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Newbie homebrew qrp question; nobody hears me
I am a new technician with code privileges. I built the following CW
transmitter for 40 meters: http://cs.okanagan.bc.ca/ve7ouc/eng/...nsmitter2.html It's a solid state 3-watter, based on an article in QST in June 1967. I used a printed circuit board instead of wiring everything together directly, as the QST article suggests. So, there are many wires running from various parts mounted on the chassis to the circuit board. I'm getting very little output. After tuning the transmitter, per the specs, and measuring the output using the method suggested by the author of the web page, I figure I'm getting 1 watt or less. I am running this into a dipole cut for 40 meters, which is 7 feet off the ground. I'm using fundamental frequency HC6/U crystals for 7110 and 7125 kHz. I've been trying for 2 weeks, at all hours of the day and night, and have had no indication that anyone hears me. I've called CQ, and I've attempted to answer CQ's. Nothing, after about 100 tries. I know it's impossible for any of you to know exactly what's wrong, but I'd like to see what opinions I can glean here. Is there any reason why I should use FT-243 crystals, as specified in the article and on the website? I used HC6/U crystals because they were easy to get. One of the transistors (Q2) is supposed to be heat sinked. I have put a large homemeade heat sink on this, using plenty of heat sink grease, and it gets so hot I can barely touch it. Also, the transmitter chirps a bit at the beginning of each transmission, but settles down after a few strokes of the key. Many thanks for any help you can give. -John Sandin KC0QWE Remove the "T" to respond by e-mail |
Several comments ....
When your output is a LOT different than you expect, likely there is something wrong. Worse, there's a good chance that a lot of your energy is being transmitted where you don't expect. One thing that I found helpful on my first homebrew adventure was to model any circuits that didn't seem to be quite right in PSpice. It's tedious, but it helped me immensely in understanding what's going on. Secondly, a 40 meter antenna 7 feet off the ground is going to radiate pretty much straight up. That means that the only time any of your energy will get back to the ground is when the flux is very high, something that is happening less and less often. Worse, 40 meters is pretty noisy, and the old novice segments really not all that heavily occupied, so not getting a response right away isn't all that surprising. If your output transistor is getting really hot you probably want to revisit your heat sink. If you have, or can borrow, a scope, take a look around and make sure that circuit is doing what you want. The heat could be telling you that a lot of your energy is being spent in parasitics. Presuming you have filtering after this transistor, that could be related to your low output, as well. If you have, or can borrow, a general coverage receiver, listen for your transmitter on your fundamental, and on the harmonic frequencies, especially the odd harmonics. You probably will be able to hear your transmitter on 21.330, but it should be a LOT weaker. If it isn't, you have a problem. Finally, I would try to find someone local (line of sight, say 10-20 miles if it's reasonably flat) and arrange a schedule. This won't take any propagation and it will give you some idea that your transmitter is working. Recognize that locals are often a lot weaker on 40 than stations more distant, but if there are huge issues then perhaps this will uncover them. Finally the chirp - get a fat wire from your power supply to the radio. Also, make sure that the power path to the oscillator is very low resistance. It doesn't take much voltage change to shift the oscillator frequency, and there is a huge inrush of current on key down, so good old E=IR tells you that with a big I it doesn't take much R! Hope this helps... ... "John Sandin" wrote in message ... I'm getting very little output. After tuning the transmitter, per the specs, and measuring the output using the method suggested by the author of the web page, I figure I'm getting 1 watt or less. I am running this into a dipole cut for 40 meters, which is 7 feet off the ground. I'm using fundamental frequency HC6/U crystals for 7110 and 7125 kHz. I've been trying for 2 weeks, at all hours of the day and night, and have had no indication that anyone hears me. I've called CQ, and I've attempted to answer CQ's. Nothing, after about 100 tries. I know it's impossible for any of you to know exactly what's wrong, but I'd like to see what opinions I can glean here. Is there any reason why I should use FT-243 crystals, as specified in the article and on the website? I used HC6/U crystals because they were easy to get. One of the transistors (Q2) is supposed to be heat sinked. I have put a large homemeade heat sink on this, using plenty of heat sink grease, and it gets so hot I can barely touch it. Also, the transmitter chirps a bit at the beginning of each transmission, but settles down after a few strokes of the key. Many thanks for any help you can give. -John Sandin KC0QWE Remove the "T" to respond by e-mail |
On Sun, 05 Oct 2003 04:42:11 GMT,
(John Sandin) wrote: I am a new technician with code privileges. I built the following CW transmitter for 40 meters: http://cs.okanagan.bc.ca/ve7ouc/eng/...nsmitter2.html It's a solid state 3-watter, based on an article in QST in June 1967. I used a printed circuit board instead of wiring everything together directly, as the QST article suggests. So, there are many wires running from various parts mounted on the chassis to the circuit board. I'm getting very little output. After tuning the transmitter, per the specs, and measuring the output using the method suggested by the author of the web page, I figure I'm getting 1 watt or less. How is this figure arrived at? How are you measuring it? 1W doesn't sound much, but it can go a long way on 40M., given an efficient antenna system with short, low-loss feeder and matched radiation resistance. I am running this into a dipole cut for 40 meters, which is 7 feet off the ground. That's *way* too low! As you must know for any ariel, you gotta get that thing up as high off the ground as you can and that's even more important at low frequencies like 7Mhz. I'm using fundamental frequency HC6/U crystals for 7110 and 7125 kHz. I've been trying for 2 weeks, at all hours of the day and night, and have had no indication that anyone hears me. I've called CQ, and I've attempted to answer CQ's. Nothing, after about 100 tries. I know it's impossible for any of you to know exactly what's wrong, but I'd like to see what opinions I can glean