[time-nuts] Lowloss cable?
What's the best small diameter (<0.25") low loss coax? I need to run about 30' from my GPS antenna to a TBolt. Best, Dick ___ 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.
Re: [time-nuts] Lowloss cable?
If your antenna has a preamp, then most any coax will do, but if you must, try LMR-240. 73, Dick, W1KSZ -Original Message- >From: Dick Moore >Sent: Jun 12, 2011 12:33 PM >To: time-nuts@febo.com >Subject: [time-nuts] Lowloss cable? > >What's the best small diameter (<0.25") low loss coax? I need to run about 30' >from my GPS antenna to a TBolt. > >Best, >Dick >___ >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. ___ 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.
Re: [time-nuts] Lowloss cable?
We used to use RG-9 at Odetics/Zyfer. What gain is your antenna? Rob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dick Moore Sent: 12 June 2011 8:34 PM To: time-nuts@febo.com Subject: [time-nuts] Lowloss cable? What's the best small diameter (<0.25") low loss coax? I need to run about 30' from my GPS antenna to a TBolt. Best, Dick ___ 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. ___ 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.
Re: [time-nuts] Lowloss cable?
High Dick, Without giving away the bank, the LMR series of coax is pretty good. But in reality a high quality version of the RG-6 Cable TV coax used by the better Cable companies is quite acceptable. If your local Cable company is one of those, you can usually tag one of the work trucks and get them to give you some. I have gotten in excess of 50 feet every time I approached them. The outer jacket is white in color and a bit thicker then standard 75 Ohm coax. If your lucky they will even put good quality "F" type connectors on for you. There are adaptors for going between "F" and BNC. BillWB6BNQ Dick Moore wrote: > What's the best small diameter (<0.25") low loss coax? I need to run about > 30' from my GPS antenna to a TBolt. > > Best, > Dick > ___ > 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. ___ 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.
Re: [time-nuts] Lowloss cable?
LMR-240 is a good choice. Attenuation is ~10dB/100'. But if you can tolerate larger diameter, LMR-400 will cut that in half. On Sun, Jun 12, 2011 at 3:33 PM, Dick Moore wrote: > What's the best small diameter (<0.25") low loss coax? I need to run about > 30' from my GPS antenna to a TBolt. > > Best, > Dick > ___ > 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. > ___ 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.
Re: [time-nuts] Lowloss cable?
I got a T-bolt from i.fluke. The antenna came with a length of 50 ohm rg58. I added 75' of TV style rg6 and it works fine with no amplification needed beyond that in the antenna. It did not seem to mind the 50 to 75 oh mismatch. I did notice with the first T-bolt I got that it could not see any birds until the local oscillator was fairly close to WWV, maybe 40-60 at 10 mHz. On 06/12/2011 12:33 PM, Dick Moore wrote: What's the best small diameter (<0.25") low loss coax? I need to run about 30' from my GPS antenna to a TBolt. Best, Dick ___ 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. -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc "The High Reliability Software" 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ 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.
Re: [time-nuts] Lowloss cable?
Dick wrote: What's the best small diameter (<0.25") low loss coax? How nuts do you want to get? You shouldn't need anything better than a good RG-59 (75 ohms) for a 30' run. For that, I'd probably use Belden 1426A if I were restricted to < 0.25". Good foam RG-6 (also 75 ohms) like Belden 1694A is better, if you can tolerate 7mm diameter (.275"), but at 30' the difference in attenuation will be less than 1 dB. Note that GPS antenna manufacturers often specify (and supply) 75 ohm RG-59 instead of 50 ohm RG-58, notwithstanding that the antennas and GPS units are 50 ohms. This is because the effects from the relatively small mismatch are more than outweighed by the typically 2 dB/100 ft. loss advantage of RG-59 over RG-58. At 1 GHz, the losses per 100' of some candidates are: 1/4" Heliax: ~4.5 dB (~5 dB at 1.5 GHz) Belden 1694A: ~6 dB (foam RG-6; 7mm diameter; some brands worse) RG-401: ~7 dB (1/4" semi-rigid coax) Belden 7808A: ~7.5 dB (low loss RG-8X; some others much worse) LMR-240: ~8 dB (low loss RG-8X) Aircell 7: ~8 dB (note: this is 7mm, a bit larger than 1/4") Belden 1426A: ~8.5 (foam RG-59; some types/brands worse) Aircell 5: ~9.4 dB (5mm OD) Best regards, Charles ___ 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.
