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About JohnSwenson

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  1. I'd like to talk about the dialectric issue some more. In my original post I said dielectric didn't matter much. This was wrong dielectric DOES matter quite a bit BUT the high quality dielectrics take a LONG time to burn in. Many of them don't sound particularly good when they are new, but can take over a month to really burn in. My initial tests only did a day worth of burnin, which not nearly long enough to find out what they sound like. I have found that polypropylene and some types of silicone rubber work very well. One important fact is you need to distinguish bet
  2. There are a couple of issues that are being confused with each other. 1: warmup of a clock box 2: warmup of an ER 3: burnin of a clock 4: burnin of an ER 5: burnin of a clock cable #1 and #2, it takes several hours for the electronics to get to an equilibrium temperature, for an ER I would go for at least 8 hours, preferably a day. Who knows how external clocks respond. But it is probably a good idea to go with similar times. This is all about all the parts on the board getting to an equilibrium temperature. #3 and #4, burnin of electronics CAN
  3. This is actually quite a good price for a small 100MHz scope. You can use this to look at a clock waveform, but there is no way you can use this to measure phase noise even close to the levels we are talking about here. John S.
  4. I had a 500 series Tektronix when I was a senior in high school, it was a dual channel model, but after buying that I couldn't afford any scope probes, so I built my own out of 35mm film cans, rather weird looking probes but they worked! That scope sat on the kitchen table for a long time, until my mom insisted I take it to my room , but that was not easy, it weighed 90lbs. That was my scope until I got out of college and got a real job and bought a brand new Tektronix (2246). Oh the joys of putting in new tubes and then spending days recalibrating the whole thing.
  5. That is exactly what it is supposed to do. The purpose of that filter is to get rid of everything above the fundamental. The reason I mentioned it was to use with a sine wave which is much more susceptible to AM noise, either from the clock itself or picked up in the cable. Most of that noise gets taken care of by the filter. If you already have a good square wave the filter is not appropriate. John S.
  6. I have had this happen with regularity in my house with different equipment. Some endpoints always get the same IP address when the DHCP server renews the lease but others seem to frequently get a new IP address which can wreak havoc with network music systems. The weird thing is that after doing this a bunch of times the all of the sudden it will then settle down and get the same address on every renewal. I never did figure this behavior out. But I don't think this is the issue here since it seems the endpoint is saying it is not getting ANY address. I have also had that happen a
  7. Now is a good time to write about what I found in the BG7TBL box that Alex sent me. First off what is inside: OCXO produces sine wave, this goes into a standard CMOS logic gate, which makes an attempt at converting the sine to square. This signal then feeds three more CMOS gates, one for each output. Outputs with sine have a multi-pole passive filter to get rid of most of the harmonics from the square waves. Square wave outputs just feed the CMOS gate output directly to the BNC jack. An important thing to note is that standard CMOS outputs (such as these) ca
  8. There is no such thing as single mode OM4, The "M" MEANS multi-mode. Single mode fibers start with OS (guess what the "S" means). John S.
  9. Hi GG, I just want to make sure you have the correct fiber cables, you say they are OM4 and OM5, these are multi mode (that's what the "M" stands for), but most modules that use 1310 are single mode. Could you check your modules, if they are in fact single mode you should be using OS fiber rather than OM. John S.
  10. I didn't put it in the clock paper but adding thermal insulation to an OCXO will probably make things worse. What you want is "thermal mass" NOT thermal insulation. An OCXO contains a crystal and circuitry in an oven to raise the temperature to the point in the crystal's curve where the temperature changes make a very small change in frequency. There is a sensor (or sensors) that measure the temperature inside and adjust the current flowing through resistances to heat the oven. This means there is "active" heating, the control circuit can control how fast the oven heats up, BUT the
  11. Phase noise is a property of any periodic signal, sine or square or in between. There seems to be some misunderstanding of what phase noise is. Here is a nice easy to understand article on it. (note in this article it specifically covers phase noise of square waves): https://blog.bliley.com/ultimate-guide-to-phase-noise John S.
  12. It is actually very easy to implement a mod to just feed the sine wave out of the OCXO to the BNC jack. I don't have the time to take the box apart and take photos etc. The concept is: Use Xacto knife to cut the trace coming off the output pin from the OCXO Unsolder (or cut pins) of the voltage regulator driving everything except the OCXO cut the wire going from the board to the BNC jack Solder another wire from the OCXO pin to the BNC jack. Presto the sine wave from the OCXO goes directly to the BNC jack. This bypasses all the circuitry
  13. Raw attenuation doesn't matter, it is how the attenuation changes with frequency that matters. So the numbers you quoted don't make any difference, what you need is the attenuation vs frequency graph. The flatter the graph below 1GHz the better. The problem is you cannot compare graphs from different companies since the scales are almost always different. Even within the same company the scales are frequently different. The Canare LV-77S spec sheet has a table for this with several of their models. You can tell by looking at this table that the LV-77S has significantly less change
  14. What impedance did you have the scope input set to? A standard inputof 1 megaohm will give very different results than a 50 ohm input. (which is much closer to 75 than 2 megaohm is). John S.
  15. One thing to try, have you listened to a UTP cable instead of the the STP cable? John S.
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