I meant to do a bunch of stuff over the weekend, mostly having to do with ApolloCon, the science fiction convention that I basically run. However, Saturday was spent away from home and Sunday found me lounging around, when I wasn't diagnosing issues with GNU Radio, and now here it is Monday, and I didn't get anything done.
So, today I'm wrapping up loose ends. I've asked one of the local rocket clubs if they would be interested in doing a thing for ApolloCon, and I (once again) faxed the room reservation form to Central Market so that we can hold convention committee meetings there.
I've got one or two other things to do, but we'll see if it happens today or a different day.
Monday, January 28, 2013
Saturday, January 26, 2013
Saturday morning, 8:30 AM
The clock at the top of the screen says it's 8:26 and I'm sitting in the vending machine alcove on the first floor of the Digital Technology Center at the North Harris campus of the Lone Star College. I'll be here today for another four hours, most likely, and I'll probably be repeating this trip for the next 14 weeks as J-Mag takes her Business English class.
I am bored.
As far as Internet, we get "both kinds" here (HTTP and HTTPS) and so my shell sessions to my main server at the house and in the Chicago data center as well as IMAP and SMTP sessions to get and send mail just timeout with the bits lost without a trace. I can post to this blog. I can do programming or whatever, as long as I don't want to check anything in to revision control because that goes over SSH. I can play "Civilization: Call to Power" as long as it's a single-player game, or maybe even fly "X-Plane 10" (I've got the disk 1 ISO on the hard drive so I don't need my physical disk.) Maybe next time I'll set up a proxy to tunnel everything through HTTP. Maybe I'll just put up with it. How hard can it be?
At least I have a computer. I had the foresight to bring it and the power supply. The library opens at 9, and I can move to a quieter, if not more comfortable, space, then. I've got snacks, I've got soda and PowerAde and something to sit on.
But I'm bored.
I am bored.
As far as Internet, we get "both kinds" here (HTTP and HTTPS) and so my shell sessions to my main server at the house and in the Chicago data center as well as IMAP and SMTP sessions to get and send mail just timeout with the bits lost without a trace. I can post to this blog. I can do programming or whatever, as long as I don't want to check anything in to revision control because that goes over SSH. I can play "Civilization: Call to Power" as long as it's a single-player game, or maybe even fly "X-Plane 10" (I've got the disk 1 ISO on the hard drive so I don't need my physical disk.) Maybe next time I'll set up a proxy to tunnel everything through HTTP. Maybe I'll just put up with it. How hard can it be?
At least I have a computer. I had the foresight to bring it and the power supply. The library opens at 9, and I can move to a quieter, if not more comfortable, space, then. I've got snacks, I've got soda and PowerAde and something to sit on.
But I'm bored.
Friday, January 25, 2013
What I'm reading, these days
Here in Houston, we have have these things called "book swaps" which are rather awkwardly named, but they're where science fiction fans get together and talk about the books they've read and they loan them out to people who are interested in them. I go to two of these groups, the "North Houston" group, which usually meets up off 249 and the "Katy Freeway" group, which meets near the Katy Freeway. (Imagine that.)
I wind up mostly reading books I get there, and right now is no exception. I just finished a collection of Neil Gaiman stories called Smoke and Mirrors that I'm borrowing from Doug of the North Houston group, and I just started a book called As the Crow Flies by Jeffrey Archer that I got from Anita at the Katy Freeway group.
I borrowed the Neil Gaiman book because I truly enjoyed Good Omens, which was a collaboration between Neil Gaiman and Terry Pratchett and I've tried to read a couple of Pratchett's books and, well, they aren't my favorites. So, I thought, maybe it was Neil Gaiman's contribution that made me like Good Omens. Judging by Smoke and Mirrors, though, that's not it. I continue to recommend Good Omens. Smoke and Mirrors, not so much.
Maybe I'll remember to talk about As the Crow Flies when I'm done with it. Perhaps not. It's kind of historical fiction, a lot like Robert B. Parker's All Our Yesterdays.
