[digitalradio] Re: NBEMS QST article/digital weak signal FM
Hi Tony, The original reason we went to DominoEx instead of MFSK16 or PSK63 was because at VHF (we were originally using SSB), transceiver drift, in addition to multipath, is a major problem and MFSK16 is much more critical for mistuning or drift (on SSB) than DominoEx. But, when using FM, frequency drift should not be as great a problem, and it may well turn out that MFSK16 will work better overall, but we have not yet made enough comparisons to find out. FM is not usually used way under limiting, so this is rather new ground for us. On SSB, between two stations that both have TCXO's, MFSK16 works really well, but unfortunately, it is not possible to control whether or not a TCXO is being used. Multipath is generally not a problem until the reflected signal is seen crossing the main signal on the waterfall, and then a slow beat note can be heard, regardless of signal strengths. At that time, the main signal is often completely cancelled by the out of phase reflected signal, and there is simply no resulting signal to decode until the reflected signal is seen to move off to the side of the main signal. Once it has, the mode with the lowest minimum S/N will work the best. Over the long path, propagation often appears to be very steady, with no atmospheric distortion, and the limiting factor is then the minimum S/N of the mode. However, at other times, there is a persistent, fast flutter, and at those times, MFSK16 might prove to be the best mode to use. We have yet to find out. As more people try using digital modes on 2 meter FM, the overall best performing mode will automatically surface, but for the longest range on digital modes (not counting CW), it is really necessary to use SSB, and in that case, we have found that MFSK16 is just too critical for tuning to be used with transceivers without a TCXO. 73, Skip KH6TY 4c. Re: NBEMS QST article/digital weak signal FM Posted by: Tony d...@optonline.net kt2q Date: Sat Feb 21, 2009 4:44 pm ((PST)) Skip, White noise tests show DominioEX-4 to be a bit more sensitive than MFSK16, but it doesn't seem to handle HF distortion nearly as well. I was surprised that it did better than MFSK16 with multipath and was wondering if you thought the better throughput was due to MFSK16 tuning issues rather than actual robustness? Tony - KHMU Announce your digital presence via our Interactive Sked Page at http://www.obriensweb.com/sked Recommended software: Winwarbler, FLDIGI, DM780, or Multipsk Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:digitalradio-dig...@yahoogroups.com mailto:digitalradio-fullfeatu...@yahoogroups.com * To unsubscribe from this group, send an email to: digitalradio-unsubscr...@yahoogroups.com * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
[digitalradio] Re: NBEMS QST article/digital weak signal FM
Hi Tony. I suppose the reason is that we are comparing MFSK16/DominoEX over FM versus MFSK16/DominoEX over SSB. I believe they are just different animals. SSB only shifts signals in frequency. FM does much more complex (in mathematical sense) transformation. Skip is doing interesting pioneering work. Digital modulation over common voice FM transceiver will have different noise and distortion properties than SSB. It will be influenced by noise properties of FM, preemphasis/deemphasis, how FM is modulated (pulling VFO inside the phase loop?) etc. Pulling varactor inside the phase loop will distort low frequencies (phase loop acts against the modulation), therefore baseband modulation is difficult. It brings back the memories of my teenage packet radio obsession. At that time the modulation modes were limited mainly by circuit complexity and there was no DSP. Common handhelds were modulated with BELL202 1200Bd two tone synchronous modulation. 9k6 enabled transceivers allowed direct modulation of the VFO varactor by bypassing all the microphone circuit, preemphasis and clipping. I suppose Skip's target is the first group of transceivers, where the modulation/demodulation amplitude and phase response is unknown. Skip, it would be interesting, if you could investigate, which modulation bandwidths and at which center audio frequency the common FM transceivers work best with common HF weak signal digital modes. Keep the good work. Someone able to do the math? 73, Vojtech OK1IAK White noise tests show DominioEX-4 to be a bit more sensitive than MFSK16, but it doesn't seem to handle HF distortion nearly as well. I was surprised that it did better than MFSK16 with multipath and was wondering if you thought the better throughput was due to MFSK16 tuning issues rather than actual robustness? Tony - KHMU
[digitalradio] Re: NBEMS QST article/digital weak signal FM