here. Is there any reason why I should use FT-243 crystals, as specified in the article and on the website? I used HC6/U crystals because they were easy to get. One of the transistors (Q2) is supposed to be heat sinked. I have put a large homemeade heat sink on this, using plenty of heat sink grease, and it gets so hot I can barely touch it. Something's wrong, then. The heat dissipated in your final transistor should equate to the output power at the antenna if the system is matched properly. Sounds like your tranny's trying to dissipate rather more than a Watt. Are you sure you don't have a feeder/matching problem somewhere? Have you cut the ariel to the right length? Are you using a balun? Have you tried a substitute balun? Also, the transmitter chirps a bit at the beginning of each transmission, but settles down after a few strokes of the key. Many thanks for any help you can give. Get another ham a couple of miles away from you to give you a signal report. It might show up something useful. -- "Windows [n.], A thirty-two bit extension and GUI shell to a sixteen bit patch to an eight bit operating system originally coded for a four bit microprocessor and produced by a two bit company." |
On Sun, 05 Oct 2003 04:42:11 GMT,
(John Sandin) wrote: I am a new technician with code privileges. I built the following CW transmitter for 40 meters: http://cs.okanagan.bc.ca/ve7ouc/eng/...nsmitter2.html It's a solid state 3-watter, based on an article in QST in June 1967. I used a printed circuit board instead of wiring everything together directly, as the QST article suggests. So, there are many wires running from various parts mounted on the chassis to the circuit board. I'm getting very little output. After tuning the transmitter, per the specs, and measuring the output using the method suggested by the author of the web page, I figure I'm getting 1 watt or less. How is this figure arrived at? How are you measuring it? 1W doesn't sound much, but it can go a long way on 40M., given an efficient antenna system with short, low-loss feeder and matched radiation resistance. I am running this into a dipole cut for 40 meters, which is 7 feet off the ground. That's *way* too low! As you must know for any ariel, you gotta get that thing up as high off the ground as you can and that's even more important at low frequencies like 7Mhz. I'm using fundamental frequency HC6/U crystals for 7110 and 7125 kHz. I've been trying for 2 weeks, at all hours of the day and night, and have had no indication that anyone hears me. I've called CQ, and I've attempted to answer CQ's. Nothing, after about 100 tries. I know it's impossible for any of you to know exactly what's wrong, but I'd like to see what opinions I can glean here. Is there any reason why I should use FT-243 crystals, as specified in the article and on the website? I used HC6/U crystals because they were easy to get. One of the transistors (Q2) is supposed to be heat sinked. I have put a large homemeade heat sink on this, using plenty of heat sink grease, and it gets so hot I can barely touch it. Something's wrong, then. The heat dissipated in your final transistor should equate to the output power at the antenna if the system is matched properly. Sounds like your tranny's trying to dissipate rather more than a Watt. Are you sure you don't have a feeder/matching problem somewhere? Have you cut the ariel to the right length? Are you using a balun? Have you tried a substitute balun? Also, the transmitter chirps a bit at the beginning of each transmission, but settles down after a few strokes of the key. Many thanks for any help you can give. Get another ham a couple of miles away from you to give you a signal report. It might show up something useful. -- "Windows [n.], A thirty-two bit extension and GUI shell to a sixteen bit patch to an eight bit operating system originally coded for a four bit microprocessor and produced by a two bit company." |
John,
I can't get your URL to bring anything up in my browser. If your final Q is getting REAL hot upon keydown in a very short period of time, I'm guessing you have some circuit issues there. I had a similar problem with a little Tuna Tin transmitter I built a couple years ago, my problem was my antenna was broken. It was not resonant on 7040, which was the crystal I had in the transmitter. It was way off. After I replaced the final a couple of times, I broke out a SWR meter and noticed the mismatch. A new dipole 15 minutes later did the trick. I run a 40m 1/2 wave dipoe in the very top of my attic peak, so it's about 30 feet off the ground...which is pretty low for 40m anyway but I get out pretty well. If you do not subscribe to QRP-L I suggest you try there for some answers. Some of the brightest low power folks in the world are there. See: http://qrp.lehigh.edu/lists/qrp-l/ 73 "John Sandin" wrote in message ... I am a new technician with code privileges. I built the following CW transmitter for 40 meters: http://cs.okanagan.bc.ca/ve7ouc/eng/...nsmitter2.html It's a solid state 3-watter, based on an article in QST in June 1967. I used a printed circuit board instead of wiring everything together directly, as the QST article suggests. So, there are many wires running from various parts mounted on the chassis to the circuit board. I'm getting very little output. After tuning the transmitter, per the specs, and measuring the output using the method suggested by the author of the web page, I figure I'm getting 1 watt or less. I am running this into a dipole cut for 40 meters, which is 7 feet off the ground. I'm using fundamental frequency HC6/U crystals for 7110 and 7125 kHz. I've been trying for 2 weeks, at all hours of the day and night, and have had no indication that anyone hears me. I've called CQ, and I've attempted to answer CQ's. Nothing, after about 100 tries. I know it's impossible for any of you to know exactly what's wrong, but I'd like to see what opinions I can glean here. Is there any reason why I should use FT-243 crystals, as specified in the article and on the website? I used HC6/U crystals because they were easy to get. One of the transistors (Q2) is supposed to be heat sinked. I have put a large homemeade heat sink on this, using plenty of heat sink grease, and it gets so hot I can barely touch it. Also, the transmitter chirps a bit at the beginning of each transmission, but settles down after a few strokes of the key. Many thanks for any help you can give. -John Sandin KC0QWE Remove the "T" to respond by e-mail |
John,
