"David Lord" <> wrote in message news:[email protected]... [] > It's very wet round here with 90 +/- 10% R/H being common in > various locations including out back of house which is often > 95%. You could only hang washing out for it to get wet. This > means leaves are soaking wet and beginning of year when I > swapped from BR304 to GPS18-LVC I was getting continuous > reach 377 but this deteriorated as trees came into leaf.
Ah, I thought you were in the UK. The 18x LVC is a lot more sensitive than the 18 (without the x), for your information. > Datasheets on some receiver chips seem to use just a crystal > but some seem to have some coupling back from output to input > but it's not clear if feedback or forward. Otherwise all trf > with agc from a peak detector but filtering time constants > aren't easy to work out as just giving a suggested capacitor > value. > > I tried similar interstage crystal coupling which produced a > good oscillator until receiver module was shielded and moved > away from aerial. That also lost me some of timecode pulses > as not enough damping. One of the times when designing by impulse response (of the envelope) rather than just bandwidth! > Maplin circuit I have shows the fast timecode but more recent > documentation from NPL doesn't mention any fast code and the > slow code shown is different to that given with the Maplin > circuit. The fast-code signal was dropped in October 1998. > I've seen widely different values used for filter of the > NE567 from about 1ms upwards. Maplin design seems to be > for loop filter of NE567 with bandwidth of about 8kHz > (depends on input level) and 1ms with option of extra > capacitor at input of Schmitt to give about 15ms to > remove fast pulses. I still think that nothing beat filtering as early as possible, in the detector stage it's rather last gasp. > I'm suspecting I've something broken on my demodulator > pcb so will be rebuilding with added 4093 and couple of > pots to try different time constants. That's just a > challenge since Conrad module with 60kHz crystal is > tiny, low power and works ok. > > The Conrad module doesn't give a 60kHz output though and > my aim was to use that as frequency reference same as > Andy Talbot (G4JNT) design. > > David Ah, I once thought of doing something similar with the 198KHz (was 200KHz) signal from Droitwich. Clever chaps those who design the modules - as you say, they do work well. 73, David _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