Hi Vojtech, Thanks for the tip. I totally forgot about the possible effect of deemphasis and what effect the center audio frequency might have. Our goal with NBEMS has always been able to reach at least 100 miles reliably, in order to span the largest expected disaster area to reach Internet or phone connectivity. We were recently surprised to find over a 117 mile path on 2 meters, that, on the average, FM with DominoEx actually worked better than SSB with DominoEx, even with the poorer S/N of FM compared to SSB. The surprise was an unexpected, consistent, fast flutter which did not seem to affect FM nearly as badly as SSB. Thanks to Tony's wondering, we will continue to evaluate different modes (and different audio center frequencies!) and post the results here. 73, Skip KH6TY Skip, it would be interesting, if you could investigate, which modulation bandwidths and at which center audio frequency the common FM transceivers work best with common HF weak signal digital modes. Keep the good work. Someone able to do the math? 73, Vojtech OK1IAK White noise tests show DominioEX-4 to be a bit more sensitive than MFSK16, but it doesn't seem to handle HF distortion nearly as well. I was surprised that it did better than MFSK16 with multipath and was wondering if you thought the better throughput was due to MFSK16 tuning issues rather than actual robustness? Tony - KHMU
[digitalradio] RFSM8000 qrg's?
Hi all! Are there CoA frequencies with RFSM8000 between individuals or dedicated frequencies with automatic stations or servers or gates with RFSM8000 modulation? We have done some good tests regionally here and would like to connect stations mostly in europe for EmComm tests. 73 de Wolf, oe7ftj Innsbruck, Austria
RE: [digitalradio] RFSM8000 qrg's?
I have RFSM8000 installed on a machine here in Canada, although it is not currently running. I have had some difficulty contacting Dmitri, and wondered if he is still actively pursuing RFSM8000. Have you heard from him ? As a result we have been testing Pactor 3 for the same purpose.. it works into the QRM/N better than RFSM8000, but is a little slower in transferring data, at least from first tests. Cab=n set RFSM8000 up on 20M, and run it 24/7 for a few days, if you want to try it from OE7. Let me know what frequency you want and I'll try to set it up over the next couple of days John VE5MU Do70QK From: digitalradio@yahoogroups.com [mailto:digitalra...@yahoogroups.com] On Behalf Of Wolf, oe7ftj Sent: Sunday, February 22, 2009 10:08 AM To: digitalradio@yahoogroups.com Subject: [digitalradio] RFSM8000 qrg's? Hi all! Are there CoA frequencies with RFSM8000 between individuals or dedicated frequencies with automatic stations or servers or gates with RFSM8000 modulation? We have done some good tests regionally here and would like to connect stations mostly in europe for EmComm tests. 73 de Wolf, oe7ftj Innsbruck, Austria
[digitalradio] Re: RFSM8000 qrg's?
Hi John! I contacted Dmitri some months ago and he sent me a trial code for hams. In the meantime he released the version 0.535 but I did have no contact with him the last few weeks. So I think he is still working on RFSM8000. In our local tests pactor3 has won the 'competition' :-) Because of all over performance and speed! But I like the idea behind RFSM8000 with the built in email gateway and ftp-server. FYI: The EmComm hams in Finland are running a datanetwork with RFSM8000 between the HQ's in the remote regions. At the time my antenna is a _very_ suboptimal wire and I intend to rebuild it in the next months, when the wx condx will be more accetpable to work on the roof ;-) Tnx, 73 de Wolf, oe7ftj --- In digitalradio@yahoogroups.com, John Bradley jbrad...@... wrote: I have RFSM8000 installed on a machine here in Canada, although it is not currently running. I have had some difficulty contacting Dmitri, and wondered if he is still actively pursuing RFSM8000. Have you heard from him ? As a result we have been testing Pactor 3 for the same purpose.. it works into the QRM/N better than RFSM8000, but is a little slower in transferring data, at least from first tests. Cab=n set RFSM8000 up on 20M, and run it 24/7 for a few days, if you want to try it from OE7. Let me know what frequency you want and I'll try to set it up over the next couple of days John VE5MU Do70QK From: digitalradio@yahoogroups.com [mailto:digitalra...@yahoogroups.com] On Behalf Of Wolf, oe7ftj Sent: Sunday, February 22, 2009 10:08 AM To: digitalradio@yahoogroups.com Subject: [digitalradio] RFSM8000 qrg's? Hi all! Are there CoA frequencies with RFSM8000 between individuals or dedicated frequencies with automatic stations or servers or gates with RFSM8000 modulation? We have done some good tests regionally here and would like to connect stations mostly in europe for EmComm tests. 73 de Wolf, oe7ftj Innsbruck, Austria
Re: [digitalradio] RFSM8000 qrg's?