I can't get your URL to bring anything up in my browser. If your final Q is getting REAL hot upon keydown in a very short period of time, I'm guessing you have some circuit issues there. I had a similar problem with a little Tuna Tin transmitter I built a couple years ago, my problem was my antenna was broken. It was not resonant on 7040, which was the crystal I had in the transmitter. It was way off. After I replaced the final a couple of times, I broke out a SWR meter and noticed the mismatch. A new dipole 15 minutes later did the trick. I run a 40m 1/2 wave dipoe in the very top of my attic peak, so it's about 30 feet off the ground...which is pretty low for 40m anyway but I get out pretty well. If you do not subscribe to QRP-L I suggest you try there for some answers. Some of the brightest low power folks in the world are there. See: http://qrp.lehigh.edu/lists/qrp-l/ 73 "John Sandin" wrote in message ... I am a new technician with code privileges. I built the following CW transmitter for 40 meters: http://cs.okanagan.bc.ca/ve7ouc/eng/...nsmitter2.html It's a solid state 3-watter, based on an article in QST in June 1967. I used a printed circuit board instead of wiring everything together directly, as the QST article suggests. So, there are many wires running from various parts mounted on the chassis to the circuit board. I'm getting very little output. After tuning the transmitter, per the specs, and measuring the output using the method suggested by the author of the web page, I figure I'm getting 1 watt or less. I am running this into a dipole cut for 40 meters, which is 7 feet off the ground. I'm using fundamental frequency HC6/U crystals for 7110 and 7125 kHz. I've been trying for 2 weeks, at all hours of the day and night, and have had no indication that anyone hears me. I've called CQ, and I've attempted to answer CQ's. Nothing, after about 100 tries. I know it's impossible for any of you to know exactly what's wrong, but I'd like to see what opinions I can glean here. Is there any reason why I should use FT-243 crystals, as specified in the article and on the website? I used HC6/U crystals because they were easy to get. One of the transistors (Q2) is supposed to be heat sinked. I have put a large homemeade heat sink on this, using plenty of heat sink grease, and it gets so hot I can barely touch it. Also, the transmitter chirps a bit at the beginning of each transmission, but settles down after a few strokes of the key. Many thanks for any help you can give. -John Sandin KC0QWE Remove the "T" to respond by e-mail |
John,
Can you post a picture of your unit somewhere(top and bottom views) so we can see what the PCB & wiring layout looks like? Many times an improper layout can lead to parasitic oscillations that will raise DC power consumption without delivering RF on the proper frequency. Joe W3JDR "John Sandin" wrote in message ... I am a new technician with code privileges. I built the following CW transmitter for 40 meters: http://cs.okanagan.bc.ca/ve7ouc/eng/...nsmitter2.html It's a solid state 3-watter, based on an article in QST in June 1967. I used a printed circuit board instead of wiring everything together directly, as the QST article suggests. So, there are many wires running from various parts mounted on the chassis to the circuit board. I'm getting very little output. After tuning the transmitter, per the specs, and measuring the output using the method suggested by the author of the web page, I figure I'm getting 1 watt or less. I am running this into a dipole cut for 40 meters, which is 7 feet off the ground. I'm using fundamental frequency HC6/U crystals for 7110 and 7125 kHz. I've been trying for 2 weeks, at all hours of the day and night, and have had no indication that anyone hears me. I've called CQ, and I've attempted to answer CQ's. Nothing, after about 100 tries. I know it's impossible for any of you to know exactly what's wrong, but I'd like to see what opinions I can glean here. Is there any reason why I should use FT-243 crystals, as specified in the article and on the website? I used HC6/U crystals because they were easy to get. One of the transistors (Q2) is supposed to be heat sinked. I have put a large homemeade heat sink on this, using plenty of heat sink grease, and it gets so hot I can barely touch it. Also, the transmitter chirps a bit at the beginning of each transmission, but settles down after a few strokes of the key. Many thanks for any help you can give. -John Sandin KC0QWE Remove the "T" to respond by e-mail |
John,
Can you post a picture of your unit somewhere(top and bottom views) so we can see what the PCB & wiring layout looks like? Many times an improper layout can lead to parasitic oscillations that will raise DC power consumption without delivering RF on the proper frequency. Joe W3JDR "John Sandin" wrote in message ... I am a new technician with code privileges. I built the following CW transmitter for 40 meters: http://cs.okanagan.bc.ca/ve7ouc/eng/...nsmitter2.html It's a solid state 3-watter, based on an article in QST in June 1967. I used a printed circuit board instead of wiring everything together directly, as the QST article suggests. So, there are many wires running from various parts mounted on the chassis to the circuit board. I'm getting very little output. After tuning the transmitter, per the specs, and measuring the output using the method suggested by the author of the web page, I figure I'm getting 1 watt or less. I am running this into a dipole cut for 40 meters, which is 7 feet off the ground. I'm using fundamental frequency HC6/U crystals for 7110 and 7125 kHz. I've been trying for 2 weeks, at all hours of the day and night, and have had no indication that anyone hears me. I've called CQ, and I've attempted to answer CQ's. Nothing, after about 100 tries. I know it's impossible for any of you to know exactly what's wrong, but I'd like to see what opinions I can glean here. Is there any reason why I should use FT-243 crystals, as specified in the article and on the website? I used HC6/U crystals because they were easy to get. One of the transistors (Q2) is supposed to be heat sinked. I have put a large homemeade heat sink on this, using plenty of heat sink grease, and it gets so hot I can barely touch it. Also, the transmitter chirps a bit at the beginning of each transmission, but settles down after a few strokes of the key. Many thanks for any help you can give. -John Sandin KC0QWE Remove the "T" to respond by e-mail |
It really doesn't matter what frequency the application is, modern
