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T3-135 - Flat or Emphasized?

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  • Lynn W. Deffenbaugh (Mr)
    I m shaking down a new T3-135 in my Alinco DR-135 and was wondering if it transmits flat or emphasized audio on RF. The reason I m asking is a marked
    Message 1 of 10 , Aug 7, 2012
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      I'm shaking down a new T3-135 in my Alinco DR-135 and was wondering if it transmits flat or emphasized audio on RF.  The reason I'm asking is a marked difference in which stations can decode my KJ4ERJ-9 (the T3-135) vs a Kenwood D700 (KJ4ERJ-11) in the same car, with nearly identical antennas and similar power settings.

      The local digi, WX4MLB-3, HAS to be copying the signal, but rarely, if ever, decodes the T3-135.  I need to contact the digi operator, but IIRC it is a KPC-3+ which I believe is subject to the rule posited by http://www.febo.com/packet/layer-one/transmit.html

      The key message underlying this page is that packet tones should come out of the receiver speaker at equal amplitudes, or with the high tone a bit louder than the low one. Under no circumstances should the low frequency tone be louder than the high tone. A properly adjusted packet station meets this requirement.

      Flat audio on RF when run through a de-emphasis at the receiver (for instance a speaker connection to the radio) will result in many TNCs being unable to decode.  If the RF signal is emphasized (sent to the radio's microphone input or "twist"ed to appear the same), then the issue doesn't manifest itself.

      I don't know where in the transmit/receive path the T3-135 hooks in with the internal DR-135 connections, but the behavior I'm observing seems to indicate flat transmitted audio.

      Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

      PS.  I've got a KPC-3+ laying around here somewhere, maybe I'll just get it hooked up, or at least fire up a sound-card receiver on 2m and see if I can capture a pair of transmissions from the T3-135 and the 700.

      PPS.  Anyone know of any good digital oscilloscope software that samples sound-card audio and can display a waveform?


    • Scott Miller
      It s supposed to be flat, or as flat as possible with the filter circuit. I ll have to set up one of the production units and check. I know in development I
      Message 2 of 10 , Aug 7, 2012
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        It's supposed to be flat, or as flat as possible with the filter circuit.  I'll have to set up one of the production units and check.  I know in development I made some changes to component values - it wouldn't hurt to make sure those changes made it into production.

        Scott

        On 8/7/2012 6:28 AM, Lynn W. Deffenbaugh (Mr) wrote:
         

        I'm shaking down a new T3-135 in my Alinco DR-135 and was wondering if it transmits flat or emphasized audio on RF.  The reason I'm asking is a marked difference in which stations can decode my KJ4ERJ-9 (the T3-135) vs a Kenwood D700 (KJ4ERJ-11) in the same car, with nearly identical antennas and similar power settings.

        The local digi, WX4MLB-3, HAS to be copying the signal, but rarely, if ever, decodes the T3-135.  I need to contact the digi operator, but IIRC it is a KPC-3+ which I believe is subject to the rule posited by http://www.febo.com/packet/layer-one/transmit.html

        The key message underlying this page is that packet tones should come out of the receiver speaker at equal amplitudes, or with the high tone a bit louder than the low one. Under no circumstances should the low frequency tone be louder than the high tone. A properly adjusted packet station meets this requirement.

        Flat audio on RF when run through a de-emphasis at the receiver (for instance a speaker connection to the radio) will result in many TNCs being unable to decode.  If the RF signal is emphasized (sent to the radio's microphone input or "twist"ed to appear the same), then the issue doesn't manifest itself.

        I don't know where in the transmit/receive path the T3-135 hooks in with the internal DR-135 connections, but the behavior I'm observing seems to indicate flat transmitted audio.

        Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

        PS.  I've got a KPC-3+ laying around here somewhere, maybe I'll just get it hooked up, or at least fire up a sound-card receiver on 2m and see if I can capture a pair of transmissions from the T3-135 and the 700.

        PPS.  Anyone know of any good digital oscilloscope software that samples sound-card audio and can display a waveform?



