Re: [time-nuts] Antenna problems
Mark is absolutely right about this Peter, the Tbolt receiver is 'deaf' by modern standards. In fact I seem to remember the Tbolt documentation specifically mentions the use of a +26dB aerial. I use a +16dB Lucent unit on top of the TV pole here in Central England and although there is enough signal, the mapping feature of Lady Heather shows that I am operating about 10dB below the expected signal level. I'll be buying a +26dB aerial very shortly so that I can upgrade the installation when it next gets serviced. You can get them from eBay for less than 30 Euros, they are purpose designed for use outside and I have never had any problem buying from China. I bought all my Tbolt gear from 'fluke.l' without a hitch and would recommend him. David On 22/08/2010 03:35, Mark J. Blair wrote: On Aug 21, 2010, at 7:15 PM, Peter Krengel wrote: Warren found out that the signals TB gets out of my small ceramic typ antenna are too weak. They are too noisy. So I had a look for a good antenna and found some commercial typs called choke-ring antenna. As they are really expensive is there any DIY solution avaliable? I think that the TBolt wants a fair amount of gain up at the antenna, based on the signal levels it reported from the roof antenna feed at work (we're in the GPS industry) compared to what I normally see from our normal GPS receivers. Mine is installed at home with a Lucent/Alcatel +26dB antenna which I believe was primarily intended for use at cellular base stations, and my TBolt sees nice, strong signals from it with about 9m of feedline. These antennas are all over eBay, both used and unused, and with or without the pole mount. The TBolt will power them with its +5V bias. An eBay search for lucent gps antenna should turn up a few antennas and several mounts at the moment. There are probably many other antennas that will work fine. I'd suggest looking around for active GPS antennas meant for outdoor fixed installations (they'll generally have a somewhat pointy radome to keep snow, birds, etc. from accumulating on them), powered by +5VDC, and with at least 20dB of gain. Used ones can be cheap. ___ 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] Phase noise measurement (was - no subject)
NXP BF862, available from digi-key. Don't these devices have relatively high flicker noise? 1/f corner is well below 100 Hz. Look at the noise voltage plots of that audio guy I cited. My results for the BF862 were the same shape, absolutely somewhat worse in amplitude because I wanted a differential input and less FETs in parallel. Most of my BF862 had abt. 12 mA IDss, btw. The input capacitance is relatively noncritical in this application (phase noise measurement) since it is shunted by the much larger output capacitance of the low pass filter at the mixer IF port. The 300 pF Cin of a single IF3602 could seriously detune the input low pass and the 200 pF feedback capacitance in a stage with substantial voltage gain would destroy the bandwidth unless cascoding is provided. I think, I'll test some Analog Devices ADA9848-2 in parallel. It's hard to beat that combination of noise, 1/f, bandwidth, offset stability and price. Such a preamp can be used as an add-on to a scope or FFT-Analyzer, too, to characterize power supplies, references or oscillator bias circuits. It's fun to enter 60 dB probe gain into a scope channel menu and still see usable traces with uV/div scale factors. ( with a low pass, of course) There are noise nuts, too! ;-) Gerhard One heroic effort for audio is here: http://www.diy-audio-engineering.org/index.php?board=2.0 HPS5.1 ___ 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] Antenna problems
Peter, There was a long thread on the list several months ago about choke-ring antennas and how to build one out of cake pans. However, the issue you describe sounds more like lack of gain/signal rather than multipath interference. I have used several types of antennas for my TBolt including ones like item 390147799311 and item 290466318345 on e..y that have worked very well in NW Florida. Just search for GPS Timing Antenna. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Peter Krengel Sent: Saturday, August 21, 2010 9:15 PM To: time-nuts@febo.com Subject: [time-nuts] Antenna problems Hi group, Warren found out that the signals TB gets out of my small ceramic typ antenna are too weak. They are too noisy. So I had a look for a good antenna and found some commercial typs called choke-ring antenna. As they are really expensive is there any DIY solution avaliable? I have a lathe so its possibly to machine rings if I get the dimensions... Thanks a lot making me a nut ;) regards Peter, DG4EK ___ 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] Antenna problems