Hi Wolf, Be sure to keep us informed as to your results. It is ironic that we can not use MIL-STD-188-110A type modulation here in the U.S. HF ham bands, at least not in the text RTTY/Data areas, with the requirement to keep the baud rate of any one tone no faster than 300 baud. The RFSM program is about the cleanest and best design I have seen for a data transfer program, especially for basic use by those not that familiar with this technology. With Winmor coming very soon for the Winlink 2000 system, and being an open protocol, there is the possibility that some of the most brilliant ham programmers might be willing to develop a peer to peer version. Perhaps even a cross platform version. It should work much deeper into the noise and QRN than the current RFSM software which required good signals due to not having the slow robust mode. Imagine having a program that could use the Winlink 2000 system, but also be able to meet the larger needs as well. 73, Rick, KV9U Wolf, oe7ftj wrote: Hi all! Are there CoA frequencies with RFSM8000 between individuals or dedicated frequencies with automatic stations or servers or gates with RFSM8000 modulation? We have done some good tests regionally here and would like to connect stations mostly in europe for EmComm tests. 73 de Wolf, oe7ftj Innsbruck, Austria
[digitalradio] Re: RFSM8000 qrg's?
Rick et al! --- In digitalradio@yahoogroups.com, Rick W mrf...@... wrote: Hi Wolf, Be sure to keep us informed as to your results. Yes I will share our experiences here in the group. It is ironic that we can not use MIL-STD-188-110A type modulation here in the U.S. HF ham bands, at least not in the text RTTY/Data areas, with the requirement to keep the baud rate of any one tone no faster than 300 baud. RFSM8000 can be switched to a socalled 'non standard' mode, which will match the legal requirements i.e. bandwidth on our bands. The RFSM program is about the cleanest and best design I have seen for a data transfer program, especially for basic use by those not that familiar with this technology. Full ack!! With Winmor coming very soon for the Winlink 2000 system, and being an open protocol, there is the possibility that some of the most brilliant ham programmers might be willing to develop a peer to peer version. Perhaps even a cross platform version. It should work much deeper into the noise and QRN than the current RFSM software which required good signals due to not having the slow robust mode. Imagine having a program that could use the Winlink 2000 system, but also be able to meet the larger needs as well. I hope the winmor developer will make a kind of 'software-modem' which can be selected out from Airmail also and not in PacLink only! 73 de Wolf, oe7ftj
RE: [digitalradio] Re: RFSM8000 qrg's?