I wind up mostly reading books I get there, and right now is no exception. I just finished a collection of Neil Gaiman stories called Smoke and Mirrors that I'm borrowing from Doug of the North Houston group, and I just started a book called As the Crow Flies by Jeffrey Archer that I got from Anita at the Katy Freeway group.
I borrowed the Neil Gaiman book because I truly enjoyed Good Omens, which was a collaboration between Neil Gaiman and Terry Pratchett and I've tried to read a couple of Pratchett's books and, well, they aren't my favorites. So, I thought, maybe it was Neil Gaiman's contribution that made me like Good Omens. Judging by Smoke and Mirrors, though, that's not it. I continue to recommend Good Omens. Smoke and Mirrors, not so much.
Maybe I'll remember to talk about As the Crow Flies when I'm done with it. Perhaps not. It's kind of historical fiction, a lot like Robert B. Parker's All Our Yesterdays.
Thursday, January 24, 2013
Software Defined Radio - Projects
Over the last couple of months, I've done a bunch of stuff with Software Defined Radio. I run Linux at home and so I have been working with GNU Radio, and I've got a couple of different kinds of radio hardware, one being a TV Receiver USB Dongle (read about my adventures getting that working) that can be convinced to generate a data stream centered on some frequency between about 70 MHz and about 1700 MHz. The other is a Softrock 40 R, which is a crystal-controlled quadrature downconverter that hears about 96 kHz of the 20m band centered around 14.070 MHz.
So far, I've mostly used the TVRO dongle to listen to FM Broadcast (87.9 MHz to 107.9 MHz in the USA) and to the local repeater (147.2 MHz in Katy, Texas) and I've rigged up a CW Receiver for the Softrock. I've been collecting my thoughts about SDR projects, and I thought I'd list a few of them.
Incidentally, it may not be intuitively obvious to the casual observer that the GNU Radio software isn't a radio application, it's a toolkit for producing radio applications. It certainly wasn't intuitively obvious to me, but then I'm widely known as someone who rarely pays attention.
Anyway, the projects. In terms of software I want to do these:
First, is a CW Skimmer like thing that works under Linux or just with the GNU Radio software.
The second would be a CW Skimmer like thing that does PSK-31 instead of CW. Update: I know such a thing exists. See for example: http://www.walter-dallmeier.de/software-by-dl4rck/rckskimmer/
Third would be a receiver that speaks rigctrld protocol (I looked, but I can't find a link) and can be used to receive satellite signals.
I think I'll start by implementing these things in Python and then convert them to C++ if it seems be an appropriate thing to do.
In terms of hardware, I want to do things like these:
A TVRO Upconverter so I can use the TVRO dongle for receiving HF signals. This will likely require hardware modifications to the dongle. I especially want to replace the antenna connector with an F connector or BNC connector or something.
In fact, I'll probably modify more than one of those dongles so I can use the UHF preamp I've bought and then so I can connect that preamp to an antenna with significant gain.
I also want to build a couple more kits, including the UHFSDR kit and ultimately I want one of those "nimblesig iii" devices I mentioned in previous blog posts.
That should keep me busy for a while, shouldn't it?
So far, I've mostly used the TVRO dongle to listen to FM Broadcast (87.9 MHz to 107.9 MHz in the USA) and to the local repeater (147.2 MHz in Katy, Texas) and I've rigged up a CW Receiver for the Softrock. I've been collecting my thoughts about SDR projects, and I thought I'd list a few of them.
Incidentally, it may not be intuitively obvious to the casual observer that the GNU Radio software isn't a radio application, it's a toolkit for producing radio applications. It certainly wasn't intuitively obvious to me, but then I'm widely known as someone who rarely pays attention.
Anyway, the projects. In terms of software I want to do these:
First, is a CW Skimmer like thing that works under Linux or just with the GNU Radio software.
The second would be a CW Skimmer like thing that does PSK-31 instead of CW. Update: I know such a thing exists. See for example: http://www.walter-dallmeier.de/software-by-dl4rck/rckskimmer/
Third would be a receiver that speaks rigctrld protocol (I looked, but I can't find a link) and can be used to receive satellite signals.
I think I'll start by implementing these things in Python and then convert them to C++ if it seems be an appropriate thing to do.
