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Changes in signal with speed

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  • qwiz@bellsouth.net
    Anyone ever pay attention to signal changes with speed of movement? Driving, in an area, that, at 30 mph, have high quality clear signal. At 70 mph, spots in
    Message 1 of 15 , Nov 30, 2011
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      Anyone ever pay attention to signal changes with speed of movement?

      Driving, in an area, that, at 30 mph, have high quality clear signal.
      At 70 mph, spots in that area cant even key the repeater. and any signal from the repeater is ,, rough at best.

      Checked this theory on a 5 Mile stretch of Hwy, making about 5 trips in same direction, low speeds, higher speeds, stopped. All using same radio. After that, I noticed the same effect in different area's,, including an area just one mile from the tower.

      Wonder if anyone is familiar with this phenomenon and knows about what speed you actually trigger signal lose.
      Just a interesting thought of interest.

      Dont seem to notice this with cell coverage. so makes me wonder if, its frequency range related or ?



      tom
    • Moe
      Tom I would also check the cars voltage & engine noise getting into the radio.In all my years playing with radios the only thing that comes to mind is called
      Message 2 of 15 , Dec 1, 2011
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        Tom I would also check the cars voltage & engine noise getting into the radio.In all my years playing with radios the only thing that comes to mind is called picked fence were the signal will fludder.

        -----Original Message-----
        From: qwiz@... <qwiz@...>
        Sent: Wednesday, November 30, 2011 9:56 PM
        To: GMRS@yahoogroups.com
        Subject: [GMRS] Changes in signal with speed


        Anyone ever pay attention to signal changes with speed of movement?

        Driving, in an area, that, at 30 mph, have high quality clear signal.
        At 70 mph, spots in that area cant even key the repeater. and any signal from the repeater is ,, rough at best.

        Checked this theory on a 5 Mile stretch of Hwy, making about 5 trips in same direction, low speeds, higher speeds, stopped. All using same radio. After that, I noticed the same effect in different area's,, including an area just one mile from the tower.

        Wonder if anyone is familiar with this phenomenon and knows about what speed you actually trigger signal lose.
        Just a interesting thought of interest.

        Dont seem to notice this with cell coverage. so makes me wonder if, its frequency range related or ?

        tom


        Reply to sender | Reply to group |

        [The entire original message is not included]

        [Non-text portions of this message have been removed]
      • Don Stiver
        SPEED HAS LITTLE TO DO WITH IT. I WOULD SAY YOU ARE HAVING COVERAGE ISSUES DUE TO OBJECTS YOU ARE PASSING BETWEEN YOU AND THE REPEATER YOU ARE USING,
        Message 3 of 15 , Dec 1, 2011
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          SPEED HAS LITTLE TO DO WITH IT. I WOULD SAY YOU ARE HAVING COVERAGE ISSUES DUE TO OBJECTS YOU ARE PASSING BETWEEN YOU AND THE REPEATER YOU ARE USING, ESPECIALLY IF THE REPEATERS ARE LOW LEVEL ( NOT LOCATED ON A TALL BUILDING OR A MOUNTAIN TOP) MY GMRS AND UHF HAM REPEATER ARE 1500 FT TUCSON AND MOST OF THE SURROUNDING AREA. I ALSO USE THE CACTUS HAM RADIO SYSTEM ALOT. I AM AN INVESTIGATOR> I DRIVE 150-250 MILES A DAY> I DO HAVE NEVER EXPERIENCED ANY EFFECT OF SPEED ON MY REPEATER USE> DON K7LHR

          [Non-text portions of this message have been removed]
        • Joel Kogen
          Yes they will I hold two lic gmrs and ham And both time the sent me a note Sent from my BlackBerry® smartphone with Nextel Direct Connect ... From: Moe
          Message 4 of 15 , Dec 1, 2011
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            Yes they will I hold two lic gmrs and ham
            And both time the sent me a note

            Sent from my BlackBerry� smartphone with Nextel Direct Connect

            -----Original Message-----
            From: Moe <moe19542000@...>
            Sender: GMRS@yahoogroups.com
            Date: Thu, 1 Dec 2011 07:30:45
            To: <GMRS@yahoogroups.com>
            Reply-To: GMRS@yahoogroups.com
            Subject: RE: [GMRS] Changes in signal with speed

            Tom I would also check the cars voltage & engine noise getting into the radio.In all my years playing with radios the only thing that comes to mind is called picked fence were the signal will fludder.

