Robert763 and 85 Guests are viewing this topic.
Quote from: mnementh on February 19, 2019, 03:45:13 pmSo... this is how MY morning has been going. How about YOURS? mnem That is my LAST custom-sleeved SATA cable. Ham fisted dwagon ? Today looks alright as I take in some caffeine but yesterday was a real bitch.........our main water pump broke, really broke. Castings smashed and gunna be a quite involved welding job that I really don't need right now. Much smaller backup pump installed.Damn Murphy !
So... this is how MY morning has been going. How about YOURS? mnem That is my LAST custom-sleeved SATA cable.
He's talking about the balun on his 20m rig; it's effed up, meaning he's TXing all kinds of RF interference when he keys up.mnemMurphy just keeps punching me in the dick today...
My ADSL router was dropping out if I keyed down on 20m. This turned out to be that damn BNC connector in my balun I mentioned earlier. No shield continuity. Check this:.....
this is the *first* 723 I have ever seen drifting downwards (after the settling period, of course). When you look at your 5 1/2 Siglent and the digits that move, maybe the meter is drifting upwards instead ?https://electronicprojectsforfun.wordpress.com/silly-circuits/silly-circuits-a-heated-lm723-reference/lm723-long-term-stability-results/
That really doesn't surprise me. I worked on a production line once. The connectors of choice on a module I was working on were MIL-STD-348 (TNC but more expensive). Assembly didn't work. Turned out that the supplier hadn't actually inserted the receptacle into the bulkhead mount connector. What did they do on the production line? Just not solder that because it wasn't there and sling it over to QA (me) to unfuck.
Quote from: Wolfgang on February 19, 2019, 09:28:56 pmthis is the *first* 723 I have ever seen drifting downwards (after the settling period, of course). When you look at your 5 1/2 Siglent and the digits that move, maybe the meter is drifting upwards instead ?https://electronicprojectsforfun.wordpress.com/silly-circuits/silly-circuits-a-heated-lm723-reference/lm723-long-term-stability-results/Nope, I have confirmed that with other DMM's. It does indeed drift downwards then settles.
More playing around with the graphics on the Siglent SDM3055. This is the old 723 based 1.000VDC reference. I knew this reference drifted downward quite a bit for about a half hour then would settle down. I now use this reference just as quick check rather than a precision calibration source.
Quote from: bd139 on February 19, 2019, 09:44:06 pmThat really doesn't surprise me. I worked on a production line once. The connectors of choice on a module I was working on were MIL-STD-348 (TNC but more expensive). Assembly didn't work. Turned out that the supplier hadn't actually inserted the receptacle into the bulkhead mount connector. What did they do on the production line? Just not solder that because it wasn't there and sling it over to QA (me) to unfuck.I would rather define it the other way round, as this is where TNC was codified: so the others are like MIL-STD-348, but cheaper.
Med, I'm not sure if you have this right or I'm misunderstanding here, but looking at your photo, the reading at 0 seconds is lower than it is at -1 seconds, that to me is a rising reading rather than a falling one, or you infact saying that after the 30 minutes or so, the reading still than that shown at the 0 line?
Quote from: med6753 on February 19, 2019, 09:46:41 pmQuote from: Wolfgang on February 19, 2019, 09:28:56 pmthis is the *first* 723 I have ever seen drifting downwards (after the settling period, of course). When you look at your 5 1/2 Siglent and the digits that move, maybe the meter is drifting upwards instead ?https://electronicprojectsforfun.wordpress.com/silly-circuits/silly-circuits-a-heated-lm723-reference/lm723-long-term-stability-results/Nope, I have confirmed that with other DMM's. It does indeed drift downwards then settles.Spock would say: fascinating. The next question is: who made your 723, and how long did you allow it to settle ?