In terms of hardware, I want to do things like these:
A TVRO Upconverter so I can use the TVRO dongle for receiving HF signals. This will likely require hardware modifications to the dongle. I especially want to replace the antenna connector with an F connector or BNC connector or something.
In fact, I'll probably modify more than one of those dongles so I can use the UHF preamp I've bought and then so I can connect that preamp to an antenna with significant gain.
I also want to build a couple more kits, including the UHFSDR kit and ultimately I want one of those "nimblesig iii" devices I mentioned in previous blog posts.
That should keep me busy for a while, shouldn't it?
Wednesday, December 9, 2009
SMOFCon 27 and Inch Pebbles
I think I may have mentioned somewhere that I put on science fiction conventions. If I haven't mentioned that, well, now you know. I work on the local Houston one, ApolloCon, and sometimes do some other things. This last weekend, was the most recent SMOFCon. Now, a SMOF is a Secret Master Of Fandom, and a SMOFCon is a convention where people who run conventions get together to talk about it with each other.
One thing I did not expect was the unofficial activities. I'm not talking about Saturday night's "probability and statistics seminar". Rather, I'm referring to the way SMOFCon was used to troll for volunteers. It makes sense, after all, because most of the people at SMOFCon are either working on a WorldCon or are experienced at working on a WorldCon and those who are in the former group are always looking for those in the latter group to come join them in whichever one they're working on now. However, I hadn't considered it in just that way.
This year's theme (SMOFCon apparently always has a theme associated with it) was Time Management and people were talking about (well, were supposed to be talking about--it didn't always happen that way) time management. Tthe panels I attended were interesting and intruiging. The problems associated with getting things done with the hard deadlines that cons are always going to have are a lot like those in the software business. Cons are often worse because the people are volunteers and they're expected to have lives that occasionally take priority and so don't always get things done when they're supposed to.
Since it was my first time there and I had very few things to say about time management that weren't being said by the panelists, and because I didn't want to occupy anyone else's time with my minutiae, I sat and listened and didn't say anything inside the panels. Just now, I figured that I have a blog so I can say anything I want and it won't interrupt anybody, so I'm doing it.
So here goes: I have often said that, for a software project, the only meaningful percentage of completion is 100, and even that might not be meaningful. What I mean by that is estimates of how far along the thing is are useless (not just practically or usually, but completely and totally unusable crap) until the very end and sometimes people will say something is finished, but it isn't really. So, you can't trust anything that isn't claimed to be done yet and you have to somehow independently verify the completion of stuff.
The problem, of course, is that a two year task has a single point of completion, and so there's only a single place to check for completion. If the end of that two-year task is two weeks before the con, then you don't want to find out then that the person who was supposed to be doing that task didn't actually do any of it. Although the proper area for this discussion is more people management than time management, the same solution was offered multiple times. Although none of the people talking about it used the term, that solution is "inch pebbles", as in milestones but smaller and more often.
The idea is to break tasks down into small chunks that can be verified and, from time to time, verify that the tasks are progressing satisfactorily. It is important that the chunks be small and that they be truly independently verifiable. Fortunately, since most tasks associated with working on a con are tasks that involve communications among departments, the independent verification is kind of built in. With software projects, one schedules demonstrations to the same end.
I like studying how other people do their jobs, and one of the reasons that I like doing that is because I can often apply lessons learned from other people to do my own job better. I suppose I shouldn't be surprised that this can flow in the other direction, too.
One thing I did not expect was the unofficial activities. I'm not talking about Saturday night's "probability and statistics seminar". Rather, I'm referring to the way SMOFCon was used to troll for volunteers. It makes sense, after all, because most of the people at SMOFCon are either working on a WorldCon or are experienced at working on a WorldCon and those who are in the former group are always looking for those in the latter group to come join them in whichever one they're working on now. However, I hadn't considered it in just that way.
This year's theme (SMOFCon apparently always has a theme associated with it) was Time Management and people were talking about (well, were supposed to be talking about--it didn't always happen that way) time management. Tthe panels I attended were interesting and intruiging. The problems associated with getting things done with the hard deadlines that cons are always going to have are a lot like those in the software business. Cons are often worse because the people are volunteers and they're expected to have lives that occasionally take priority and so don't always get things done when they're supposed to.