Hi I am running a typical 30 ish db antenna and about 50 feet of TV satellite coax on my GPSDO farm. The feed line goes into an HP +/- 3 db 4 way splitter. That splitter feeds a set of four passive eight way splitters. The coax and 8 way splitters dump at least 12 db before anything gets to a receiver. Everything from z3805's to TBolts show very good signal to noise. The TBolts run the same sort of +/- 2 ns others have reported seeing with Lady Heather. I would not spend a fortune on a fancy antenna without trying a modern $30 (surplus) timing antenna first. Bob On Aug 21, 2010, at 10:15 PM, Peter Krengel krengelda...@gmx.de wrote: Hi group, Warren found out that the signals TB gets out of my small ceramic typ antenna are too weak. They are too noisy. So I had a look for a good antenna and found some commercial typs called choke-ring antenna. As they are really expensive is there any DIY solution avaliable? I have a lathe so its possibly to machine rings if I get the dimensions... Thanks a lot making me a nut ;) regards Peter, DG4EK ___ 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] Antenna problems
Peter-- Antenna gain and placement make a lot of difference. Yesterday I swapped out my old Trimble active patch antenna (24 - 26 dBc) for an HP/Symmetricom 58532A antenna (30+ dBc). It's on the roof of our two story house, at the end of probably 20 meters of reasonable quality feedline (LMR400). As Warren will attest, my signal levels (which weren't too bad before), are now much better, with 48 dBc readings in the central ring, elevations above 60 degrees, with a relatively clear view of the sky. As the manufacturer's literature suggests, the Thunderbolt was designed for high gain antennas, and is pretty damn deaf in comparison to most modern designs. But then part of being a time-nut is getting equipment considered obsolete by many to outperform its original specifications. I'm still doing signal strength measurements (in Lady Heather, S - A - D, and Z for Zoom if you want to see a larger plot). Over 36 to 48 hours, that will show me if I still have problems with nearby trees. I also use an HP/Symmetricom GPS splitter, the 58535A. The splitter, antenna, and the antenna mount (as well as the thunderbolt) were all sourced from eBay. There are more of the 58532A antennas available from the same seller (in Hong Kong) currently, at a reasonable price. Unfortunately, the folks selling the splitters seem to know what they have, and have priced them accordingly. Putting on my VHF/UHF ham radio hat for a moment, you know that good feedline and good connectors are a must. Sloppy practices and poor quality in feedline and connectors can easily cost you 6dB or more at the relatively low frequency of 1.5 GHz, not tolerable in such weak signal work as GPS. And take Warren's advice -- I think he has quite the sideline tuning up Thunderbolts around the world! He's given me many useful suggestions, and more interesting questions to ponder. Best 73 de Bob K6RTM in Silicon Valley. ___ 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] Antenna problems
Thanks Mark David for the tips Peter, DG4EK - Original Message - From: time-nuts-requ...@febo.com To: time-nuts@febo.com Sent: Sunday, August 22, 2010 2:00 PM Subject: time-nuts Digest, Vol 73, Issue 95 Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to time-nuts-requ...@febo.com You can reach the person managing the list at time-nuts-ow...@febo.com When replying, please edit your Subject line so it is more specific than Re: Contents of time-nuts digest... Today's Topics: 1. Antenna problems (Peter Krengel) 2. Re: Antenna problems (Mark J. Blair) 3. Re: Antenna problems (David Bobbett) 4. Re: Phase noise measurement (was - no subject) (dk...@arcor.de) -- Message: 1 Date: Sun, 22 Aug 2010 04:15:26 +0200 From: Peter Krengel krengelda...@gmx.de Subject: [time-nuts] Antenna problems To: time-nuts@febo.com Message-ID: 8a8fa241387e4bdba95d68da228a4...@xpserver Content-Type: text/plain; charset=iso-8859-1 Hi group, Warren found out that the signals TB gets out of my small ceramic typ antenna are too weak. They are too noisy. So I had a look for a good antenna and found some commercial typs called choke-ring antenna. As they are really expensive is there any DIY solution avaliable? I have a lathe so its possibly to machine rings if I get the dimensions... Thanks a lot making me a nut ;) regards Peter, DG4EK -- Message: 2 Date: Sat, 21 Aug 2010 19:35:37 -0700 From: Mark J. Blair n...