[time-nuts] LORAN C Antenna...
Those are the counterpoise for the antenna and increases the efficiency of the antenna. Burt, K6OQK At 08:33 AM 8/23/2012, time-nuts-requ...@febo.com wrote What are those rays spreading from the tower base? Are they the artificial ground plane made by wires? On Thu, Aug 23, 2012 at 3:15 AM, paul swed paulsw...@gmail.com wrote: Great pix. Thanks. My tower isn't quite that large. Look at the cables! Regards Paul WB8TSL On Wed, Aug 22, 2012 at 8:01 PM, Michael Blazer mbla...@satx.rr.com wrote: Wow, what a view. How does the advice go, Don't look down? On 8/22/2012 9:22 AM, Poul-Henning Kamp wrote: http://www.jan-mayen.no/ press news Look for 21. august. The last picture is particularly interesting: http://www.jan-mayen.no/nyhet/**2012/08_august/C-%20mast/C-** mast%208b.JPG http://www.jan-mayen.no/nyhet/2012/08_august/C-%20mast/C-mast%208b.JPG Burt I. Weiner Associates Broadcast Technical Services Glendale, California U.S.A. b...@att.net www.biwa.cc K6OQK ___ 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] LORAN C antenna thoughts from the group
In message aanlktikgjbl4yvpifgp8edfqfiracaarmxhi5jqso...@mail.gmail.com, paul swed writes: OK now that I can actually receive the 90070 chain in the US. What might be a better antenna then my whip and preamp? A big loop and preamp? A tall vertical over a ground plane. Tried 67 ft that yielded little. How might reception be improved in the US? I built a trivial loop based on a design-idea I found at vlf.it http://phk.freebsd.dk/loran-c/Antenna/ It's basically a loop with an AD797 amplifier and some power-filtering, didn't even write a schematic for it... -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] LORAN C antenna thoughts from the group
A beverage at 100 KC must be 10-60 miles? Granted I have beverages at higher frequency. But at 100 KC it will be far from directional at any reasonable length. So I think thats a bit costly. On Tue, Dec 21, 2010 at 11:33 AM, Bill Janssen bi...@ieee.org wrote: paul swed wrote: OK now that I can actually receive the 90070 chain in the US. What might be a better antenna then my whip and preamp? A big loop and preamp? A tall vertical over a ground plane. Tried 67 ft that yielded little. How might reception be improved in the US? Thanks 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. Do a Google search for a Beverage Antenna. If you have room for it. Bill K7NOM ___ 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] LORAN C antenna thoughts from the group
I remember reading somewhere that the envelope of the LORAN pulses was shaped to reduce the transmitted BW. Does anybody have a reference for that, and relatedly, what does the BW of the antenna have to be? Typically, loops are about 90 KHz to 110 KHz, but can that be narrowed down? Best, -John == In message aanlktikgjbl4yvpifgp8edfqfiracaarmxhi5jqso...@mail.gmail.com, paul swed writes: OK now that I can actually receive the 90070 chain in the US. What might be a better antenna then my whip and preamp? A big loop and preamp? A tall vertical over a ground plane. Tried 67 ft that yielded little. How might reception be improved in the US? I built a trivial loop based on a design-idea I found at vlf.it http://phk.freebsd.dk/loran-c/Antenna/ It's basically a loop with an AD797 amplifier and some power-filtering, didn't even write a schematic for it... -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] LORAN C antenna thoughts from the group
In message 53187.12.6.201.2.1292957970.squir...@popaccts.quikus.com, J. Fors ter writes: I remember reading somewhere that the envelope of the LORAN pulses was shaped to reduce the transmitted BW. The envelope is designed for two things: sensible BW and ease of production. There is some math musing about it in the Radiation Lab book. Does anybody have a reference for that, and relatedly, what does the BW of the antenna have to be? Typically, loops are about 90 KHz to 110 KHz, but can that be narrowed down? In principle you can make it as narrow as you want, and compensate for the resulting pulse-shape distortion in your receiver. Going much wider than 30kHz (85-115kHz) usually results in more interference from CW signals than improvement to the loran signal. You can see a typical power spectrum at the bottom of this page: http://phk.freebsd.dk/loran-c/Antenna/ Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] LORAN C antenna thoughts from the group
I was more interested in reducing the BW, rather than increasing it. Years ago, I bought up some of the resuidual of Appelco, a New Hampshire LORAN company that made units for Raytheon. Included were a bunch of active tunable filters, designed to tune out interference. However, there is no documentation. I was just toying with the idea that a good shielded (possibly active) loop, the tunable filters, and an Austron 2100F might still be usable on the east coast. FWIW, -John In message 53187.12.6.201.2.1292957970.squir...@popaccts.quikus.com, J. Fors ter writes: I remember reading somewhere that the envelope of the LORAN pulses was shaped to reduce the transmitted BW. The envelope is designed for two things: sensible BW and ease of production. There is some math musing about it in the Radiation Lab book. Does anybody have a reference for that, and relatedly, what does the BW of the antenna have to be? Typically, loops are about 90 KHz to 110 KHz, but can that be narrowed down? In principle you can make it as narrow as you want, and compensate for the resulting pulse-shape distortion in your receiver. Going much wider than 30kHz (85-115kHz) usually results in more interference from CW signals than improvement to the loran signal. You can see a typical power spectrum at the bottom of this page: http://phk.freebsd.dk/loran-c/Antenna/ Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] LORAN C antenna thoughts from the group
