I finally made the leap into the new Google-authenticated scheme on blogger.com. It was a good thing I did, because I found quite a number of user comments for the blog that were pending. All moderation requests were going to an obsolete email address.
Apologies to readers who made great comments along the way. They should now be posted.
-Martin
Friday, February 16, 2007
Thursday, December 07, 2006
Experiments with picopower
On a recent evening at the W1YU Club at Yale, we had a program on QRP operation. That got me thinking. What equipment do I have for QRP work?
Well, I have an Elecraft XG-2. It puts out a fairly well calibrated 50 μVolts into 50 ohms. That is about 50 picoWatts on 20, 40, or 80 meters.
So here is my QRP transmitter. All it needs is a CR-2032 battery. I find it is tricky to send CW with the power switch, so I attached an old straight key. The coax goes to a 3-element SteppIR at 40 ft.
What can we do with 50 pW on 20 meters? First, try listening for it on my main rig, the Orion using a 40 M dipole. There it is, about S2 on 14.060 MHz. It is stronger if I aim the beam south, toward the dipole.
I tried a quick "CQ" just in case... But the band was dead. No response, no surprise!
Next I tried using my Icom R8500 set up temporarily in the car, with a 15 foot wire strung out over the trunk. The '8500 is not a great CW rig - it doesn't even have the narrow filter, but otherwise it fills the bill.
First test: yes I can hear the signal in my driveway, about 60 ft from the beam. I drove away to a point about 300 M away and gave a listen. (Auto noise was hopeless - I had to shut off the Acura completely before I could get near the noise floor.) Nothing at 300 M. Drove closer and closer, but still nothing positive. Finally, the signal was there at S1 about 2 houses away from mine -- maybe 50 M. It would have been usable for a QRS CW QSO.
(If we had a more appropriate receiver filter system and receive antenna, we might have gotten 10 dB more sensitivity.)
OK - if 50 meters is the range for 50 pW, what can we calculate? How about if we had 50 microwatts instead? That's a million times more power, and the square root of a million is 1,000. (We assume the inverse square law works, although really we're in the near field at only 50 M separation.) So what range would we expect for 50 μW? A thousand times more -- 50 kM or about 30 miles, at least for free space line of sight.
One day, I may throw together a 50 μW "QRO" rig to check this prediction.
Another calculation: 50 M is 28.6 milli-miles, so we have 571 million miles per Watt. It wasn't a two-way QSO, but would this be a record?
[Miles per Watt, as others have noted, is a nonsense ratio. For a constant signal to noise ratio, "miles" will vary with the square root of power, not linearly in power. In other words, the record should go to the QSO with the highest "miles per square root of Watts".]
[5/22/08: Photo restored.]
Well, I have an Elecraft XG-2. It puts out a fairly well calibrated 50 μVolts into 50 ohms. That is about 50 picoWatts on 20, 40, or 80 meters.
So here is my QRP transmitter. All it needs is a CR-2032 battery. I find it is tricky to send CW with the power switch, so I attached an old straight key. The coax goes to a 3-element SteppIR at 40 ft.
What can we do with 50 pW on 20 meters? First, try listening for it on my main rig, the Orion using a 40 M dipole. There it is, about S2 on 14.060 MHz. It is stronger if I aim the beam south, toward the dipole.
I tried a quick "CQ" just in case... But the band was dead. No response, no surprise!
Next I tried using my Icom R8500 set up temporarily in the car, with a 15 foot wire strung out over the trunk. The '8500 is not a great CW rig - it doesn't even have the narrow filter, but otherwise it fills the bill.
First test: yes I can hear the signal in my driveway, about 60 ft from the beam. I drove away to a point about 300 M away and gave a listen. (Auto noise was hopeless - I had to shut off the Acura completely before I could get near the noise floor.) Nothing at 300 M. Drove closer and closer, but still nothing positive. Finally, the signal was there at S1 about 2 houses away from mine -- maybe 50 M. It would have been usable for a QRS CW QSO.
(If we had a more appropriate receiver filter system and receive antenna, we might have gotten 10 dB more sensitivity.)
OK - if 50 meters is the range for 50 pW, what can we calculate? How about if we had 50 microwatts instead? That's a million times more power, and the square root of a million is 1,000. (We assume the inverse square law works, although really we're in the near field at only 50 M separation.) So what range would we expect for 50 μW? A thousand times more -- 50 kM or about 30 miles, at least for free space line of sight.
