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#1
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amplifier
Hi there.
Another Amateur that is involved with volunteering with schools and such is looking at launching a baloon with an HF transmitter on board. The band of operation is 80 meters. He is looking at some type of a beacon that will send data via BPSK modulation and needs 10 to 20 watts of transmit power at the output port. For an input to the unit he has 0dBm or 1 milliwatt of RF at the operating frequency. This looks like it would require 40 to 43 dB of gain to get to the level that he needs for output. Does anyone have suggestions of places to look on the web for application notes and/or schematics for amplifiers along these lines? I have done some searching on Google and found a few things but most of them take inputs of 30dBm or so and only take that level up to 40dBm. He still needs to bridge the gap from 0 dBm to 30 dBm in that instance. Any information that you can help with is greatly appreciated. Al Butler ka0ies |
#2
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This looks like it would require 40 to 43 dB of gain to get to the level
that he needs for output. Does anyone have suggestions of places to look on the web for application notes and/or schematics for amplifiers along these lines? I have done some searching on Google and found a few things but most of them take inputs of 30dBm or so and only take that level up to 40dBm. He still needs to bridge the gap from 0 dBm to 30 dBm in that instance. Hmmm. Seems to me that many of the VFO-and-mixer QRP CW/SSB transmitter projects might have suitable designs... a few milliwatts out of the mixer and bandpass filter, into a one- or two-gain-stage driver which would then push power out to the final transistor(s). Let's see. The Small Wonder Labs PSK-20 transmitters seem like a good place to start looking. The schematic shows that the transmit circuitry uses a Minicircuits TUF-1 mixer. According to the Minicircuits web page, this takes as input a +7 dBm local oscillator and up to 1 dBm of RF. It has a conversion loss in the 7-8 dBm range, so you'd end up with somewhere around -6 dBm at most coming out of it. The PSK-20 transmitter buffers this through a transistor, then through a MAR-35M monolithic amplifier, and then through a 2SC1970 and 2SC1971, and ends up with 2.5 watts of power. Seems to me that you could probably fiddle with this final stage a bit (double up on the 2SC1971, heatsink 'em, run at a higher current level, and adjust the driver circuitry to suit) and end up with 10 watts out. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
#3
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Dave Platt wrote:
This looks like it would require 40 to 43 dB of gain to get to the level that he needs for output. Does anyone have suggestions of places to look on the web for application notes and/or schematics for amplifiers along these lines? I have done some searching on Google and found a few things but most of them take inputs of 30dBm or so and only take that level up to 40dBm. He still needs to bridge the gap from 0 dBm to 30 dBm in that instance. Hmmm. Seems to me that many of the VFO-and-mixer QRP CW/SSB transmitter projects might have suitable designs... a few milliwatts out of the mixer and bandpass filter, into a one- or two-gain-stage driver which would then push power out to the final transistor(s). Let's see. The Small Wonder Labs PSK-20 transmitters seem like a good place to start looking. The schematic shows that the transmit circuitry uses a Minicircuits TUF-1 mixer. According to the Minicircuits web page, this takes as input a +7 dBm local oscillator and up to 1 dBm of RF. It has a conversion loss in the 7-8 dBm range, so you'd end up with somewhere around -6 dBm at most coming out of it. The PSK-20 transmitter buffers this through a transistor, then through a MAR-35M monolithic amplifier, and then through a 2SC1970 and 2SC1971, and ends up with 2.5 watts of power. Seems to me that you could probably fiddle with this final stage a bit (double up on the 2SC1971, heatsink 'em, run at a higher current level, and adjust the driver circuitry to suit) and end up with 10 watts out. Thanks for the information. I will check it out and pass it on to the persons that were looking for it. Al Butler ka0ies |
#4
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Dave Platt wrote:
This looks like it would require 40 to 43 dB of gain to get to the level that he needs for output. Does anyone have suggestions of places to look on the web for application notes and/or schematics for amplifiers along these lines? I have done some searching on Google and found a few things but most of them take inputs of 30dBm or so and only take that level up to 40dBm. He still needs to bridge the gap from 0 dBm to 30 dBm in that instance. Hmmm. Seems to me that many of the VFO-and-mixer QRP CW/SSB transmitter projects might have suitable designs... a few milliwatts out of the mixer and bandpass filter, into a one- or two-gain-stage driver which would then push power out to the final transistor(s). Let's see. The Small Wonder Labs PSK-20 transmitters seem like a good place to start looking. The schematic shows that the transmit circuitry uses a Minicircuits TUF-1 mixer. According to the Minicircuits web page, this takes as input a +7 dBm local oscillator and up to 1 dBm of RF. It has a conversion loss in the 7-8 dBm range, so you'd end up with somewhere around -6 dBm at most coming out of it. The PSK-20 transmitter buffers this through a transistor, then through a MAR-35M monolithic amplifier, and then through a 2SC1970 and 2SC1971, and ends up with 2.5 watts of power. Seems to me that you could probably fiddle with this final stage a bit (double up on the 2SC1971, heatsink 'em, run at a higher current level, and adjust the driver circuitry to suit) and end up with 10 watts out. Thanks for the information. I will check it out and pass it on to the persons that were looking for it. Al Butler ka0ies |
#5
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Shouldn't be too difficult to come up with the brute-force answer, but
I have to ask: Why? That is, why so much power? And why 80 meters? I'd think you'd want to use a higher frequency so that the antenna would be easier, and if the balloon is aloft and line-of-sight, even a watt should be more than enough to hear it loud-and-clear. Sending up an amplifier and a power plant that will run it at 10 watts output will take quite a bit of balloon displacement. I think it may be worth asking some system-design questions to see if he can reach a more optimal solution. Cheers, Tom Allan Butler wrote in message news:mRmEb.595184$Fm2.545419@attbi_s04... Hi there. Another Amateur that is involved with volunteering with schools and such is looking at launching a baloon with an HF transmitter on board. The band of operation is 80 meters. He is looking at some type of a beacon that will send data via BPSK modulation and needs 10 to 20 watts of transmit power at the output port. For an input to the unit he has 0dBm or 1 milliwatt of RF at the operating frequency. This looks like it would require 40 to 43 dB of gain to get to the level that he needs for output. Does anyone have suggestions of places to look on the web for application notes and/or schematics for amplifiers along these lines? I have done some searching on Google and found a few things but most of them take inputs of 30dBm or so and only take that level up to 40dBm. He still needs to bridge the gap from 0 dBm to 30 dBm in that instance. Any information that you can help with is greatly appreciated. Al Butler ka0ies |
#6
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Looking at the Dave Benson schematics is a good suggestion ... I would also
look at Elecraft who also has manuals online with schematics. I would also look at the hfpacker amp (www.hfprojects.com). This was a project ran a couple years ago to build an amp to basically take the QRP rigs in the 2.5 watt range to 30 watts or so. The design actually could do it with a watt of drive but they put an attenuator in the front to allow flexibility with different rigs that didn't have completely adjustable output power. But I also have to ask the same question Tom asks. 80 is a noisy band, and one that demands large antennas. To get past the noise you need power, and that adds a lot of weight. Don't forget, you not only have the amp to carry around, but you gotta carry the DC to run all this, too. If you are line of sight, then you can go very high in frequency, but certainly in the higher parts of the HF spectrum, the antennas are more manageable and the bands are quieter, which means power is less of an issue. You could even go to VHF but then the whole construction thing becomes more challenging. But then, if you are looking for a 100-200 mile path, then 80 probably is the ticket, but you're going to have to constrain your playing to days when the A index is low. Indeed, I would suspect you would want to be balooning in the daylight - precisely when 80 is very noisy. So you better be paying close attention to the propagation reports if you want to hear your baloon. ... "Tom Bruhns" wrote in message m... Shouldn't be too difficult to come up with the brute-force answer, but I have to ask: Why? |