Hi Wolf we have the same problem here, waiting for warm WX to do antenna work, not like our cousins to the south. Keep us posted... By the way, also had the ham key, but it has become corrupted , so RFSM8000 thinks my call is OK5tw or something like that John From: digitalradio@yahoogroups.com [mailto:digitalra...@yahoogroups.com] On Behalf Of Wolf, oe7ftj Sent: Sunday, February 22, 2009 11:55 AM To: digitalradio@yahoogroups.com Subject: [digitalradio] Re: RFSM8000 qrg's? Hi John! I contacted Dmitri some months ago and he sent me a trial code for hams. In the meantime he released the version 0.535 but I did have no contact with him the last few weeks. So I think he is still working on RFSM8000. In our local tests pactor3 has won the 'competition' :-) Because of all over performance and speed! But I like the idea behind RFSM8000 with the built in email gateway and ftp-server. FYI: The EmComm hams in Finland are running a datanetwork with RFSM8000 between the HQ's in the remote regions. At the time my antenna is a _very_ suboptimal wire and I intend to rebuild it in the next months, when the wx condx will be more accetpable to work on the roof ;-) Tnx, 73 de Wolf, oe7ftj --- In digitalradio@yahoogroups.com mailto:digitalradio%40yahoogroups.com , John Bradley jbrad...@... wrote: I have RFSM8000 installed on a machine here in Canada, although it is not currently running. I have had some difficulty contacting Dmitri, and wondered if he is still actively pursuing RFSM8000. Have you heard from him ? As a result we have been testing Pactor 3 for the same purpose.. it works into the QRM/N better than RFSM8000, but is a little slower in transferring data, at least from first tests. Cab=n set RFSM8000 up on 20M, and run it 24/7 for a few days, if you want to try it from OE7. Let me know what frequency you want and I'll try to set it up over the next couple of days John VE5MU Do70QK From: digitalradio@yahoogroups.com mailto:digitalradio%40yahoogroups.com [mailto:digitalradio@yahoogroups.com mailto:digitalradio%40yahoogroups.com ] On Behalf Of Wolf, oe7ftj Sent: Sunday, February 22, 2009 10:08 AM To: digitalradio@yahoogroups.com mailto:digitalradio%40yahoogroups.com Subject: [digitalradio] RFSM8000 qrg's? Hi all! Are there CoA frequencies with RFSM8000 between individuals or dedicated frequencies with automatic stations or servers or gates with RFSM8000 modulation? We have done some good tests regionally here and would like to connect stations mostly in europe for EmComm tests. 73 de Wolf, oe7ftj Innsbruck, Austria
Re: [digitalradio] Re: RFSM8000 qrg's?
The non-standard protocol is a slightly slower, but less bandwidth to fit in the passband of many ham rigs. The baud rate is still 2400 baud of course so can not be used in the HF RTTY/Data portions of the bands here in the U.S. It may be legal in our MF (160 meter) band and in the phone/image portions of the HF bands but the FCC refuses to answer my request for clarification, among a number of other questions. The rules here are usually reasonable, but not with digital technology. This is especially true of using mixed modes such as image and text and documents or what I would consider to be fax. I know that some hams openly violate what you can send on the RTTY/Data portions, but I am just not willing to do this. Example is sending a document such as a weather map on Winlink 2000. It used to be completely illegal, but thankfully one petitioner got the rule changed so that at least we can use up to 500 Hz bandwidth modes. But you can not legally do it with the wide modes in that area of the bands. The WINMOR protocol is an open documented protocol and the author hopes that others will implement that protocol into any kind of application they wish. Also, ... since WINMOR is designed PRIMARILY as a message oriented protocol (pure binary error free transmission using fairly long forwarding blocks (~ 6 sec) The first applications are specifically for messages. And that is the client program that accepts mail from standard mail clients and a server to connect to the Winlink 2000 system. What I find very helpful is that a DLL may be eventually made available, but the author feels that there are too many changes that will occur for a while yet such as additional coding changes. Overall, this has the potential to be a sea change. 73, Rick, KV9U Wolf, oe7ftj wrote: Rick et al! --- In digitalradio@yahoogroups.com, Rick W mrf...@... wrote: Hi Wolf, Be sure to keep us informed as to your results. Yes I will share our experiences here in the group. It is ironic that we can not use MIL-STD-188-110A type modulation here in the U.S. HF ham bands, at least not in the text RTTY/Data areas, with the requirement to keep the baud rate of any one tone no faster than 300 baud. RFSM8000 can be switched to a socalled 'non standard' mode, which will match the legal requirements i.e. bandwidth on our bands. The RFSM program is about the cleanest and best design I have seen for a data transfer program, especially for basic use by those not that familiar with this technology. Full ack!! With Winmor coming very soon for the Winlink 2000 system, and being an open protocol, there is the possibility that some of the most brilliant ham programmers might be willing to develop a peer to peer version. Perhaps even a cross platform version. It should work much deeper into the noise and QRN than the current RFSM software which required good signals due to not having the slow robust mode. Imagine having a program that could use the Winlink 2000 system, but also be able to meet the larger needs as well. I hope the winmor developer will make a kind of 'software-modem' which can be selected out from Airmail also and not in PacLink only! 73 de Wolf, oe7ftj Announce your digital presence via our Interactive Sked Page at http://www.obriensweb.com/sked Recommended software: Winwarbler, FLDIGI, DM780, or Multipsk Yahoo! Groups Links No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.0.237 / Virus Database: 270.11.2/1965 - Release Date: 02/21/09 15:36:00
[digitalradio] Modes - What are they and What about New Developement??
