February 2008 - AMSAT-BB - mailman.amsat.org

Doppler tuning for linux?
by Bruce Robertson 11 Feb '08

11 Feb '08

Gang: Linux has several tracking programs, including the venerable predict, and it has the hamlib library that abstracts out the control of radios. However, as far as I can tell, there is no doppler tuning glue that does all the heavy lifting done by, e.g., instantune or the SatPC32 code or other DDE-based programs. Is this true? If it is, it seems to me, with the increasing proliferation of embedded linux, that something along these lines could be pretty handy.

1 0

Re: Automatic doppler tracking of DSB
by James Whitfield 11 Feb '08

11 Feb '08

Many thanks to each of you who have replied to my inquiry. VE7LDH: I am curious what got you to thinking about Doppler frequency tracking on the BPSK signals. Did you consider a specific approach on how? Had it occurred to you that it might have application beyond BPSK or AO-16? If you would rather not post the reply, you may contact me directly. KD6OZH: Your reference to pilot carrier technique allowed me to find some interesting web reading, mostly IEEE and patent stuff. QEX had nothing of interest and the AMSAT journal does not seem to be available prior to 1995. Pilot carriers seem to have been proven to be workable, but not advantageous in the long run. I do not have the expertise to demonstrate, but I suspect that a pilot carrier required a minimum power to acquire and maintain lock on the signal and that the more modulation power being sent, the more pilot carrier power needed to maintain the lock. I will comment more below, but with a Costas Loop, the more power in the modulation information, the easier it is to acquire and maintain lock. As a result, a pilot carrier consumes power without benefit, while at the same time, as you suggest, accurate satellite data allows the shift to be predicted. Tuning the radio becomes something that can be learned by the "handy" or built into the radio. From my limited experience it seems intimidating and more than a touch expensive. Nothing suggests that DSB will work, or that it might become popular if it did work. If DSB had ever been considered, it seems to have been cast aside pretty quickly. That may have been due to the double bandwidth of DSB. I was somewhat puzzled that AO-16 had used DSB downlink. I can only assume that the weight penalty for an SSB transmitter was traded for what was intended to be single channel BPSK. If the downlink design had been multiple BPSK, it would have required a more powerful transmitter and DSB bandwidth would have been a bigger problem. KD6BD and ZL1TYF: I am glad that I sparked an exchange of ideas. My first thought concerning CTCSS is that it shouldn't be necessary. The time for the Costas Loop to lock should be no worse than the time for a VOX circuit to key a transmitter. That is an opinion based on faith in the concept and the building skills of someone much better than I. But I suggest that it would do no harm. At least no more harm to the equipment than someone using very long AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHs! between words. The Costas loop would be able to maintain lock. It fact it seems to me that the level of CTCSS should be specifically set low, to barely maintain lock. The engergy to acquire the signal should come from speech, particularly intelligent speech rather than someone whistling into the mike. As for a standardized tone, and again this comes from my personal bias that a tone should not be required to make the system work, I fail to see the purpose of standardizing the tone. The Costas Loop will not care what tone is used. It could even be a BPSK8 signal at 50 Hz with your callsign ID and latitude / longitude co-ordinates. I would not suggest using a 1KHz tone unless you expect everyone listening to have a sharp filter, or just listen to it. Adjust the tone for "minimum lock maintenance signal strength with no audio" to reduce the annoyance. You asked about multiple overlaping uplinks. I am not sure that I understand. If we are talking about AO-16 with an FM uplink, is this really a problem? If this was a translating repeater ( sorry if I used the wrong term, I go back before OSCAR, but I am pretty new to this stuff. It took me several hours to find a clear reference to TCA. Once I did it was obvious that is the point that has zero doppler shift and maximum doppler rate... ) then two signals in the uplink passband would result in two signals in the downlink. With an FM receiver providing audio to a DSB transmitter, you are going to hear what the FM receiver locks onto. If that is one strong signal, or the interference between two weak signals that cannot maintain lock, you are going to get one signal to downlink. Here is a slightly ficticious example: I live in Kansas and tune my FM radio to a frequency unused in the local area, but that is used in both Denver and Dallas. Most of the time, I don't hear any music from the radio. If a meteor streaks over Cheyenne, I hear Denver until the meteor trail fades. If a meteor comes in over Austin, I hear Dallas. If the meteor comes overhead, I hear the overlap of Denver and Dallas which is probably unintelligible. Using the measured downlink Doppler shift to derive the proper uplink shift. By theory, the shift is proportional to frequency. So multiply the downlink shift by the ratio of the uplink frequency to the downlink frequency. For AO-16, it is a waste of effort since the uplink is FM. If on the other hand you had a DSB uplink that you were monitoring to correct your shift through a translating repeater, you would a much more complex situation that would depend not only on the uplink and downlink frequencies, but the inverting or non-inverting type of repeater... The control function math is getting me confused so I think you would need to break the loop somewhere to prevent instability or oscillation. What my years of flight control development tell me is to design the system from the ground up with each transmitter fixed and just compensate at each receiver. If AO-16 is manifesting a residual "pilot carrier" it may be an indication of an imbalance in what I can only presume is a double balanced mixer. On the other hand if the uplink FM receiver does not have the functionality of a squelch, there may be a "real" DSB downlink of the audio received by the uplink. The difference would be obvious to a synchronous detector. Thank you again for your input. James n5gui