transistors have good gain well into the UHF range and VHF parasitic oscillations can occur even in an audio application Joe W3JDR "Paul Burridge" wrote in message ... On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote: John, Can you post a picture of your unit somewhere(top and bottom views) so we can see what the PCB & wiring layout looks like? Many times an improper layout can lead to parasitic oscillations that will raise DC power consumption without delivering RF on the proper frequency. It's worth a try, John. But 7Mhz is practically DC these days so strays and paracitics shouldn't be too much of a problem. One thing I meant to suggest in my earlier post was that the OP should try transmitting into a known good 50 ohm dummy load and seeing if his final tranny still gets as hot. That ought to be a real good clue as to whether he does have some probem with his matching/antenna/feedline etc.. -- "Windows [n.], A thirty-two bit extension and GUI shell to a sixteen bit patch to an eight bit operating system originally coded for a four bit microprocessor and produced by a two bit company." |
It really doesn't matter what frequency the application is, modern
transistors have good gain well into the UHF range and VHF parasitic oscillations can occur even in an audio application Joe W3JDR "Paul Burridge" wrote in message ... On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote: John, Can you post a picture of your unit somewhere(top and bottom views) so we can see what the PCB & wiring layout looks like? Many times an improper layout can lead to parasitic oscillations that will raise DC power consumption without delivering RF on the proper frequency. It's worth a try, John. But 7Mhz is practically DC these days so strays and paracitics shouldn't be too much of a problem. One thing I meant to suggest in my earlier post was that the OP should try transmitting into a known good 50 ohm dummy load and seeing if his final tranny still gets as hot. That ought to be a real good clue as to whether he does have some probem with his matching/antenna/feedline etc.. -- "Windows [n.], A thirty-two bit extension and GUI shell to a sixteen bit patch to an eight bit operating system originally coded for a four bit microprocessor and produced by a two bit company." |
On Sun, 05 Oct 2003 13:50:43 +0100, Paul Burridge
wrote: snip I'm getting very little output. After tuning the transmitter, per the specs, and measuring the output using the method suggested by the author of the web page, I figure I'm getting 1 watt or less. How is this figure arrived at? How are you measuring it? 1W doesn't sound much, but it can go a long way on 40M., given an efficient antenna system with short, low-loss feeder and matched radiation resistance. Voltage is measured across my 50 ohm dummy load and rectified using a ..05 mfd ceramic disc cap and a 1N34A diode. Then I'm calculating thusly: Power = (Voltage x Voltage) / 50 I'm taking the author's word that this works for a ballpark estimate. I'm measuring 7 volts across the load, maximum, which works out to 1 watt or less. I've verified that my meter is accurate. I am running this into a dipole cut for 40 meters, which is 7 feet off the ground. That's *way* too low! As you must know for any ariel, you gotta get that thing up as high off the ground as you can and that's even more important at low frequencies like 7Mhz. We have a mess of power lines around the house, so it's hard to find a spot to even get it 7 feet high in a straight line. I'm thinking about trying it on the roof, which is about 20 feet high at the highest point, and mabye angling it in the center. One of the transistors (Q2) is supposed to be heat sinked. I have put a large homemeade heat sink on this, using plenty of heat sink grease, and it gets so hot I can barely touch it. Something's wrong, then. The heat dissipated in your final transistor should equate to the output power at the antenna if the system is matched properly. Sounds like your tranny's trying to dissipate rather more than a Watt. Are you sure you don't have a feeder/matching problem somewhere? Have you cut the ariel to the right length? Are you using a balun? Have you tried a substitute balun? The length of each element is 32' 11", which I calculated for use at 7110 kHz. There's no balun; I'm using coax, the shield is connected to one element and the center conductor is connected to the other. The coax might be 75 ohm. Pretty soon I'll have RG-58 for the entire run, but right now it's a mix of RG-6/U and RG-59/U. Get another ham a couple of miles away from you to give you a signal report. It might show up something useful. I will do that. Thanks. -- -John Sandin KC0QWE Remove the "T" to respond by e-mail |
On Sun, 05 Oct 2003 13:50:43 +0100, Paul Burridge
wrote: snip I'm getting very little output. After tuning the transmitter, per the specs, and measuring the output using the method suggested by the author of the web page, I figure I'm getting 1 watt or less. How is this figure arrived at? How are you measuring it? 1W doesn't sound much, but it can go a long way on 40M., given an efficient antenna system with short, low-loss feeder and matched radiation resistance. Voltage is measured across my 50 ohm dummy load and rectified using a ..05 mfd ceramic disc cap and a 1N34A diode. Then I'm calculating thusly: Power = (Voltage x Voltage) / 50 I'm taking the author's word that this works for a ballpark estimate. I'm measuring 7 volts across the load, maximum, which works out to 1 watt or less. I've verified that my meter is accurate. I am running this into a dipole cut for 40 meters, which is 7 feet off the ground. That's *way* too low! As you must know for any ariel, you gotta get that thing up as high off the ground as you can and that's even more important at low frequencies like 7Mhz. We have a mess of power lines around the house, so it's hard to find a spot to even get it 7 feet high in a straight line. I'm thinking about trying it on the roof, which is about 20 feet high at the highest point, and mabye angling it in the center. One of the transistors (Q2) is supposed to be heat sinked. I have put a large homemeade heat sink on this, using plenty of heat sink grease, and it gets so hot I can barely touch it. Something's wrong, then. The heat dissipated in your final transistor should equate to the output power at the antenna if the system is matched properly. Sounds like your tranny's trying to dissipate rather more than a Watt. Are you sure you don't have a feeder/matching problem somewhere? Have you cut the ariel to the right length? Are you using a balun? Have you tried a substitute balun? The length of each element is 32' 11", which I calculated for use at 7110 kHz. There's no balun; I'm using coax, the shield is connected to one element and the center conductor is connected to the other. The coax might be 75 ohm. Pretty soon I'll have RG-58 for the entire run, but right now it's a mix of RG-6/U and RG-59/U. Get another ham a couple of miles away from you to give you a signal report. It might show up something useful. I will do that. Thanks. -- -John Sandin KC0QWE Remove the "T" to respond by e-mail |
I will try to do that sometime during the next day or so. The author