            -----Original Message-----
            From: qwiz@... <qwiz@...>
            Sent: Wednesday, November 30, 2011 9:56 PM
            To: GMRS@yahoogroups.com
            Subject: [GMRS] Changes in signal with speed


            Anyone ever pay attention to signal changes with speed of movement?

            Driving, in an area, that, at 30 mph, have high quality clear signal.
            At 70 mph, spots in that area cant even key the repeater. and any signal from the repeater is ,, rough at best.

            Checked this theory on a 5 Mile stretch of Hwy, making about 5 trips in same direction, low speeds, higher speeds, stopped. All using same radio. After that, I noticed the same effect in different area's,, including an area just one mile from the tower.

            Wonder if anyone is familiar with this phenomenon and knows about what speed you actually trigger signal lose.
            Just a interesting thought of interest.

            Dont seem to notice this with cell coverage. so makes me wonder if, its frequency range related or ?

            tom


            Reply to sender | Reply to group |

            [The entire original message is not included]

            [Non-text portions of this message have been removed]




            [Non-text portions of this message have been removed]
          • A Hoecker
            Tom, Your radio transmitted signal is traveling at a speed of approximately 186,000 MILES PER SECOND!! I would suggest if you add or subtract even 100 MPH from
            Message 5 of 15 , Dec 1, 2011
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              Tom,
              Your radio transmitted signal is traveling at a speed of approximately
              186,000 MILES PER SECOND!! I would suggest if you add or subtract even
              100 MPH from that speed you could not tell the difference!

              You did not mention if you are using an external Roof Top antenna or if
              you are holding a hand held unit using the rubber ducky (attenuator)
              antenna? This info would be helpful. If it is a rooftop antenna and
              perhaps a Mag Mount style we could search for answers there. If it is a
              solidly mounted and well grounded external antenna better yet. Please
              let us know.

              If this is a hand held unit there are a few things that COULD come into
              the picture. What is the traffic like around your car when this is
              happening? You did not mention where you are traveling and how far away
              is the receiving station? Is this a repeater station?

              In weak signal areas you may be getting blocking and added gain from
              other vehicles, large trucks in particular. This might seem worse if you
              are passing them rapidly however I would suspect an antenna problem.
              Please let us know what you have on the roof or in your hand for an
              antenna and we can go from there.

              August
              ================================================================================
              hem rapidly however I would suspect an antenna
              problem. Please let us know what you have on the roof or in your
              hand for an antenna and we can go from there.<br>
              <br>
              August<br>
              ================================================================================<br>
              </body>
              </html>
            • David A. Behar
              Hi Tom, Are you using a mobile antenna, or is this a handheld with its own antenna? David ... From: qwiz@bellsouth.net Sent: Wednesday, November 30, 2011 7:56
              Message 6 of 15 , Dec 1, 2011
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                Hi Tom,

                Are you using a mobile antenna, or is this a handheld with its own antenna?

                David

                ----- Original Message -----
                From: qwiz@...
                Sent: Wednesday, November 30, 2011 7:56 PM

                Anyone ever pay attention to signal changes with speed of movement?

                Driving, in an area, that, at 30 mph, have high quality clear signal.
                At 70 mph, spots in that area cant even key the repeater. and any signal from the repeater is ,, rough at best.

                Checked this theory on a 5 Mile stretch of Hwy, making about 5 trips in same direction, low speeds, higher speeds, stopped. All using same radio. After that, I noticed the same effect in different area's,, including an area just one mile from the tower.

                Wonder if anyone is familiar with this phenomenon and knows about what speed you actually trigger signal lose.
                Just a interesting thought of interest.

                Dont seem to notice this with cell coverage. so makes me wonder if, its frequency range related or ?

                tom


                [Non-text portions of this message have been removed]
              • Joe Leikhim
                There are several parameters which affect radio propagation. Log Normal fading which is the slow attenuation of the signal along the path from the transmitter
                Message 7 of 15 , Dec 1, 2011
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                  There are several parameters which affect radio propagation. Log Normal
                  fading which is the slow attenuation of the signal along the path from
                  the transmitter to the receiver, Rayleigh fading which is fast fading
                  and includes signal cancellations from reflected signals arriving at the
                  receiver and Doppler shift.