4 5

Service Manual
by David Barber 11 Feb '08

11 Feb '08

Anyone have a service manual in pdf or other format for a Marconi Instruments (IFR) 6960B power meter please?

1 0

SAT contacts and eQSL (And LOTW)
by John W Lee 11 Feb '08

11 Feb '08

Hello Jay, I dread getting into this discussion because it will cause an avalanche of e-mail! First of all, E-QSL's don't count for any meaningful awards. Too bad. It would be nice if they did. I still upload my logs every month faithfully year after year. LOTW confirmations DO count for DXCC and WAS. I spent a lot of time figuring out what it took to get satellite QSO's uploaded that actually were correct. I don't know how many log programs actually export all the correct required info for satellite contacts. My program does not, so what I've been doing is this: Exporting the non-satellite contacts and satellite contacts separately. This way I can massage the ADIF file to make the satellite contacts correct for LOTW and E-QSL. Satellite contacts need to have some additional information: 1. The "band" or "freq" should be the UPLINK frequency (your transmit). 2. Then you need "band_rx" <band_rx:4>70CM, for instance. 3. Then you need "sat_name" <sat_name:5>AO-51 for instance. 4. Then you need "prop_mode" <prop_mode:3>SAT for instance Any contacts that match all the correct info will be confirmed as satellite QSO's. These changes in the ADIF file are not hard to do unless you operate on a lot of different satellites then you have to do them in bunches. Recently all of my Sat QSO's are on mode J "V/U" so I just have to do a wholesale "add in" of the "band_rx" and "prop_mode" part on every QSO. When I log the QSO's in the computer I put the sat name in the "comment" field. So when editing I do a wholesale change (search & replace) "comment" to "sat_name". Not a big job, and it makes things work. I've got a few countries confirmed on LOTW for satellite QSO's but I have a feeling there are a lot of folks that uploaded their stuff without the required info, so the confirmations don't happen. And I get a ton of "70CM" and "2M" FM E-QSL's which I know are not right. Also, I went and exported all the AO-40 QSO's, fixed the file up, sent it in to LOTW and don't think I got a single confirmation on any of it. Too bad again! Does this help ? 73, John, K6YK

1 0

Re: AO-51 Fail ????
by gouldsmi＠bellsouth.net 11 Feb '08

11 Feb '08

AO-51 is fine. The repeater was off due to an automatic shut down of the satellite from not receiving a command for a number of days. This was my fault for not increasing the shut down time while I was out of town. Drew, KO4MA turned the transmitters back on and set the power levels and frequencies tonight - Thanks Drew. 73, Gould, WA4SXM -------------- Original message from Dale-KL7XJ <daleh(a)alaska.net>: -------------- > Andrew Glasbrenner wrote: > > The 145.920/435.300 FM repeater is back on as of about 0025Z. I'll get > > S-band restarted next pass. > > > > 73, Drew KO4MA > > > > ----- Original Message ----- > > From: "CE3SOC Raul Romero" > > To: "Amsat-Bb(a)Amsat.Org" > > Sent: Sunday, February 10, 2008 7:14 PM > > Subject: [amsat-bb] AO-51 Fail ???? > > > > > Drew, > Thanks for all you do. Hope it is not a serious event. You folks have > done some great > work with this Satellite. > > 73, Dale KL7XJ > _______________________________________________ > Sent via AMSAT-BB(a)amsat.org. Opinions expressed are those of the author. > Not an AMSAT-NA member? Join now to support the amateur satellite program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb

1 0

Re: Linear transponder without duplex?
by Anthony Monteiro 11 Feb '08

11 Feb '08

Hi Bill, A more modern version would be SATPC32 available from AMSAT but it will not run on my old 20 mhz 386 laptop! 73, Tony AA2TX At 09:33 PM 2/10/2008, Bill Dzurilla wrote: >Thanks again Tony. These programs look interesting, >even though rather old. I'll check them out, would >like to try VO-52. >73, Bill >--- Anthony Monteiro <aa2tx(a)comcast.net> wrote: > > > At 02:30 PM 2/10/2008, Bill Dzurilla wrote: > > >I know full duplex is the best, but is there a > > >practical way to work VO-52 and other linear > > >transponder birds w/o duplex? > > > > > >73, Bill NZ5N > > > > Hi Bill, > > > > Yes. It is not really all that difficult either. > > I have made contacts on VO-52 and other satellites > > using just an FT-817 and omni antennas and also > > mobile while driving to and from work using an > > FT-100 with an ATAS vertical. > > > > I used an old 386 laptop running InstantTrack and > > InstantTune software to set the radio VFOs. Using > > this software, it is not much different than > > doing regular HF contacts. You just tune with the > > radio dial to find a station or a clear spot and > > then you PTT. The software does all the work of > > setting the VFOs and doppler tracking. > > > > Please feel free to email me if you would like > > more info. > > > > 73, > > Tony AA2TX > > > > > > > > > > > > > > > > > > > > >____________________________________________________________________________________ >Never miss a thing. Make Yahoo your home page. >http://www.yahoo.com/r/hs

1 0

Re: LVB
by gouldsmi＠bellsouth.net 11 Feb '08

11 Feb '08

Hello Ron, I have two of them running on two computers using XP and Win98. THE FTDI drivers are specific to the operating system you are using. I did have to install/uninstall/install the FTDI drivers a couple of times. Others have gotten it the first time. Check out the documents with the FTDI drivers, they are helpful. 73, Gould, WA4SXM -------------- Original message from "Ronald A. Stunden" <ve7yc(a)shaw.ca>: -------------- > Anyone running the Tracker with Satpc32 under USB? or dies anyone > have what the proper TIDI drive is?? Tks ron > > _______________________________________________ > Sent via AMSAT-BB(a)amsat.org. Opinions expressed are those of the author. > Not an AMSAT-NA member? Join now to support the amateur satellite program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb

1 0

wasamata wit MODE A AO-7
by w7lrd＠comcast.net 11 Feb '08

11 Feb '08

Hello Just finished AOS to LOS CQ'ing on AO-7. Yes it is in mode A with excellent downlink signals. Not as strong as mode B, but very useable. No one to chat with. 73 Bob W7LRD Seattle -- "if this were easy, everyone would be doing it"

1 0

FT-847 Serial Port Communications
by Gary Schuchardt 11 Feb '08

11 Feb '08

I have a problem involving the 9 pin serial port on the back of my FT-847 Yaesu transceiver. When I try to use a null modem cable between the rig and my PC on either COM 1 or 2, the rig will not respond to compatible rig controller (CAT) nor a memory management program. The COM ports have been tested as well as the use of two different PCs. Neither null modem cable works. I have tried to use the Menu feature on the FT-847 to match baud rate between radio and PC COM port. Has anyone had a problem like this with the Yaesu FT-847? I would appreciate knowing. Thank you. Gary N0EZH

4 4

AO-51 Fail ????
by CE3SOC Raul Romero 11 Feb '08

11 Feb '08

Orbit 19009 not heard bird fail ???? 00:10 UTC 435.300 and 435.150 not copy 73 Raul

4 4