Hi All, I am hoping with the number of members in this group that someone might be able to answer my question. Many years ago, as we know radio started off with CW, then AM was developed, with an improvement to only use one part of the AM carrier to produce SSB with carrier or SSB suppressed carrier. Then somebody developed FM. Now in my view this gives 4 actual modes? But I see you say (Maybe), we have all the digital modes. But are these actually modes? Why I ask and the reason for the question, is these are still using one of the current 4 above, over a SSB carrier for the likes of PSK-31, SSTV etc, or FM for the likes of Packet. So will the future be able to bring us anything new that will improve the usablility of radio? Doing a search on Google brings up thousands of hits, but none actually answer the questions, most also class each digital type as a mode. Would be very interested in your thoughts. If you do not feel this is the fourm to reply, a direct email to sparcnz(nospam)@gmail.com will be fine. (please remove the (nospam) before sending, I am trying to limit the amount of spam) Regards and thanks for looking at this thread. Kevin, ZL1KFM. Get Skype and call me for free. sparc_nz Description: Binary data
[digitalradio] Re: Modes - What are they and What about New Developement??
- What about... Angle modulation Double-sideband reduced-carrier transmission Double-sideband suppressed carrier Hierarchical modulation Higher-order modulation Wavelet modulation -- In digitalradio@yahoogroups.com, Gmail - Kevin, Natalia, Stacey Rochelle spar...@... wrote: Hi All, I am hoping with the number of members in this group that someone might be able to answer my question. Many years ago, as we know radio started off with CW, then AM was developed, with an improvement to only use one part of the AM carrier to produce SSB with carrier or SSB suppressed carrier. Then somebody developed FM. Now in my view this gives 4 actual modes? But I see you say (Maybe), we have all the digital modes. But are these actually modes? Why I ask and the reason for the question, is these are still using one of the current 4 above, over a SSB carrier for the likes of PSK-31, SSTV etc, or FM for the likes of Packet. So will the future be able to bring us anything new that will improve the usablility of radio? Doing a search on Google brings up thousands of hits, but none actually answer the questions, most also class each digital type as a mode. Would be very interested in your thoughts. If you do not feel this is the fourm to reply, a direct email to sparcnz(nospam)@gmail.com will be fine. (please remove the (nospam) before sending, I am trying to limit the amount of spam) Regards and thanks for looking at this thread. Kevin, ZL1KFM. Get Skype and call me for free.
Re: [digitalradio] Re: Modes - What are they and What about New Developement??
