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Re: Strength measurements with RTL-SDR dongle

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  • Bookcollector
    I m not sure exactly what I m measuring. What I m comparing is the level of the ATSC carrier in relation to the area of the signal immediately surrounding it.
    Message 1 of 16 , Jan 21, 2013
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      I'm not sure exactly what I'm measuring. What I'm comparing is the level of the ATSC carrier in relation to the area of the signal immediately surrounding it. If I spread out from 1kHz to 250kHz bandwidth it makes no difference. If I look at the whole 2mHz that I'm able to see, the peak is still the same. I believe that the display is based on the 2 mHz of spectrum the SDR is looking at. If I tune to the edge of a channel then the noise level where no signal is present is another 10 db down, more or less. So what I'm measuring when I say that the ATSC carrier is 20db above the noise is that the carrier (xx0.31mHz)is 20 db above the surrounding noise (which is signal) and about 30 db above a quiet frequency with no signal. Of course, the entire signal (adjacent noise level) is also reduced with a weak carrier.
      Ernie
      W6KAP

      --- In HDTV-in-SFbay@yahoogroups.com, Ron Economos wrote:
      >
      > Be aware that your filter bandwidth on the SDR will make a
      > huge difference in detecting carriers. A 6 kHz filter bandwidth
      > gives you a 30 dB advantage over a regular ATSC receiver
      > that must use a 6 MHz bandwidth.
      >
      > Ron W6RZ
      >
      > On 1/21/2013 12:10 PM, Bookcollector wrote:
      > >
      > > Thanks for the info. KOFY is doing an excellent job of keeping their
      > > signal in the horizontal plane over a 110 mile path. It sometimes
      > > fades but is the most consistent of the Sutro transmitters at my
      > > location (38.489/-120.589).
      > >
      > > Channel 7 is stronger today and the rapid fading is less obvious. It
      > > almost sounds like the signal is coming through an Altamont Pass wind
      > > mill.
      > >
      > > I adjusted the contrast on the waterfall and now I see carriers that
      > > are just above the noise on 15 and 31. I think 15 is Reno PBS. I
      > > notice that the channel 47 I am seeing is about 30khz high with
      > > carrier on 668.313. Or maybe I'm just seeing the offset today and not
      > > the carrier. I think that is 68 in Novato and its one of the strongest
      > > stations I receive on the horizontal antenna.
      > >
      > > Do tuners have an AFC that makes a small difference in ATSC carrier
      > > frequency immaterial?
      > >
      > > I ordered a cable to interface my 91XG antenna to the dongle. It will
      > > be interesting to see what level of quieting is needed to receive a
      > > signal.
      > > Ernie
      > > W6KAP
      > >
      >
    • Ron Economos
      Are you using the SDR# software? Ron W6RZ
      Message 2 of 16 , Jan 21, 2013
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        Are you using the SDR# software?

        Ron W6RZ

        On 1/21/2013 9:56 PM, Bookcollector wrote:
         

        I'm not sure exactly what I'm measuring. What I'm comparing is the level of the ATSC carrier in relation to the area of the signal immediately surrounding it. If I spread out from 1kHz to 250kHz bandwidth it makes no difference. If I look at the whole 2mHz that I'm able to see, the peak is still the same. I believe that the display is based on the 2 mHz of spectrum the SDR is looking at. If I tune to the edge of a channel then the noise level where no signal is present is another 10 db down, more or less. So what I'm measuring when I say that the ATSC carrier is 20db above the noise is that the carrier (xx0.31mHz)is 20 db above the surrounding noise (which is signal) and about 30 db above a quiet frequency with no signal. Of course, the entire signal (adjacent noise level) is also reduced with a weak carrier.
        Ernie
        W6KAP

        --- In HDTV-in-SFbay@yahoogroups.com, Ron Economos wrote:
        >
        > Be aware that your filter bandwidth on the SDR will make a
        > huge difference in detecting carriers. A 6 kHz filter bandwidth
        > gives you a 30 dB advantage over a regular ATSC receiver
        > that must use a 6 MHz bandwidth.
        >
        > Ron W6RZ
        >
        > On 1/21/2013 12:10 PM, Bookcollector wrote:
        > >
        > > Thanks for the info. KOFY is doing an excellent job of keeping their
        > > signal in the horizontal plane over a 110 mile path. It sometimes
        > > fades but is the most consistent of the Sutro transmitters at my
        > > location (38.489/-120.589).
        > >
        > > Channel 7 is stronger today and the rapid fading is less obvious. It
        > > almost sounds like the signal is coming through an Altamont Pass wind
        > > mill.
        > >
        > > I adjusted the contrast on the waterfall and now I see carriers that
        > > are just above the noise on 15 and 31. I think 15 is Reno PBS. I
        > > notice that the channel 47 I am seeing is about 30khz high with
        > > carrier on 668.313. Or maybe I'm just seeing the offset today and not
        > > the carrier. I think that is 68 in Novato and its one of the strongest
        > > stations I receive on the horizontal antenna.
        > >
        > > Do tuners have an AFC that makes a small difference in ATSC carrier
        > > frequency immaterial?
        > >
        > > I ordered a cable to interface my 91XG antenna to the dongle. It will
        > > be interesting to see what level of quieting is needed to receive a
        > > signal.
        > > Ernie
        > > W6KAP
        > >
        >

      • Larry Kenney
        Ernie... Here are some observations I noted to be of special interest in your list of stations received your new dongle. It appears that 40 db is the maximum
        Message 3 of 16 , Jan 22, 2013
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          Ernie...