of the website says that the layout isn't critical, and his version of the project works great. But when I look at the original QST article and the photos of how they did it (all direct-wired), I'm amazed at how simple they were able to keep the assembly. So now I'm wondering why I bothered to use a printed circuit board in the first place. On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote: John, Can you post a picture of your unit somewhere(top and bottom views) so we can see what the PCB & wiring layout looks like? Many times an improper layout can lead to parasitic oscillations that will raise DC power consumption without delivering RF on the proper frequency. Joe W3JDR -John Sandin KC0QWE Remove the "T" to respond by e-mail |
I will try to do that sometime during the next day or so. The author
of the website says that the layout isn't critical, and his version of the project works great. But when I look at the original QST article and the photos of how they did it (all direct-wired), I'm amazed at how simple they were able to keep the assembly. So now I'm wondering why I bothered to use a printed circuit board in the first place. On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote: John, Can you post a picture of your unit somewhere(top and bottom views) so we can see what the PCB & wiring layout looks like? Many times an improper layout can lead to parasitic oscillations that will raise DC power consumption without delivering RF on the proper frequency. Joe W3JDR -John Sandin KC0QWE Remove the "T" to respond by e-mail |
The fact that the connection between the top of L2 and the base of Q2 is
marked as coax is probably a clue that layout is critical. ... "Roy Lewallen" wrote in message ... A hot transistor combined with low output power makes me suspect that the transistor is either parasitically oscillating or trying to produce a lot of harmonic energy. |
The fact that the connection between the top of L2 and the base of Q2 is
marked as coax is probably a clue that layout is critical. ... "Roy Lewallen" wrote in message ... A hot transistor combined with low output power makes me suspect that the transistor is either parasitically oscillating or trying to produce a lot of harmonic energy. |
Working people with one watt can be challenging, but certainly not
impossible. In the course of a few years, I worked (and confirmed) all 50 states and 33 countries on 40 meters with about 1.5 watts output. Your antenna height is a big handicap. 7 feet is severely low for a 40 meter antenna. While you'll still be able to hear stations just fine, it'll produce a very weak signal from an already weak transmitter. If there's any way possible, make the antenna higher. I'd strive for at least 30 feet if possible; higher than that is better yet. Another option is to use a vertical. With even a poor to moderate ground system -- even a couple of ground radials (more would be better) -- it'll do much better than the very low dipole. A hot transistor combined with low output power makes me suspect that the transistor is either parasitically oscillating or trying to produce a lot of harmonic energy. That means that you could be producing only a tiny amount of power on the desired frequency -- much less than even a watt. Pull the antenna off your receiver and tune around. Does the signal from your rig sound hissy or hashy? Are the signals at harmonic frequencies as strong as or stronger than the signal at the desired frequency? Set up a sked with a ham that's a few miles away (whom you can locate through a local club), and have him tell you what your signal sounds like. Have him listen for harmonics, birdies, or other signs of instability. Finally, you need to be aware that a crystal-controlled transmitter can be a big handicap these days. People don't often tune off their own frequency to listen, and they're likely to have a pretty narrow filter, so you're not likely to get a response unless you're lucky enough to be very close to their frequency. That said, your success rate should be higher when calling someone than when calling CQ, since people are more prone to respond to a weak signal calling them than to one calling CQ. But only if you're on their frequency so they can hear you. I couldn't get the link to the URL to work, so couldn't look at the transmitter schematic. However, after you get the other problems fixed, consider modifying the rig to VXO operation (where you're able to move the frequency a bit) if it's not already VXO. There's no reason you can't substitute HC-6 crystals for FT-243 in a rig like this. Roy Lewallen, W7EL John Sandin wrote: I am a new technician with code privileges. I built the following CW transmitter for 40 meters: http://cs.okanagan.bc.ca/ve7ouc/eng/...nsmitter2.html It's a solid state 3-watter, based on an article in QST in June 1967. I used a printed circuit board instead of wiring everything together directly, as the QST article suggests. So, there are many wires running from various parts mounted on the chassis to the circuit board. I'm getting very little output. After tuning the transmitter, per the specs, and measuring the output using the method suggested by the author of the web page, I figure I'm getting 1 watt or less. I am running this into a dipole cut for 40 meters, which is 7 feet off the ground. I'm using fundamental frequency HC6/U crystals for 7110 and 7125 kHz. I've been trying for 2 weeks, at all hours of the day and night, and have had no indication that anyone hears me. I've called CQ, and I've attempted to answer CQ's. Nothing, after about 100 tries. I know it's impossible for any of you to know exactly what's wrong, but I'd like to see what opinions I can glean here. Is there any reason why I should use FT-243 crystals, as specified in the article and on the website? I used HC6/U crystals because they were easy to get. One of the transistors (Q2) is supposed to be heat sinked. I have put a large homemeade heat sink on this, using plenty of heat sink grease, and it gets so hot I can barely touch it. Also, the transmitter chirps a bit at the beginning of each transmission, but settles down after a few strokes of the key. Many thanks for any help you can give. -John Sandin KC0QWE Remove the "T" to respond by e-mail |
Working people with one watt can be challenging, but certainly not
