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Cold Start Test of JC1

Jim Sky All Messages By This Member #181 Hi Folks, Below is a picture of a cold start test I ran today.? The receiver was warmed up 4 hours before the test to stabilize it.? With the unpowered cold JC1 connected and a 50 ohm dummy load antenna the output measured -119.93 dBm.? With the power applied to the JC1 and the serial connection made with the computer and dummy load termination -119.71 dBm measured.? A 0.2 dB increase.? The picture below shows when the relay was engaged and the noise source connected to the receiver. 20 dB of attenuation from the PE4302 modules plus a 6 dB in line attenuator brings the noise source output as close to 100MK as possible.? After fully warming up, the output was -79.58 dBm and continued to hold that value until the end of the trial. That is an equivalent temperature of 99.730 MK.? That is only one hundredth of a dB from 100MK.? I thus recommend a 20 minute warm up before using the JC1. The output is amazingly stable after warm up. I believe the 0.2 dB increase in noise when the unit is powered on is acceptable.? After looking closely at my build of the prototype, I don't think I should ship it.? It is reliant on a lot of un-washered hardware (screw) connections and I didn't build it with shipping in mind.??I have ordered two of these cheap blue cabinets from Amazon and exactly two of the arrived dented. They are not tough.?I think it would be unlikely to arrive in the condition I sent it.? The MKII on the other hand is built like a little tank.? Much tougher.? If someone else wants to build a JC1 with shipping in mind, please do, but I cannot afford the time to build another one right now.? I am far behind where I hoped to be on the PDS archive.? I have to get back to it.?? If Dave wants to measure the accuracy of the SDRuno measurements with the SDRPlay1As then that might add confidence for some, but I am convinced it is very good.
Richard Flagg #184 开云体育 Hi Jim, Are you sure that you are not in saturation with this test. To check, reduce the calibrator temp by say 3 dB and make sure you read a 3 dB drop in signal. Just wonder about saturation, since you are operating 40 dB above the RSP1A noise floor. dick On 5/12/2023 4:51 PM, Jim Sky wrote: toggle quoted message Show quoted text Hi Folks, Below is a picture of a cold start test I ran today.? The receiver was warmed up 4 hours before the test to stabilize it.? With the unpowered cold JC1 connected and a 50 ohm dummy load antenna the output measured -119.93 dBm.? With the power applied to the JC1 and the serial connection made with the computer and dummy load termination -119.71 dBm measured.? A 0.2 dB increase.? The picture below shows when the relay was engaged and the noise source connected to the receiver. 20 dB of attenuation from the PE4302 modules plus a 6 dB in line attenuator brings the noise source output as close to 100MK as possible.? After fully warming up, the output was -79.58 dBm and continued to hold that value until the end of the trial. That is an equivalent temperature of 99.730 MK.? That is only one hundredth of a dB from 100MK.? I thus recommend a 20 minute warm up before using the JC1. The output is amazingly stable after warm up. I believe the 0.2 dB increase in noise when the unit is powered on is acceptable.? After looking closely at my build of the prototype, I don't think I should ship it.? It is reliant on a lot of un-washered hardware (screw) connections and I didn't build it with shipping in mind.??I have ordered two of these cheap blue cabinets from Amazon and exactly two of the arrived dented. They are not tough.?I think it would be unlikely to arrive in the condition I sent it.? The MKII on the other hand is built like a little tank.? Much tougher.? If someone else wants to build a JC1 with shipping in mind, please do, but I cannot afford the time to build another one right now.? I am far behind where I hoped to be on the PDS archive.? I have to get back to it.?? If Dave wants to measure the accuracy of the SDRuno measurements with the SDRPlay1As then that might add confidence for some, but I am convinced it is very good.
Jim Sky All Messages By This Member #185 OK Dick, good thing to check.? It looks good to me. I tried both ways, up and down, and it was right on 3 dB. Jim
Richard Flagg #186 开云体育 Always good to check for saturation - I have gotten fooled more than once. On 5/12/2023 8:47 PM, Jim Sky wrote: toggle quoted message Show quoted text OK Dick, good thing to check.? It looks good to me. I tried both ways, up and down, and it was right on 3 dB. Jim
Richard Flagg #187 开云体育 Jim, I am playing with the Characterizer and have a problem The Characterizer display looks like it is stepping thru frequencies but the SDRUno frequency display is not changing. When I enter a new single frequency the SDRUno doesnt change either. As usual I must have done something wrong. dick On 5/12/2023 8:47 PM, Jim Sky wrote: toggle quoted message Show quoted text OK Dick, good thing to check.? It looks good to me. I tried both ways, up and down, and it was right on 3 dB. Jim
Jim Sky All Messages By This Member #188 开云体育 I wonder if the SDRuno version matters.? What version are you using?? I will have to check tomorrow because my computer is updating but I think I have 1.4.0 or something close. Jim On 5/13/2023 3:32 AM, Richard Flagg wrote: toggle quoted message Show quoted text Jim, I am playing with the Characterizer and have a problem The Characterizer display looks like it is stepping thru frequencies but the SDRUno frequency display is not changing. When I enter a new single frequency the SDRUno doesnt change either. As usual I must have done something wrong. dick On 5/12/2023 8:47 PM, Jim Sky wrote: OK Dick, good thing to check.? It looks good to me. I tried both ways, up and down, and it was right on 3 dB. Jim
Richard Flagg #189 开云体育 I have 1.40.2 Its funny cause the SDR sits there on a fixed frequency but the Characterizzer steps thru all its freqs and draws a nice plot You are either up really late or up really early On 5/12/2023 10:04 PM, Jim Sky wrote: toggle quoted message Show quoted text I wonder if the SDRuno version matters.? What version are you using?? I will have to check tomorrow because my computer is updating but I think I have 1.4.0 or something close. Jim On 5/13/2023 3:32 AM, Richard Flagg wrote: Jim, I am playing with the Characterizer and have a problem The Characterizer display looks like it is stepping thru frequencies but the SDRUno frequency display is not changing. When I enter a new single frequency the SDRUno doesnt change either. As usual I must have done something wrong. dick On 5/12/2023 8:47 PM, Jim Sky wrote: OK Dick, good thing to check.? It looks good to me. I tried both ways, up and down, and it was right on 3 dB. Jim

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