          Here are some observations I noted to be of special interest in your list of stations received your new dongle.

          It appears that 40 db is the maximum strength indicated.  That's higher than any of the DTV receivers I've seen.  33 db is the highest signal strength I've seen on a TV.

          Your best signals are from the Walnut Grove transmitters for channels 21 and 25, which just happen to be the two CBS owned stations, but I'm surprised at the difference in strengths received from the transmitters there.  KCRA is only 18 db.

          Several stations much further away give you some surprisingly strong signals, but especially noteworthy are KEMO 32 from Mt. Saint Helena, northeast of Santa Rosa, and KICU 36 from Monument Peak, 35 miles south of San Francisco, both at 30 db.
          KQEH 50 from Monument Peak also did well at 20 db.

          I'm also surprised at how well you received some of the stations transmitting from Sutro Tower:
          KGO 7 and KQED 30 both at 20 db
          KCNS 39 at 18 db

          Mt. San Bruno didn't fair so well:
          KNTV 12 and KKPX 41 (not identified) only at 10 db
          and KTSF 27 at 0.

          My best guesses for the unidentified signals you received are:
          20 - K20JX, with transmitter located southwest of Lincoln
          24 - KNVN, Chico, with transmitter east of Red Bluff
          34 - KFSF 66 from Sutro Tower
          41 - KKPX 65 from Mt. San Bruno, as noted above
          44 - KTVU 2 from Sutro Tower
          47 - KTLN 68 transmitting from Novato
          49 - KSAO a low power station transmitting from southeast of Folsom

          Thanks for sharing your findings.

          You'll find a list of all stations within 100 miles of San Francisco listed on my DTV Station Lists:

          Larry, WB9LOZ
          SF

          - - -

          On Jan 20, 2013, at 7:54 PM, Bookcollector wrote:

           

          I recently acquired on EBay a dongle meant for DVB-T reception in Europe but which works with software as a software defined receiver from 24mHz to 1700 mHz. (a $12.50 investment, by the way)

          I decided to look at the ATSC carrier frequencies of the digital TV stations using a 440 mhz vertical non-directional antenna mounted atop a 100 foot pine tree. Here is my result:

          RF Channel db above noise
          14 30 KTNC-42
          15 0 analog 15 received
          16 0
          17 0
          18 30 KUVS-19
          19 0 KOFY-20 no signal received on the vertical at the same time my wife watching ch 20 on a 20 foot high antenna
          20 30 unknown
          21 40 KMAX-31
          22 0 analog 22 received
          23 20 KEZT-23
          24 5 unknown
          25 40 KOVR-13
          26 20 KTFK-64
          27 0
          28 18 KKPM-65(heterodyne)
          29 10 KPIX-5
          30 20 KQED-9
          31 0
          32 30 KEMO-50
          33 15 KMTP-32
          34 10 unknown
          35 18 KCRA-3
          36 30 KICU-36
          38 10 KRON-4
          39 18 KCNS-38
          40 30 KTXL-40
          41 10 unknown
          42 25 KMSX-14 (heterodyne)
          43 12 KCSM-60
          44 25 unknown
          45 25 KBCA-44
          46 20 KQCA-58
          47 10 unknown
          48 30 KSPX-29
          49 9 unknown
          50 20 KQEH-54
          51 25 KBIT-8 (heterodyne)

          2 0
          3 30 KCSO-33
          4 10 unknown
          5 0
          6 0 6 analog received
          7 20 KGO-7 (rapid fading to 10db at about twice per second. only signal with fading)
          8 20 KSBW-8
          9 30 KVIE-6
          10 30 KXTV-10
          11 0
          12 10 KNTV-11
          13 0

          Several questions - How far above quieting must an ATSC signal be to be watchable? Why would KOFY show no signal into a vertical antenna while it is being watched on a horizontal? KOFY is our most consistent Bay Area channel. On channels 26, 39, 43, and 47 I noticed another signal of equal strength 27.5kHz above the ATSC carrier {.3375}. Any idea what it is?
          Ernie
          W6KAP


        • Bookcollector
          Yes, using SDRSharp with a dongle that has the R820T tuner. Ernie
          Message 4 of 16 , Jan 22, 2013
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            Yes, using SDRSharp with a dongle that has the R820T tuner.
            Ernie