      • Lynn W. Deffenbaugh (Mr)
        But I thought the over-the-air standard for AX.25 packet was emphasized audio? I m certainly not an expert on such things, but since many (if not most?) TNC
        Message 3 of 10 , Aug 7, 2012
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          But I thought the over-the-air standard for AX.25 packet was emphasized audio?  I'm certainly not an expert on such things, but since many (if not most?) TNC hookups are via radio microphone and speaker connections, this results in emphasized signals over the air (high is louder) and deemphasis on receive flattens it back out on the way to the TNC.

          If over-the-air audio is flat because of a non-microphone radio connection, then a deemphasizing receiver will end up with low tones higher which is what (apparently) some hardware decoder chips have trouble decoding.

          Just asking and trying to explain the difference in KJ4ERJ-11 (D700) and KJ4ERJ-9 (T3-135/Alinco) reception at WX4MLB-3 as well as on a road trip across the state the other weekend.

          Lynn (D) - Author of APRSISCE for Windows Mobile and Win32

          PS.  Still looking to set up a recording jig to capture waveforms from my various TNCs for comparison.  Of course, I'll also have to determine if my iCom 706/Signalink USB setup is deemphasizing on receive or providing me flat over-the-air levels.

          On 8/7/2012 2:13 PM, Scott Miller wrote:
          It's supposed to be flat, or as flat as possible with the filter circuit.  I'll have to set up one of the production units and check.  I know in development I made some changes to component values - it wouldn't hurt to make sure those changes made it into production.

          Scott

          On 8/7/2012 6:28 AM, Lynn W. Deffenbaugh (Mr) wrote:
           

          I'm shaking down a new T3-135 in my Alinco DR-135 and was wondering if it transmits flat or emphasized audio on RF.  The reason I'm asking is a marked difference in which stations can decode my KJ4ERJ-9 (the T3-135) vs a Kenwood D700 (KJ4ERJ-11) in the same car, with nearly identical antennas and similar power settings.

          The local digi, WX4MLB-3, HAS to be copying the signal, but rarely, if ever, decodes the T3-135.  I need to contact the digi operator, but IIRC it is a KPC-3+ which I believe is subject to the rule posited by http://www.febo.com/packet/layer-one/transmit.html

          The key message underlying this page is that packet tones should come out of the receiver speaker at equal amplitudes, or with the high tone a bit louder than the low one. Under no circumstances should the low frequency tone be louder than the high tone. A properly adjusted packet station meets this requirement.

          Flat audio on RF when run through a de-emphasis at the receiver (for instance a speaker connection to the radio) will result in many TNCs being unable to decode.  If the RF signal is emphasized (sent to the radio's microphone input or "twist"ed to appear the same), then the issue doesn't manifest itself.

          I don't know where in the transmit/receive path the T3-135 hooks in with the internal DR-135 connections, but the behavior I'm observing seems to indicate flat transmitted audio.

          Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

          PS.  I've got a KPC-3+ laying around here somewhere, maybe I'll just get it hooked up, or at least fire up a sound-card receiver on 2m and see if I can capture a pair of transmissions from the T3-135 and the 700.

          PPS.  Anyone know of any good digital oscilloscope software that samples sound-card audio and can display a waveform?




        • Curt, WE7U
          ... As I recall Kenwood does the flat-audio thing, and most others that hook TNC s to radios do the pre/de-emphasis bit. An excellent page about twist and
          Message 4 of 10 , Aug 7, 2012
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            On Tue, 7 Aug 2012, Lynn W. Deffenbaugh (Mr) wrote:

            > But I thought the over-the-air standard for AX.25 packet was emphasized
            > audio? I'm certainly not an expert on such things, but since many (if not
            > most?) TNC hookups are via radio microphone and speaker connections, this
            > results in emphasized signals over the air (high is louder) and deemphasis on
            > receive flattens it back out on the way to the TNC.
            >
            > If over-the-air audio is flat because of a non-microphone radio connection,
            > then a deemphasizing receiver will end up with low tones higher which is what
            > (apparently) some hardware decoder chips have trouble decoding.
            >
            > Just asking and trying to explain the difference in KJ4ERJ-11 (D700) and
            > KJ4ERJ-9 (T3-135/Alinco) reception at WX4MLB-3 as well as on a road trip
            > across the state the other weekend.