impossible. In the course of a few years, I worked (and confirmed) all 50 states and 33 countries on 40 meters with about 1.5 watts output. Your antenna height is a big handicap. 7 feet is severely low for a 40 meter antenna. While you'll still be able to hear stations just fine, it'll produce a very weak signal from an already weak transmitter. If there's any way possible, make the antenna higher. I'd strive for at least 30 feet if possible; higher than that is better yet. Another option is to use a vertical. With even a poor to moderate ground system -- even a couple of ground radials (more would be better) -- it'll do much better than the very low dipole. A hot transistor combined with low output power makes me suspect that the transistor is either parasitically oscillating or trying to produce a lot of harmonic energy. That means that you could be producing only a tiny amount of power on the desired frequency -- much less than even a watt. Pull the antenna off your receiver and tune around. Does the signal from your rig sound hissy or hashy? Are the signals at harmonic frequencies as strong as or stronger than the signal at the desired frequency? Set up a sked with a ham that's a few miles away (whom you can locate through a local club), and have him tell you what your signal sounds like. Have him listen for harmonics, birdies, or other signs of instability. Finally, you need to be aware that a crystal-controlled transmitter can be a big handicap these days. People don't often tune off their own frequency to listen, and they're likely to have a pretty narrow filter, so you're not likely to get a response unless you're lucky enough to be very close to their frequency. That said, your success rate should be higher when calling someone than when calling CQ, since people are more prone to respond to a weak signal calling them than to one calling CQ. But only if you're on their frequency so they can hear you. I couldn't get the link to the URL to work, so couldn't look at the transmitter schematic. However, after you get the other problems fixed, consider modifying the rig to VXO operation (where you're able to move the frequency a bit) if it's not already VXO. There's no reason you can't substitute HC-6 crystals for FT-243 in a rig like this. Roy Lewallen, W7EL John Sandin wrote: I am a new technician with code privileges. I built the following CW transmitter for 40 meters: http://cs.okanagan.bc.ca/ve7ouc/eng/...nsmitter2.html It's a solid state 3-watter, based on an article in QST in June 1967. I used a printed circuit board instead of wiring everything together directly, as the QST article suggests. So, there are many wires running from various parts mounted on the chassis to the circuit board. I'm getting very little output. After tuning the transmitter, per the specs, and measuring the output using the method suggested by the author of the web page, I figure I'm getting 1 watt or less. I am running this into a dipole cut for 40 meters, which is 7 feet off the ground. I'm using fundamental frequency HC6/U crystals for 7110 and 7125 kHz. I've been trying for 2 weeks, at all hours of the day and night, and have had no indication that anyone hears me. I've called CQ, and I've attempted to answer CQ's. Nothing, after about 100 tries. I know it's impossible for any of you to know exactly what's wrong, but I'd like to see what opinions I can glean here. Is there any reason why I should use FT-243 crystals, as specified in the article and on the website? I used HC6/U crystals because they were easy to get. One of the transistors (Q2) is supposed to be heat sinked. I have put a large homemeade heat sink on this, using plenty of heat sink grease, and it gets so hot I can barely touch it. Also, the transmitter chirps a bit at the beginning of each transmission, but settles down after a few strokes of the key. Many thanks for any help you can give. -John Sandin KC0QWE Remove the "T" to respond by e-mail |
The circuit you describe should be delivering approximately the peak
voltage, not RMS, so the formula is more like V X V / 100. At 7 volts peak, that means you're putting out around 1/2 watt. That's a lot below the 3 watt figure you mentioned, so you should track down why it's so much lower. Pay special care to the circuit components in the final transistor output (collector) circuit, and make sure the inductors are built as described and the components are connected correctly. Roy Lewallen, W7EL John Sandin wrote: . . . Voltage is measured across my 50 ohm dummy load and rectified using a .05 mfd ceramic disc cap and a 1N34A diode. Then I'm calculating thusly: Power = (Voltage x Voltage) / 50 I'm taking the author's word that this works for a ballpark estimate. I'm measuring 7 volts across the load, maximum, which works out to 1 watt or less. I've verified that my meter is accurate. . . . |
The circuit you describe should be delivering approximately the peak
voltage, not RMS, so the formula is more like V X V / 100. At 7 volts peak, that means you're putting out around 1/2 watt. That's a lot below the 3 watt figure you mentioned, so you should track down why it's so much lower. Pay special care to the circuit components in the final transistor output (collector) circuit, and make sure the inductors are built as described and the components are connected correctly. Roy Lewallen, W7EL John Sandin wrote: . . . Voltage is measured across my 50 ohm dummy load and rectified using a .05 mfd ceramic disc cap and a 1N34A diode. Then I'm calculating thusly: Power = (Voltage x Voltage) / 50 I'm taking the author's word that this works for a ballpark estimate. I'm measuring 7 volts across the load, maximum, which works out to 1 watt or less. I've verified that my meter is accurate. . . . |
On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote: John, Can you post a picture of your unit somewhere(top and bottom views) so we can see what the PCB & wiring layout looks like? I want to thank everyone. I never dreamed that I'd get so many great responses, within a few hours of my original post. I have put up a website with a link to the web page that inspired me to do this. Below that are a bunch of pics of my project. Any comments and advice are welcome. I guess it would have been easier and even cheaper to buy a kit. But I had fun building this, and I guess I'll have almost as much fun rebuilding it. -John Sandin KC0QWE Remove the "T" to respond by e-mail |
On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote: John, Can you post a picture of your unit somewhere(top and bottom views) so we can see what the PCB & wiring layout looks like? I want to thank everyone. I never dreamed that I'd get so many great responses, within a few hours of my original post. I have put up a website with a link to the web page that inspired me to do this. Below that are a bunch of pics of my project. Any comments and advice are welcome. I guess it would have been easier and even cheaper to buy a kit. But I had fun building this, and I guess I'll have almost as much fun rebuilding it. -John Sandin KC0QWE Remove the "T" to respond by e-mail |
Here's the link to my project website..