#7
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xpyttl wrote:
Looking at the Dave Benson schematics is a good suggestion ... I would also look at Elecraft who also has manuals online with schematics. I would also look at the hfpacker amp (www.hfprojects.com). This was a project ran a couple years ago to build an amp to basically take the QRP rigs in the 2.5 watt range to 30 watts or so. The design actually could do it with a watt of drive but they put an attenuator in the front to allow flexibility with different rigs that didn't have completely adjustable output power. But I also have to ask the same question Tom asks. 80 is a noisy band, and one that demands large antennas. To get past the noise you need power, and that adds a lot of weight. Don't forget, you not only have the amp to carry around, but you gotta carry the DC to run all this, too. If you are line of sight, then you can go very high in frequency, but certainly in the higher parts of the HF spectrum, the antennas are more manageable and the bands are quieter, which means power is less of an issue. You could even go to VHF but then the whole construction thing becomes more challenging. But then, if you are looking for a 100-200 mile path, then 80 probably is the ticket, but you're going to have to constrain your playing to days when the A index is low. Indeed, I would suspect you would want to be balooning in the daylight - precisely when 80 is very noisy. So you better be paying close attention to the propagation reports if you want to hear your baloon. .. "Tom Bruhns" wrote in message m... Shouldn't be too difficult to come up with the brute-force answer, but I have to ask: Why? I was a little distracted by the main path of the conversation that we were having so I didn't ask at that time why they wanted 80 meters for a beacon from that high. I also realize that it is going to take a fair amount of battery to keep this thing going for any period of time. These people do a lot with GPS. Maybe they are hoping to pass GPS location data to the ground crew after the payload lands so that they can go right to it and pick it up. I have no idea what they are doing with antenna ideas or anything like that. Now, what was his phone number? :-) In the mean time thanks for the information. I will get to looking at it and pass it on. Al Butler ka0ies |
#8
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"Allan Butler" wrote in message
news:91vEb.426793$ao4.1361630@attbi_s51... xpyttl wrote: I was a little distracted by the main path of the conversation that we were having so I didn't ask at that time why they wanted 80 meters for a beacon from that high. I also realize that it is going to take a fair amount of battery to keep this thing going for any period of time. These people do a lot with GPS. Maybe they are hoping to pass GPS location data to the ground crew after the payload lands so that they can go right to it and pick it up. I have no idea what they are doing with antenna ideas or anything like that. Now, what was his phone number? :-) In the mean time thanks for the information. I will get to looking at it and pass it on. Al Butler ka0ies Al - You have 2 very large helpful balloon organizations (NSTAR) in the Omaha / Kansas City corridor .... using GPS, VHF (2 meters, 70 cm, etc.) with VERY favorable results. 80 meters is a poor choice for project -- and 20 to 30 watts will be a power hog (weight) that is counter intuitive with what is trying to be accomplished. LOW WEIGHT and HIGH PERFORMANCE are your criteria. Check out the NSTAR light weight camera -- sending video at UHF to ground ! (you can't do this with 80 meters) NSTAR http://www.nstar.org/ Edge of Space Sciences http://www.eoss.org/ansrecap/ar_060/recap55.htm RCKARA http://www.rckara.org/project_traveler/2001a/ NSTAR 2004 Flight Schedule Future Flights Here's our flight schedule for 2004. Those without a listed location will be from our usual sites (near Treynor IA or west of Omaha NE). a.. 04A - Mid to late February (SSTV scheduled) b.. 04B - March 20 - Central Plains Severe Weather Symposium - Lincoln NE (SSTV scheduled) c.. 04C - April 17 - Strategic Air and Space Museum Family Day - Ashland NE (SSTV scheduled) d.. 04D - Mid to late May e.. 04E - July 3 or 4 - Great Plains Super Launch - Hutchinson KS f.. 04F - Mid to late August g.. Perhaps 04G and 04H before the end of the year W9GB |