            As I recall Kenwood does the flat-audio thing, and most others that hook TNC's to radios do the pre/de-emphasis bit.

            An excellent page about twist and pre/de-emphasis by John Ackermann, N8UR:

            http://www.febo.com/packet/layer-one/transmit.html

            It doesn't appear to cover the flat vs. pre/de-emphasis subject though.

            There's this one too which points to another page about optimizing receive performance. Didn't see anything about flat audio on these two pages either.

            http://www.febo.com/packet/layer-one/index.html

            --
            Curt, WE7U. http://wetnet.net/~we7u
            APRS in Search and Rescue: http://wetnet.net/~we7u/search_and_rescue.html
          • Curt, WE7U
            ... I seem to remembers seeing something about a 20dB hit if you re going between a flat-reponse packet TNC/rig and a pre/de-emphasis packet TNC/rig. I can t
            Message 5 of 10 , Aug 7, 2012
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              On Tue, 7 Aug 2012, Curt, WE7U wrote:

              > As I recall Kenwood does the flat-audio thing, and most others that hook
              > TNC's to radios do the pre/de-emphasis bit.
              >
              > An excellent page about twist and pre/de-emphasis by John Ackermann, N8UR:
              >
              > http://www.febo.com/packet/layer-one/transmit.html
              >
              > It doesn't appear to cover the flat vs. pre/de-emphasis subject though.
              >
              > There's this one too which points to another page about optimizing receive
              > performance. Didn't see anything about flat audio on these two pages either.
              >
              > http://www.febo.com/packet/layer-one/index.html

              I seem to remembers seeing something about a 20dB hit if you're going between a flat-reponse packet TNC/rig and a pre/de-emphasis packet TNC/rig. I can't find that anywhere now with a quick search.

              The reason I mentioned Kenwood above is that they were the first ones that I remember hearing of who starting doing flat-audio in the commercial APRS radios. I'm going to assume they did that because the radios were capable of both 9600 and 1200 baud, where with 9600 baud you want flat audio. They took a shortcut by doing flat-audio with the 1200 baud stuff too. So any repeaters out there that run D700's or D710's are not going to perform well for rovers using pre/de-emphasis with 1200 baud.

              Can anyone provide a link to reasoning for the 20dB hit when crossing "modes" here?

              --
              Curt, WE7U. http://wetnet.net/~we7u
              APRS: Where it's at! http://www.xastir.org
            • Curt, WE7U
              ... seem to remembers? I type fast than I spell sometimes. ... Found this: http://www.tapr.org/pipermail/aprssig/2005-April/005545.html It mentions this near
              Message 6 of 10 , Aug 7, 2012
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                On Tue, 7 Aug 2012, Curt, WE7U wrote:

                > I seem to remembers seeing something about a 20dB hit if you're going between

                seem to remembers? I type fast than I spell sometimes.


                > a flat-reponse packet TNC/rig and a pre/de-emphasis packet TNC/rig. I can't
                > find that anywhere now with a quick search.
                >
                > The reason I mentioned Kenwood above is that they were the first ones that I
                > remember hearing of who starting doing flat-audio in the commercial APRS
                > radios. I'm going to assume they did that because the radios were capable of
                > both 9600 and 1200 baud, where with 9600 baud you want flat audio. They took
                > a shortcut by doing flat-audio with the 1200 baud stuff too. So any
                > repeaters out there that run D700's or D710's are not going to perform well
                > for rovers using pre/de-emphasis with 1200 baud.
                >
                > Can anyone provide a link to reasoning for the 20dB hit when crossing "modes"
                > here?