Since it was my first time there and I had very few things to say about time management that weren't being said by the panelists, and because I didn't want to occupy anyone else's time with my minutiae, I sat and listened and didn't say anything inside the panels. Just now, I figured that I have a blog so I can say anything I want and it won't interrupt anybody, so I'm doing it.
So here goes: I have often said that, for a software project, the only meaningful percentage of completion is 100, and even that might not be meaningful. What I mean by that is estimates of how far along the thing is are useless (not just practically or usually, but completely and totally unusable crap) until the very end and sometimes people will say something is finished, but it isn't really. So, you can't trust anything that isn't claimed to be done yet and you have to somehow independently verify the completion of stuff.
The problem, of course, is that a two year task has a single point of completion, and so there's only a single place to check for completion. If the end of that two-year task is two weeks before the con, then you don't want to find out then that the person who was supposed to be doing that task didn't actually do any of it. Although the proper area for this discussion is more people management than time management, the same solution was offered multiple times. Although none of the people talking about it used the term, that solution is "inch pebbles", as in milestones but smaller and more often.
The idea is to break tasks down into small chunks that can be verified and, from time to time, verify that the tasks are progressing satisfactorily. It is important that the chunks be small and that they be truly independently verifiable. Fortunately, since most tasks associated with working on a con are tasks that involve communications among departments, the independent verification is kind of built in. With software projects, one schedules demonstrations to the same end.
I like studying how other people do their jobs, and one of the reasons that I like doing that is because I can often apply lessons learned from other people to do my own job better. I suppose I shouldn't be surprised that this can flow in the other direction, too.
Saturday, October 31, 2009
Cheap Microwave Gear?
In my last blog post, I mentioned my conversation with Andy W5ACM at a Houston QRP Society meeting where he challenged me to make contacts through OSCAR-51 before criticizing it. That conversation has borne more fruit by sparking another idea, and I thought I'd write it down before I went on to
work on other things.
That conversation, now nearly three months past, was a general condemnation of what I saw as the direction of AMSAT in the late 1980's and early 1990's. Back then, the thrust seemed, to me, to be toward satellites with high (40,000km+) apogees and S-Band (2400 MHz) equipment. Back then, I saw that as suicidal because S-Band transceivers were not available to the radio amateur at any price and one would pay several times the cost of a VHF transceiver for an S-band transverter.
Since that time, some radios have had support for L-Band (1300 MHz) as an option, but I still know of no options for S-Band except upconverters and downconverters which allow the use of a VHF or UHF radio on the S-Band.
Anyway, since I was trying to make contacts through satellites, I thought it would be a good idea to subscribe to AMSAT's "amsat-bb" mailing list. The amount of noise in that list's signal is not bad for a general discussion mailing list, and it had an announcement a while back that I found interesting.
You see, it turns out that a guy named Paul Wade, W1GHZ has designed some transverters, and announcement was made on amsat-bb for a group putting together a group buy of parts to kit out transverters based on his design. I briefly considered the ordering some of the kits which, sadly, I decided I couldn't afford right now, but the important thing to understand about these kits is that you can build an L-Band or S-Band transverter based upon them for around $100 each, plus whatever you consider a couple of hours of your time to be worth, and for a hobby activity I consider my time to be worth a negative amount.
Another reason that I decided to pass on one of these kits is because of how they work and what, precisely, they do. You see, they are cheap because they use inexpensive non-microwave components and printed circuit boards and deal with the losses that those choices imply by inserting cheap and readily-available MMIC (Monolithic Microwave Integrated Circuit) amplifiers. Local-oscillators suitable for use in microwave transverters have proven to be a problem in the past, but if you use a frequency that is a multiple of a frequency that is commonly used in desktop computerers, that's not a problem any more.
