. The
3uV signal in this case has about 10dB SNR, more than enough for solid
copy. In practice,
this situation would never occur since most transmitters are far
noisier than my xtal generator, and the transmitter noise would bury
any weak signal 2 kHz away. Receiver design has clearly advanced to the
point where it far exceeds transmitter design.
IMD Dynamic Range:
Here is a comparison of IMD DR with the standalone LP-PAN, and
through the K3. The setup is the same as the one for the BDR test
above, except that both the xtal oscillator and the HP-8640B are set to
the same level. Signal levels
are -33dBm (S9 + 40dB), and signal spacing is an amazing 500Hz! The
slightly wider signal on the left is the HP, but it's still excellent
phase noise performance compared to today's synthesized generators, and
stands up well against the xtal oscillator. As you can see in the top picture for the
standalone LP-PAN, IMD DR is
>90dB, with no extraneous distortion products. Quite amazing for
The bottom picture was taken
K3 in line, with the K3 preamp Off. You can readily see the effect of
K3 phase noise by comparison. Reciprocal mixing with the K3 synthesizer
sidebands produces a noise hump around the signals. This is actually
excellent performance for a synthesizer, but clearly degrades close-in
dynamic range. We have also picked up some
leakage / isolation:
Because LP-PAN connects to an unprotected IF port on the
radio, it is important that any LO leakage in the rig's passband be
This is something I spent a lot of time on in design and testing. As a
result, the measured LO signal at the input of LP-PAN is -135dBm
(~0.05uV). Adding in an
estimated 20dB+ isolation for the buffer in the K3, this should be a
more than adequate amount of isolation to prevent any
issues with the
K3. In my initial testing, I have not been able to detect LP-PAN's LO
in my K3, confirming that the leakage is below the noise floor of the
K3. For comparison, the LO
leakage of a couple SoftRock
Jack, K8ZOA and I checked, measured about -40dBm (S9+33dB)...
almost 100dB higher than the buffered LP-PAN.
I also added more filtering to the input of LP-PAN to filter out the
numerous spurious signals I found in the K3 IF output. These signals
include LO leakage from the K3, plus harmonics and
mixing products of them. The picture on the left shows the K3 IF output
with one signal in the passband over an 80 MHz span. The second
picture shows the same conditions with my filter installed. In
practice, I see a number of products sliding through the panadapter
display as I tune without the filter, but none with it.
Here is the response of a
of the filter. I could probably reduce the bandwidth, but at the
expense of loss and ease of tuning.The K3 already has more loss than I
would like from antenna jack to IF output, and I am being careful not
to add to it. I think this filter is appropriate for
the application, and is more tolerant of component variations. I use
variable caps and 2% precision SMD coils in the filter, and
tuning is just a simple matter of peaking the two variable caps.
To minimize installation problems, I
added transformer coupling of the IF port and mil spec audio xfmrs,
all with "ground lift" jumpers
minimize hum and noise in the audio interface. Audio output is 600 ohms
to allow driving any sound card, and one channel has an adjustable load
to balance out any termination variations in the sound card / cabling.
This level of detail is required to acheive the image rejection that we
are able to get, which rivals a superhet with xtal filtering when
carefully adjusted. The outputs can also be
either balanced or unbalanced mode for further isolation when a
professional sound card with balanced inputs is available. As the
PowerSDR screen shots show, there are no spurious
hum or noise signals from the audio interface in my installation...
even at the 0 Hz center frequency.
Using LP-PAN as a spectrum analyzer:
One of the more useful pieces of test equipment for ham use, but also
one of the more expensive, is a spectrum analyzer. An example of a good
use of LP-PAN in this regard is a project I worked on. I was
asked by the FDIM
organizers to build and test their 2008 Dayton Buildathon
project, a 10W QRP amplifier for CW/SSB. I have a Tektronix 7L13
spectrum analyzer, and normally use this for testing spurious emissions
like harmonic suppression and IMD. The
Tek works great for checking harmonics, and IMD with fairly wide tone
spacing, but is not so good at displaying IMD with 1200 Hz tone spacing
is commonly used to check SSB amplifiers.
Below are displays from the Tek with tones spaced 20 kHz, and LP-PAN
with tones spaced 1200 Hz. You can see where the resolution bandwidth
of LP-PAN/PowerSDR is quite welcome. The same would hold true for other
decoding applications like SpectrumLab or SpectraVue. The panadapter
display could actually be zoomed in much more if needed These pictures
were not taken under the same conditions of drive level, so cannot be
directly, but you can see the similarities. Looking at 20 kHz spaced
tones on LP-PAN results in traces that are thin vertical lines because
of the enhanced resolution bandwidth.
If the transmitter output is attenuated to about -20dBm, the distortion
of the K3 and LP-PAN can essentially be ignored, as it will be below
noise floor. This guarantees that the testing hardware will not color
the results. It still leaves at least 80dB of measuring range, which is
comparable to a professional spectrum analyzer.
All test results were obtained using an E-MU 0202 USB sound card.
Similar results can also be obtained with the M-Audio Firewire
Audiophile card (96 kHz sampling) and E-MU 1212m PCI sound card (192
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