@nf6x.net Subject: Re: [time-nuts] Antenna problems To: Discussion of precise time and frequency measurement time-nuts@febo.com Message-ID: 9334af5c-b13e-4916-ad59-30fb646fb...@nf6x.net Content-Type: text/plain; charset=us-ascii On Aug 21, 2010, at 7:15 PM, Peter Krengel wrote: Warren found out that the signals TB gets out of my small ceramic typ antenna are too weak. They are too noisy. So I had a look for a good antenna and found some commercial typs called choke-ring antenna. As they are really expensive is there any DIY solution avaliable? I think that the TBolt wants a fair amount of gain up at the antenna, based on the signal levels it reported from the roof antenna feed at work (we're in the GPS industry) compared to what I normally see from our normal GPS receivers. Mine is installed at home with a Lucent/Alcatel +26dB antenna which I believe was primarily intended for use at cellular base stations, and my TBolt sees nice, strong signals from it with about 9m of feedline. These antennas are all over eBay, both used and unused, and with or without the pole mount. The TBolt will power them with its +5V bias. An eBay search for lucent gps antenna should turn up a few antennas and several mounts at the moment. There are probably many other antennas that will work fine. I'd suggest looking around for active GPS antennas meant for outdoor fixed installations (they'll generally have a somewhat pointy radome to keep snow, birds, etc. from accumulating on them), powered by +5VDC, and with at least 20dB of gain. Used ones can be cheap. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. -- Message: 3 Date: Sun, 22 Aug 2010 09:58:59 +0100 From: David Bobbett d.bobb...@tiscali.co.uk Subject: Re: [time-nuts] Antenna problems To: Discussion of precise time and frequency measurement time-nuts@febo.com Message-ID: 4c70e6d3.7040...@tiscali.co.uk Content-Type: text/plain; charset=ISO-8859-1; format=flowed Mark is absolutely right about this Peter, the Tbolt receiver is 'deaf' by modern standards. In fact I seem to remember the Tbolt documentation specifically mentions the use of a +26dB aerial. I use a +16dB Lucent unit on top of the TV pole here in Central England and although there is enough signal, the mapping feature of Lady Heather shows that I am operating about 10dB below the expected signal level. I'll be buying a +26dB aerial very shortly so that I can upgrade the installation when it next gets serviced. You can get them from eBay for less than 30 Euros, they are purpose designed for use outside and I have never had any problem buying from China. I bought all my Tbolt gear from 'fluke.l' without a hitch and would recommend him. David On 22/08/2010 03:35, Mark J. Blair wrote: On Aug 21, 2010, at 7:15 PM, Peter Krengel wrote: Warren found out that the signals TB gets out of my small ceramic typ antenna are too weak. They are too noisy. So I had a look for a good antenna and found some commercial typs called choke-ring antenna. As they are really expensive is there any DIY solution avaliable? I think that the TBolt wants a fair amount of gain up at the antenna, based on the signal
Re: [time-nuts] Phase noise measurement (was - no subject)
I think, I'll test some Analog Devices ADA9848-2 in parallel. It's hard to beat that combination of noise, 1/f, bandwidth, offset stability and price. Oooops, ADA4898-2 http://www.analog.com/en/amplifiers-and-comparators/operational-amplifiers-op-amps/ada4898-2/products/product.html sorry for the confusion, Charles! Gerhard ___ 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] Phase noise measurement (was - no subject)
The link isnt particularly useful as guests cant view the attachments and registration is disabled Bruce dk...@arcor.de wrote: Wenzel Audio Amp referred to in this email. Perfect! I drive with it a 3561A and a 7L5! Works for me. The only problem is getting any more 2SK369. Any recommendations? NXP BF862, available from digi-key. I have used it in a similar hookup with good success. Its virtue is the low noise voltage AND low input capacitance at the same time. You could deploy MANY of them in parallel until you get into the capacitance range of a single Interfet device. One heroic effort for audio is here: http://www.diy-audio-engineering.org/index.php?board=2.0 HPS5.1 I currently use 3 pairs of SSM2210 in front of a AD797. regards, Gerhard ___ 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] Phase noise measurement (was - no subject)
