- Saving LCD screens that were under water - 2 Updates
- Selectivity vs. sensitivity - 4 Updates
- Displayport to DVI-D cables without voltage shift board - 1 Update
| mike <ham789@netzero.net>: Jun 09 05:08AM -0700 On 6/7/2018 10:46 PM, Jeff Liebermann wrote: > and in PSI: > <http://www.pumpworld.com/vapor-pressure-chart.htm> > 25 Torr or 0.5 PSI look right. If my google is right, HVAC systems are typically evacuated below 500 microns to get all the water out. That's more like 0.5 Torr. My memory is vague, but somewhere under 2000 microns was where the pressure stopped decreasing due to water contamination. With even the slightest leak in the system, I couldn't get there. |
| Jeff Liebermann <jeffl@cruzio.com>: Jun 09 08:28AM -0700 >> 25 Torr or 0.5 PSI look right. >If my google is right, HVAC systems are typically evacuated below >500 microns to get all the water out. That's more like 0.5 Torr. The point at which water starts to boil at room temp is 20,300 microns of Hg or 0.393 PSIA or about 20 Torr. Presumably, that's when the water starts to turn to vapor which can the be removed by the pump. However, at this pressure, it will take forever, so a much lower vacuum is probably more practical. Whether it needs 40x more, I don't know. >the pressure stopped decreasing due to water contamination. >With even the slightest >leak in the system, I couldn't get there. When I filled my aquarium with water, applied a vacuum, and looked for bubbles, in order to check for leaks, I found quite a few. These were duly plugged with RTV. I had no trouble going down to what I thought was 200 milliTorr (0.00386 PSI), but now I'm not so sure. I have the vacuum pump and gauge and might be able to try again, but not for a while. I would need to build a new vacuum test chamber and don't have the time, bench space, fresh vacuum oil, fittings, rebuild kit, etc. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
| Jon Elson <elson@pico-systems.com>: Jun 08 01:56PM -0500 On Thu, 07 Jun 2018 20:32:03 -0400, micky wrote: > I want a newer car radio for my 2005 Toyota Solara, and I live in > Baltimore and want to be able to receive WAMU, 88.5 and WCSP > (c-span)90.1, from DC. If you are really IN Baltimore, there's no way you can get DC stations on a car radio. I lived on the Eastern Shore of VA for a while, and I did listen to my favorite DC stations, but I built a Yagi antenna and pointed it up into the sky. That was a fixed location and home stereo equipment, not a car radio. That worked pretty well, but you got a lot of flutter any time an airplane was crossing in the middle. If you are expecting to get the info from a few specs listed on the outside of the box, I wouldn't bother. Those specs are not likely to be very accurate or useful by comparison. Jon |
| dplatt@coop.radagast.org (Dave Platt): Jun 08 03:15PM -0700 In article <pfe2lg$17p0$1@gioia.aioe.org>, >selectivity is the opposite to sensivity. By no means. They're almost orthogonal in principle, although in practice they may tend to go in opposite directions. Sensitivity is a measure of how well a tuner picks up the desired (on-frequency) signal... that is, how weak a "wanted" signal it can detect. Selectivity is a measure of how well a tuner _rejects_ non-desired signals (on adjacent channels, alternate channels, and further away)... that is, how strong an "unwanted" signal it can filter out. Cheap tuners may be both insensitive, and not very selective. Really good FM tuners can be highly selective, _and_ highly sensitive. This generally requires having at least one stage of selectivity (i.e. one or more tuned stages) before the first RF amplifier - these stages keep strong, off-frequency signals from overloading the amp. Tuners that are beloved of the "FM DX" crowd will tend to have: - Quite a few stages of selectivity in the front-end. You'll see tuners described as having 3, 4, 5, or more "sections" in the front end - each section is a tuned circuit. Commonly, one section tunes the local oscillator, and the rest provide RF selectivity before the mixer. - Several different bandwidths available in the IF section. A narrow IF (more stages of IF filtering, and/or more-narrowly-tuned filters in each stage) provides better selectivity. This can be at the cost of sensitivity (each IF filter stage adds some amount of loss, even to the desired signal) so a good narrow-IF design will include additional stages of IF amplification to make up the losses and restore the sensitivity. - Post-detection filters, after the FM detector and before the stereo-multiplex decoder. These help filter out "birdies" and IBOC digital sub-carrier noise, from FM stations on adjacent or alternate channels. |
| jurb6006@gmail.com: Jun 08 09:42PM -0700 >"selectivity is the opposite to sensivity. " No, it is not. |
| jurb6006@gmail.com: Jun 08 09:47PM -0700 >"Tuners that are beloved of the "FM DX" crowd will tend to have: " I want one with continuously variable IF bandwidth on the front. |
| Jeroni Paul <JERONI.PAUL@terra.es>: Jun 08 06:16PM -0700 I bought three DisplayPort to DVI-D cables cheap from china and only one works. This one is slightly different and has a small SMD board inside the DP connector - the voltage level shifter. The other two have no board but the wires directly soldered to the plug. I wonder if these two cables are fake or if they may work with some devices, maybe some DVI inputs accept wider voltage ranges or some cards willing to output DVI voltages in the DP output. |
| You received this digest because you're subscribed to updates for this group. You can change your settings on the group membership page. To unsubscribe from this group and stop receiving emails from it send an email to sci.electronics.repair+unsubscribe@googlegroups.com. |
No Response to "Digest for sci.electronics.repair@googlegroups.com - 7 updates in 3 topics"
Post a Comment