John I believe that it is usable certainly from the pre-amplified whip that I picked up 90070 last night on. The downside is you have to be awake at 0300. One of those nights. As I mentioned my GPS comparison was not very good because I forgot to rehook the gps antenna up to the hp3801. Do. Explains that pretty well. Is there a real advantage to a 4 or 6 foot big loop compared to a small loop? I use a 3 foot loop on wwvb/preamp and that works well. One other point on the wavefrom on loran c. It was constructed to minimize the impact of skywave influence on the receiver. Essentially making it easier for the receiver to distinguish between the two. Thast what I hadread in the loran docs. Regards Paul. PS I thought the bw was +/- 10KC and even wider. On Tue, Dec 21, 2010 at 3:11 PM, J. Forster j...@quik.com wrote: I was more interested in reducing the BW, rather than increasing it. Years ago, I bought up some of the resuidual of Appelco, a New Hampshire LORAN company that made units for Raytheon. Included were a bunch of active tunable filters, designed to tune out interference. However, there is no documentation. I was just toying with the idea that a good shielded (possibly active) loop, the tunable filters, and an Austron 2100F might still be usable on the east coast. FWIW, -John In message 53187.12.6.201.2.1292957970.squir...@popaccts.quikus.com, J. Fors ter writes: I remember reading somewhere that the envelope of the LORAN pulses was shaped to reduce the transmitted BW. The envelope is designed for two things: sensible BW and ease of production. There is some math musing about it in the Radiation Lab book. Does anybody have a reference for that, and relatedly, what does the BW of the antenna have to be? Typically, loops are about 90 KHz to 110 KHz, but can that be narrowed down? In principle you can make it as narrow as you want, and compensate for the resulting pulse-shape distortion in your receiver. Going much wider than 30kHz (85-115kHz) usually results in more interference from CW signals than improvement to the loran signal. You can see a typical power spectrum at the bottom of this page: http://phk.freebsd.dk/loran-c/Antenna/ Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] LORAN C antenna thoughts from the group
In message aanlktimsqshe+yehhhydw2v2edj855sszt78mpqch...@mail.gmail.com, paul swed writes: Is there a real advantage to a 4 or 6 foot big loop compared to a small loop? I use a 3 foot loop on wwvb/preamp and that works well. There is a very good and simple explanation of the theory behind loops here: http://www.vlf.it/octoloop/rlt-n4ywk.htm Sensitivity rises with the area of your loop, so doubling the diameter gives you four times the signal, which may or may not be a relevant low number of dB. One other point on the wavefrom on loran c. It was constructed to minimize the impact of skywave influence on the receiver. Essentially making it easier for the receiver to distinguish between the two. Thast what I hadread in the loran docs. Yes, this is why you should always zoom in on the 3rd positive zero-crossing. Inside the announced service areas, the skywave will never arrive early enough to disturb the groundwave at that point. PS I thought the bw was +/- 10KC and even wider. Yes, it is, but the amount of actual energy once you get past +/- 10kHz or 15kHz is very very limited. The perfect bandwidth is where the S/N of the loran-C signal is 1:1, but I have never found a good way to determine that automatically. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] LORAN C antenna thoughts from the group
Thanks will read the link. Think I have in the past but did not have a need. I might guess 4 db would be quite helpful in this effort. I still have some garbage I am seeing that I will need to hunt down. But its not within the house so that really makes things interesting. On Tue, Dec 21, 2010 at 5:14 PM, Poul-Henning Kamp p...@phk.freebsd.dkwrote: In message aanlktimsqshe+yehhhydw2v2edj855sszt78mpqch...@mail.gmail.comaanlktimsqshe%2byehhhydw2v2edj855sszt78mpqch...@mail.gmail.com, paul swed writes: Is there a real advantage to a 4 or 6 foot big loop compared to a small loop? I use a 3 foot loop on wwvb/preamp and that works well. There is a very good and simple explanation of the theory behind loops here: http://www.vlf.it/octoloop/rlt-n4ywk.htm Sensitivity rises with the area of your loop, so doubling the diameter gives you four times the signal, which may or may not be a relevant low number of dB. One other point on the wavefrom on loran c. It was constructed to minimize the impact of skywave influence on the receiver. Essentially making it easier for the receiver to distinguish between the two. Thast what I hadread in the loran docs. Yes, this is why you should always zoom in on the 3rd positive zero-crossing. Inside the announced service areas, the skywave will never arrive early enough to disturb the groundwave at that point. PS I thought the bw was +/- 10KC and even wider. Yes, it is, but the amount of actual energy once you get past +/- 10kHz or 15kHz is very very limited. The perfect bandwidth is where the S/N of the loran-C signal is 1:1, but I have never found a good way to determine that automatically. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY In message [EMAIL PROTECTED], Didier Juges writes: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Poul, I should have remembered, as I now recall seeing your page (duh!), thanks!!! Do you know the bandwidth you achieved? A loop antenna is more or less flat until the stray capacitance of the loop windings take it down. I put a low-pass filter which cuts around 300-500 kHz on this one, because I have a MW transmitter at 1062 kHz only 30 km from my house. And that is the other good reason to use a loop: you can null out one strong signal with the orientation. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY In message [EMAIL PROTECTED], Didier Juges writes: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY OK, thanks for the useful information . I thought you might have resonated the loop to get some filtering ahead of the preamp, which is what I would have done, not knowing any better... I also use that antenna for various other VLF experiments, DCF77, MSF etc, so I didn't want to make it too resonant. [...]so I may tune the loop and get some filtering. If you're doing your own LORAN-C receiver in software like me, then it is a useful fact to remember that you can do pretty much anything you want to your antenna signal, as long as you do the same to the Loran-C reference pulse you use in your algorithms: I have received quite acceptable LORAN-C signals with a 3kHz bandwidth by correlating with a reference pulse that had been through the same filter. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY OK, thanks for the useful information . I thought you might have resonated the loop to get some filtering ahead of the preamp, which is what I would have done, not knowing any better... If I use a ferrite rod, it will most likely have too much stray capacitance to be broad band, but the air loop as you have done is not too big, so I may try both. Looking at the spectrum analyzer plots, it seems I do not have too many competing signals around here, so on the one hand, a broad band loop should work nicely, on the other hand, there is no other signal around I am interested in, so I may tune the loop and get some filtering. Thanks, Didier -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Poul-Henning Kamp Sent: Wednesday, November 14, 2007 2:25 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] LORAN-C antenna A loop antenna is more or less flat until the stray capacitance of the loop windings take it down. I put a low-pass filter which cuts around 300-500 kHz on this one, because I have a MW transmitter at 1062 kHz only 30 km from my house. And that is the other good reason to use a loop: you can null out one strong signal with the orientation. -- Poul-Henning Kamp ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY It is possible to tune a loop to resonate at the frequency of interest. I think that's what he was asking. Regards. Max. K 4 O D S. Email: [EMAIL PROTECTED] Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Music site: http://www.maxsmusicplace.com To subscribe to the fun with tubes group send an email to, [EMAIL PROTECTED] - Original Message - From: Poul-Henning Kamp [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wednesday, November 14, 2007 2:24 AM Subject: Re: [time-nuts] LORAN-C antenna In message [EMAIL PROTECTED], Didier Juges writes: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Poul, I should have remembered, as I now recall seeing your page (duh!), thanks!!! Do you know the bandwidth you achieved? A loop antenna is more or less flat until the stray capacitance of the loop windings take it down. I put a low-pass filter which cuts around 300-500 kHz on this one, because I have a MW transmitter at 1062 kHz only 30 km from my house. And that is the other good reason to use a loop: you can null out one strong signal with the orientation. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.503 / Virus Database: 269.15.32/1131 - Release Date: 11/14/2007 4:54 PM ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I have read with some interest the thread on LORAN-C antennae. Although over 20 years since I was actively involved with Austron LORAN-C, I have data sheets and an installation instruction sheet on their 2026W Whip and 2021L Loop antennae. All give dimensions which may be of use if anyone is planning to construct. Email me off list for scanned copies (PDF) - approx 7.5M file. Cheers Rob Kimberley -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Stan W1LE Sent: 13 November 2007 03:02 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] LORAN-C antenna ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hello Didier, I am using a commercial active whip antenna, McKay-Dymek model DA100A. It is outside on a tripod, about 12' to the base. Very broadband and omnidirectional. I use for VLF RX on 137 and 185 KHz as well as RX during HF FMTs. A resonant magnetic loop antenna may have enough bandwidth, but will be (bi)directional. 100 KHz Loran-C stations near you are: Malone, FL, master on GRI 79800 and secondary (W) on GRI 89700 Jupiter, FL, secondary (Y) on GRI 79800 also secondary stations in Carolina Beach, NC and Grangeville, LA if you need station exact lat and long, let me know. Stan, W1LE FN41sr Cape Cod Didier Juges wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Speaking of Loran, I have an old Loran receiver (origin forgotten) and no antenna. Is it possible to build a Loran antenna? I understand Loran uses narrow pulses of 100 kHz, so the antenna must have sufficient bandwidth to let the front edge of the pulse go undistorted. On the other hand, there are lots of spurious signals at these frequencies, so some selectivity is probably necessary. I am not sure what design would be best. I have made ferrite bar antennas for other long-wave reception, but it was narrow band, so I am not sure these designs would work. I live on the Gulf coast of North-West Florida, and therefore I believe I am not too far from a Loran station, so I probably do not need extreme sensitivity. Any suggestion welcome. Thanks in advance, Didier KO4BB ___ 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. ___ 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] LORAN-C antenna
That last shot looked a little better. It's a tough thing to see on an SA - being just groups of pulses. It takes max-hold a little while to build things up with a digital display. -Carl On Mon, 2007-11-12 at 22:23 -0600, Didier Juges wrote: ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Bill is correct - 10V should do it; these couplers were fed DC up the coax with ~10mH of choke from a circuit that could detect whether the load of the amplifier was present or shorted (essentially open and short DC antenna status bits so the unit could complain of errors in the interconnection if required). That circuit supplied voltage that was a couple Si drops away from the +V rail in the receiver. As long as the emitter follower doesn't dissipate too much power, you're probably in a satisfactory operating range for Vin - take a look across the output resistor and calculate for your particular voltage. These were the third generation of LORAN-C receivers I worked on at this company. Now I do feel old. Thanks for posting the schematic, Bill - having worked for them for so many years I didn't feel all that comfortable doing so myself - although now that you've done so, I can comment on it ;-) -Carl On Tue, 2007-11-13 at 04:05 -0800, WB6BNQ wrote: Didier, This should