            --- In HDTV-in-SFbay@yahoogroups.com, Ron Economos wrote:
            >
            > Are you using the SDR# software?
            >
            > Ron W6RZ
            >
            > On 1/21/2013 9:56 PM, Bookcollector wrote:
            > >
            > > I'm not sure exactly what I'm measuring. What I'm comparing is the
            > > level of the ATSC carrier in relation to the area of the signal
            > > immediately surrounding it. If I spread out from 1kHz to 250kHz
            > > bandwidth it makes no difference. If I look at the whole 2mHz that I'm
            > > able to see, the peak is still the same. I believe that the display is
            > > based on the 2 mHz of spectrum the SDR is looking at. If I tune to the
            > > edge of a channel then the noise level where no signal is present is
            > > another 10 db down, more or less. So what I'm measuring when I say
            > > that the ATSC carrier is 20db above the noise is that the carrier
            > > (xx0.31mHz)is 20 db above the surrounding noise (which is signal) and
            > > about 30 db above a quiet frequency with no signal. Of course, the
            > > entire signal (adjacent noise level) is also reduced with a weak carrier.
            > > Ernie
            > > W6KAP
            > >
            > > --- In HDTV-in-SFbay@yahoogroups.com
            > > , Ron Economos wrote:
            > > >
            > > > Be aware that your filter bandwidth on the SDR will make a
            > > > huge difference in detecting carriers. A 6 kHz filter bandwidth
            > > > gives you a 30 dB advantage over a regular ATSC receiver
            > > > that must use a 6 MHz bandwidth.
            > > >
            > > > Ron W6RZ
            > > >
            > > > On 1/21/2013 12:10 PM, Bookcollector wrote:
            > > > >
            > > > > Thanks for the info. KOFY is doing an excellent job of keeping their
            > > > > signal in the horizontal plane over a 110 mile path. It sometimes
            > > > > fades but is the most consistent of the Sutro transmitters at my
            > > > > location (38.489/-120.589).
            > > > >
            > > > > Channel 7 is stronger today and the rapid fading is less obvious. It
            > > > > almost sounds like the signal is coming through an Altamont Pass wind
            > > > > mill.
            > > > >
            > > > > I adjusted the contrast on the waterfall and now I see carriers that
            > > > > are just above the noise on 15 and 31. I think 15 is Reno PBS. I
            > > > > notice that the channel 47 I am seeing is about 30khz high with
            > > > > carrier on 668.313. Or maybe I'm just seeing the offset today and not
            > > > > the carrier. I think that is 68 in Novato and its one of the
            > > strongest
            > > > > stations I receive on the horizontal antenna.
            > > > >
            > > > > Do tuners have an AFC that makes a small difference in ATSC carrier
            > > > > frequency immaterial?
            > > > >
            > > > > I ordered a cable to interface my 91XG antenna to the dongle. It will
            > > > > be interesting to see what level of quieting is needed to receive a
            > > > > signal.
            > > > > Ernie
            > > > > W6KAP
            > > > >
            > > >
            > >
            >
          • Bookcollector
            Thanks for the comments. Conditions vary a lot. Last night I scanned 72 channels while my usual scan is less than 45. I remeasured today and the maximum
            Message 5 of 16 , Jan 22, 2013
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              Thanks for the comments. Conditions vary a lot. Last night I scanned 72 channels while my usual scan is less than 45. I remeasured today and the maximum signal was 30db above adjacent noise (signal). In addition to the 100 foot high vertical with 100 feet of hardline and 100 feet of 9913 on it, I also measured signal with the tiny 4 inch antenna that came with the dongle. The antenna was taped to my window.
              -----high antenna 4 inch antenna
              Ch db above noise ---db above noise---Station-Yesterday

              2----0-----------------0------------------------
              3----20----------------15--------------KCSO--------30
              4----trace on waterfall -0-------------K04QR-------10
              5----0-----------------0
              6----0-----------------0
              7----30+rapid fade-----faint trace------KGO--------20
              8----23----------------0----------------KSBW-------20
              9----23----------------12---------------KVIE-------30
              10---30----------------trace------------KXTV-------30
              11---0-----------------0
              12---trace-------------0----------------KNTV-------10
              13---faint trace-------0 -------------Reno-------0
              14---10----------------10---------------KTNC-------30
              15---0-----------------0----------------Reno PBS---2
              16---trace on offset---0----------------Reno Univision-0
              17---0-----------------0
              18---27----------------22---------------KUVS-------30
              19---15----------------faint trace------KOFY-------0
              20---20----------------10---------------KCVU Chico-30
              21---30----------------20---------------KMAX-------40?
              22---0-----------------0
              23---30----------------20---------------KEZT-------20
              24---faint trace-------0----------------KNVN Chico-5
              25---30----------------25---------------KOVR-------40?
              26---25----------------10---------------KTFK-------20
              27---0-----------------0
              28---10/20 on offset het-6--------------KFTL SF/KMMW Stockton-18
              29---15----------------trace------------KPIX-------10
              30---15----------------trace------------KQED-------20
              31---0-----------------0
              32---10----------------15?--------------KEMO-------30
              33---6-----------------20---------------KMTP-------15
              34---15----------------0----------------KFSF-------10
              35---10----------------20---------------KCRA-------18
              36---15----------------15---------------KICU-------30
              37---
              38---12----------------12---------------KRON-------10
              39---0-----------------20 on offset-----KCNS-------18
              40---27----------------30---------------KTXL-------30
              41---0-----------------15---------------KKPX-------10
              42---20----------------15 with het------KMSX/KAXT?-25
              43---15 at offset------12 at offset-----KCSM-------20 offset
              44---10----------------slight trace-----KTVU-------25
              45---12----------------12---------------KBCA-------25
              46---8-----------------23---------------KQCA-------20
              47---trace-------------25 25khz high----KTLN-------10
              48---trace-------------23---------------KSPX-------30
              49---trace-------------6----------------KSTS-------9
              50---10----------------10---------------KQEH-------20
              51---20----------------28---------------KBTV-------25 het

