Magnus Danielson wrote: > > Pointer to good phase stable cable with suitable connectors would be > apprechiated. >
I've had good success with Andrew FSJ-1-50 in gps applications. I prefer LDF-4-50 for tower runs, not because of the improved loss performance but the mechanical handling characteristics. In terms of connectors, well I'd expect to be running something like the above cables into the equipment room and terminating into lightning surge protection - so N-type connectors are a fair bet - IMD suffers if you make many connect/disconnect cycles but in most cases I'd not anticipate any issues. As for tailing down to the GPS receiver using a none 50r connector (concerns about mismatch) I suspect the discontinuity at the input caused by "bodging" a nominally F-type connector onto a 50R ptfe cable will be no worse than the bump caused by the transition from cable to PCB in the receiver. remember the inner conductor of the cable is the actual transition to the connector so there are d/D dimension changes there anyway. I expect you could remove the connector and run a small cable right to the receiver input if you felt the need AND you were sure the RX S11 really made it worth while. Evidence from another post here suggests it isn't. > Oh. The electrical length change for many reasons. Physical length change is > only part of it. The dielectrum change properties with temperature, and the > changed wave-equation may change speed significantly larger than the length > extention. I suspect humidity in cable to be part of it too. > I agree. Two things I've experienced with flexible cables measured at install and subsequently as part of the ongoing maintenance regime: First - even when very carefully installed, phase often changes slightly within a day or so of install. I suspect this is due to the cable being taken from the roll and placed into position. There is inevitable relative movement of the conductors as the dielectric changes shape. The evidence for this being that the *change* is more pronounced if the run has curves at the minimum bend radius for the cable. After the cable has gone through a few temperature cycles it settles and the cable only changes if the weatherproofing hasn't been done properly or someone subsequently damages the cable (rigger maybe stands on it or hits it with steelwork etc...) Second - water ingression caused by pressure changes in the cable (caused by diurnal temperature cycling) is very likely even in dry environments. Condensation that forms on connectors and even on the waterproofing material itself can be drawn into joints as the pressure changes (hot cold) - each day a tiny bit of moisture ingresses until the cable fails, maybe it takes a week maybe a year but unless its properly waterproofed it will eventually fail. Connectors that have inherent waterproofing such as DIN 7:16 can be problematic if water is allowed to collect on the connector by incorrectly adding a tape cover. Shrouded link yagi antenna can literally fill up with litres of water even though they are carefully sealed with rubber gaskets. Sorry I'm rambling on... Regards Paul > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- 73 de Paul GW8IZR IO73TI http://www.gw8izr.com _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.