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.
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).
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.
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.
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…
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….
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.
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 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
Too easy to homebrew from the $22 Amazon original to peel out
So….Who will be the first to hack one of these things to use for hauling antenna lines up into trees for Field Day? They will be forever honored in the Halls of HamHacks.
A simple solenoid that is remotely activated to pull a pin and drop the line should do the job. The challenge is probably finding a solenoid that is light enough to be lifted by the drone when combined with the weight/drag of the line. Which leads to the question of “what’s the payload capacity(if any)?”