Hi Typo, FLX should be FXL helix. Sorry about that.
Bob On Aug 29, 2014, at 2:36 PM, Bob Camp <[email protected]> wrote: > Hi > > Well if you want to run 600’ you either will need some fancy coax or a couple > inline amps. > > LMR400 is roughly 5 db per 100’ when new. At 300’ that’s 15 db plus > connectors (maybe another db) brand new. Figure that it will degrade another > 3 or 4 db before it dies. Net is about a 20 db loss. That’s certainly more > than a 26 db antenna preamp will handle and still deliver a 15 db net gain. > > You could go to FLX-1480 and drop the attenuation to the point that a 600’ > run would not matter. It’s debatable if you can save any money on a smaller > diameter / custom order helix even on a 600’ order. You local cable TV outfit > might have a half mile spare spool sitting around gathering dust …. > > Bob > > On Aug 29, 2014, at 2:00 PM, Dan Kemppainen <[email protected]> wrote: > >> Hi Bob, >> >> House is tucked in against a tree line to the south of my field. >> Lab/shop is on the north side of the house. I need to go north and east >> into the yard/field to get a good view of the sky east-south-west. (In >> the shop, the southern half of the view is blocked by trees, and I get >> no birds just south of straight up...) >> >> I can run a coax across the yard (towards alternate GPS antenna location >> show in image, north is up in image). I can run right out the shop wall >> as far north and east as practical. At 150 feet or more, I get most of >> the sky. At 600 Feet, I get pretty much get everything above ~10 degrees >> elevation for 360 degrees around. And I'm further away from any noise >> sources in the house also. >> >> There is lots of room, 660Ft by 1200Ft field. Right on top of the hill). >> I have lots of sky without anything else around (if I run cable). Is >> there a practical reason not to take advantage of it? >> >> This is as much a mental exercise, as a practical problem, so any input >> is most welcome! :) >> >> See image. >> >> Dan >> >> On 8/29/2014 1:28 PM, Bob Camp wrote: >>> Hi >>> >>> Most GPS antennas have a preamp in them. All of the common Time Nut >>> antennas have one. Gain varies from the mid twenties to over 40db between >>> models. You really do not want much more gain than you need, so more is not >>> generally better. >>> >>> Satellite TV coax is the material of choice for GPS antennas. It’s cheap >>> and low loss. If you need to run 150’, that’s quite a castle you live in. I >>> typically find that adding another 50’ gets me just about anywhere I need >>> to go. I might have ten or twenty feet of coax already involved in getting >>> to the nearest window. That still nets out well below 100’. >>> >>> Bob >>> >>> >>> On Aug 29, 2014, at 11:55 AM, Dan Kemppainen <[email protected]> wrote: >>> >>>> Björn and Tom, >>>> >>>> Thanks for the links. It helps visualize things a lot! Our snow was >>>> unusually weird last year. It stuck on everything, any stick larger than >>>> a pencil had at least basket ball sized hunks of snow on it. That's >>>> probably a worst case scenario, tho. >>>> >>>> Joe, >>>> >>>> OK on the study of snow. It's good to know that it doesn't attenuate the >>>> GPS a lot. That's good information to have in the back of my head! >>>> >>>> We're just east of Minnesota (Upper Michigan). The air coming over the >>>> big lake warms up, picks up water and dumps it on us all winter long. >>>> Because of the lake effect we're lots warmer than Minnesota, but a lot >>>> whiter too! :) >>>> >>>> >>>> The next question that comes to mind, is how much cable is too much >>>> cable from the antenna to GPS? Granted every environment is different, >>>> so lets assume you add 150 ft of cable to gain 30% to 40% more sky view >>>> to the south, is the trade off worth while? Pick a coax, say something >>>> like RG-6 (mismatch and all) or something like LMR-400. Is there a >>>> practical limit? Does temperature changing the length of the cable make >>>> any noticeable difference for a Timing GPS? >>>> >>>> Dang it! I'm getting bit this time-nuts bug now! >>>> >>>> Dan >>>> >>>> On 8/29/2014 10:34 AM, [email protected] wrote: >>>>> I had to study this issue once. The question was if we needed to >>>>> provide antenna heaters in the far North. Like Minnesota and Alaska. >>>>> >>>>> Turns out that snow and ice are almost transparent to 1.5 GHz, while a >>>>> fat seagull perching on the antenna was a problem, so we did the tall >>>>> cone and let it go at that. >>>>> >>>>> The only exception to the transparency is salty sea ice, which can >>>>> accumulate on shipboard equipment. >>>>> >>>>> Joe Gwinn >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>> >>> >>> >> <Tapiola.jpg> > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