It's my bad this one so I did post mortem. Basically as it's a balun it's spending its life 8m in the air up a pole in the pissing english rain. Figured I'd waterproof it. So the connector was assembled as these layers:1. BNC shell2. plastic hammond box3. solder lug4. lock washer5. nutWhen I then sealed this with epoxy, the epoxy worked its way between the lock washer and the solder lug and the ground connection went. I just built another one and I did two changes to make sure this doesn't happen. Firstly this order:1. BNC shell2. plastic hammond box3. lock washer4. solder lug5. nutI also skipped using the solder lug entirely and just used it as pressure plate for the chassis/lock washer. I got the whole assembly tight then fluxed up the BNC shell and the nut and soldered the balun's internal coax straight to the BNC shell thus avoiding any joints which are pressure only.Works nicely. Flat 1.0:1 SWR up to 10MHz. Then 1.1:1 up to 30MHz. No funky SWR on pole shorts either. Hopefully this will solve my HF problems.Edit: My portable antenna is slightly less shit in this respect. The balun is made by just wrapping the feed round a FT43 and cable tying it to the center piece. Don't think that would last 2 minutes in a permanent installEdit 2: I've also used liquid tape all over the outside of this only as it doesn't get sucked under anything via capillary action.
Quote from: Wolfgang on February 19, 2019, 10:23:44 pmQuote from: med6753 on February 19, 2019, 09:46:41 pmQuote from: Wolfgang on February 19, 2019, 09:28:56 pmthis is the *first* 723 I have ever seen drifting downwards (after the settling period, of course). When you look at your 5 1/2 Siglent and the digits that move, maybe the meter is drifting upwards instead ?https://electronicprojectsforfun.wordpress.com/silly-circuits/silly-circuits-a-heated-lm723-reference/lm723-long-term-stability-results/Nope, I have confirmed that with other DMM's. It does indeed drift downwards then settles.Spock would say: fascinating. The next question is: who made your 723, and how long did you allow it to settle ?I don't recall who made the 723. I'll have to take it apart and look. It takes a good 30 - 45 minutes to settle down. Here's a copy of the schematic.
Quote from: Specmaster on February 19, 2019, 10:30:41 pmMed, I'm not sure if you have this right or I'm misunderstanding here, but looking at your photo, the reading at 0 seconds is lower than it is at -1 seconds, that to me is a rising reading rather than a falling one, or you infact saying that after the 30 minutes or so, the reading still than that shown at the 0 line?The graph moves left to right. 0 seconds is "now", then 30 seconds ago, then 1 minute ago, etc. Therefore, the voltage is decreasing over time.
@med you are well into the voltnuttery hole watching trend plots of VRefs about seals the deal Next step LM399 Vref for more stability then realise you cant measure its drift without 6 1/2 digits .........
Quote from: beanflying on February 19, 2019, 11:55:18 pm@med you are well into the voltnuttery hole watching trend plots of VRefs about seals the deal Next step LM399 Vref for more stability then realise you cant measure its drift without 6 1/2 digits .........So in essence you're agreeing that it is OK for 5.5 digit meters
Quote from: Specmaster on February 20, 2019, 12:05:39 amQuote from: beanflying on February 19, 2019, 11:55:18 pm@med you are well into the voltnuttery hole watching trend plots of VRefs about seals the deal Next step LM399 Vref for more stability then realise you cant measure its drift without 6 1/2 digits .........So in essence you're agreeing that it is OK for 5.5 digit meters Depending on how you want to use that reference. If you want to use it as a transfer standard then it needs to me more stable than the Meter you are going to so 3.5 and 4.5 no problems generally even for Chinese Cheapies. If you are trying to look at the drift of the Ref at 5 1/2 places and beyond you need to make sure both the Vref and Meter are stable and at a fairly fixed Temp. The problem then becomes which Ref is drifting and by how much is it the Meter or the Vref or both? Initial Aging drift is an issue and as the link Wolfgang put above the plastic cases 'can be' an issue on some packages. So you need to look at the Ref over days and then repeat later what you found to see how the Ref is settling. It becomes more of a probability and sadistics issue more than just a simple flick it on and test issue.