              The tiny antenna with almost no feedline seemed to beat the high antenna in the 30s and 40s. On UHF we have to balance feedline loss against antenna height. The height gives us access to more stations, avoids attenuation due to the forest, but then we have the issue of getting the signal back down to the tuner. I got a demonstration of this trying to receive and decode ADS-B aircraft signals on 1090 mHz. The high antenna heard nothing while the little 4 inch antenna copied signals even inside the house. For radio, I can mount the dongle (tuner) at the antenna, waterproof it, and run up to 50 feet of USB cable to the computer and eliminate the loss. For TV, it would require a different kind of dongle, more expensive I think.

              This study confirms that the reason channel 3 is often not watchable here is that there is less signal on the ground or at tree-top level than the other Walnut Grove transmitters.

              KQEH is seldom watchable here although the signals seem to be reaching my location even at ground level. Will have to experiment with that one.

              The rapid fading on KGO seems consistent. It could involve interference from channel 7 in Redding which comes in on occasion, although no hetrodyne is heard. It may be that they are so close in frequency that the twice per second fading is the heterodyne.

              Channel 28 was interesting. There were two carriers, one on channel at 10db and one on offset at 20 db. I can hear the heterodyne and see each signal separately. I think one is a low power Stockton station and the other is KFVL in San Francisco which I have seen on occasion. I think that 49 may be KSTS as I've seen it once or twice.

              Channel 4 must be KO4QR in Lakeport. I have a two meter path into Clear Lake and I don't see any other likely suspects.

              KTLN consistently gets the highest numbers in the 90s on my Dish converter but doesn't seem to rate highly on these antennas.

              I've been at the KCVU transmitter site and I was able to work my UHF repeater from there with about an S7 signal received back. Hard to say if there was ducting on that day or not, so I suspect that channel 20 is KCVU.

              I may have over estimated the 40db signal margins. When the noise (signal) floor is moving around so much it's hard to get an accurate reading. The stronger signal probably also increased the floor and I didn't notice it.
              Ernie
              W6KAP

              --- In HDTV-in-SFbay@yahoogroups.com, Larry Kenney wrote:
              >
              > Ernie...
              >
              > Here are some observations I noted to be of special interest in your list of stations received your new dongle.
              >
              > It appears that 40 db is the maximum strength indicated. That's higher than any of the DTV receivers I've seen. 33 db is the highest signal strength I've seen on a TV.
              >
              > Your best signals are from the Walnut Grove transmitters for channels 21 and 25, which just happen to be the two CBS owned stations, but I'm surprised at the difference in strengths received from the transmitters there. KCRA is only 18 db.
              >
              > Several stations much further away give you some surprisingly strong signals, but especially noteworthy are KEMO 32 from Mt. Saint Helena, northeast of Santa Rosa, and KICU 36 from Monument Peak, 35 miles south of San Francisco, both at 30 db.
              > KQEH 50 from Monument Peak also did well at 20 db.
              >
              > I'm also surprised at how well you received some of the stations transmitting from Sutro Tower:
              > KGO 7 and KQED 30 both at 20 db
              > KCNS 39 at 18 db
              >
              > Mt. San Bruno didn't fair so well:
              > KNTV 12 and KKPX 41 (not identified) only at 10 db
              > and KTSF 27 at 0.
              >
              > My best guesses for the unidentified signals you received are:
              > 20 - K20JX, with transmitter located southwest of Lincoln
              > 24 - KNVN, Chico, with transmitter east of Red Bluff
              > 34 - KFSF 66 from Sutro Tower
              > 41 - KKPX 65 from Mt. San Bruno, as noted above
              > 44 - KTVU 2 from Sutro Tower
              > 47 - KTLN 68 transmitting from Novato
              > 49 - KSAO a low power station transmitting from southeast of Folsom
              >
              > Thanks for sharing your findings.
              >
              > You'll find a list of all stations within 100 miles of San Francisco listed on my DTV Station Lists:
              > http://www.choisser.com/sfonair2.html
              >
              > Larry, WB9LOZ
              > SF
              >
              > - - -
            • Ron Economos
              Isn t the filter bandwidth displayed on the left like this picture of the program (showing 14.110 kHz)? http://sdrsharp.com/downloads/sdrsharp.png Ron
              Message 6 of 16 , Jan 22, 2013
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                Isn't the filter bandwidth displayed on the left like this
                picture of the program (showing 14.110 kHz)?