jog Carl Walker's memory. Here is the schematic for the NorthStar M1 LORAN receiver WHIP preamp that has filtering. The M1 is an aircraft unit that I snagged along with the preamp. It is a re-draw of a schematic sent to me by NorthStar. Obviously, the whip size on an aircraft is small. So you should use a whip that is not to long (maybe up to 3 feet) or it may overload the preamp. Also, the preamp is powered by voltage fed up the coax. At the moment I do not remember what the voltage level is. Perhaps Carl can add to this ??? If not I can dig the thing out and plug it all in to see what the voltage level is on the coax. I can tell you this, it is not over 12 volts as that is the power to the whole unit. My guess, at the moment, is that it is around +8 volts. Well, I dug up the M1 paper work. I have the user and installation manuals, such as they are, and neither of them say anything about anything that is useful. So I will have to take some time tomorrow and power it up to see what the voltage is. BillWB6BNQ Didier Juges wrote: Speaking of Loran, I have an old Loran receiver (origin forgotten) and no antenna. Is it possible to build a Loran antenna? I understand Loran uses narrow pulses of 100 kHz, so the antenna must have sufficient bandwidth to let the front edge of the pulse go undistorted. On the other hand, there are lots of spurious signals at these frequencies, so some selectivity is probably necessary. I am not sure what design would be best. I have made ferrite bar antennas for other long-wave reception, but it was narrow band, so I am not sure these designs would work. I live on the Gulf coast of North-West Florida, and therefore I believe I am not too far from a Loran station, so I probably do not need extreme sensitivity. Any suggestion welcome. Thanks in advance, Didier KO4BB ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Didier Juges said the following on 11/12/2007 10:48 PM: I have tried to listen with my HP 3586 and my 80 meter antenna (which is actually about 20m long and 50 feet up at one end, 30 feet up at the other end), but I have not heard or seen (on the scope) anything like a time signal. Tonight, what I hear sounds more like farm equipment in the harvest season. That's LORAN... it's a group of short pulses with a rapid (1 ms) repetition rate that sounds like a buzzsaw or something similar. The signal spreads around 20 kHz +/- the 100 kHz center frequency. John ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Didier Juges said the following on 11/12/2007 11:02 PM: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I get this (see picture) with the spectrum analyzer and my wire antenna. That looks a lot cleaner than what I hear on the HP 3586. The spectrum analyzer was in peak hold, because the signal has on/off modulation at several Hz. I got the picture after about one minute. The picture is here: http://www.ko4bb.com/Timing/Loran.jpg (sorry it's 2.2 MB) Is that the Loran signal? Seems too narrow, based on your comment (20% bandwidth) That's it. John ___ 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] LORAN-C antenna
Didier Juges wrote: Is it possible to build a Loran antenna? Yes. For my Austron 2100 I built an active ferrite rod antenna which works very well. Much better than an active rod since by using the magnetic field component, it rejects a lot of the local interference (tv timebases and computer monitors etc.,) that the rod picks up. I am several hundred miles from my nearest Loran station however, so the signal is not that strong... I filled a ferrite rod (from an old BC receiver) with a bifilar winding of wire wrap wire, parallel C to resonate at 100 kHz and the center tap grounded. This feeds the gates of a two FET push pull amp, the output of which is transformed into a medium / low impedance to feed the Rx. 12 Volts DC power is multiplexed onto the coax feed line. As is, it was too selective, but a 10 k Ohm R across the antenna rod seems to be enough damping for it to work well. I also use a similar one for WWVB, but here you need all the selectivity you can get and it is in fact so selective that some temperature compensation was necessary. Not a major project, and it fits neatly into some bits of plastic plumbing, a lot smaller than any wire loop would be. Dan ac6ao ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY In message [EMAIL PROTECTED], Dan Rae writes: I filled a ferrite rod (from an old BC receiver) with a bifilar winding of wire wrap wire, parallel C to resonate at 100 kHz and the center tap grounded. For Loran-C too much resonance is not a good thing, so make sure you keep Q reasonably low. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] LORAN-C antenna
I have used a Palomar Engineers loop antenna, together with their loop amplifier, feeding the output directly to the input of my oscilloscope. I devised a programmable counter to divide the 5 MHz output of an HP10811A down to the group repetition interval (GRI) of my local Loran-C chain. The purpose was to calibrate the HP10811A. It worked well enough for my purpose, back in the 1970s, when I was experimenting with coherent CW (CCW). --- Jim Maynard, K7KK Salem, Oregon, USA -- Original Message -- Received: Mon, 12 Nov 2007 04:11:59 PM PST From: Didier Juges [EMAIL PROTECTED] To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Subject: [time-nuts] LORAN-C antenna Speaking of Loran, I have an old Loran receiver (origin forgotten) and no antenna. Is it possible to build a Loran antenna? I understand Loran uses narrow pulses of 100 kHz, so the antenna must have sufficient bandwidth to let the front edge of the pulse go undistorted. On the other hand, there are lots of spurious signals at these frequencies, so some selectivity is probably necessary. I am not sure what design would be best. I have made ferrite bar antennas for other long-wave reception, but it was narrow band, so I am not sure these designs would work. I live on the Gulf coast of North-West Florida, and therefore I believe I am not too far from a Loran station, so I probably do not need extreme sensitivity. Any suggestion welcome. Thanks in advance, Didier KO4BB ___ 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.