Andrew, Now that you mention it I have heard of DSB suppressed carrier, but none of the others. But isn't DSB acutally AM? Either with or without the carrier? I will have to look at this. I will have to have a look at these other modes, couple of them sound interesting. Thanks for the info Kevin, ZL1KFM. Get Skype and call me for free. - Original Message - From: Andrew O'Brien To: digitalradio@yahoogroups.com Sent: Monday, February 23, 2009 1:19 PM Subject: [digitalradio] Re: Modes - What are they and What about New Developement?? - What about... Angle modulation Double-sideband reduced-carrier transmission Double-sideband suppressed carrier Hierarchical modulation Higher-order modulation Wavelet modulation -- In digitalradio@yahoogroups.com, Gmail - Kevin, Natalia, Stacey Rochelle spar...@... wrote: Hi All, I am hoping with the number of members in this group that someone might be able to answer my question. Many years ago, as we know radio started off with CW, then AM was developed, with an improvement to only use one part of the AM carrier to produce SSB with carrier or SSB suppressed carrier. Then somebody developed FM. Now in my view this gives 4 actual modes? But I see you say (Maybe), we have all the digital modes. But are these actually modes? Why I ask and the reason for the question, is these are still using one of the current 4 above, over a SSB carrier for the likes of PSK-31, SSTV etc, or FM for the likes of Packet. So will the future be able to bring us anything new that will improve the usablility of radio? Doing a search on Google brings up thousands of hits, but none actually answer the questions, most also class each digital type as a mode. Would be very interested in your thoughts. If you do not feel this is the fourm to reply, a direct email to sparcnz(nospam)@gmail.com will be fine. (please remove the (nospam) before sending, I am trying to limit the amount of spam) Regards and thanks for looking at this thread. Kevin, ZL1KFM. Get Skype and call me for free. sparc_nz Description: Binary data
Re: [digitalradio] Re: Modes - What are they and What about New Developement??
--- On Sun, 2/22/09, Gmail - Kevin, Natalia, Stacey Rochelle spar...@gmail.com wrote: From: Gmail - Kevin, Natalia, Stacey Rochelle spar...@gmail.com Subject: Re: [digitalradio] Re: Modes - What are they and What about New Developement?? To: digitalradio@yahoogroups.com Date: Sunday, February 22, 2009, 7:43 PM Andrew, Now that you mention it I have heard of DSB suppressed carrier, but none of the others. But isn't DSB acutally AM? Either with or without the carrier? I will have to look at this. I will have to have a look at these other modes, couple of them sound interesting. Thanks for the info Kevin, ZL1KFM. DSB can be thought of as AM with the carrier removed. SSB is usually one sideband with the carrier removed. You can have ssb and a carrier and pick it up on a normal AM receiver. If you insert the carrier to a DSB signal then you have normal AM. It is sometimes a play on words. SSB is normally thought of as one sideband and supressed carrier. DSB is usually both sidebands and supressed carrier. AM is both sidebands and the carrier.
[digitalradio] illinoisdigital group
I was able to contact Mark, WB9QZB, and he indicated that his yahoo e-mail account and the group were disabled by Yahoo with no notice or explanation. It is very difficult to even contact Yahoo customer service, which is offshore, but he is working through corporate in California to attempt to get the group restored. 73, Rick, KV9U
Re: [digitalradio] Modes - What are they and What about New Developement??
Hi Kevin, Perhaps it might help to use the ITU three symbol Classification of Emissions? The first symbol considers the main carrier modulation with letters such as A = DSB AM, B = independent sidebands, etc. This would give you the AM modes and the F = FM and G = PM modulation types. Then they include the second symbol which is the nature of the signal that is modulating the main carrier such as 0 = no modulation, 1 = quantized or digital signal with no subcarrier, 2 = quantized or digital signal with sub carrier and 3 single analog channel. Finally, they include the third symbol or type of information to be transmitted such as N = no information, A = telegraphy using manual aural reception, B = telegraphy using machine automatic reception, C = facsimile, D = Data, telecommand, telemetry, E = telephony, F = TV, etc. The various digital modes are really a combination of base modulation with the addition of a quantized signal, plus the type of information. The only modulation that hams typical use are AM and FM/PM and if digital modes are used, they are superimposed on the base modulation. Hope that might shed some light on the matter. 73, Rick, KV9U Gmail - Kevin, Natalia, Stacey Rochelle wrote: Hi All, I am hoping with the number of members in this group that someone might be able to answer my question. Many years ago, as we know radio started off with CW, then AM was developed, with an improvement to only use one part of the AM carrier to produce SSB with carrier or SSB suppressed carrier. Then somebody developed FM. Now in my view this gives 4 actual modes? But I see you say (Maybe), we have all the digital modes. But are these actually modes? Why I ask and the reason for the question, is these are still using one of the current 4 above, over a SSB carrier for the likes of PSK-31, SSTV etc, or FM for the likes of Packet. So will the future be able to bring us anything new that will improve the usablility of radio? Doing a search on Google brings up thousands of hits, but none actually answer the questions, most also class each digital type as a mode. Would be very interested in your thoughts. If you do not feel this is the fourm to reply, a direct email to sparcnz(nospam)@gmail.com will be fine. (please remove the (nospam) before sending, I am trying to limit the amount of spam) Regards and thanks for looking at this thread. Kevin, ZL1KFM.
