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Simple 50 ohm preamp with +30 dBm OIP3

Steve Ratzlaff All Messages By This Member #20309 I've uploaded to the Files a relatively simple one transistor 50 ohm preamp with +30 dBm OIP3 that can be built using common transistors and used to check your own IMD test set. I tried seven different transistors, three different types, different brands. Use a power supply you can set to 12.0 volts, as IMD is sensitive to supply voltage, to obtain the same results that I got. /g/loopantennas/files/50%20ohm%20Preamp%20with%20+30%20dBm%20OIP3 73, Steve AA7U
W0LEV All Messages By This Member #20311 Steve, I've built a number of preamps similar to this.? I use them for low VHF to ELF and lower HF frequencies.? I've measured it to be relatively flat through 30 MHz.? I've typically used the 2N5109.?? It works well and others should build it as its relatively simple and easy to build.? I have used 43 material for the output transformer. Dave - W?LEV toggle quoted message Show quoted text On Wed, Oct 9, 2024 at 6:04?PM Steve Ratzlaff via <ratzlaffsteve=[email protected]> wrote: I've uploaded to the Files a relatively simple one transistor 50 ohm preamp with +30 dBm OIP3 that can be built using common transistors and used to check your own IMD test set. I tried seven different transistors, three different types, different brands. Use a power supply you can set to 12.0 volts, as IMD is sensitive to supply voltage, to obtain the same results that I got. /g/loopantennas/files/50%20ohm%20Preamp%20with%20+30%20dBm%20OIP3 73, Steve AA7U -- Dave - W?LEV
Steve Ratzlaff All Messages By This Member #20313 开云体育 This circuit does not make a good preamp--it overloads too easily. As the info in the Files states, it's for making a test IMD preamp that can be duplicated with a characterized OIP3. Recent posts have been about trying to measure IMD of preamps. Steve On 10/9/2024 12:10 PM, W0LEV via groups.io wrote: toggle quoted message Show quoted text Steve, I've built a number of preamps similar to this.? I use them for low VHF to ELF and lower HF frequencies.? I've measured it to be relatively flat through 30 MHz.? I've typically used the 2N5109.?? It works well and others should build it as its relatively simple and easy to build.? I have used 43 material for the output transformer. Dave - W?LEV On Wed, Oct 9, 2024 at 6:04?PM Steve Ratzlaff via <ratzlaffsteve=[email protected]> wrote: I've uploaded to the Files a relatively simple one transistor 50 ohm preamp with +30 dBm OIP3 that can be built using common transistors and used to check your own IMD test set. I tried seven different transistors, three different types, different brands. Use a power supply you can set to 12.0 volts, as IMD is sensitive to supply voltage, to obtain the same results that I got. /g/loopantennas/files/50%20ohm%20Preamp%20with%20+30%20dBm%20OIP3 73, Steve AA7U -- Dave - W?LEV
Johan Bodin All Messages By This Member #20314 Steve, did you measure the frequency response? The properties of the output transformer and the RFC in the base biasing circuit will of course have influence on the frequency response but I am just curious. 73 Johan SM6LKM Steve Ratzlaff wrote: toggle quoted message Show quoted text I've uploaded to the Files a relatively simple one transistor 50 ohm preamp with +30 dBm OIP3 that can be built using common transistors and used to check your own IMD test set. I tried seven different transistors, three different types, different brands. Use a power supply you can set to 12.0 volts, as IMD is sensitive to supply voltage, to obtain the same results that I got. /g/loopantennas/files/50%20ohm%20Preamp%20with%20+30%20dBm%20OIP3 73, Steve AA7U
Steve Ratzlaff All Messages By This Member #20315 Yes, I swept each of the seven transistors I tried. This is typical, and the gain for the last one, 2N4401, unmarked brand: 0.2 MHz +16.1 dB gain 0.5 MHz +16.3 dB gain 1 MHz +16.3 dB gain 5 MHz +16.1 dB gain 10 MHz +15.8 dB gain 20 MHz +14.9 dB gain 30 MHz +14.0 dB gain Steve toggle quoted message Show quoted text On 10/9/2024 11:37 AM, Johan Bodin via groups.io wrote: Steve, did you measure the frequency response? The properties of the output transformer and the RFC in the base biasing circuit will of course have influence on the frequency response but I am just curious. 73 Johan SM6LKM Steve Ratzlaff wrote: I've uploaded to the Files a relatively simple one transistor 50 ohm preamp with +30 dBm OIP3 that can be built using common transistors and used to check your own IMD test set. I tried seven different transistors, three different types, different brands. Use a power supply you can set to 12.0 volts, as IMD is sensitive to supply voltage, to obtain the same results that I got. /g/loopantennas/files/50%20ohm%20Preamp%20with%20+30%20dBm%20OIP3 73, Steve AA7U

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