                http://sdrsharp.com/downloads/sdrsharp.png

                Ron

                On 1/22/2013 2:03 PM, Bookcollector wrote:
                 

                Yes, using SDRSharp with a dongle that has the R820T tuner.
                Ernie

                --- In HDTV-in-SFbay@yahoogroups.com, Ron Economos wrote:
                >
                > Are you using the SDR# software?
                >
                > Ron W6RZ
                >
                > On 1/21/2013 9:56 PM, Bookcollector wrote:
                > >
                > > I'm not sure exactly what I'm measuring. What I'm comparing is the
                > > level of the ATSC carrier in relation to the area of the signal
                > > immediately surrounding it. If I spread out from 1kHz to 250kHz
                > > bandwidth it makes no difference. If I look at the whole 2mHz that I'm
                > > able to see, the peak is still the same. I believe that the display is
                > > based on the 2 mHz of spectrum the SDR is looking at. If I tune to the
                > > edge of a channel then the noise level where no signal is present is
                > > another 10 db down, more or less. So what I'm measuring when I say
                > > that the ATSC carrier is 20db above the noise is that the carrier
                > > (xx0.31mHz)is 20 db above the surrounding noise (which is signal) and
                > > about 30 db above a quiet frequency with no signal. Of course, the
                > > entire signal (adjacent noise level) is also reduced with a weak carrier.
                > > Ernie
                > > W6KAP
                > >
                > > --- In HDTV-in-SFbay@yahoogroups.com
                > > , Ron Economos wrote:
                > > >
                > > > Be aware that your filter bandwidth on the SDR will make a
                > > > huge difference in detecting carriers. A 6 kHz filter bandwidth
                > > > gives you a 30 dB advantage over a regular ATSC receiver
                > > > that must use a 6 MHz bandwidth.
                > > >
                > > > Ron W6RZ
                > > >
                > > > On 1/21/2013 12:10 PM, Bookcollector wrote:
                > > > >
                > > > > Thanks for the info. KOFY is doing an excellent job of keeping their
                > > > > signal in the horizontal plane over a 110 mile path. It sometimes
                > > > > fades but is the most consistent of the Sutro transmitters at my
                > > > > location (38.489/-120.589).
                > > > >
                > > > > Channel 7 is stronger today and the rapid fading is less obvious. It
                > > > > almost sounds like the signal is coming through an Altamont Pass wind
                > > > > mill.
                > > > >
                > > > > I adjusted the contrast on the waterfall and now I see carriers that
                > > > > are just above the noise on 15 and 31. I think 15 is Reno PBS. I
                > > > > notice that the channel 47 I am seeing is about 30khz high with
                > > > > carrier on 668.313. Or maybe I'm just seeing the offset today and not
                > > > > the carrier. I think that is 68 in Novato and its one of the
                > > strongest
                > > > > stations I receive on the horizontal antenna.
                > > > >
                > > > > Do tuners have an AFC that makes a small difference in ATSC carrier
                > > > > frequency immaterial?
                > > > >
                > > > > I ordered a cable to interface my 91XG antenna to the dongle. It will
                > > > > be interesting to see what level of quieting is needed to receive a
                > > > > signal.
                > > > > Ernie
                > > > > W6KAP
                > > > >
                > > >


              • Bookcollector
                Yes the bandwidth is continuously adjustable and is displayed on the left side, but the screen displays up to two megaHertz at a time and signal levels don t
                Message 7 of 16 , Jan 22, 2013
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                  Yes the bandwidth is continuously adjustable and is displayed on the left side, but the screen displays up to two megaHertz at a time and signal levels don't change when narrowing the bandwidth or narrowing the spectrum displayed. The only thing that will change the signal level is opening configuration and changing the RF Gain. You can change the bandspread to display only about 100 hz and the level of a signal remains the same as when it displayed 2 mHz. You can narrow the filter to 600 Hz or widen it to 250000 and no difference.

                  I thought I was ordering a neat toy but it has turned out to be no toy, but a capable SDR and spectrum monitor 24-1700mHz. I was just reading someone's post about SDRs written in 2010 and the guy was saying that it would cost in the thousands to buy an SDR that really worked at VHF and UHF frequencies. How time flies! I listened to the NA QSO Party last weekend on 10 meters and after getting used to the waterfall and figuring out how to use it to tune SSB signals, it was very competitive with my IC-706mkIIg.