Re: [digitalradio] illinoisdigital group
Just a note here to anyone who is the owner of any Yahoo Group. NEVER have just a single owner email address. At a minimum use a second email address of your own from a different domain and make that person an owner too. If there is only one owner and that address bounces for some reason you can end up in yahoo hell trying to get things running again. Tim, N9PUZ Rick W wrote: I was able to contact Mark, WB9QZB, and he indicated that his yahoo e-mail account and the group were disabled by Yahoo with no notice or explanation. It is very difficult to even contact Yahoo customer service, which is offshore, but he is working through corporate in California to attempt to get the group restored. 73, Rick, KV9U
RE: [digitalradio] Modes - What are they and What about New Developement??
There are three characteristics you can change on an RF signal: amplitude (CW, AM, SSB, etc), phase, and frequency. Even then if you squint a little phase and frequency modulation become basically the same. So the fundamental methods of modulating a signal are all known and used. Nothing new there. Mixing those in various ways gives all the different digital modes of operation. What has been realized in with the advent of digital signal processing (DSP) is all the modulation and modes are mathematically related using sine and cosine functions that are mixed to provide the final signal. The real unknown is how to maximize throughput to approach the Shannon Limit. An open question is whether deciphering such a message can be done in a reasonable time frame. We currently have digital techniques which are efficient but are only suitable for message passing, not chatting or voice, since the latency is on the order of seconds. - 73 - Rud Merriam K5RUD ARES AEC Montgomery County, TX http://TheHamNetwork.net http://thehamnetwork.net/ -Original Message- From: Gmail - Kevin, Natalia, Stacey Rochelle [mailto:spar...@gmail.com] Sent: Sunday, February 22, 2009 5:30 PM To: digitalradio@yahoogroups.com Subject: [digitalradio] Modes - What are they and What about New Developement?? Hi All, I am hoping with the number of members in this group that someone might be able to answer my question. Many years ago, as we know radio started off with CW, then AM was developed, with an improvement to only use one part of the AM carrier to produce SSB with carrier or SSB suppressed carrier. Then somebody developed FM. Now in my view this gives 4 actual modes? But I see you say (Maybe), we have all the digital modes. But are these actually modes? Why I ask and the reason for the question, is these are still using one of the current 4 above, over a SSB carrier for the likes of PSK-31, SSTV etc, or FM for the likes of Packet. So will the future be able to bring us anything new that will improve the usablility of radio? Doing a search on Google brings up thousands of hits, but none actually answer the questions, most also class each digital type as a mode. Would be very interested in your thoughts. If you do not feel this is the fourm to reply, a direct email to sparcnz(nospam)@gmail.com will be fine. (please remove the (nospam) before sending, I am trying to limit the amount of spam) Regards and thanks for looking at this thread. Kevin, ZL1KFM. skype:sparc_nz?call My status Get Skype http://www.skype.com/go/download and call me for free. sparc_nz Description: Binary data
Re: [digitalradio] Re: NBEMS QST article/digital weak signal FM
Vojtech, Thank you for that explanation. I didn't know the modulation mode would make a difference. It would have been interesting to test the theory with Skip. Unfortunately, we live too far apart for VHF/FM. Thanks again... Tony - K2MO - Original Message - From: Vojtech Bubnik bubn...