                  To put in simple perspective:

                  If you are within line of site of the transmitter, and in a relatively
                  flat open area and drive slowly toward or away from the transmitter
                  (while still in line of sight, you will experience log normal fading and
                  the signal will smoothly vary in signal strength with relatively small
                  variation around the mean.

                  If you do the same experiement in a built up area of buildings, or in rough terrain, reflections will arrive at the receiver and may be in phase or out of phase with the main signal. The in phase signals are additive in power and will contribute to a modest increase in signal strenght. If they arrive out of phase, they can rapidly create a subtraction in power that can be observed as sharp loss of signal strength in several 10's to as much as 40 dB cancellation. This is the Rayleigh fading component and if you are traveling quickly, the cancellations can arrive in such quick succession as to create audible static noise and eventual blocking of the squelch. If you drive or walk slowly, the signal fades and reappears slow enough that moving the antenna a few inches (at UHF wavelenghts) will recapture a strong signal.

                  If you tune a distant FM broadcast station on a clear channel,using your car radio, you can test this theory easily.

                  The doppler effect is insignificant to 462 MHz analog signals but becomes an important component at higher frequencies and high speed digital signals.



                  --
                  Joe Leikhim

                  Leikhim and Associates
                  Communications Consultants
                  Oviedo, Florida

                  www.Leikhim.com

                  JLeikhim@...

                  407-982-0446

                  Note to GMail Account users. Due to an abnormally high volume of spam originating from bogus GMail accounts, I have found it necessary to block certain GMail traffic. Please phone me if you believe your message was not received.
                • Joe Leikhim
                  Tom; I missed the second half of your question. The speed is frequency/wavelength dependent and also depends a great deal on signal power. Rayleigh fading can
                  Message 8 of 15 , Dec 1, 2011
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                    Tom;
                    I missed the second half of your question.

                    The speed is frequency/wavelength dependent and also depends a great
                    deal on signal power. Rayleigh fading can be largely overcome by a 10 to
                    20 dB increase in signal strength.

                    Cellular systems which use CDMA as most do, employ what is called a RAKE
                    receiver that receives several signals simultaneously (all the
                    reflections as well as main signal) and in post processing takes all of
                    the out of phase information and correlates it with the in phase signals
                    thus overcoming the Rayleigh fading. In this way, the reflected signals
                    (multi-path) which were bad for analog signals and older digial
                    technology, are put to good use reconstituting a better signal. It is as
                    they say "magic"!

                    More here:

                    http://en.wikipedia.org/wiki/Rake_receiver

                    --
                    Joe Leikhim

                    Leikhim and Associates
                    Communications Consultants
                    Oviedo, Florida

                    www.Leikhim.com

                    JLeikhim@...

                    407-982-0446

                    Note to GMail Account users. Due to an abnormally high volume of spam originating from bogus GMail accounts, I have found it necessary to block certain GMail traffic. Please phone me if you believe your message was not received.
                  • qwiz@bellsouth.net
                    Yea, I am familiar with picketing. I have used / dealt with two way radio since my mid teen years when i was a member of the fire department. Have had /
                    Message 9 of 15 , Dec 1, 2011
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                      Yea, I am familiar with picketing. I have used / dealt with two way radio since my mid teen years when i was a member of the fire department. Have had / dealt with them many times over the years.

                      I was using the hand held w/rubberduckie. It does not appear to be environmental.

                      If i the start and stop points, are, about 5 miles apart. and between 5 to 8 miles from the tower. I know my tower is not prime as it is a personal tower i put up myself because I cant get into commercial tower sites locally.

                      this same travel point, at about 30 miles an hour, I can transmit and receive very clearly at all points along that route.

                      at 70 miles an hour, the same route gets a lot of static on receive, and spotty transmissions.

                      I made the trip about 10 times one day at different speeds when I noticed some spotty transmissions in an area that should be red hot.

                      In all my 25 years of dealing with radio's. fire, ems, and private. I had never noticed this. so, I figure it was tower location, coupled with the movement. This is a mountainous area in southeastern Kentucky. But in this particular route, I was able to see the drastic change from crystal clear to very fussy pending speed of travel over numerous trips.

                      Tom
                    • Facility 406 DM09
                      Wonder if anyone is familiar with this phenomenon and knows about what speed you actually trigger signal lose. That would be just faster than the speed of
                      Message 10 of 15 , Dec 1, 2011
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                        "Wonder if anyone is familiar with this phenomenon and knows about what
                        speed you actually trigger signal lose."

