I tested this board for use in a HF step calibrator project for Radio Jove. My unit had a boosted voltage of 28v rather than 38. This actually a fairly common voltage required for external noise surces and the designer may have copied that idea from a commercial design. There really is no reason to do this unless you add an option to take the zener voltage source from an external piece of equipment like a noise figure meter.We rejected this deesign because the HF noise output varied by several dBm from 15 to 30MHz,though it might work better at higher frequencies, The second problem is the heat issue. A lot of heat isn't usually desired in a piece of test equipment.
I have one of these. Measured 7Vpp on my scope, which should be around +18-24 dBm I guess. This device gets *hot* when turned on for a long time, and I removed the LED as the strong light was really annoying. However, we can't live without those gadgets :)
Thanks for reverse engineering the schematic on this noise source. In checking the Datasheet on the MMIC amplifier, isn’t the device rated at 5v, not 12v? This probably explains why the amplifiers are running so hot? I guess I will attempt adding a 5v regulator to the MMICs power as it appears to be a mistake in the design.
In guitar effects pedals if we connect to linear power supply or a battery its fairly clean no noise But when i connect to a normal switch mode power supply which is not exactly made for effects pedal or a audio circuits we can hear a squeeling /whining switch mode noise.. Do you think there is a any solution to that? Can i take any wall wart and add or mod something to make it clean?
You could probably get rid of a lot of it with a simple LC filter. I don't have much experience with switch mode power supplies though, and from what I understand if you load them down with too much capacitance they start to act up. I'd recommend asking on diyAudio or a similar forum (although don't be surprised if they tell you to scrap the SMPS wall wart and buy a linear supply - they love their linear supplies over there).
Is interesting that filtering of noise source does not exhibit knee or humps that were there when you used the tracking generator. Any idea of the cause? Perhaps the rbw setting changed?
can you explain why you want the capacitor and resistors after the diode, to only pass the AC of the noise, and then limit it with the resistors, rather than just the raw noise coming from the diode?
I tested this board for use in a HF step calibrator project for Radio Jove. My unit had a boosted voltage of 28v rather than 38. This actually a fairly common voltage required for external noise surces and the designer may have copied that idea from a commercial design. There really is no reason to do this unless you add an option to take the zener voltage source from an external piece of equipment like a noise figure meter.We rejected this deesign because the HF noise output varied by several dBm from 15 to 30MHz,though it might work better at higher frequencies, The second problem is the heat issue. A lot of heat isn't usually desired in a piece of test equipment.
I have one of these. Measured 7Vpp on my scope, which should be around +18-24 dBm I guess. This device gets *hot* when turned on for a long time, and I removed the LED as the strong light was really annoying. However, we can't live without those gadgets :)
Thanks for reverse engineering the schematic on this noise source. In checking the Datasheet on the MMIC amplifier, isn’t the device rated at 5v, not 12v? This probably explains why the amplifiers are running so hot? I guess I will attempt adding a 5v regulator to the MMICs power as it appears to be a mistake in the design.
In guitar effects pedals if we connect to linear power supply or a battery its fairly clean no noise
But when i connect to a normal switch mode power supply which is not exactly made for effects pedal or a audio circuits we can hear a squeeling /whining switch mode noise..
Do you think there is a any solution to that?
Can i take any wall wart and add or mod something to make it clean?
You could probably get rid of a lot of it with a simple LC filter. I don't have much experience with switch mode power supplies though, and from what I understand if you load them down with too much capacitance they start to act up. I'd recommend asking on diyAudio or a similar forum (although don't be surprised if they tell you to scrap the SMPS wall wart and buy a linear supply - they love their linear supplies over there).
Is interesting that filtering of noise source does not exhibit knee or humps that were there when you used the tracking generator. Any idea of the cause? Perhaps the rbw setting changed?
interesting
i never knew how a noice gen might work
can you explain why you want the capacitor and resistors after the diode, to only pass the AC of the noise, and then limit it with the resistors, rather than just the raw noise coming from the diode?
you need the resistor to ground to reference the signal. the noise needs to average to zero volts so the following gain stages don't clip.
at what freq does it start to roll off?
I don't know. my equipment stops at 1GHz. I use it here:
ua-cam.com/video/e7xCVEBs1CM/v-deo.html