@seznam.cz To: digitalradio@yahoogroups.com Sent: Sunday, February 22, 2009 7:53 AM Subject: [digitalradio] Re: NBEMS QST article/digital weak signal FM Hi Tony. I suppose the reason is that we are comparing MFSK16/DominoEX over FM versus MFSK16/DominoEX over SSB. I believe they are just different animals. SSB only shifts signals in frequency. FM does much more complex (in mathematical sense) transformation. Skip is doing interesting pioneering work. Digital modulation over common voice FM transceiver will have different noise and distortion properties than SSB. It will be influenced by noise properties of FM, preemphasis/deemphasis, how FM is modulated (pulling VFO inside the phase loop?) etc. Pulling varactor inside the phase loop will distort low frequencies (phase loop acts against the modulation), therefore baseband modulation is difficult. It brings back the memories of my teenage packet radio obsession. At that time the modulation modes were limited mainly by circuit complexity and there was no DSP. Common handhelds were modulated with BELL202 1200Bd two tone synchronous modulation. 9k6 enabled transceivers allowed direct modulation of the VFO varactor by bypassing all the microphone circuit, preemphasis and clipping. I suppose Skip's target is the first group of transceivers, where the modulation/demodulation amplitude and phase response is unknown. Skip, it would be interesting, if you could investigate, which modulation bandwidths and at which center audio frequency the common FM transceivers work best with common HF weak signal digital modes. Keep the good work. Someone able to do the math? 73, Vojtech OK1IAK White noise tests show DominioEX-4 to be a bit more sensitive than MFSK16, but it doesn't seem to handle HF distortion nearly as well. I was surprised that it did better than MFSK16 with multipath and was wondering if you thought the better throughput was due to MFSK16 tuning issues rather than actual robustness? Tony - KHMU
Re: [digitalradio] Re: NBEMS QST article/digital weak signal FM
Skip, The surprise was an unexpected, consistent, fast flutter which did not seem to affect FM nearly as badly as SSB. I recently had a 100+ mile QSO on 2 meter CW. The contact involved a lot of aircraft scatter with frequency shifts in excess of 50Hz. There were other signal components mixed in as well. Sine your digital mode tests involved FM and SSB, I would imagine that the lack of Doppler on FM would add stability to the signal and could be part of the reason for the improvement. We see this often with FM satellites where the Doppler shift is not detected in the audio as it is on on SSB/CW satellites. Just a thought... Tony - K2MO - Original Message - From: kh6ty kh...@comcast.net To: digitalradio@yahoogroups.com Sent: Sunday, February 22, 2009 8:58 AM Subject: [digitalradio] Re: NBEMS QST article/digital weak signal FM Hi Vojtech, Thanks for the tip. I totally forgot about the possible effect of deemphasis and what effect the center audio frequency might have. Our goal with NBEMS has always been able to reach at least 100 miles reliably, in order to span the largest expected disaster area to reach Internet or phone connectivity. We were recently surprised to find over a 117 mile path on 2 meters, that, on the average, FM with DominoEx actually worked better than SSB with DominoEx, even with the poorer S/N of FM compared to SSB. The surprise was an unexpected, consistent, fast flutter which did not seem to affect FM nearly as badly as SSB. Thanks to Tony's wondering, we will continue to evaluate different modes (and different audio center frequencies!) and post the results here. 73, Skip KH6TY Skip, it would be interesting, if you could investigate, which modulation bandwidths and at which center audio frequency the common FM transceivers work best with common HF weak signal digital modes. Keep the good work. Someone able to do the math? 73, Vojtech OK1IAK White noise tests show DominioEX-4 to be a bit more sensitive than MFSK16, but it doesn't seem to handle HF distortion nearly as well. I was surprised that it did better than MFSK16 with multipath and was wondering if you thought the better throughput was due to MFSK16 tuning issues rather than actual robustness? Tony - KHMU
[digitalradio] FREQUENCIES RFSM8000 and MIL-Re: RFSM8000 qrg's?
Hi Wolf, 1806.0 --- In digitalradio@yahoogroups.com, Wolf, oe7ftj wolf.hoel...@... wrote: Hi all! Are there CoA frequencies with RFSM8000 between individuals or dedicated frequencies with automatic stations or servers or gates with RFSM8000 modulation? We have done some good tests regionally here and would like to connect stations mostly in europe for EmComm tests. 73 de Wolf, oe7ftj Innsbruck, Austria