What is a problem is the fact that the frequencies of the oscillators and such were chosen to translate the output of a 2-meter (144-148 MHz) transmitter into the small signal part of the L-Band and S-Band and, well, I'm interested in signals in the satellite part, not the small signal part. To use the L-Band converter to work AO-51, I'd need to drive it with an FM transmitter on 116.7 MHz. Of course, I don't have a transmitter that emits anything on 116.7 MHz, let alone FM. (It's in the aircraft band, and airplane radios are AM.)
So, what to do? I could modify my IC-706MkIIG such that it isn't restricted to just transmitting within the ham bands, but I'm not really that enthusiastic about opening up my main radio and taking a soldering iron to its innards. I could also find a different oscillator frequency that would just happen to be cheap, common, and which had a harmonic that feel into the range of about 1120 to 1125 MHz, but I gave that up after about an hour. Besides, it occurred to me, the venerable Icom wasn't necessarily the appropriate equipment to drive a transverter. Transverters don't need a lot of drive and typically can't deal with very much driver, and so I'd have to do something to ensure that I didn't accidentally blow up whatever transverter I got.
I then observed that this wasn't a problem on receive because lots of radios have general-coverage receivers so it doesn't matter if a downconverter puts the signals I'm interested in at some frequency I wasn't allowed to transmit on. What I needed, I thought, was a special purpose exciter that could generate FM signals (or, really, any mode) on any frequency from 100 MHz to 150 MHz but which wouldn't generate too much power for the upconverter to handle. I thought that would be an appropriate companion device for those really cool transverters.
With that in mind, I set out to see if anyone has done this already, and I couldn't find where anyone had. However, what I did find was that all the hard parts are done. A search for "exciter transverter" led me to a 1993 QST article by Rick Campbell KK7B "A Multimode Phasing Exciter for 1 to 500 MHz". To be honest, I don't think that it's really an exciter. I think that it's really just a modulator that needs a carrier signal (two of them, 90 degrees out of phase, to be specific) to modulate.
So, where to get the carrier signal? It would be best if the frequency were synthesized and what I know about PLL-based frequency synthesizers suggests that they really aren't all that easy to work with. Then, I remembered hearing about a technology called DDS, for "Direct Digital Synthesis", which is a radically different technology for synthesizing a signal than using a PLL, but had the limitation of requiring that the signal be lower in frequency than a reference, and so was limited to relatively low frequencies.
When I searched for "direct digital synthesis arrl" (because "direct digital synthesis" isn't specific enough and the other article was found at arrl.org) the first link was to an article in the current (or next--it isn't clear) issue of QEX magazine about a device based upon a thing called the "NimbleSig III" DDS synthesizer, designed by Thomas Alldread VA7TA.
So, I searched for "NimbleSig III" and found an amazing device that can generate two signals each with a specified independent frequency and phase shift at anywhere from 100 kHz to 200 MHz. Um, wow. This is just what the doctor ordered and why the preacher danced. Combined with KK7B's device, I can use it to generate AM, FM, SSB, CW and anything else that can be derived from those over the entire desired 100 MHz to 150 MHz frequency range. Of course, these things aren't available assembled, or as kits, but as bare printed circuit boards, and they use all surface-mount parts. I've never done surface mount, but this is a powerful inducement for me to try.
The thing is, although I haven't tried to price the parts just yet, I can probably build each one of these devices for around $100. So, I could build an S-Band or L-Band transmitter for less than $300 and get the downconverter I'd need, so I can receive, too, for free. I wonder if anybody's done this?
work on other things.
That conversation, now nearly three months past, was a general condemnation of what I saw as the direction of AMSAT in the late 1980's and early 1990's. Back then, the thrust seemed, to me, to be toward satellites with high (40,000km+) apogees and S-Band (2400 MHz) equipment. Back then, I saw that as suicidal because S-Band transceivers were not available to the radio amateur at any price and one would pay several times the cost of a VHF transceiver for an S-band transverter.
Since that time, some radios have had support for L-Band (1300 MHz) as an option, but I still know of no options for S-Band except upconverters and downconverters which allow the use of a VHF or UHF radio on the S-Band.
Anyway, since I was trying to make contacts through satellites, I thought it would be a good idea to subscribe to AMSAT's "amsat-bb" mailing list. The amount of noise in that list's signal is not bad for a general discussion mailing list, and it had an announcement a while back that I found interesting.