                        That would be just faster than the speed of light. Think about this...
                        Some spacecraft travel around 35,000 MPH. They don't have the problem your
                        describing, so speed isn't a factor.

                        Most antennas flex at high speed and in a fringe areas, areas with heavy
                        foliage or obstructions, the change in polarization can be enough to cause
                        dropouts.

                        I was testing a military antenna once against a 5/8 wavelength whip. At 60
                        MPH, the whip, about 4' long had drops, and fades in signal from a fixed
                        source due to flexing, the Military antenna, about 12" tall, 1" thick and
                        not able to flex, did not.

                        As for the lack of this with your cellular coverage, cellular is digital,
                        there is a delay while the bits the system receives and assembles before
                        producing what you hear is put into order and gaps filled for
                        "uninterruptible service". I notice this with a digital system in one of my
                        trucks. I pass under obstructions, can see the fades and complete drops in
                        signal strength, if I get any glitch it's about ten seconds later when I'm
                        in the clear, but only if I pass under and object slowly and there is too
                        much loss of data.

                        Kurt
                      • wa2ntw
                        If it is not picket fencing then have you checked the cable and antenna at the repeater? A bad antenna is not easy to find but I had one that got hit by
                        Message 11 of 15 , Dec 1, 2011
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                          If it is not picket fencing then have you checked the cable and antenna at the repeater? A bad antenna is not easy to find but
                          I had one that got hit by lightning and showed no outside marks but
                          the inside was not pretty. Borrow a watt meter and check forward and
                          reverse power. If reverse is low then check at the antenna itself and see if it is the same reading.
                          The next question is how close to trees are you? Evergreens in particular can cause the effect you are describing.
                          Lastly have you checked your portable on another repeater?
                          450 Mhz has some strange effects versus VHF.


                          --- In GMRS@yahoogroups.com, "qwiz@..." <qwiz@...> wrote:
                          >
                          >
                          > Yea, I am familiar with picketing. I have used / dealt with two way radio since my mid teen years when i was a member of the fire department. Have had / dealt with them many times over the years.
                          >
                          > I was using the hand held w/rubberduckie. It does not appear to be environmental.
                          >
                          > If i the start and stop points, are, about 5 miles apart. and between 5 to 8 miles from the tower. I know my tower is not prime as it is a personal tower i put up myself because I cant get into commercial tower sites locally.
                          >
                          > this same travel point, at about 30 miles an hour, I can transmit and receive very clearly at all points along that route.
                          >
                          > at 70 miles an hour, the same route gets a lot of static on receive, and spotty transmissions.
                          >
                          > I made the trip about 10 times one day at different speeds when I noticed some spotty transmissions in an area that should be red hot.
                          >
                          > In all my 25 years of dealing with radio's. fire, ems, and private. I had never noticed this. so, I figure it was tower location, coupled with the movement. This is a mountainous area in southeastern Kentucky. But in this particular route, I was able to see the drastic change from crystal clear to very fussy pending speed of travel over numerous trips.
                          >
                          > Tom
                          >
                        • Tom
                          Well now, the repeater area is clear of evergreens, a few mature tree s around, but the antenna is actually above all but one , maybe two of the tree s on
                          Message 12 of 15 , Dec 1, 2011
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                            Well now, the repeater area is clear of evergreens, a few mature
                            tree's around, but the antenna is actually above all but one , maybe two
                            of the tree's on that mountain at maybe 100 from them.

                            the area I noticed this effect in, is actually an area that has some of
                            the national forest, with a lot of Pine, other evergreen tree's.
                            in fact, the area is sorta a straight shot through a valley. maybe
                            could explain the effect based on what you and some of the others have
                            commented.


                            I have never tried to use a watt meter to check the forward/reverse
                            power. Know of a good info sheet somewhere on line i can take a look
                            at so that I dont do any damage while trying to do so?