[time-nuts] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Speaking of Loran, I have an old Loran receiver (origin forgotten) and no antenna. Is it possible to build a Loran antenna? I understand Loran uses narrow pulses of 100 kHz, so the antenna must have sufficient bandwidth to let the front edge of the pulse go undistorted. On the other hand, there are lots of spurious signals at these frequencies, so some selectivity is probably necessary. I am not sure what design would be best. I have made ferrite bar antennas for other long-wave reception, but it was narrow band, so I am not sure these designs would work. I live on the Gulf coast of North-West Florida, and therefore I believe I am not too far from a Loran station, so I probably do not need extreme sensitivity. Any suggestion welcome. Thanks in advance, Didier KO4BB ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY You're probably pretty close to the Jupiter, Florida station. A piece of wire will probably do the trick. John Didier Juges said the following on 11/12/2007 07:11 PM: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Speaking of Loran, I have an old Loran receiver (origin forgotten) and no antenna. Is it possible to build a Loran antenna? I understand Loran uses narrow pulses of 100 kHz, so the antenna must have sufficient bandwidth to let the front edge of the pulse go undistorted. On the other hand, there are lots of spurious signals at these frequencies, so some selectivity is probably necessary. I am not sure what design would be best. I have made ferrite bar antennas for other long-wave reception, but it was narrow band, so I am not sure these designs would work. I live on the Gulf coast of North-West Florida, and therefore I believe I am not too far from a Loran station, so I probably do not need extreme sensitivity. Any suggestion welcome. Thanks in advance, Didier KO4BB ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY DJ, Actually, you are closest to the Malone, FL LORAN, about 30 miles due south of Dothan, AL. They run 800kW into a 700 foot monopole array. For more info see http://www.uscg.mil/d8/lorstamalone/default.asp . --Mike Niswonger, W4CMN Didier Juges wrote: Speaking of Loran, I have an old Loran receiver (origin forgotten) and no antenna. Is it possible to build a Loran antenna? I understand Loran uses narrow pulses of 100 kHz, so the antenna must have sufficient bandwidth to let the front edge of the pulse go undistorted. On the other hand, there are lots of spurious signals at these frequencies, so some selectivity is probably necessary. I am not sure what design would be best. I have made ferrite bar antennas for other long-wave reception, but it was narrow band, so I am not sure these designs would work. I live on the Gulf coast of North-West Florida, and therefore I believe I am not too far from a Loran station, so I probably do not need extreme sensitivity. Any suggestion welcome. Thanks in advance, Didier KO4BB ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Didier, that ought to be just about in your back yard!! I did some consulting for one of the Dothan TV stations last year (what's amazing is that the transmitter is actually in Florida!). Anyway, on my way there from a military reunion in Texas, we stopped in Shalimar to visit my old roommate that didn't make the reunion. If I had known then where you live, I would have stopped by to see you... He's probably about a mile from your place! Daun -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mike Niswonger Sent: Monday, November 12, 2007 7:59 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] LORAN-C antenna ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY DJ, Actually, you are closest to the Malone, FL LORAN, about 30 miles due south of Dothan, AL. They run 800kW into a 700 foot monopole array. For more info see http://www.uscg.mil/d8/lorstamalone/default.asp . --Mike Niswonger, W4CMN Didier Juges wrote: Speaking of Loran, I have an old Loran receiver (origin forgotten) and no antenna. Is it possible to build a Loran antenna? I understand Loran uses narrow pulses of 100 kHz, so the antenna must have sufficient bandwidth to let the front edge of the pulse go undistorted. On the other hand, there are lots of spurious signals at these frequencies, so some selectivity is probably necessary. I am not sure what design would be best. I have made ferrite bar antennas for other long-wave reception, but it was narrow band, so I am not sure these designs would work. I live on the Gulf coast of North-West Florida, and therefore I believe I am not too far from a Loran station, so I probably do not need extreme sensitivity. Any suggestion welcome. Thanks in advance, Didier KO4BB ___ 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. ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY You can build your own LORAN-C antenna coupler without too much trouble. A lifetime or so ago, I was one of the analog design team at the company that made Northstar LORAN-C receivers for marine and aircraft navigation. The first generation of receivers used an active coupler (MOSFET amplifier) with some high frequency roll-off to avoid BC band overload. These receivers were quite simple, with bandpass filters and a couple tunable notch filters to eliminate interference close to the LORAN-C band - before some hard limiting to allow the uP and sampler logic to process the information. This basic type of antenna coupler is what I'm using at home (with a distribution buffer amplifier) for the 2100F, 2000C, and the various WWVB receivers; this has been quite satisfactory - given the low-pass filtering in the coupler allows both 60 KHz and 100 KHz signals through quite nicely. Based on your location, you may or may not have interfering VLF signals in the neighborhood of LORAN-C; there's only one real way to find out - have a look with the spectrum analyzer at the output of whatever you devise for an antenna coupler amplifier and see what's there. Also bear in mind the receiver itself is generally designed with filtering of its own (may or may not have internal, fixed notch filters for close in interference in addition to some band-pass filtering), and may not require that you do all that much external filtering in the coupler itself. I must admit I've not snooped around in either Austron for some time, and the details of the those receiver designs escape me at the moment. If LORAN-C is all you're interested in receiving, you'd do well with a bit of bandpass filtering before the amplifier stage in the antenna coupler to avoid overload and interference both above and below the desired signal. The energy in a LORAN-C pulse is very broadband (a 20% bandwidth pulse), so making a filter that's as flat in amplitude and group delay distortion over the 90-110 KHz band helps preserve pulse envelope shape and zero crossings; liner-phase filters work quite well here - although the skirt selectivity might not be all that you'd like. Preserving pulse fidelity is the key here. Pulse envelope shape is often critical - since many receivers use the envelope shape of the pulse to determine