You see, it turns out that a guy named Paul Wade, W1GHZ has designed some transverters, and announcement was made on amsat-bb for a group putting together a group buy of parts to kit out transverters based on his design. I briefly considered the ordering some of the kits which, sadly, I decided I couldn't afford right now, but the important thing to understand about these kits is that you can build an L-Band or S-Band transverter based upon them for around $100 each, plus whatever you consider a couple of hours of your time to be worth, and for a hobby activity I consider my time to be worth a negative amount.
Another reason that I decided to pass on one of these kits is because of how they work and what, precisely, they do. You see, they are cheap because they use inexpensive non-microwave components and printed circuit boards and deal with the losses that those choices imply by inserting cheap and readily-available MMIC (Monolithic Microwave Integrated Circuit) amplifiers. Local-oscillators suitable for use in microwave transverters have proven to be a problem in the past, but if you use a frequency that is a multiple of a frequency that is commonly used in desktop computerers, that's not a problem any more.
What is a problem is the fact that the frequencies of the oscillators and such were chosen to translate the output of a 2-meter (144-148 MHz) transmitter into the small signal part of the L-Band and S-Band and, well, I'm interested in signals in the satellite part, not the small signal part. To use the L-Band converter to work AO-51, I'd need to drive it with an FM transmitter on 116.7 MHz. Of course, I don't have a transmitter that emits anything on 116.7 MHz, let alone FM. (It's in the aircraft band, and airplane radios are AM.)
So, what to do? I could modify my IC-706MkIIG such that it isn't restricted to just transmitting within the ham bands, but I'm not really that enthusiastic about opening up my main radio and taking a soldering iron to its innards. I could also find a different oscillator frequency that would just happen to be cheap, common, and which had a harmonic that feel into the range of about 1120 to 1125 MHz, but I gave that up after about an hour. Besides, it occurred to me, the venerable Icom wasn't necessarily the appropriate equipment to drive a transverter. Transverters don't need a lot of drive and typically can't deal with very much driver, and so I'd have to do something to ensure that I didn't accidentally blow up whatever transverter I got.
I then observed that this wasn't a problem on receive because lots of radios have general-coverage receivers so it doesn't matter if a downconverter puts the signals I'm interested in at some frequency I wasn't allowed to transmit on. What I needed, I thought, was a special purpose exciter that could generate FM signals (or, really, any mode) on any frequency from 100 MHz to 150 MHz but which wouldn't generate too much power for the upconverter to handle. I thought that would be an appropriate companion device for those really cool transverters.
With that in mind, I set out to see if anyone has done this already, and I couldn't find where anyone had. However, what I did find was that all the hard parts are done. A search for "exciter transverter" led me to a 1993 QST article by Rick Campbell KK7B "A Multimode Phasing Exciter for 1 to 500 MHz". To be honest, I don't think that it's really an exciter. I think that it's really just a modulator that needs a carrier signal (two of them, 90 degrees out of phase, to be specific) to modulate.
So, where to get the carrier signal? It would be best if the frequency were synthesized and what I know about PLL-based frequency synthesizers suggests that they really aren't all that easy to work with. Then, I remembered hearing about a technology called DDS, for "Direct Digital Synthesis", which is a radically different technology for synthesizing a signal than using a PLL, but had the limitation of requiring that the signal be lower in frequency than a reference, and so was limited to relatively low frequencies.
When I searched for "direct digital synthesis arrl" (because "direct digital synthesis" isn't specific enough and the other article was found at arrl.org) the first link was to an article in the current (or next--it isn't clear) issue of QEX magazine about a device based upon a thing called the "NimbleSig III" DDS synthesizer, designed by Thomas Alldread VA7TA.
So, I searched for "NimbleSig III" and found an amazing device that can generate two signals each with a specified independent frequency and phase shift at anywhere from 100 kHz to 200 MHz. Um, wow. This is just what the doctor ordered and why the preacher danced. Combined with KK7B's device, I can use it to generate AM, FM, SSB, CW and anything else that can be derived from those over the entire desired 100 MHz to 150 MHz frequency range. Of course, these things aren't available assembled, or as kits, but as bare printed circuit boards, and they use all surface-mount parts. I've never done surface mount, but this is a powerful inducement for me to try.