                            Tom




                            On 12/1/2011 4:42 PM, wa2ntw wrote:
                            >
                            > If it is not picket fencing then have you checked the cable and
                            > antenna at the repeater? A bad antenna is not easy to find but
                            > I had one that got hit by lightning and showed no outside marks but
                            > the inside was not pretty. Borrow a watt meter and check forward and
                            > reverse power. If reverse is low then check at the antenna itself and
                            > see if it is the same reading.
                            > The next question is how close to trees are you? Evergreens in
                            > particular can cause the effect you are describing.
                            > Lastly have you checked your portable on another repeater?
                            > 450 Mhz has some strange effects versus VHF.
                            >
                            > --- In GMRS@yahoogroups.com <mailto:GMRS%40yahoogroups.com>,
                            > "qwiz@..." <qwiz@...> wrote:
                            > >
                            > >
                            > > Yea, I am familiar with picketing. I have used / dealt with two way
                            > radio since my mid teen years when i was a member of the fire
                            > department. Have had / dealt with them many times over the years.
                            > >
                            > > I was using the hand held w/rubberduckie. It does not appear to be
                            > environmental.
                            > >
                            > > If i the start and stop points, are, about 5 miles apart. and
                            > between 5 to 8 miles from the tower. I know my tower is not prime as
                            > it is a personal tower i put up myself because I cant get into
                            > commercial tower sites locally.
                            > >
                            > > this same travel point, at about 30 miles an hour, I can transmit
                            > and receive very clearly at all points along that route.
                            > >
                            > > at 70 miles an hour, the same route gets a lot of static on receive,
                            > and spotty transmissions.
                            > >
                            > > I made the trip about 10 times one day at different speeds when I
                            > noticed some spotty transmissions in an area that should be red hot.
                            > >
                            > > In all my 25 years of dealing with radio's. fire, ems, and private.
                            > I had never noticed this. so, I figure it was tower location, coupled
                            > with the movement. This is a mountainous area in southeastern
                            > Kentucky. But in this particular route, I was able to see the drastic
                            > change from crystal clear to very fussy pending speed of travel over
                            > numerous trips.
                            > >
                            > > Tom
                            > >
                            >
                            >



                            [Non-text portions of this message have been removed]
                          • Tom
                            Hey, Joe.. Thanks for all the thought and comment on this. after reading all the comments, maybe the area where the effect is occurring could account for it?
                            Message 13 of 15 , Dec 1, 2011
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                              Hey, Joe..

                              Thanks for all the thought and comment on this. after reading all the
                              comments, maybe the area where the effect is occurring could account for it?

                              a rather straight shot through a valley in a national forest area with
                              lots of ever green vegetation.

                              At any rate, Prolly(Kentucky Hillbilly showing through here :-D ) not
                              something I will be able to have a large impact on with the tower height
                              i am currently at.

                              Just had never seen speed have an effect on it. but at the point i
                              tested the though, its all i could come up with,, crystal clear all the
                              way at 30mph totally 10-1 at 70 mph

                              Man, I wish I could get into a good tower spot.

                              Tom


                              On 12/1/2011 1:33 PM, Joe Leikhim wrote:
                              >
                              > There are several parameters which affect radio propagation. Log Normal
                              > fading which is the slow attenuation of the signal along the path from
                              > the transmitter to the receiver, Rayleigh fading which is fast fading
                              > and includes signal cancellations from reflected signals arriving at the
                              > receiver and Doppler shift.
                              >
                              > To put in simple perspective:
                              >
                              > If you are within line of site of the transmitter, and in a relatively
                              > flat open area and drive slowly toward or away from the transmitter
                              > (while still in line of sight, you will experience log normal fading and
                              > the signal will smoothly vary in signal strength with relatively small
                              > variation around the mean.
                              >
                              > If you do the same experiement in a built up area of buildings, or in
                              > rough terrain, reflections will arrive at the receiver and may be in
                              > phase or out of phase with the main signal. The in phase signals are
                              > additive in power and will contribute to a modest increase in signal
                              > strenght. If they arrive out of phase, they can rapidly create a
                              > subtraction in power that can be observed as sharp loss of signal
                              > strength in several 10's to as much as 40 dB cancellation. This is the
                              > Rayleigh fading component and if you are traveling quickly, the
                              > cancellations can arrive in such quick succession as to create audible
                              > static noise and eventual blocking of the squelch. If you drive or
                              > walk slowly, the signal fades and reappears slow enough that moving
                              > the antenna a few inches (at UHF wavelenghts) will recapture a strong
                              > signal.
                              >
                              > If you tune a distant FM broadcast station on a clear channel,using
                              > your car radio, you can test this theory easily.
                              >
                              > The doppler effect is insignificant to 462 MHz analog signals but
                              > becomes an important component at higher frequencies and high speed
                              > digital signals.
                              >
                              > --
                              > Joe Leikhim
                              >
                              > Leikhim and Associates
                              > Communications Consultants
                              > Oviedo, Florida
                              >
                              > www.Leikhim.com
                              >
                              > JLeikhim@... <mailto:JLeikhim%40Leikhim.com>
                              >
                              > 407-982-0446
                              >
                              > Note to GMail Account users. Due to an abnormally high volume of spam
                              > originating from bogus GMail accounts, I have found it necessary to
                              > block certain GMail traffic. Please phone me if you believe your
                              > message was not received.
                              >
                              >