                  I see that they have similar dongles for ATSC TV that run about $30-40, but no SDR capability yet there.
                  Ernie
                  W6KAP

                  --- In HDTV-in-SFbay@yahoogroups.com, Ron Economos wrote:
                  >
                  > Isn't the filter bandwidth displayed on the left like this
                  > picture of the program (showing 14.110 kHz)?
                  >
                  > http://sdrsharp.com/downloads/sdrsharp.png
                  >
                  > Ron
                  >
                  > On 1/22/2013 2:03 PM, Bookcollector wrote:
                  > >
                  > > Yes, using SDRSharp with a dongle that has the R820T tuner.
                  > > Ernie
                  > >
                  > > --- In HDTV-in-SFbay@yahoogroups.com
                  > > , Ron Economos wrote:
                  > > >
                  > > > Are you using the SDR# software?
                  > > >
                  > > > Ron W6RZ
                  > > >
                  > > > On 1/21/2013 9:56 PM, Bookcollector wrote:
                  > > > >
                  > > > > I'm not sure exactly what I'm measuring. What I'm comparing is the
                  > > > > level of the ATSC carrier in relation to the area of the signal
                  > > > > immediately surrounding it. If I spread out from 1kHz to 250kHz
                  > > > > bandwidth it makes no difference. If I look at the whole 2mHz that
                  > > I'm
                  > > > > able to see, the peak is still the same. I believe that the
                  > > display is
                  > > > > based on the 2 mHz of spectrum the SDR is looking at. If I tune to
                  > > the
                  > > > > edge of a channel then the noise level where no signal is present is
                  > > > > another 10 db down, more or less. So what I'm measuring when I say
                  > > > > that the ATSC carrier is 20db above the noise is that the carrier
                  > > > > (xx0.31mHz)is 20 db above the surrounding noise (which is signal) and
                  > > > > about 30 db above a quiet frequency with no signal. Of course, the
                  > > > > entire signal (adjacent noise level) is also reduced with a weak
                  > > carrier.
                  > > > > Ernie
                  > > > > W6KAP
                  > > > >
                  > > > > --- In HDTV-in-SFbay@yahoogroups.com
                  > >
                  > > > > , Ron Economos wrote:
                  > > > > >
                  > > > > > Be aware that your filter bandwidth on the SDR will make a
                  > > > > > huge difference in detecting carriers. A 6 kHz filter bandwidth
                  > > > > > gives you a 30 dB advantage over a regular ATSC receiver
                  > > > > > that must use a 6 MHz bandwidth.
                  > > > > >
                  > > > > > Ron W6RZ
                  > > > > >
                  > > > > > On 1/21/2013 12:10 PM, Bookcollector wrote:
                  > > > > > >
                  > > > > > > Thanks for the info. KOFY is doing an excellent job of keeping
                  > > their
                  > > > > > > signal in the horizontal plane over a 110 mile path. It sometimes
                  > > > > > > fades but is the most consistent of the Sutro transmitters at my
                  > > > > > > location (38.489/-120.589).
                  > > > > > >
                  > > > > > > Channel 7 is stronger today and the rapid fading is less
                  > > obvious. It
                  > > > > > > almost sounds like the signal is coming through an Altamont
                  > > Pass wind
                  > > > > > > mill.
                  > > > > > >
                  > > > > > > I adjusted the contrast on the waterfall and now I see
                  > > carriers that
                  > > > > > > are just above the noise on 15 and 31. I think 15 is Reno PBS. I
                  > > > > > > notice that the channel 47 I am seeing is about 30khz high with
                  > > > > > > carrier on 668.313. Or maybe I'm just seeing the offset today
                  > > and not
                  > > > > > > the carrier. I think that is 68 in Novato and its one of the
                  > > > > strongest
                  > > > > > > stations I receive on the horizontal antenna.
                  > > > > > >
                  > > > > > > Do tuners have an AFC that makes a small difference in ATSC
                  > > carrier
                  > > > > > > frequency immaterial?
                  > > > > > >
                  > > > > > > I ordered a cable to interface my 91XG antenna to the dongle.
                  > > It will
                  > > > > > > be interesting to see what level of quieting is needed to
                  > > receive a
                  > > > > > > signal.
                  > > > > > > Ernie
                  > > > > > > W6KAP
                  > > > > > >
                  > > > > >
                  > >
                  >
                • Ron Economos
                  I would expect the noise floor to change when varying the filter bandwidth. The thermal noise floor should be equal to: P = kTB where B is equal to bandwidth
                  Message 8 of 16 , Jan 23, 2013
                  • 0 Attachment
                    I would expect the noise floor to change when varying the
                    filter bandwidth. The thermal noise floor should be equal to:

                    P = kTB

                    where B is equal to bandwidth (k is Boltzmann's constant
                    and T is temperature) . For room temperature, the
                    thermal noise floor in dBm can be simplified to:

                    P(dBm) = -174 + 10log (B)

                    So for a 6 MHz bandwidth, the noise floor is at -106 dBm, but
                    at 10 kHz, it's at -134 dBm. Since we're interested in signal to
                    noise ratio, the filter bandwidth makes a big difference.