The thing is, although I haven't tried to price the parts just yet, I can probably build each one of these devices for around $100. So, I could build an S-Band or L-Band transmitter for less than $300 and get the downconverter I'd need, so I can receive, too, for free. I wonder if anybody's done this?
Thursday, September 17, 2009
AO-51 Success!
This evening, I was able, using the AO-51 satellite, to successfully communicate with KG6NUB who is near the San Francisco Bay area of California. Hooray! I don't know what I'm going to do with myself now that I've achieved the goal of making a satellite contact.
Use the satellite to work some more stations, I guess. Maybe use different satellites. I've been working toward making satellite contacts with my own station for almost 30 years, and it has finally worked.
Tonight's success was made possible by the fact that sometimes AO-51 is set up for "QRP" (low-power for non-ham types) operation. In QRP mode, it does not require that I set a PL tone, so I can use my old TR-9000 as the transmitter, which puts out 10 Watts, the maximum allowed, but doesn't have PL tone capability. However, it does mean that I can't use an amplifier or an antenna that isn't omnidirectional. In fact, here is a picture of my transmitting antenna:
It's just a dipole, made of some leftover 12-gauge house wiring, that's hung from the ceiling.
Here's my receiving antenna. Actually, there are three antennas in this photo.
The antenna on the right is a "Texas Potato Masher" which I built wrong, so it doesn't really work. Over the next little while, I'll be figuring out how to fix it. On the left are two "Arrow" antennas built on the same spar, a piece of 3/4 inch square dowel. Perpendicular to the plane of the photo is the 2-meter antenna, which I can't use when using AO-51's QRP mode, and the 70-cm antenna is at right angles to it so you can just barely see it. The 70-cm Arrow is the receiving antenna that worked well enought. I can't seem to work the satellite when it is west of me, but north west to north seems to work okay. My guess is that it's due to the trees to the south and southwest.
All three antennas are mounted on an altazimuth mount I build based on a similar mount described on the AMSAT site. The main difference is that I built mine to be all PVC since I didn't feel like paying for a metal tripod.
The antennas and mount and a duplexer, a piece not shown, are the culmination of several weeks of effort, and it all worked. Like I said, I don't know what I'm going to do with myself, now.
Use the satellite to work some more stations, I guess. Maybe use different satellites. I've been working toward making satellite contacts with my own station for almost 30 years, and it has finally worked.
Tonight's success was made possible by the fact that sometimes AO-51 is set up for "QRP" (low-power for non-ham types) operation. In QRP mode, it does not require that I set a PL tone, so I can use my old TR-9000 as the transmitter, which puts out 10 Watts, the maximum allowed, but doesn't have PL tone capability. However, it does mean that I can't use an amplifier or an antenna that isn't omnidirectional. In fact, here is a picture of my transmitting antenna:
It's just a dipole, made of some leftover 12-gauge house wiring, that's hung from the ceiling.Here's my receiving antenna. Actually, there are three antennas in this photo.
The antenna on the right is a "Texas Potato Masher" which I built wrong, so it doesn't really work. Over the next little while, I'll be figuring out how to fix it. On the left are two "Arrow" antennas built on the same spar, a piece of 3/4 inch square dowel. Perpendicular to the plane of the photo is the 2-meter antenna, which I can't use when using AO-51's QRP mode, and the 70-cm antenna is at right angles to it so you can just barely see it. The 70-cm Arrow is the receiving antenna that worked well enought. I can't seem to work the satellite when it is west of me, but north west to north seems to work okay. My guess is that it's due to the trees to the south and southwest.All three antennas are mounted on an altazimuth mount I build based on a similar mount described on the AMSAT site. The main difference is that I built mine to be all PVC since I didn't feel like paying for a metal tripod.
The antennas and mount and a duplexer, a piece not shown, are the culmination of several weeks of effort, and it all worked. Like I said, I don't know what I'm going to do with myself, now.
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