http://www.kcnet.com/~oyster/transmi...ansmitter.html On Mon, 06 Oct 2003 02:56:38 GMT, (John Sandin) wrote: On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote: John, Can you post a picture of your unit somewhere(top and bottom views) so we can see what the PCB & wiring layout looks like? I want to thank everyone. I never dreamed that I'd get so many great responses, within a few hours of my original post. I have put up a website with a link to the web page that inspired me to do this. Below that are a bunch of pics of my project. Any comments and advice are welcome. I guess it would have been easier and even cheaper to buy a kit. But I had fun building this, and I guess I'll have almost as much fun rebuilding it. -John Sandin KC0QWE Remove the "T" to respond by e-mail -John Sandin KC0QWE Remove the "T" to respond by e-mail |
Here's the link to my project website..
http://www.kcnet.com/~oyster/transmi...ansmitter.html On Mon, 06 Oct 2003 02:56:38 GMT, (John Sandin) wrote: On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote: John, Can you post a picture of your unit somewhere(top and bottom views) so we can see what the PCB & wiring layout looks like? I want to thank everyone. I never dreamed that I'd get so many great responses, within a few hours of my original post. I have put up a website with a link to the web page that inspired me to do this. Below that are a bunch of pics of my project. Any comments and advice are welcome. I guess it would have been easier and even cheaper to buy a kit. But I had fun building this, and I guess I'll have almost as much fun rebuilding it. -John Sandin KC0QWE Remove the "T" to respond by e-mail -John Sandin KC0QWE Remove the "T" to respond by e-mail |
John,
I had a look. The outside cosmetics are very nice, but the internal wiring is kind of scary for RF. I suspect you have a lot of coupling between the wires that are bundled together. In a more ideal setup, the PCB would have been mounted directly on or very near to the two coils and tuning caps. Here are my suggestions for troublehooting. Do them one at a time and see if any of them make a major difference: 1) Remove the lowpass filter and mearure the RF output again . Maybe the filter cutoff frequency is wrong. 2) Unbundle the wires and spread them apart. Does that improve anything? 3) Remove any interconnect wiring that isn't absolutely essential for RF operation. Strap the switch lines to their proper state on the PCB & remove lamp wiring. See if that improves things. 4) Measure the overall DC current and the DC current into the amplifier stage only. When the amplifier is driven properly, getting 3 watts RF out will require about 4-5 watts of DC into the final (Vfinal x Ifinal). If the current is much too low, check out whether the oscillator stage is driving it properly. If it's too high for the RF you're seeing, check the final stage tuning and possibility of an oscillation. Good Luck, Joe W3JDR "John Sandin" wrote in message ... Here's the link to my project website.. http://www.kcnet.com/~oyster/transmi...ansmitter.html On Mon, 06 Oct 2003 02:56:38 GMT, (John Sandin) wrote: On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote: John, Can you post a picture of your unit somewhere(top and bottom views) so we can see what the PCB & wiring layout looks like? I want to thank everyone. I never dreamed that I'd get so many great responses, within a few hours of my original post. I have put up a website with a link to the web page that inspired me to do this. Below that are a bunch of pics of my project. Any comments and advice are welcome. I guess it would have been easier and even cheaper to buy a kit. But I had fun building this, and I guess I'll have almost as much fun rebuilding it. -John Sandin KC0QWE Remove the "T" to respond by e-mail -John Sandin KC0QWE Remove the "T" to respond by e-mail |
John,
I had a look. The outside cosmetics are very nice, but the internal wiring is kind of scary for RF. I suspect you have a lot of coupling between the wires that are bundled together. In a more ideal setup, the PCB would have been mounted directly on or very near to the two coils and tuning caps. Here are my suggestions for troublehooting. Do them one at a time and see if any of them make a major difference: 1) Remove the lowpass filter and mearure the RF output again . Maybe the filter cutoff frequency is wrong. 2) Unbundle the wires and spread them apart. Does that improve anything? 3) Remove any interconnect wiring that isn't absolutely essential for RF operation. Strap the switch lines to their proper state on the PCB & remove lamp wiring. See if that improves things. 4) Measure the overall DC current and the DC current into the amplifier stage only. When the amplifier is driven properly, getting 3 watts RF out will require about 4-5 watts of DC into the final (Vfinal x Ifinal). If the current is much too low, check out whether the oscillator stage is driving it properly. If it's too high for the RF you're seeing, check the final stage tuning and possibility of an oscillation. Good Luck, Joe W3JDR "John Sandin" wrote in message ... Here's the link to my project website.. http://www.kcnet.com/~oyster/transmi...ansmitter.html On Mon, 06 Oct 2003 02:56:38 GMT, (John Sandin) wrote: On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote: John, Can you post a picture of your unit somewhere(top and bottom views) so we can see what the PCB & wiring layout looks like? I want to thank everyone. I never dreamed that I'd get so many great responses, within a few hours of my original post. I have put up a website with a link to the web page that inspired me to do this. Below that are a bunch of pics of my project. Any comments and advice are welcome. I guess it would have been easier and even cheaper to buy a kit. But I had fun building this, and I guess I'll have almost as much fun rebuilding it. -John Sandin KC0QWE Remove the "T" to respond by e-mail -John Sandin KC0QWE Remove the "T" to respond by e-mail |
"John Sandin" wrote in message
... I guess it would have been easier and even cheaper to buy a kit. But I had fun building this, and I guess I'll have almost as much fun rebuilding it. One of the wonderful things about amateur radio is that there are so many facets to explore. Each of us finds his own favorites, but in my mind, there are few things in life as fun as building and operating your own equipment. Your low pass filter leaps out at me. Typically, the coil windings are spread out over 80% of the toroid, rather than 20%. If, in fact, this was the intent of the low pass filter design, then your inductances could be quite a way off. Not only would this change the cutoff frequency of your LPF (raising it most probably, so not likely the direct cause of low output), but it would also change the impedance the transmitter sees. (I'm leaping to the conclusion here that the LPF is between the transmitter and the antenna). What this means is that the transmitter isn't seeing 50 ohms even if your antenna is resonant. This would result in the final heating, and could also favor the parasitics that I suspect we have going on here. As you explore what's going on here, keep in mind that these things aren't magic, what they do is always goverened by the laws of physics. Validate by measurement that what you think is happening is, in fact, what is going on. You really don't need a ton of test equipment. Granted, lacking lots of gear, each measurement can be a bit of a project in itself, but once you have a DMM and have built an RF probe (about a buck's worth of parts), you can make pretty much any measurement if you think it through. ... |