One day, I may throw together a 50 μW "QRO" rig to check this prediction.
Another calculation: 50 M is 28.6 milli-miles, so we have 571 million miles per Watt. It wasn't a two-way QSO, but would this be a record?
[Miles per Watt, as others have noted, is a nonsense ratio. For a constant signal to noise ratio, "miles" will vary with the square root of power, not linearly in power. In other words, the record should go to the QSO with the highest "miles per square root of Watts".]
[5/22/08: Photo restored.]
Friday, November 17, 2006
Known by the company we keep
I see we made the big time with a listing in AwfulBlogs.
You know what the doctor says, when you say "it hurts when I do this"? He says, "well then don't do it any more."
Moving on...
You know what the doctor says, when you say "it hurts when I do this"? He says, "well then don't do it any more."
Moving on...
Rigserve
Rigserve is a new approach to local and remote control of ham rigs, inspired by work on Hamlib. Rigserve is an IP network server, programmed in Python, that provides a simple text-based interface to control an arbitrarily large number of rigs. The code is compatible with Linux-like OSs and Windows. Rig backends are provided initially for the Ten-Tec Orion (I and II) and the Icom R8500.
See hamlib-developer.blogspot.com and www.aa6e.net/aa6e/software for more information.
See hamlib-developer.blogspot.com and www.aa6e.net/aa6e/software for more information.
Saturday, September 30, 2006
Hamlib, reloaded
The Hamlib project has been working on a rig-independent API for software developers that will allow them to connect to a wide variety of ham rigs without worry about their individual interface quirks.
Lately, we have begun discussing how this project can envolve into a "version 2". There is a new blog at hamlib-developer.blogspot.com to support development of Hamlib. If you want to take an active part in the Hamlib project through this blog, please contact me.
The Hamlib project is supported at sourceforge.net/projects/hamlib, which provides a mailing list, CVS, and other amenities.
Lately, we have begun discussing how this project can envolve into a "version 2". There is a new blog at hamlib-developer.blogspot.com to support development of Hamlib. If you want to take an active part in the Hamlib project through this blog, please contact me.
The Hamlib project is supported at sourceforge.net/projects/hamlib, which provides a mailing list, CVS, and other amenities.
DXCC at last?
After some 49 years in amateur radio, I tallied up my QSL connection and found 101 "entities". If the League agrees, there will be a new piece of wallpaper for me - DXCC. At this pace, I will be on the honor role in about 150 years.
Thursday, September 21, 2006
ARRL LOTW on Linux Fedora Core 5
If you're a hard-core Linux ham and you want to use the ARRL's "Logbook of the World" (LOTW), you are in for some work. The Linux binary software distribution is provided only for Fedora Core 3 distribution, which is now well out of date. You have to compile from source code, and even the source code is out of date with respect to current (Fedora Core 5) compilers and libraries.
Here is my cookbook recipe for how I did it on my FC5 system. I believe I've incorporated all the steps, but I would welcome your feedback if you try to replicate the results.
Fedora Core 6 is right around the corner, and FC6 may possibly require further modifications.
Added Note: The procedure has been found to work as recently as the Fedora 8 release. (12/2007)
Here is my cookbook recipe for how I did it on my FC5 system. I believe I've incorporated all the steps, but I would welcome your feedback if you try to replicate the results.
Fedora Core 6 is right around the corner, and FC6 may possibly require further modifications.
Added Note: The procedure has been found to work as recently as the Fedora 8 release. (12/2007)
Thursday, August 10, 2006
SteppIR Power Consumption
Checking the power consumption of the control system of my SteppIR 3-element Yagi:
(All readings were taken from a "Kill-A-Watt" device.)
It is interesting that turning the "power" on or off has little effect on AC power drain. It just shuts off the panel lights, as far as one can tell. According to Internet sources, a bias current continues to flow to the stepping motors when the controller is "off". This helps prevent the element lengths from drifting.
| Condition | AC power drain |
| Power Brick only (controller disconnected) | 1 W |
| Controller "off" | 10 W |
| Controller "on" (idle) | 10 W |
| Elements slewing | 30-40 W |
| D connector disconnected | 3 W |
(All readings were taken from a "Kill-A-Watt" device.)
It is interesting that turning the "power" on or off has little effect on AC power drain. It just shuts off the panel lights, as far as one can tell. According to Internet sources, a bias current continues to flow to the stepping motors when the controller is "off". This helps prevent the element lengths from drifting.
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