which zero crossing to track when cycle-selecting. The other thing to bear in mind is that if you'd like to use a short length of wire for your receiving antenna, the impedance of the input bandpass filter needs to be quite high; as an example, we used 8 foot CB-type whips for marine applications - and to approximate this antenna length with 50 Ohm signal sources, we used a 20 pF series cap at 100 KHz. It's also interesting to note the diurnal effects due to sky-wave contamination of the pulses that was mentioned earlier. Depending on amplitude and delay of this sky-wave signal, it's quite possible to get vector-sum effects that cause the perceived zero crossings of the pulse to shift in time. Since the ionosphere isn't stable in height, and the sky-wave signal often is greater in amplitude than the ground wave signal by 10 to 20 dB, the point at which your receiver is tracking may appear to be time displaced in a jittery sort-of way (based on delay and amplitude of the sky-wave signal) - and the receiver tracking loops will follow this displacement early and late in time - making the oscillator appear to be unstable. I believe this to be one possible cause for the degradation of stated accuracy by the 2100F for a given oscillator during the evening hours. I see the degradation clearly here - whether the receiver is driven by the Austron xtal oscillator, or the HP5061. Changes of two to three orders of reported magnitude are not uncommon for the frequency offset display on my receiver between daytime and nighttime operation. Here we have another reason to maintain pulse fidelity - since too narrow a filter selectivity will tend to distort and suppress the rise time of the pulse envelope, causing a receiver to select a zero crossing later than desired in the pulse to track - late enough in the pulse to allow the sky-waves to have more effect on the zero crossing its trying to track. I'd be happy to share some ideas on LORAN antenna couplers and their design if anyone is interested - drop me a line. -Carl WA1RAJ ___ 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] LORAN-C antenna
Hello Didier, I am using a commercial active whip antenna, McKay-Dymek model DA100A. It is outside on a tripod, about 12' to the base. Very broadband and omnidirectional. I use for VLF RX on 137 and 185 KHz as well as RX during HF FMTs. A resonant magnetic loop antenna may have enough bandwidth, but will be (bi)directional. 100 KHz Loran-C stations near you are: Malone, FL, master on GRI 79800 and secondary (W) on GRI 89700 Jupiter, FL, secondary (Y) on GRI 79800 also secondary stations in Carolina Beach, NC and Grangeville, LA if you need station exact lat and long, let me know. Stan, W1LE FN41sr Cape Cod Didier Juges wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Speaking of Loran, I have an old Loran receiver (origin forgotten) and no antenna. Is it possible to build a Loran antenna? I understand Loran uses narrow pulses of 100 kHz, so the antenna must have sufficient bandwidth to let the front edge of the pulse go undistorted. On the other hand, there are lots of spurious signals at these frequencies, so some selectivity is probably necessary. I am not sure what design would be best. I have made ferrite bar antennas for other long-wave reception, but it was narrow band, so I am not sure these designs would work. I live on the Gulf coast of North-West Florida, and therefore I believe I am not too far from a Loran station, so I probably do not need extreme sensitivity. Any suggestion welcome. Thanks in advance, Didier KO4BB ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Is it possible to build a Loran antenna? Sure. There are plenty of plans out there or LF, mostly loops, diamonds, squares and E-probes. Try google. If that doesn't work, I'll chase down the set of links I have. I built a loop on a pair of crossed dowels that worked fine with my SRS FS700 with a balun. There's a loop calculator out there on the web that will help you get in the right neighborhood in terms of diameter and number of windings. I eventually bought an LF Engineering H-900 [1]. The H-900 is really nice, although I would prefer it had been connectorized at the antenna end. [1] http://www.lfengineering.com/pdf/H900inst.pdf -ch ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Well, Shalimar is pretty big, when you want to cross it by foot... Would probably take an hour from end to end. Next time you are in the area, let me know :-) I have tried to listen with my HP 3586 and my 80 meter antenna (which is actually about 20m long and 50 feet up at one end, 30 feet up at the other end), but I have not heard or seen (on the scope) anything like a time signal. Tonight, what I hear sounds more like farm equipment in the harvest season. Didier KO4BB -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Daun Yeagley Sent: Monday, November 12, 2007 7:51 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] LORAN-C antenna Didier, that ought to be just about in your back yard!! I did some consulting for one of the Dothan TV stations last year (what's amazing is that the transmitter is actually in Florida!). Anyway, on my way there from a military reunion in Texas, we stopped in Shalimar to visit my old roommate that didn't make the reunion. If I had known then where you live, I would have stopped by to see you... He's probably about a mile from your place! Daun -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mike Niswonger Sent: Monday, November 12, 2007 7:59 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] LORAN-C antenna ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY DJ, Actually, you are closest to the Malone, FL LORAN, about 30 miles due south of Dothan, AL. They run 800kW into a 700 foot monopole array. For more info see http://www.uscg.mil/d8/lorstamalone/default.asp . --Mike Niswonger, W4CMN Didier Juges wrote: Speaking of Loran, I have an old Loran receiver (origin forgotten) and no antenna. Is it possible to build a Loran antenna? I understand Loran uses narrow pulses of 100 kHz, so the antenna must have sufficient bandwidth to let the front edge of the pulse go undistorted. On the other hand, there are lots of spurious signals at these frequencies, so some selectivity is probably necessary. I am not sure what design would be best. I have made ferrite bar antennas for other long-wave reception, but it was narrow band, so I am not sure these designs would work. I live on the Gulf coast of North-West Florida, and therefore I believe I am not too far from a Loran station, so I probably do not need extreme sensitivity. Any suggestion welcome. Thanks in advance, Didier KO4BB ___ 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. ___ 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] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I get this (see picture) with the spectrum analyzer and my wire antenna. That looks a lot cleaner than what I hear on the HP 3586. The spectrum analyzer was in peak hold, because the signal has on/off modulation at several Hz. I got the picture after about one minute. The picture is here: http://www.ko4bb.com/Timing/Loran.jpg (sorry it's 2.2 MB) Is that the Loran signal? Seems too narrow, based on your comment (20% bandwidth) If so, I would like to find something smaller and maybe more portable than my 20m wire up the tower :-) Didier KO4BB -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Carl Walker Sent: Monday, November 12, 2007 8:31 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] LORAN-C antenna You can build your own LORAN-C antenna coupler without too much trouble. A lifetime or so ago, I was one of the analog design team at the company that made Northstar LORAN-C receivers for marine and aircraft navigation. The first generation of receivers used an active coupler (MOSFET amplifier) with some high frequency roll-off to avoid BC band overload. These receivers were quite simple, with bandpass filters and a couple tunable notch filters to eliminate interference close to the LORAN-C band - before some hard limiting to allow the uP and sampler logic to process the information. This basic type of antenna coupler is what I'm using at home (with a distribution buffer amplifier) for the 2100F, 2000C, and the various WWVB receivers; this has been quite satisfactory - given the low-pass filtering in the coupler allows both 60 KHz and 100 KHz signals through quite nicely. Based on your location, you may or may not have interfering VLF signals in the neighborhood of LORAN-C; there's only one real way to find out - have a look with the spectrum analyzer at the output of whatever you devise for an antenna coupler amplifier and see what's there. Also bear in mind the receiver itself is generally designed with filtering of its own (may or may not have internal, fixed notch filters for close in interference in addition to some band-pass filtering), and may not require that you do all that much external filtering in the coupler itself. I must admit I've not snooped around in either Austron for some time, and the details of the those receiver designs escape me at the moment. If LORAN-C is all you're interested in receiving, you'd do well with a bit of bandpass filtering before the amplifier stage in the antenna coupler to avoid overload and interference both above and below the desired signal. The energy in a LORAN-C pulse is very broadband (a 20% bandwidth pulse), so making a filter that's as flat in amplitude and group delay distortion over the 90-110 KHz band helps preserve pulse envelope shape and zero crossings; liner-phase filters work quite well here - although the skirt selectivity might not be all that you'd like. Preserving pulse fidelity is the key here. Pulse envelope shape is often critical - since many receivers use the envelope shape of the pulse to determine which zero crossing to track when cycle-selecting. The other thing to bear in mind is that if you'd like to use a short length of wire for your receiving antenna, the impedance of the input bandpass filter needs to be quite high; as an example, we used 8 foot CB-type whips for marine applications - and to approximate this antenna length with 50 Ohm signal sources, we used a 20 pF series cap at 100 KHz. It's also interesting to note the diurnal effects due to sky-wave contamination of the pulses that was mentioned earlier. Depending on amplitude and delay of this sky-wave signal, it's quite possible to get vector-sum effects that cause the perceived zero crossings of the pulse to shift in time. Since the ionosphere isn't stable in height, and the sky-wave signal often is greater in amplitude than the ground wave signal by 10 to 20 dB, the point at which your receiver is tracking may appear to be time displaced in a jittery sort-of way (based on delay and amplitude of the sky-wave signal) - and the receiver tracking loops will follow this displacement early and late in time - making the oscillator appear to be unstable. I believe this to be one possible cause for the degradation of stated accuracy by the 2100F for a given oscillator during the evening hours. I see the degradation clearly here - whether the receiver is driven by the Austron xtal oscillator, or the HP5061. Changes of two to three orders of reported magnitude are not uncommon for the frequency offset display on my receiver between daytime and nighttime operation. Here we have another reason to maintain pulse fidelity - since too narrow a filter selectivity will tend to distort
Re: [time-nuts] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I took another shot with the analyzer set to 10 kHz RBW, and the signal now looks more like 20 kHz wide. See http://www.ko4bb.com/Timing/Loran-2.jpg Didier -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Didier Juges Sent: Monday, November 12, 2007 10:02 PM To: [EMAIL PROTECTED]; 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] LORAN-C antenna I get this (see picture) with the spectrum analyzer and my wire antenna. That looks a lot cleaner than what I hear on the HP 3586. The spectrum analyzer was in peak hold, because the signal has on/off modulation at several Hz. I got the picture after about one minute. The picture is here: http://www.ko4bb.com/Timing/Loran.jpg (sorry it's 2.2 MB) Is that the Loran signal? Seems too narrow, based on your comment (20% bandwidth) If so, I would like to find something smaller and maybe more portable than my 20m wire up the tower :-) Didier KO4BB -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Carl Walker Sent: Monday, November 12, 2007 8:31 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] LORAN-C antenna You can build your own LORAN-C antenna coupler without too much trouble. A lifetime or so ago, I was one of the analog design team at the company that made Northstar LORAN-C receivers for marine and aircraft navigation. The first generation of receivers used an active coupler (MOSFET amplifier) with some high frequency roll-off to avoid BC band overload. These receivers were quite simple, with bandpass filters and a couple tunable notch filters to eliminate interference close to the LORAN-C band - before some hard limiting to allow the uP and sampler logic to process the information. This basic type of antenna coupler is what I'm using at home (with a distribution buffer amplifier) for the 2100F, 2000C, and the various WWVB receivers; this has been quite satisfactory - given the low-pass filtering in the coupler allows both 60 KHz and 100 KHz signals through quite nicely. Based on your location, you may or may not have interfering VLF signals in the neighborhood of LORAN-C; there's only one real way to find out - have a look with the spectrum analyzer at the output of whatever you devise for an antenna coupler amplifier and see what's there. Also bear in mind the receiver itself is generally designed with filtering of its own (may or may not have internal, fixed notch filters for close in interference in addition to some band-pass filtering), and may not require that you do all that much external filtering in the coupler itself. I must admit I've not snooped around in either Austron for some time, and the details of the those receiver designs escape me at the moment. If LORAN-C is all