                Found this:

                http://www.tapr.org/pipermail/aprssig/2005-April/005545.html

                It mentions this near the end:

                "De-emphasis applied to a signal already transmitted "flat" will result in the high tone being 6 dB LOWER in level than the low tone."

                --
                Curt, WE7U. http://wetnet.net/~we7u
                Babysitting your tracker: http://info.aprs.net/index.php?title=ControlOperator
              • Bill Vodall
                ... True... ... I thought it was more like 6db. This article from QEX goes into the twist in detail... ... ... the nice article A High-Performance Sound-Card
                Message 7 of 10 , Aug 7, 2012
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                  > The reason I mentioned Kenwood above is that they were the first ones that I remember hearing of who starting doing flat-audio in the commercial APRS radios. I'm going to assume they did that because the radios were capable of both 9600 and 1200 baud, where with 9600 baud you want flat audio. They took a shortcut by doing flat-audio with the 1200 baud stuff too. So any repeaters out there that run D700's or D710's are not going to perform well for rovers using pre/de-emphasis with 1200 baud.

                  True...

                  > Can anyone provide a link to reasoning for the 20dB hit when crossing "modes" here?

                  I thought it was more like 6db.


                  This article from QEX goes into the twist in detail...

                  ----------------
                  ... the nice article "A High-Performance Sound-Card AX.25 Modem" in
                  QEX for July-August 2012 by Sivan Toledo 4X6IZ (a member of this
                  group)?

                  You can read the article here:
                  http://www.tau.ac.il/~stoledo/Bib/Pubs/QEX-JulAug-2012.pdf

                  and he blogs about it here:
                  https://sivantoledotech.wordpress.com/2012/07/18/ax25-modem/
                  >
                • James Ewen
                  Pre/deemphasis is a 6 dB per octave roll off on frequency response. The 20 dB hit on performance is talking about how not matching the pre/deemphasis would
                  Message 8 of 10 , Aug 7, 2012
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                    Pre/deemphasis is a 6 dB per octave roll off on frequency response.

                    The 20 dB hit on performance is talking about how not matching the
                    pre/deemphasis would affect total throughput, and may be a subjective
                    measurement.

                    Need to read the article to know what they are saying.




                    On 8/7/12, Bill Vodall <wa7nwp@...> wrote:
                    >> The reason I mentioned Kenwood above is that they were the first ones that
                    >> I remember hearing of who starting doing flat-audio in the commercial APRS
                    >> radios. I'm going to assume they did that because the radios were capable
                    >> of both 9600 and 1200 baud, where with 9600 baud you want flat audio.
                    >> They took a shortcut by doing flat-audio with the 1200 baud stuff too. So
                    >> any repeaters out there that run D700's or D710's are not going to perform
                    >> well for rovers using pre/de-emphasis with 1200 baud.
                    >
                    > True...
                    >
                    >> Can anyone provide a link to reasoning for the 20dB hit when crossing
                    >> "modes" here?
                    >
                    > I thought it was more like 6db.
                    >
                    >
                    > This article from QEX goes into the twist in detail...
                    >
                    > ----------------
                    > ... the nice article "A High-Performance Sound-Card AX.25 Modem" in
                    > QEX for July-August 2012 by Sivan Toledo 4X6IZ (a member of this
                    > group)?
                    >
                    > You can read the article here:
                    > http://www.tau.ac.il/~stoledo/Bib/Pubs/QEX-JulAug-2012.pdf
                    >
                    > and he blogs about it here:
                    > https://sivantoledotech.wordpress.com/2012/07/18/ax25-modem/
                    >>
                    >
                    >
                    > ------------------------------------
                    >
                    > Yahoo! Groups Links
                    >
                    >
                    >
                    >

                    --
                    Sent from my mobile device

                    James
                    VE6SRV
                  • Scott Miller
                    I think my design goal was actually about 1/2 normal pre-emphasis to split the difference, actually. I ve got to go find my notes.
                    Message 9 of 10 , Aug 7, 2012
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                      I think my design goal was actually about 1/2 normal pre-emphasis to split the difference, actually.  I've got to go find my notes.