                              [Non-text portions of this message have been removed]
                            • Jack
                              tom, where in KY? ... From: Tom Sent: Thursday, December 01, 2011 7:40 PM To: GMRS@yahoogroups.com Subject: Re: [GMRS] Re: Changes in signal with speed Hey,
                              Message 14 of 15 , Dec 1, 2011
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                                tom, where in KY?

                                -----Original Message-----
                                From: Tom
                                Sent: Thursday, December 01, 2011 7:40 PM
                                To: GMRS@yahoogroups.com
                                Subject: Re: [GMRS] Re: Changes in signal with speed

                                Hey, Joe..

                                Thanks for all the thought and comment on this. after reading all the
                                comments, maybe the area where the effect is occurring could account for it?

                                a rather straight shot through a valley in a national forest area with
                                lots of ever green vegetation.

                                At any rate, Prolly(Kentucky Hillbilly showing through here :-D ) not
                                something I will be able to have a large impact on with the tower height
                                i am currently at.

                                Just had never seen speed have an effect on it. but at the point i
                                tested the though, its all i could come up with,, crystal clear all the
                                way at 30mph totally 10-1 at 70 mph

                                Man, I wish I could get into a good tower spot.

                                Tom


                                On 12/1/2011 1:33 PM, Joe Leikhim wrote:
                                >
                                > There are several parameters which affect radio propagation. Log Normal
                                > fading which is the slow attenuation of the signal along the path from
                                > the transmitter to the receiver, Rayleigh fading which is fast fading
                                > and includes signal cancellations from reflected signals arriving at the
                                > receiver and Doppler shift.
                                >
                                > To put in simple perspective:
                                >
                                > If you are within line of site of the transmitter, and in a relatively
                                > flat open area and drive slowly toward or away from the transmitter
                                > (while still in line of sight, you will experience log normal fading and
                                > the signal will smoothly vary in signal strength with relatively small
                                > variation around the mean.
                                >
                                > If you do the same experiement in a built up area of buildings, or in
                                > rough terrain, reflections will arrive at the receiver and may be in
                                > phase or out of phase with the main signal. The in phase signals are
                                > additive in power and will contribute to a modest increase in signal
                                > strenght. If they arrive out of phase, they can rapidly create a
                                > subtraction in power that can be observed as sharp loss of signal
                                > strength in several 10's to as much as 40 dB cancellation. This is the
                                > Rayleigh fading component and if you are traveling quickly, the
                                > cancellations can arrive in such quick succession as to create audible
                                > static noise and eventual blocking of the squelch. If you drive or
                                > walk slowly, the signal fades and reappears slow enough that moving
                                > the antenna a few inches (at UHF wavelenghts) will recapture a strong
                                > signal.
                                >
                                > If you tune a distant FM broadcast station on a clear channel,using
                                > your car radio, you can test this theory easily.
                                >
                                > The doppler effect is insignificant to 462 MHz analog signals but
                                > becomes an important component at higher frequencies and high speed
                                > digital signals.
                                >
                                > --
                                > Joe Leikhim
                                >
                                > Leikhim and Associates
                                > Communications Consultants
                                > Oviedo, Florida
                                >
                                > www.Leikhim.com
                                >
                                > JLeikhim@... <mailto:JLeikhim%40Leikhim.com>
                                >
                                > 407-982-0446
                                >
                                > Note to GMail Account users. Due to an abnormally high volume of spam
                                > originating from bogus GMail accounts, I have found it necessary to
                                > block certain GMail traffic. Please phone me if you believe your
                                > message was not received.
                                >
                                >



                                [Non-text portions of this message have been removed]



                                ------------------------------------

                                Yahoo! Groups Links
                              • Tom
                                Corbin, London area s. Closest to Corbin but coverage area to both. Tom ... [Non-text portions of this message have been removed]
                                Message 15 of 15 , Dec 1, 2011
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                                  Corbin, London area's. Closest to Corbin but coverage area to both.

