Radio W4KAZ

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Si570 Programmable Oscillator for Softrock CWSkimmers – or for “Whatevah”

Note: More links at bottom of page:  This is a simple-to-build programmable oscillator for use with the Softrock Lite kits for CW skimmer and input to the Reverse Beacon Network.  It uses the Si570 chip and an AtTiny85-20 programmed with the PE0FKO firmware used for the Softrock Ensemble kits.

Currently a programmed ATTiny chip is available separately from K5NWA.  The firmware is available for download, so programming the AtTiny is also an option.  The PE0FKO site also provides the required USB device driver, software, and guidance on using them.  (links)  The Si570 is available from Digikey(digikey part#:336-2518-ND,  manufacturer part:570CAC000141DG).(SiLabs 570CAC000141DG part )

The oscillator itself is pretty simple, and is the bare essential hardware required for re-programming the oscillator for a needed single frequency to use with a Softrock Lite II rx.  It is based on what I saw in the the schematic of the Softrock Ensemble RX, nothing original, just pared down and hijacked from the original Ensemble design.  The Si570 part itself is the bulk of the expense of the oscillator, and the cost of the Si570 chip is almost as much as the Softrock Lite kit itself.    The oscillator signal is fed into the divider through a 10K voltage divider as in the Softrock RX.

So why?

The RX Ensemble kit is a viable alternative expense wise.  It really depends on the intended usage.  Using separate Softrock Lites as single band CW skimmers leads to the choice of a programmable oscillator for customizing the center frequencies, especially for the high bands.  The method used for 20m using the third harmonic seems to result in a decrease in dynamic range.  That results in an increase in false mirror images being reported to RBN by the CW skimmer as actual spots.  Using the Si570, the oscillators can be set at the frequencies needed by the Softrocks, i.e. 4 times the center frequency.  (for 96Khz bandwidth the oscillator would need to be: 20m=56.188, 15m=84.188, and 10m=112.16).   A programmable oscillator also allows switching from 96Khz to 192 Khz bandwidth(20m=56.38,15m=84.38, and 10m=112.38).  Keeping just the bottom half of a 192Khz bandwidth CW skimmer would at a minimum eliminate at least 50% of bad mirror image spots.  There are also likely to be fewer stations CQ’ing below the “.096″ section of a band(e.g., most often there is not so much regular CWactivity above 28.096 as there is below).  That is the idea anyway.

The Oscillator Prototype:

The first version is deadbugged on a bit of board scrounged from the parts bin.  Not many parts, but a bit more PCB real estate would have been better.  Functional rather than esthetic.  The USB connection is via the usb cable end clipped from an old computer mouse in the parts bin(unlabeled black coil in left of photo).   “Engineer the possible”.

Si570 oscillator board for 10m Softrock CW skimmer

Si570 oscillator board for 10m Softrock CW skimmer

Testing the board resulted in three build mistakes to debug:  a missing 5v connection to the ATTiny and the reversal in polarity on both zener diodes across the USB data pins.  These mistakes prevented function without damage to the components.  After correction of the build errors the software was able to function with the Si570 as needed for both programming the oscillator(‘startup’) frequency and running as a stand-alone oscillator.

The Si570 when programmed for 112.36Mc was found to have an actual oscillation at close to 28.090 exactly from the Softrock divider, as measured with TS-590 and Elecraft K2.  This was with the oscillator inserted in-circuit as the Softrock Lite oscillator via a transformer(5 bifilar turns on a type 43 torroid core) and a 2.2k resistor.  The frequency is very consistent and stable when the power is cycled on/off.

Easy measurement of the actual frequency in place is good enough for initial setting up of the skimmer software. A few KC either way will make little difference in a CW skimmer set-up, as final adjustments were done in CW skimmer software to put the skimmer signals ‘on frequency’.  In this case the CW skimmer center frequency is nearly identical to the Si570 programmed frequency.  That has not been the case with the versions using ordinary crystal oscillators, those having a bit more drift.

A new Softrock Lite II is the 10m test bed, with 15m revision to follow.  These two bands suffer the most from poor dynamic range and false mirror images.  If the modified softrocks perform as desired it will be time to pair these two bands with the best of the sound cards available.  That will be a separate game of trial and error.  The 20m softrock skimmer may also be retrofit, as using the third harmonic for the softrock center frequencies seems to adversely impact the dynamic range.