"John Sandin" wrote in message
... I guess it would have been easier and even cheaper to buy a kit. But I had fun building this, and I guess I'll have almost as much fun rebuilding it. One of the wonderful things about amateur radio is that there are so many facets to explore. Each of us finds his own favorites, but in my mind, there are few things in life as fun as building and operating your own equipment. Your low pass filter leaps out at me. Typically, the coil windings are spread out over 80% of the toroid, rather than 20%. If, in fact, this was the intent of the low pass filter design, then your inductances could be quite a way off. Not only would this change the cutoff frequency of your LPF (raising it most probably, so not likely the direct cause of low output), but it would also change the impedance the transmitter sees. (I'm leaping to the conclusion here that the LPF is between the transmitter and the antenna). What this means is that the transmitter isn't seeing 50 ohms even if your antenna is resonant. This would result in the final heating, and could also favor the parasitics that I suspect we have going on here. As you explore what's going on here, keep in mind that these things aren't magic, what they do is always goverened by the laws of physics. Validate by measurement that what you think is happening is, in fact, what is going on. You really don't need a ton of test equipment. Granted, lacking lots of gear, each measurement can be a bit of a project in itself, but once you have a DMM and have built an RF probe (about a buck's worth of parts), you can make pretty much any measurement if you think it through. ... |
John Sandin wrote: Here's the link to my project website.. http://www.kcnet.com/~oyster/transmi...ansmitter.html Your heatsink (at least, I think it's the heatsink) is inefficient (finless), and you mentioned using lots of heat sink grease. You *can* have too much grease. Putting in a bigger sink with fins and a small amount of heatsink compound won't fix your problem - but it may be a good idea, once you have fixed it. The fact that the xsistor is heating up at least means that the rig is "making power". If we assume that the power it's making is RF at the right frequency, then suspect the output circuit from the collector outwards up to and including the antenna. And, with your antenna at 7 feet, and fed by a questionable mix of coax, it may be the source of the trouble. Try feeding the rig into a good 50 ohm dummy load and see if that allows the transistor to run cooler. |
John Sandin wrote: Here's the link to my project website.. http://www.kcnet.com/~oyster/transmi...ansmitter.html Your heatsink (at least, I think it's the heatsink) is inefficient (finless), and you mentioned using lots of heat sink grease. You *can* have too much grease. Putting in a bigger sink with fins and a small amount of heatsink compound won't fix your problem - but it may be a good idea, once you have fixed it. The fact that the xsistor is heating up at least means that the rig is "making power". If we assume that the power it's making is RF at the right frequency, then suspect the output circuit from the collector outwards up to and including the antenna. And, with your antenna at 7 feet, and fed by a questionable mix of coax, it may be the source of the trouble. Try feeding the rig into a good 50 ohm dummy load and see if that allows the transistor to run cooler. |
(John Sandin) wrote in message ...
I am a new technician with code privileges. I built the following CW transmitter for 40 meters: http://cs.okanagan.bc.ca/ve7ouc/eng/...nsmitter2.html It's a solid state 3-watter, based on an article in QST in June 1967. I used a printed circuit board instead of wiring everything together directly, as the QST article suggests. So, there are many wires running from various parts mounted on the chassis to the circuit board. I think all those wires, and the stray L and C they introduce, is the heart of your problem with getting it to work right. I'd try building it as close to the way the original article showed as possible. An inexpensive bread or cake pan can be a good chassis, and easy to wrok. I am running this into a dipole cut for 40 meters, which is 7 feet off the ground. I'm using fundamental frequency HC6/U crystals for 7110 and 7125 kHz. I've been trying for 2 weeks, at all hours of the day and night, and have had no indication that anyone hears me. I've called CQ, and I've attempted to answer CQ's. Nothing, after about 100 tries. 7 feet off the ground is less than 1/16 wavelength on 40 meters. That's just too low. One of the transistors (Q2) is supposed to be heat sinked. I have put a large homemeade heat sink on this, using plenty of heat sink grease, and it gets so hot I can barely touch it. That's not right. You may have cooked that transistor. 73 es GL de Jim, N2EY |
(John Sandin) wrote in message ...
I am a new technician with code privileges. I built the following CW transmitter for 40 meters: http://cs.okanagan.bc.ca/ve7ouc/eng/...nsmitter2.html It's a solid state 3-watter, based on an article in QST in June 1967. I used a printed circuit board instead of wiring everything together directly, as the QST article suggests. So, there are many wires running from various parts mounted on the chassis to the circuit board. I think all those wires, and the stray L and C they introduce, is the heart of your problem with getting it to work right. I'd try building it as close to the way the original article showed as possible. An inexpensive bread or cake pan can be a good chassis, and easy to wrok. I am running this into a dipole cut for 40 meters, which is 7 feet off the ground. I'm using fundamental frequency HC6/U crystals for 7110 and 7125 kHz. I've been trying for 2 weeks, at all hours of the day and night, and have had no indication that anyone hears me. I've called CQ, and I've attempted to answer CQ's. Nothing, after about 100 tries. 7 feet off the ground is less than 1/16 wavelength on 40 meters. That's just too low. One of the transistors (Q2) is supposed to be heat sinked. I have put a large homemeade heat sink on this, using plenty of heat sink grease, and it gets so hot I can barely touch it. That's not right. You may have cooked that transistor. 73 es GL de Jim, N2EY |
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