you're interested in receiving, you'd do well with a bit of bandpass filtering before the amplifier stage in the antenna coupler to avoid overload and interference both above and below the desired signal. The energy in a LORAN-C pulse is very broadband (a 20% bandwidth pulse), so making a filter that's as flat in amplitude and group delay distortion over the 90-110 KHz band helps preserve pulse envelope shape and zero crossings; liner-phase filters work quite well here - although the skirt selectivity might not be all that you'd like. Preserving pulse fidelity is the key here. Pulse envelope shape is often critical - since many receivers use the envelope shape of the pulse to determine which zero crossing to track when cycle-selecting. The other thing to bear in mind is that if you'd like to use a short length of wire for your receiving antenna, the impedance of the input bandpass filter needs to be quite high; as an example, we used 8 foot CB-type whips for marine applications - and to approximate this antenna length with 50 Ohm signal sources, we used a 20 pF series cap at 100 KHz. It's also interesting to note the diurnal effects due to sky-wave contamination of the pulses that was mentioned earlier. Depending on amplitude and delay of this sky-wave signal, it's quite possible to get vector-sum effects that cause the perceived zero crossings of the pulse to shift in time. Since the ionosphere isn't stable in height, and the sky-wave signal often is greater in amplitude than the ground wave signal by 10 to 20 dB, the point at which your receiver is tracking may appear to be time displaced in a jittery sort-of way (based on delay and amplitude of the sky-wave signal) - and the receiver tracking loops will follow this displacement early and late in time - making the oscillator appear
Re: [time-nuts] LORAN-C antenna
Didier, Here is the USCG web site that has a lot of technical explanation on LORAN. http://www.navcen.uscg.gov/loran/ LORAN is a series of pulses that are transmitted from a master and several slave stations for any particular chain. Each chain has its particular repetition rate. Your spectrum display looks about right as you are most likely be seeing more then a single chain. The aggregate of all those pulses would look like a bell curve unless you were able to speed up the spectrum analyzer fast enough to catch the individual pules. The left side bar on the above web page has 2 pages worth looking at as a starter. The first would be the LORAN-C User handbook and then the LORAN-C Signal Spec links. BillWB6BNQ Didier Juges wrote: I get this (see picture) with the spectrum analyzer and my wire antenna. That looks a lot cleaner than what I hear on the HP 3586. The spectrum analyzer was in peak hold, because the signal has on/off modulation at several Hz. I got the picture after about one minute. The picture is here: http://www.ko4bb.com/Timing/Loran.jpg (sorry it's 2.2 MB) Is that the Loran signal? Seems too narrow, based on your comment (20% bandwidth) If so, I would like to find something smaller and maybe more portable than my 20m wire up the tower :-) Didier KO4BB -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Carl Walker Sent: Monday, November 12, 2007 8:31 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] LORAN-C antenna You can build your own LORAN-C antenna coupler without too much trouble. A lifetime or so ago, I was one of the analog design team at the company that made Northstar LORAN-C receivers for marine and aircraft navigation. The first generation of receivers used an active coupler (MOSFET amplifier) with some high frequency roll-off to avoid BC band overload. These receivers were quite simple, with bandpass filters and a couple tunable notch filters to eliminate interference close to the LORAN-C band - before some hard limiting to allow the uP and sampler logic to process the information. This basic type of antenna coupler is what I'm using at home (with a distribution buffer amplifier) for the 2100F, 2000C, and the various WWVB receivers; this has been quite satisfactory - given the low-pass filtering in the coupler allows both 60 KHz and 100 KHz signals through quite nicely. Based on your location, you may or may not have interfering VLF signals in the neighborhood of LORAN-C; there's only one real way to find out - have a look with the spectrum analyzer at the output of whatever you devise for an antenna coupler amplifier and see what's there. Also bear in mind the receiver itself is generally designed with filtering of its own (may or may not have internal, fixed notch filters for close in interference in addition to some band-pass filtering), and may not require that you do all that much external filtering in the coupler itself. I must admit I've not snooped around in either Austron for some time, and the details of the those receiver designs escape me at the moment. If LORAN-C is all you're interested in receiving, you'd do well with a bit of bandpass filtering before the amplifier stage in the antenna coupler to avoid overload and interference both above and below the desired signal. The energy in a LORAN-C pulse is very broadband (a 20% bandwidth pulse), so making a filter that's as flat in amplitude and group delay distortion over the 90-110 KHz band helps preserve pulse envelope shape and zero crossings; liner-phase filters work quite well here - although the skirt selectivity might not be all that you'd like. Preserving pulse fidelity is the key here. Pulse envelope shape is often critical - since many receivers use the envelope shape of the pulse to determine which zero crossing to track when cycle-selecting. The other thing to bear in mind is that if you'd like to use a short length of wire for your receiving antenna, the impedance of the input bandpass filter needs to be quite high; as an example, we used 8 foot CB-type whips for marine applications - and to approximate this antenna length with 50 Ohm signal sources, we used a 20 pF series cap at 100 KHz. It's also interesting to note the diurnal effects due to sky-wave contamination of the pulses that was mentioned earlier. Depending on amplitude and delay of this sky-wave signal, it's quite possible to get vector-sum effects that cause the perceived zero crossings of the pulse to shift in time. Since the ionosphere isn't stable in height, and the sky-wave signal often is greater in amplitude than the ground wave signal by 10 to 20 dB, the point at which your receiver is tracking may appear to be time displaced in a jittery sort-of way (based on delay and amplitude of the sky
Re: [time-nuts] LORAN-C antenna
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY In message [EMAIL PROTECTED], Didier Juges writes: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Speaking of Loran, I have an old Loran receiver (origin forgotten) and no antenna. Is it possible to build a Loran antenna? I built one following roughly the instructions from an AD797 based design I found at vlf.it. See:http://phk.freebsd.dk/loran-c -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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.