Photo of 10m Skimmer

Photo of 10m Skimmer at W4KAZ

As an aside, the first 10m center frequency chosen was 28.060 into a 192Kc bandwidth sound card. Horrible choice, as it was close enough to the 15m harmonic that interference spikes were present on both bands every 900hz.  Resetting the Si570 oscillator to place the center Fo for 10m at 28.080 greatly reduced(but not eliminate) the problem.  Currently set on 28.090 as of 20150414.  More tinkering required, and migrating the 15m Softrock over to an Si570 oscillator may help.

The current Skimmer package for 20m, 15m and 10m.  20m and 15m will likely be re-worked to use  Si570 oscillators.

The current Skimmer package for 20m, 15m and 10m. 20m and 15m will likely be re-worked to use Si570 oscillators.

LINK LIST:

  1. W4KAZ Schematic

    Schematic for W4KAZ version of si570 oscillator

    Schematic for W4KAZ version of si570 oscillator

  2. W4KAZ BareBones Parts List (PDF) (HTML with links)
  3. KB9YIG Five Dash softrock products page
  4. K5NWA ATTiny85 page
  5. PE0FKO Firmware page
  6. Document:

 

WPX SSB Prep

The 2011 NR3X Multi Single from N1LN.

And 2014 WW4LL, most local M2 leader.

Skimmer File Extracts Summer of 2014

File extracts for three summer contests from four skimmer stations for May 2014’s CQ WPX and June’s JARL All Asia and ARRL FD.  The files are by skimmer spotting station and are sorted in datetime order.

Spots from K1TTT

Spots from W1NT

Spots from W4KAZ

Spots from KM3T

CW Skimmer Station for WPX CW 2013

Some repairs to the skimmer station set up have been made after losing the 20m and 10m softrocks.  Both were probably damaged due to modifications I made to the voltage regulation circuits.  That appeared to eventually fry the QSD chip, which is the heart of a softrock.

The 20m skimmer was replaced completely with a new softrock lite.  10m is pending re-work, but replacement would probably be the best bet.

So for WPX 2013 there are five bands available, 160m through 15m.  These will be active during WPX intermittently.  I intend to bring them up and down based upon my own operating.  The skimmer will be down when I am operating.

Other changes made to the skimmer station include loading windows XP onto the Optiplex 360 that had been running windows vista.  Vista was able to run one instance of CW skimmer, but was not able to support two instances simultaneously due to sound card conflicts.  Windows XP does not seem to have a problem with the two sound cards, and is an OS supported by CWSkimmer(Vista is NOT supported by skimmer).

 

CW Skimmer Errors and RBN spots

After several contests, monitoring of the softrock skimmers has turned up a bit of a problem with using softrocks as the skimmer platform.  Very strong signals are producing a mirror image that is often reported as a spot to the RBN.  Certain to be annoying for the S&P packet crowd during a contest.  Annoying enough that a few flame mails have arrived.

The volume of the bad spots is relatively low on the lower bands, and more common on the higher bands.  40m is somewhere in the middle, with most of the bad spots being sent for domestic USA stations.

The problem is a combination of the hardware and software, both contributing to the problem.  A software fix could potentially be made to CW skimmer or to the RBN aggregator to correct for the problem.  Will inquire to the authors…..

In the meantime the best solution available is to throttle the RBN aggregator to allow only spots below the center frequency to be reported.  For example, the 15m skimmer is based on a softrock with a center frequency at approximately 21044.5Mc.  So for the duration of the ARRL DX CW contest, an entry in the “Notched Frequencies” will be active to not report 21044.5-21100 to the RBN.

That solution does nothing to correct for half of the possible bad spots(i.e., a strong signal above the center frequency whose mirror image is being spotted below the softrock center frequency).  But it should alleviate many/most of the actual bad spots, since most run stations prefer to operate as low in the band as they are able.

Open to other suggestions short of replacing the softrocks with better (yet unaffordable) hardware.

Update 20130217, 2140Z:  There are new versions of both skimmer and aggregator.  Perhaps upgrade will help.

More on Xonar DX Experiments

A thread over on the softrock user group list spurred the curiosity…..: http://groups.yahoo.com/group/softrock40/message/68324

G4ZFQ has  RightMark test data for a high end Xonar D2X card, as well as several others.  An internet search found other RightMark tests of several other Xonar cards, all of whose test data show curve trends remarkably similar to those of the D2X, albeit with somewhat worse IMD, spurious, and noise figures.

The curiosity is the test data shows a roll off on the frequencies above 50khz.  The nature of the loopback test is an issue, but it also seems likely that using a sound card as the source may be having an effect on the test results at the higher edges of the sound card frequency response.  But signal generators as input to the tests shows the same general trend.  SDR at wider bandwidths pushes at these edges of a ‘sound’ card’s ability….So perhaps the SDR software is compensating for the expected performance drop-off at frequencies above audible levels?