Re: [time-nuts] Lowloss cable?
rich...@hughes.net said: > What's the best small diameter (<0.25") low loss coax? I need to run about > 30' from my GPS antenna to a TBolt. There are two sources of attenuation. One is the dielectric losses. The other is resistance, primarily skin effect on the center conductor. Most modern coax uses foam polyethylene for the dielectric. It's pretty good. To reduce the resistive losses, you want a bigger center conductor. The useful cross section is the circumference times the skin depth. There are two ways to get a bigger center conductor. One is to use 75 ohm coax rather than 50. For most GPS gear, that gives an impedance mismatch, but that is probably smaller than the reduced attenuation. (It obviously depends on the length. We should be able to compute the cross over length.) The other approach is to use a bigger outside diameter. The impedance depends on ratio of the inside of the shield and the outside of the center conductor. So if you make the center conductor bigger to reduce skin effect, you have to make the outside bigger to keep the same impedance. There are 2 types of 75 ohm coax readily available. One is RG-59 at roughly 1/4 inch dia. The other is RG-6 at roughly 1/3 inch dia. You can get all sorts of numbers (attenuation vs frequency, size) with a bit of googling. Any consumer electronics place will have them in the cable TV section. They come in various lengths with F connectors. You will need adapters and/or to install connectors. -- These are my opinions, not necessarily my employer's. I hate spam. ___ 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.
Re: [time-nuts] Lowloss cable?
For a given OD the centre conductor will be SMALLER diameter for 75 ohm cable wrpt 50 ohm cable. Google for the whole minimum loss/highest power xfer capability etc issue as regards coax cable diameter and impedance. All std textbook stuff. Or used to be! DaveB, NZ - Original Message - From: "Hal Murray" To: "Discussion of precise time and frequency measurement" Sent: Monday, June 13, 2011 1:38 PM Subject: Re: [time-nuts] Lowloss cable? rich...@hughes.net said: What's the best small diameter (<0.25") low loss coax? I need to run about 30' from my GPS antenna to a TBolt. There are two sources of attenuation. One is the dielectric losses. The other is resistance, primarily skin effect on the center conductor. Most modern coax uses foam polyethylene for the dielectric. It's pretty good. To reduce the resistive losses, you want a bigger center conductor. The useful cross section is the circumference times the skin depth. There are two ways to get a bigger center conductor. One is to use 75 ohm coax rather than 50. For most GPS gear, that gives an impedance mismatch, but that is probably smaller than the reduced attenuation. (It obviously depends on the length. We should be able to compute the cross over length.) The other approach is to use a bigger outside diameter. The impedance depends on ratio of the inside of the shield and the outside of the center conductor. So if you make the center conductor bigger to reduce skin effect, you have to make the outside bigger to keep the same impedance. There are 2 types of 75 ohm coax readily available. One is RG-59 at roughly 1/4 inch dia. The other is RG-6 at roughly 1/3 inch dia. You can get all sorts of numbers (attenuation vs frequency, size) with a bit of googling. Any consumer electronics place will have them in the cable TV section. They come in various lengths with F connectors. You will need adapters and/or to install connectors. -- These are my opinions, not necessarily my employer's. I hate spam. ___ 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. ___ 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.
Re: [time-nuts] Lowloss cable?
On 6/12/11 7:57 PM, Dave Brown wrote: For a given OD the centre conductor will be SMALLER diameter for 75 ohm cable wrpt 50 ohm cable. Google for the whole minimum loss/highest power xfer capability etc issue as regards coax cable diameter and impedance. All std textbook stuff. Or used to be! DaveB, NZ http://www.microwaves101.com/encyclopedia/why50ohms.cfm lowest loss is at 77 ohms for air dielectric Other tricky aspects in real systems.. Higher Z might have lower loss because IR losses dominate, and higher Z is lower current (for the same power), hence the popularity of open wire ladder line. If the line is short (compared to a wavelength.. probably not an issue for GPS, except in jumpers internal to equipment), loss due to mismatch gets trickier (because you don't have a complete cycle) ___ 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.
Re: [time-nuts] Lowloss cable?
On Sun, Jun 12, 2011 at 12:33 PM, Dick Moore wrote: > What's the best small diameter (<0.25") low loss coax? I need to run about > 30' from my GPS antenna to a TBolt. Low loss and a 0.25" diameter don't go together. The loss generally depends on the diameter. The way to figure out what to buy is to first specify the allowable loss you can tolerate, then buy whatever cable has that much loss over a 30 foot run at the GPS frequency. if 0.25" really is a hard requirement then the answer is LMR240. But why are you limited to only 0.25"? -- Chris Albertson Redondo Beach, California ___ 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.
Re: [time-nuts] Lowloss cable?
What's the best small diameter (<0.25") low loss coax? I need to run about 30' from my GPS antenna to a TBolt. Best, Dick If the antenna has a pre-amp, then just use "satellite TV cable", even though the losses and impedance aren't quite what you might like. Cheers, David GM8ARV -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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.