#9
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"Allan Butler" wrote in message
news:91vEb.426793$ao4.1361630@attbi_s51... xpyttl wrote: I was a little distracted by the main path of the conversation that we were having so I didn't ask at that time why they wanted 80 meters for a beacon from that high. I also realize that it is going to take a fair amount of battery to keep this thing going for any period of time. These people do a lot with GPS. Maybe they are hoping to pass GPS location data to the ground crew after the payload lands so that they can go right to it and pick it up. I have no idea what they are doing with antenna ideas or anything like that. Now, what was his phone number? :-) In the mean time thanks for the information. I will get to looking at it and pass it on. Al Butler ka0ies Al - You have 2 very large helpful balloon organizations (NSTAR) in the Omaha / Kansas City corridor .... using GPS, VHF (2 meters, 70 cm, etc.) with VERY favorable results. 80 meters is a poor choice for project -- and 20 to 30 watts will be a power hog (weight) that is counter intuitive with what is trying to be accomplished. LOW WEIGHT and HIGH PERFORMANCE are your criteria. Check out the NSTAR light weight camera -- sending video at UHF to ground ! (you can't do this with 80 meters) NSTAR http://www.nstar.org/ Edge of Space Sciences http://www.eoss.org/ansrecap/ar_060/recap55.htm RCKARA http://www.rckara.org/project_traveler/2001a/ NSTAR 2004 Flight Schedule Future Flights Here's our flight schedule for 2004. Those without a listed location will be from our usual sites (near Treynor IA or west of Omaha NE). a.. 04A - Mid to late February (SSTV scheduled) b.. 04B - March 20 - Central Plains Severe Weather Symposium - Lincoln NE (SSTV scheduled) c.. 04C - April 17 - Strategic Air and Space Museum Family Day - Ashland NE (SSTV scheduled) d.. 04D - Mid to late May e.. 04E - July 3 or 4 - Great Plains Super Launch - Hutchinson KS f.. 04F - Mid to late August g.. Perhaps 04G and 04H before the end of the year W9GB |
#10
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xpyttl wrote:
Looking at the Dave Benson schematics is a good suggestion ... I would also look at Elecraft who also has manuals online with schematics. I would also look at the hfpacker amp (www.hfprojects.com). This was a project ran a couple years ago to build an amp to basically take the QRP rigs in the 2.5 watt range to 30 watts or so. The design actually could do it with a watt of drive but they put an attenuator in the front to allow flexibility with different rigs that didn't have completely adjustable output power. But I also have to ask the same question Tom asks. 80 is a noisy band, and one that demands large antennas. To get past the noise you need power, and that adds a lot of weight. Don't forget, you not only have the amp to carry around, but you gotta carry the DC to run all this, too. If you are line of sight, then you can go very high in frequency, but certainly in the higher parts of the HF spectrum, the antennas are more manageable and the bands are quieter, which means power is less of an issue. You could even go to VHF but then the whole construction thing becomes more challenging. But then, if you are looking for a 100-200 mile path, then 80 probably is the ticket, but you're going to have to constrain your playing to days when the A index is low. Indeed, I would suspect you would want to be balooning in the daylight - precisely when 80 is very noisy. So you better be paying close attention to the propagation reports if you want to hear your baloon. .. "Tom Bruhns" wrote in message m... Shouldn't be too difficult to come up with the brute-force answer, but I have to ask: Why? I was a little distracted by the main path of the conversation that we were having so I didn't ask at that time why they wanted 80 meters for a beacon from that high. I also realize that it is going to take a fair amount of battery to keep this thing going for any period of time. These people do a lot with GPS. Maybe they are hoping to pass GPS location data to the ground crew after the payload lands so that they can go right to it and pick it up. I have no idea what they are doing with antenna ideas or anything like that. Now, what was his phone number? :-) In the mean time thanks for the information. I will get to looking at it and pass it on. Al Butler ka0ies |
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