The Test- (Pertinent Excerpt from list post):

Having not yet thought of a better way to do a meaningful real-world test on the sound card with what is available in the KazShack, I fired up the 80m softrock on the xonar DX.

Test condx:
Transmitting a cw signal(a string of dashes at about 18wpm) at 5w into a dummy load on separate radio, noting the SNR readings obtained by CW skimmer from the SoftRock center frequency(353395x) to its upper limit. With the xonar DX set to 192khz scan rate, the actual upper limit on the readings was 3629.60. SoftRock connected to normal antenna system, a NE facing K9AY with W7IUV pre-amp. In summary, a sound card test using the SoftRock system as input source.

fq….—-SNR(dB)
3534.5—-42

3543-3593-42-40

3603——37
3613——35
3623——32
3629.6—-36

After CW skimmer collected a bit of data, the SNR readings above 3600 improved to 37-39.

So the worst case for CW skimmer(as currently configured) using a Xonar DX is being 6db less sensitive at the upper edge of the 192khz bandwidth than it is at the center. That is actually a lot better than I expected for an audio device pressed into service outside normal audio ranges (and I already liked the Xonar DX).

My curiosity is now nagging me to run the same tests on all of the other in-shack cards more methodically at their maximum scan rates(mostly 96khz), and to find a lower level outside signal source. I’ll try to recruit a fellow in the near field who will better be able to generate a low level test signal.  It would be useful to see what happens at the band edges when the best copy close to the center of the SoftRock’s scan range starts out at 20dB, 10dB, or 6dB SNR.

But with the WX here improving, all of that might not happen for several months.
;)

Engineer the Possible…

Xonar DX es SoftRock CW Skimmer

Yesterday, having not yet thought of a better way to do a meaningful real-world test on the sound card with what is available in the KazShack, I fired up the 80m softrock on the ASUS Xonar DX for a bit of putzing around.

Test condx:
Transmitting a cw signal(a string of dashes at about 18wpm) at 5w into a dummy load on separate radio, noting the SNR readings obtained by CW skimmer from the SoftRock center frequency(353395x) to its upper limit. With the xonar DX set to 192khz scan rate, the actual upper limit on the readings was 3629.60. SoftRock connected to normal antenna system, a NE facing K9AY with W7IUV pre-amp. In summary, a sound card test using the SoftRock system as input source.

fq….—-SNR(dB)
3534.5—-42

3543-3593-42-40

3603——37
3613——35
3623——32
3629.6—-36

After CW skimmer collected a bit of data, the SNR readings above 3600 improved to 37-39.

So the worst case for CW skimmer(as currently configured) using a Xonar DX is being 6db less sensitive at the upper edge of the 192khz bandwidth than it is at the center. That is actually a lot better than I expected for an audio device pressed into service outside normal audio ranges (and I already liked the Xonar DX).

My curiosity is now nagging me to run the same tests on all of the other in-shack cards more methodically at their maximum scan rates(mostly 96khz), and to find a lower level outside signal source. I’ll try to recruit a fellow in the near field who will better be able to generate a low level test signal.

But with the WX here improving, all of that might not happen for several months. ;)

engineer the possible….
73 de w4kaz

Upgraded to Ubuntu 12.04 LTS (Precise Pangolin)

My testing sandbox server is running on an ancient Dell Optiplex 280 minitower, which has a P4 processor and 2gb of ram.  Its been chugging along placidly on Ubuntu 10.04LTS.  The 12.04LTS version has been popping up for a bit, and it seemed like it was being reported as a very solid release.

The install running in my VirtualBox partition went smoothly enough, but that was only a leap from 11.x to 12.04.  Upgrading from 10.04 is a couple of levels to jump, so the possibility for problems increases.

So with some amount of trepidation I decided to run the upgrade process on the 10.04 sandbox. If the upgrade should barf completely, its not a tremendous loss.  If it works, the 12.04LTS version is supposed to be good through 2017(if I recall the upgrade notes correctly).

The upgrade seems to have been completely successful, with zero impact on the test bed.  Sweeeeeet….. The 10.04LTS was mostly a plain vanilla install, but its nice that it made the leap with so little intervention.

This upgrade went far more easily than a prior upgrade(from 8.10 to 9.04).  Very happy to see the Ubuntu developers have made the upgrade process so user friendly.

Very.  Nice.  Work.