                                  Tom

                                  On 12/1/2011 8:13 PM, Jack wrote:
                                  >
                                  > tom, where in KY?
                                  >
                                  > -----Original Message-----
                                  > From: Tom
                                  > Sent: Thursday, December 01, 2011 7:40 PM
                                  > To: GMRS@yahoogroups.com <mailto:GMRS%40yahoogroups.com>
                                  > Subject: Re: [GMRS] Re: Changes in signal with speed
                                  >
                                  > Hey, Joe..
                                  >
                                  > Thanks for all the thought and comment on this. after reading all the
                                  > comments, maybe the area where the effect is occurring could account
                                  > for it?
                                  >
                                  > a rather straight shot through a valley in a national forest area with
                                  > lots of ever green vegetation.
                                  >
                                  > At any rate, Prolly(Kentucky Hillbilly showing through here :-D ) not
                                  > something I will be able to have a large impact on with the tower height
                                  > i am currently at.
                                  >
                                  > Just had never seen speed have an effect on it. but at the point i
                                  > tested the though, its all i could come up with,, crystal clear all the
                                  > way at 30mph totally 10-1 at 70 mph
                                  >
                                  > Man, I wish I could get into a good tower spot.
                                  >
                                  > Tom
                                  >
                                  > On 12/1/2011 1:33 PM, Joe Leikhim wrote:
                                  > >
                                  > > There are several parameters which affect radio propagation. Log Normal
                                  > > fading which is the slow attenuation of the signal along the path from
                                  > > the transmitter to the receiver, Rayleigh fading which is fast fading
                                  > > and includes signal cancellations from reflected signals arriving at the
                                  > > receiver and Doppler shift.
                                  > >
                                  > > To put in simple perspective:
                                  > >
                                  > > If you are within line of site of the transmitter, and in a relatively
                                  > > flat open area and drive slowly toward or away from the transmitter
                                  > > (while still in line of sight, you will experience log normal fading and
                                  > > the signal will smoothly vary in signal strength with relatively small
                                  > > variation around the mean.
                                  > >
                                  > > If you do the same experiement in a built up area of buildings, or in
                                  > > rough terrain, reflections will arrive at the receiver and may be in
                                  > > phase or out of phase with the main signal. The in phase signals are
                                  > > additive in power and will contribute to a modest increase in signal
                                  > > strenght. If they arrive out of phase, they can rapidly create a
                                  > > subtraction in power that can be observed as sharp loss of signal
                                  > > strength in several 10's to as much as 40 dB cancellation. This is the
                                  > > Rayleigh fading component and if you are traveling quickly, the
                                  > > cancellations can arrive in such quick succession as to create audible
                                  > > static noise and eventual blocking of the squelch. If you drive or
                                  > > walk slowly, the signal fades and reappears slow enough that moving
                                  > > the antenna a few inches (at UHF wavelenghts) will recapture a strong
                                  > > signal.
                                  > >
                                  > > If you tune a distant FM broadcast station on a clear channel,using
                                  > > your car radio, you can test this theory easily.
                                  > >
                                  > > The doppler effect is insignificant to 462 MHz analog signals but
                                  > > becomes an important component at higher frequencies and high speed
                                  > > digital signals.
                                  > >
                                  > > --
                                  > > Joe Leikhim
                                  > >
                                  > > Leikhim and Associates
                                  > > Communications Consultants
                                  > > Oviedo, Florida
                                  > >
                                  > > www.Leikhim.com
                                  > >
                                  > > JLeikhim@... <mailto:JLeikhim%40Leikhim.com>
                                  > <mailto:JLeikhim%40Leikhim.com>
                                  > >
                                  > > 407-982-0446
                                  > >
                                  > > Note to GMail Account users. Due to an abnormally high volume of spam
                                  > > originating from bogus GMail accounts, I have found it necessary to
                                  > > block certain GMail traffic. Please phone me if you believe your
                                  > > message was not received.
                                  > >
                                  > >
                                  >
                                  > [Non-text portions of this message have been removed]
                                  >
                                  > ------------------------------------
                                  >
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                                  >
                                  >



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