Hi Most of the data sheets on RG-6 Quad show it around 9 db per 100’. Like any of the “old” (RG) specs, there really is no control on who does what with a given type of cable. The direct burial versions seem to be a little more consistent.
Bob > On Apr 20, 2016, at 6:48 PM, Pete Stephenson <[email protected]> wrote: > > On Wed, Apr 20, 2016 at 10:41 PM, Ryan Stasel <[email protected]> wrote: >> All, >> >> I’m going to be installing a “permanent” antenna at home, and will need a >> run of about 100ft to get from my workstation, to the mast I’ll be mounting >> the antenna on (Symmetricom 58532A). I’ve seen some indication that both the >> antenna and the Trimble Thunderbolt won’t have any issues with running over >> 75ohm cable, but thought I’d ask the “experts” whether I’d be better off >> with some RG6 Quad-shield, or LMR400 (I’ve got a local source that doesn’t >> know what LMR400 is, or what it’s worth)? >> >> Obviously I’d prefer to run and crimp RG6, but if I’d be better off with >> LMR400, I’d rather run that now than go back into the crawlspace again. =) > > I'm hardly an expert, but according to the Times Microwave calculator > at <http://www.timesmicrowave.com/calculator/>, RG6 (of unspecified > type, presumably double not quad-shielded) at 1542MHz will have a loss > of 12dB over a 100ft length. LMR400 will have a loss of 5.2dB over > that same length. > > The datasheet for your specific cable should show the loss figures. > > The 58532A has an amplifier with a gain of >30dB, so it should work > well even at moderate cable lengths. > > Keep in mind that the Thunderbolt Starter kit came with a Trimble > Bullet antenna (similar gain to the 58532A) and 75 feet of RG6; it'll > almost certainly work fine with 100ft of cable: the manual for the > Thunderbolt recommends RG-59 cable (presumably because it's cheap and > common) and states "The maximum practical cable run is just over 100 > feet." A graph in the manual shows RG-59 losing 15dB over 100ft, > > To be safe, you could always test it by connecting the 100ft of cable > to the antenna and putting it outside in a more convenient location > that has a similar view as your mast and seeing how the Thunderbolt > likes it. > > Also, keep in mind that the 58516A splitter can have between +3 and -3 > dB of gain depending on your luck as to how it was made. The manual > says that for relatively lossy RG-213 cable and the worst case > performance of the 58516A, you should be fine with up to 174 feet of > cable with no line amplifier. > >> Also, if it helps, I’ll probably have a Symmetricom/HP 58516A at/near the >> T-bolt so I can experiment with other GPS(DO)s as well (especially one of >> the JRMiller boards I bought and built (but never finished) ages ago). Which >> brings the question, will the T-bolt provide the oomph needed to power that >> splitter and the antenna over that length of cable? > > Short answer: Yes. > > Longer answer: The Thunderbolt manual says it can supply 5V at up to > 45mA. The 58532A antenna draws a max of 27mA (with 20mA being > typical). The 58516A splitter manual draws it uses 10mA. Worst case > usage is 37mA, which is within the limits for the Thunderbolt. > > Considering both conductors, 100ft of LMR400 has a DC resistance of > 0.304 ohms, so the voltage drop would only be 0.01V over that length. > That's well within specs for the antenna (5V +/- 0.5V) and the > splitter (4.5 to 30V). > > The specs for Belden 1189AP quad-shield RG6/U cable with a copper-clad > steel center conductor and aluminum braid lists the total resistance > for both conductors to be 3.28 ohms over 100 feet. That's a worst-case > voltage drop of 0.12V over that distance, again within spec for both > devices. > > In short, LMR400 would be a better choice in terms of both signal > attenuation and DC resistance, but the difference is more or less > academic and either cable should work fine. > > Cheers! > -Pete > > -- > Pete Stephenson > _______________________________________________ > 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. _______________________________________________ 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.