So now the file server is good to go and can remain stable for the foreseeable future.  Time to get back to hacking up some web apps for graphing the Reverse Beacon network data extracts.

Not so happy with the UNITY desktop, but at least it is easy to revert back to Gnome.  Unity is kinda like the new Windows 8 – ButtHole Ugly.  The very last thing I want is an interface that looks like a tablet.  Bleh.

Never have understood why OS developers seem to think that 30 years of accumulated OS familiarity is so readily cast aside for their own vision of ease-of-use.  Too little customer contact….  Most customers want their interfaces to function the same way they functioned yesterday(providing they actually worked yesterday), and changed only if they were broken.  AKA, “New Coke Syndrome”.

Coke Classic pleeze…..add gold rum and lime….

Skimmer Station

Added a new page to the skimmer station fun facts list.

The new page describes observations from using several different sound cards for both music and as the interface for SoftRock software defined radios and the CW Skimmer software.

Re-purposed HyperDawg as Antenna Launcher

Ran across the hyper dog ball launcher a couple of years ago, and the potential for re-purposed applications for hanging antenna supports seemed obvious.  It is not as much fun as a pneumatic launcher, but it sure is easily understood by any boy of 8.  No air pump required.

The modified hyper dog 
The hyper dog ball launcer modified to launc lines for antennas Photo of tennis ball modified for use as line launcher

The normal slingshot type Wrist-Rocket/Crossman slingshot launcher has served the purpose for years, but not always without problems.  A 1-oz(28g) lead weight works, but not without a relatively high rate of mis-fires, line tangles, and “Oh S**t!” moments.  The hyper dog is a lot less likely to draw whining complaints from those inclined to wring their hands and moan about things that don’t really concern them..”See, its just a tennis ball.  Now p**s off!”

The hyper dog has a much larger pouch designed for use with tennis balls.  A slight bit of hacking to the hardware gives a nice re-purposed tool for lofting lines into all of those beautiful deciduous biological antenna supports lining the back yard.  So far it has been a lot more reliable in actual usage than the ole trusty Crossman, although Field Day proved its not impossible to Dork Up.  [You Know Who You Are….lol]

The reel deal:

Here the body was altered by adding a cheap spin-cast zebco reel picked up for $2 at a yard sale.  A spinning reel or open faced casting reel might be better, but I have used the zebco’s since I was 6yo.   Being more familiar with the Zebco quirks and limitations is useful. For most, a spinning reel is probably the best option.  10 or 12lb test line has proven the best choice over the years – light enough to fly, strong enough to pull, and not impossible to break if it becomes hopelessly snarled at altitude.

The reel is simply attached below the ball carrier with a couple of hose clamps.  That was later wrapped with an ugly mess of electrical tape just to reduce the number of exposed sharp edges.

Yes, the tennis balls work FB.

To modify the tennis balls, they were  just drilled with a 9/64 bit.  A loop of 1/8th braided nylon cord is secured to a small hardware store drywall toggle bolt/spring bolt. Then just cram the bolt/cord through the hole, reaming the hole out slightly if needed[leaving most of the loop of cord hanging out!].    The base of the cord is sealed at the hole with a goop of liquid nails or hot glue or some-such.  The loop of cord is about 6 inches long(~150mm), and the spring bolt serves the same purpose it normally does by providing a large area preventing pull-out.  After drying completely – good to go.

The tennis balls seem to be a good compromise between weight and a non-destructive & non-threatening projectile. [Just don’t try to pull them back up through the tree-too fast!].   The ‘trick’ to success with it seems to be making sure the cord on the tennis balls clear the end of the slingshot.  It seems to work best when the corded end of the ball is facing  up(i.e., at the top of the pouch when pulled back for a shot).

What’s the catch?

The only genuine problem I have with it is that it has a “long draw”.  Being impishly short my arms are not long enough to get the maximum performance out of the rig.  But despite that it works much better than the regular slingshot with fewer snags and mis-fires. It easily sends the tennis balls up to about 90 feet(~30m).  The canopy here prevents anything higher, so no real top-end found yet.

I suspect golf balls would be the ultimate high-flying projectile for rural locations.  Too much window glass and nervous-Nelly neighbors around the home QTH for me to try golf balls here.   A day-break early morning experiment for the future…. ;)

There is somebody here on the east coast marketing these re-branded as antenna launchers, and asking $80.  See Radiowavz Hyper Hanger, now $90USD….

Too easy to homebrew from the $22 Amazon original to peel out 80 samolies 90 GreenStamps, but it is there as an option. (!~yikes~!)