                    Your actual noise floor will be degraded by the noise figure of the
                    dongle and any man made noise at your location.

                    BTW, the pics you posted to the group photo folder are too small
                    to be able to see much.

                    Ron

                    On 1/22/2013 8:46 PM, Bookcollector wrote:
                     

                    Yes the bandwidth is continuously adjustable and is displayed on the left side, but the screen displays up to two megaHertz at a time and signal levels don't change when narrowing the bandwidth or narrowing the spectrum displayed. The only thing that will change the signal level is opening configuration and changing the RF Gain. You can change the bandspread to display only about 100 hz and the level of a signal remains the same as when it displayed 2 mHz. You can narrow the filter to 600 Hz or widen it to 250000 and no difference.

                    I thought I was ordering a neat toy but it has turned out to be no toy, but a capable SDR and spectrum monitor 24-1700mHz. I was just reading someone's post about SDRs written in 2010 and the guy was saying that it would cost in the thousands to buy an SDR that really worked at VHF and UHF frequencies. How time flies! I listened to the NA QSO Party last weekend on 10 meters and after getting used to the waterfall and figuring out how to use it to tune SSB signals, it was very competitive with my IC-706mkIIg.

                    I see that they have similar dongles for ATSC TV that run about $30-40, but no SDR capability yet there.
                    Ernie
                    W6KAP

                    --- In HDTV-in-SFbay@yahoogroups.com, Ron Economos wrote:
                    >
                    > Isn't the filter bandwidth displayed on the left like this
                    > picture of the program (showing 14.110 kHz)?
                    >
                    > http://sdrsharp.com/downloads/sdrsharp.png
                    >
                    > Ron
                    >
                    > On 1/22/2013 2:03 PM, Bookcollector wrote:
                    > >
                    > > Yes, using SDRSharp with a dongle that has the R820T tuner.
                    > > Ernie
                    > >
                    > > --- In HDTV-in-SFbay@yahoogroups.com
                    > > , Ron Economos wrote:
                    > > >
                    > > > Are you using the SDR# software?
                    > > >
                    > > > Ron W6RZ
                    > > >
                    > > > On 1/21/2013 9:56 PM, Bookcollector wrote:
                    > > > >
                    > > > > I'm not sure exactly what I'm measuring. What I'm comparing is the
                    > > > > level of the ATSC carrier in relation to the area of the signal
                    > > > > immediately surrounding it. If I spread out from 1kHz to 250kHz
                    > > > > bandwidth it makes no difference. If I look at the whole 2mHz that
                    > > I'm
                    > > > > able to see, the peak is still the same. I believe that the
                    > > display is
                    > > > > based on the 2 mHz of spectrum the SDR is looking at. If I tune to
                    > > the
                    > > > > edge of a channel then the noise level where no signal is present is
                    > > > > another 10 db down, more or less. So what I'm measuring when I say
                    > > > > that the ATSC carrier is 20db above the noise is that the carrier
                    > > > > (xx0.31mHz)is 20 db above the surrounding noise (which is signal) and
                    > > > > about 30 db above a quiet frequency with no signal. Of course, the
                    > > > > entire signal (adjacent noise level) is also reduced with a weak
                    > > carrier.
                    > > > > Ernie
                    > > > > W6KAP
                    > > > >
                    > > > > --- In HDTV-in-SFbay@yahoogroups.com
                    > >
                    > > > > , Ron Economos wrote:
                    > > > > >
                    > > > > > Be aware that your filter bandwidth on the SDR will make a
                    > > > > > huge difference in detecting carriers. A 6 kHz filter bandwidth
                    > > > > > gives you a 30 dB advantage over a regular ATSC receiver
                    > > > > > that must use a 6 MHz bandwidth.
                    > > > > >
                    > > > > > Ron W6RZ
                    > > > > >
                    > > > > > On 1/21/2013 12:10 PM, Bookcollector wrote:
                    > > > > > >
                    > > > > > > Thanks for the info. KOFY is doing an excellent job of keeping
                    > > their
                    > > > > > > signal in the horizontal plane over a 110 mile path. It sometimes
                    > > > > > > fades but is the most consistent of the Sutro transmitters at my
                    > > > > > > location (38.489/-120.589).
                    > > > > > >
                    > > > > > > Channel 7 is stronger today and the rapid fading is less
                    > > obvious. It
                    > > > > > > almost sounds like the signal is coming through an Altamont
                    > > Pass wind
                    > > > > > > mill.
                    > > > > > >
                    > > > > > > I adjusted the contrast on the waterfall and now I see
                    > > carriers that
                    > > > > > > are just above the noise on 15 and 31. I think 15 is Reno PBS. I
                    > > > > > > notice that the channel 47 I am seeing is about 30khz high with
                    > > > > > > carrier on 668.313. Or maybe I'm just seeing the offset today
                    > > and not
                    > > > > > > the carrier. I think that is 68 in Novato and its one of the
                    > > > > strongest
                    > > > > > > stations I receive on the horizontal antenna.
                    > > > > > >
                    > > > > > > Do tuners have an AFC that makes a small difference in ATSC
                    > > carrier
                    > > > > > > frequency immaterial?
                    > > > > > >
                    > > > > > > I ordered a cable to interface my 91XG antenna to the dongle.
                    > > It will
                    > > > > > > be interesting to see what level of quieting is needed to
                    > > receive a
                    > > > > > > signal.
                    > > > > > > Ernie
                    > > > > > > W6KAP
                    > > > > > >
                    > > > > >