http://www.synaesthesia.ca/LNschematics.html Is a better link, in that one can actually view the circuit schematics. There are a few simple refinements that will dramatically improve the low frequency PSRR of the single ended JFET circuits in the HPS5.1: 1) split the 3k3 resistor feeding the green LEDs into into 2 series 1k6 resistors and bypass the common node of these 2 resistors to ground. This low pass filters the noise current flowing in the LEDs due to power supply noise. 2) It would probably be even more effective if the base of the cascode transistor were driven by a voltage equal to the JFET source voltage plus about 3.7V. It should, for example, be possible to use a selected JFET to do this. 3) The output servo should drive the noninverting input of the opamp via a CBCS cascode (or equivalent) with a load resistor connected to the input stage positive supply rail. This should improve the PSRR dramatically. I use something similar in one of my low noise preamps albeit with a few LEDs in series with the resistor to provide most of the voltage drop as in my case the required voltage drop is reasonably predictable. This reduces the noise contribution from the servo integrator. Bruce Bruce Griffiths wrote: The link isnt particularly useful as guests cant view the attachments and registration is disabled Bruce dk...@arcor.de wrote: Wenzel Audio Amp referred to in this email. Perfect! I drive with it a 3561A and a 7L5! Works for me. The only problem is getting any more 2SK369. Any recommendations? NXP BF862, available from digi-key. I have used it in a similar hookup with good success. Its virtue is the low noise voltage AND low input capacitance at the same time. You could deploy MANY of them in parallel until you get into the capacitance range of a single Interfet device. One heroic effort for audio is here: http://www.diy-audio-engineering.org/index.php?board=2.0 HPS5.1 I currently use 3 pairs of SSM2210 in front of a AD797. regards, Gerhard ___ 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] Phase noise measurement (was - no subject)
The noise measurements for the HPSs 5.1 preamp: http://www.synaesthesia.ca/LNmeasurements.html indicate that while the high frequency noise is about 2.2x lower than an optimised single ended 2SK369 preamp its flicker noise is far higher. If one uses 5 2SK369's connected in parallel the flicker noise should be even lower whilst the high frequency noise will be comparable/ If the feedback resistor values are reduced perhaps 3 @SK369BLs will suffice. Even lower flicker noise should be achievable if IF9030s are substituted for the 2SK369s. Bruce Bruce Griffiths wrote: http://www.synaesthesia.ca/LNschematics.html Is a better link, in that one can actually view the circuit schematics. There are a few simple refinements that will dramatically improve the low frequency PSRR of the single ended JFET circuits in the HPS5.1: 1) split the 3k3 resistor feeding the green LEDs into into 2 series 1k6 resistors and bypass the common node of these 2 resistors to ground. This low pass filters the noise current flowing in the LEDs due to power supply noise. 2) It would probably be even more effective if the base of the cascode transistor were driven by a voltage equal to the JFET source voltage plus about 3.7V. It should, for example, be possible to use a selected JFET to do this. 3) The output servo should drive the noninverting input of the opamp via a CBCS cascode (or equivalent) with a load resistor connected to the input stage positive supply rail. This should improve the PSRR dramatically. I use something similar in one of my low noise preamps albeit with a few LEDs in series with the resistor to provide most of the voltage drop as in my case the required voltage drop is reasonably predictable. This reduces the noise contribution from the servo integrator. Bruce Bruce Griffiths wrote: The link isnt particularly useful as guests cant view the attachments and registration is disabled Bruce dk...@arcor.de wrote: Wenzel Audio Amp referred to in this email. Perfect! I drive with it a 3561A and a 7L5! Works for me. The only problem is getting any more 2SK369. Any recommendations? NXP BF862, available from digi-key. I have used it in a similar hookup with good success. Its virtue is the low noise voltage AND low input capacitance at the same time. You could deploy MANY of them in parallel until you get into the capacitance range of a single Interfet device. One heroic effort for audio is here: http://www.diy-audio-engineering.org/index.php?board=2.0 HPS5.1 I currently use 3 pairs of SSM2210 in front of a AD797. regards, Gerhard ___ 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.