                      On 8/7/2012 11:19 AM, Lynn W. Deffenbaugh (Mr) wrote:
                       

                      But I thought the over-the-air standard for AX.25 packet was emphasized audio?  I'm certainly not an expert on such things, but since many (if not most?) TNC hookups are via radio microphone and speaker connections, this results in emphasized signals over the air (high is louder) and deemphasis on receive flattens it back out on the way to the TNC.

                      If over-the-air audio is flat because of a non-microphone radio connection, then a deemphasizing receiver will end up with low tones higher which is what (apparently) some hardware decoder chips have trouble decoding.

                      Just asking and trying to explain the difference in KJ4ERJ-11 (D700) and KJ4ERJ-9 (T3-135/Alinco) reception at WX4MLB-3 as well as on a road trip across the state the other weekend.

                      Lynn (D) - Author of APRSISCE for Windows Mobile and Win32

                      PS.  Still looking to set up a recording jig to capture waveforms from my various TNCs for comparison.  Of course, I'll also have to determine if my iCom 706/Signalink USB setup is deemphasizing on receive or providing me flat over-the-air levels.

                      On 8/7/2012 2:13 PM, Scott Miller wrote:
                      It's supposed to be flat, or as flat as possible with the filter circuit.  I'll have to set up one of the production units and check.  I know in development I made some changes to component values - it wouldn't hurt to make sure those changes made it into production.

                      Scott

                      On 8/7/2012 6:28 AM, Lynn W. Deffenbaugh (Mr) wrote:
                       

                      I'm shaking down a new T3-135 in my Alinco DR-135 and was wondering if it transmits flat or emphasized audio on RF.  The reason I'm asking is a marked difference in which stations can decode my KJ4ERJ-9 (the T3-135) vs a Kenwood D700 (KJ4ERJ-11) in the same car, with nearly identical antennas and similar power settings.

                      The local digi, WX4MLB-3, HAS to be copying the signal, but rarely, if ever, decodes the T3-135.  I need to contact the digi operator, but IIRC it is a KPC-3+ which I believe is subject to the rule posited by http://www.febo.com/packet/layer-one/transmit.html

                      The key message underlying this page is that packet tones should come out of the receiver speaker at equal amplitudes, or with the high tone a bit louder than the low one. Under no circumstances should the low frequency tone be louder than the high tone. A properly adjusted packet station meets this requirement.

                      Flat audio on RF when run through a de-emphasis at the receiver (for instance a speaker connection to the radio) will result in many TNCs being unable to decode.  If the RF signal is emphasized (sent to the radio's microphone input or "twist"ed to appear the same), then the issue doesn't manifest itself.

                      I don't know where in the transmit/receive path the T3-135 hooks in with the internal DR-135 connections, but the behavior I'm observing seems to indicate flat transmitted audio.

                      Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

                      PS.  I've got a KPC-3+ laying around here somewhere, maybe I'll just get it hooked up, or at least fire up a sound-card receiver on 2m and see if I can capture a pair of transmissions from the T3-135 and the 700.

                      PPS.  Anyone know of any good digital oscilloscope software that samples sound-card audio and can display a waveform?





                    • Dave Miller
                      Timely Topic, After getting my T2-301 back operational I have been noticing that some stations are not copying me. In particular one of the real high profile
                      Message 10 of 10 , Aug 7, 2012
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                        Timely Topic,
                        After getting my T2-301 back operational I have been noticing that some stations are not copying me. In particular one of the real high profile ones. Checking on a service monitor my T2-301 seems to be flat with no twist. Is there any way to adjust it for some twist and see if things improve?
                        Thanks
                        Dave

                        --- In tracker2@yahoogroups.com, Scott Miller <scott@...> wrote:
                        >
                        > I think my design goal was actually about 1/2 normal pre-emphasis to
                        > split the difference, actually. I've got to go find my notes.
                        >
                        > On 8/7/2012 11:19 AM, Lynn W. Deffenbaugh (Mr) wrote:
                        > >
                        > > But I thought the over-the-air standard for AX.25 packet was
                        > > emphasized audio? I'm certainly not an expert on such things, but
                        > > since many (if not most?) TNC hookups are via radio microphone and
                        > > speaker connections, this results in emphasized signals over the air
                        > > (high is louder) and deemphasis on receive flattens it back out on the
                        > > way to the TNC.
                        > >
                        > > If over-the-air audio is flat because of a non-microphone radio
                        > > connection, then a deemphasizing receiver will end up with low tones
                        > > higher which is what (apparently) some hardware decoder chips have
                        > > trouble decoding.
                        > >
                        > > Just asking and trying to explain the difference in KJ4ERJ-11 (D700)
                        > > and KJ4ERJ-9 (T3-135/Alinco) reception at WX4MLB-3 as well as on a
                        > > road trip across the state the other weekend.
                        > >
                        > > Lynn (D) - Author of APRSISCE for Windows Mobile and Win32
                        > >
                        > > PS. Still looking to set up a recording jig to capture waveforms from
                        > > my various TNCs for comparison. Of course, I'll also have to
                        > > determine if my iCom 706/Signalink USB setup is deemphasizing on
                        > > receive or providing me flat over-the-air levels.
                        > >
                        > > On 8/7/2012 2:13 PM, Scott Miller wrote:
                        > >> It's supposed to be flat, or as flat as possible with the filter
                        > >> circuit. I'll have to set up one of the production units and check.
                        > >> I know in development I made some changes to component values - it
                        > >> wouldn't hurt to make sure those changes made it into production.
                        > >>
                        > >> Scott
                        > >>
                        > >> On 8/7/2012 6:28 AM, Lynn W. Deffenbaugh (Mr) wrote:
                        > >>>
                        > >>> I'm shaking down a new T3-135 in my Alinco DR-135 and was wondering
                        > >>> if it transmits flat or emphasized audio on RF. The reason I'm
                        > >>> asking is a marked difference in which stations can decode my
                        > >>> KJ4ERJ-9 (the T3-135) vs a Kenwood D700 (KJ4ERJ-11) in the same car,
                        > >>> with nearly identical antennas and similar power settings.
                        > >>>
                        > >>> The local digi, WX4MLB-3, HAS to be copying the signal, but rarely,
                        > >>> if ever, decodes the T3-135. I need to contact the digi operator,
                        > >>> but IIRC it is a KPC-3+ which I believe is subject to the rule
                        > >>> posited by http://www.febo.com/packet/layer-one/transmit.html
                        > >>>
                        > >>>> The key message underlying this page is that /packet tones should
                        > >>>> come out of the receiver speaker at equal amplitudes, or with the
                        > >>>> high tone a bit louder than the low one. *Under no circumstances
                        > >>>> should the low frequency tone be louder than the high tone*/. A
                        > >>>> properly adjusted packet station meets this requirement.
                        > >>>
                        > >>> Flat audio on RF when run through a de-emphasis at the receiver (for
                        > >>> instance a speaker connection to the radio) will result in many TNCs
                        > >>> being unable to decode. If the RF signal is emphasized (sent to the
                        > >>> radio's microphone input or "twist"ed to appear the same), then the
                        > >>> issue doesn't manifest itself.
                        > >>>
                        > >>> I don't know where in the transmit/receive path the T3-135 hooks in
                        > >>> with the internal DR-135 connections, but the behavior I'm observing
                        > >>> seems to indicate flat transmitted audio.
                        > >>>
                        > >>> Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32
                        > >>>
                        > >>> PS. I've got a KPC-3+ laying around here somewhere, maybe I'll just
                        > >>> get it hooked up, or at least fire up a sound-card receiver on 2m
                        > >>> and see if I can capture a pair of transmissions from the T3-135 and
                        > >>> the 700.
                        > >>>
                        > >>> PPS. Anyone know of any good digital oscilloscope software that
                        > >>> samples sound-card audio and can display a waveform?
                        > >>>
                        > >>>
                        > >>
                        > >
                        > >
                        >
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