                  • Ernest L. Kapphahn
                    Select original to view the full screen. Ernie
                    Message 9 of 16 , Jan 23, 2013
                    • 0 Attachment
                      Select "original" to view the full screen.
                      Ernie

                      On 1/23/2013 4:51 PM, Ron Economos wrote:
                       

                      I would expect the noise floor to change when varying the
                      filter bandwidth. The thermal noise floor should be equal to:

                      P = kTB

                      where B is equal to bandwidth (k is Boltzmann's constant
                      and T is temperature) . For room temperature, the
                      thermal noise floor in dBm can be simplified to:

                      P(dBm) = -174 + 10log (B)

                      So for a 6 MHz bandwidth, the noise floor is at -106 dBm, but
                      at 10 kHz, it's at -134 dBm. Since we're interested in signal to
                      noise ratio, the filter bandwidth makes a big difference.

                      Your actual noise floor will be degraded by the noise figure of the
                      dongle and any man made noise at your location.

                      BTW, the pics you posted to the group photo folder are too small
                      to be able to see much.

                      Ron

                      On 1/22/2013 8:46 PM, Bookcollector wrote:

                       

                      Yes the bandwidth is continuously adjustable and is displayed on the left side, but the screen displays up to two megaHertz at a time and signal levels don't change when narrowing the bandwidth or narrowing the spectrum displayed. The only thing that will change the signal level is opening configuration and changing the RF Gain. You can change the bandspread to display only about 100 hz and the level of a signal remains the same as when it displayed 2 mHz. You can narrow the filter to 600 Hz or widen it to 250000 and no difference.

                      I thought I was ordering a neat toy but it has turned out to be no toy, but a capable SDR and spectrum monitor 24-1700mHz. I was just reading someone's post about SDRs written in 2010 and the guy was saying that it would cost in the thousands to buy an SDR that really worked at VHF and UHF frequencies. How time flies! I listened to the NA QSO Party last weekend on 10 meters and after getting used to the waterfall and figuring out how to use it to tune SSB signals, it was very competitive with my IC-706mkIIg.

                      I see that they have similar dongles for ATSC TV that run about $30-40, but no SDR capability yet there.
                      Ernie
                      W6KAP

                      --- In HDTV-in-SFbay@yahoogroups.com, Ron Economos wrote:
                      >
                      > Isn't the filter bandwidth displayed on the left like this
                      > picture of the program (showing 14.110 kHz)?
                      >
                      > http://sdrsharp.com/downloads/sdrsharp.png
                      >
                      > Ron
                      >
                      > On 1/22/2013 2:03 PM, Bookcollector wrote:
                      > >
                      > > Yes, using SDRSharp with a dongle that has the R820T tuner.
                      > > Ernie
                      > >
                      > > --- In HDTV-in-SFbay@yahoogroups.com
                      > > , Ron Economos wrote:
                      > > >
                      > > > Are you using the SDR# software?
                      > > >
                      > > > Ron W6RZ
                      > > >
                      > > > On 1/21/2013 9:56 PM, Bookcollector wrote:
                      > > > >
                      > > > > I'm not sure exactly what I'm measuring. What I'm comparing is the
                      > > > > level of the ATSC carrier in relation to the area of the signal
                      > > > > immediately surrounding it. If I spread out from 1kHz to 250kHz
                      > > > > bandwidth it makes no difference. If I look at the whole 2mHz that
                      > > I'm
                      > > > > able to see, the peak is still the same. I believe that the
                      > > display is
                      > > > > based on the 2 mHz of spectrum the SDR is looking at. If I tune to
                      > > the
                      > > > > edge of a channel then the noise level where no signal is present is
                      > > > > another 10 db down, more or less. So what I'm measuring when I say
                      > > > > that the ATSC carrier is 20db above the noise is that the carrier
                      > > > > (xx0.31mHz)is 20 db above the surrounding noise (which is signal) and
                      > > > > about 30 db above a quiet frequency with no signal. Of course, the
                      > > > > entire signal (adjacent noise level) is also reduced with a weak
                      > > carrier.
                      > > > > Ernie
                      > > > > W6KAP
                      > > > >
                      > > > > --- In HDTV-in-SFbay@yahoogroups.com
                      > >
                      > > > > , Ron Economos wrote:
                      > > > > >
                      > > > > > Be aware that your filter bandwidth on the SDR will make a
                      > > > > > huge difference in detecting carriers. A 6 kHz filter bandwidth
                      > > > > > gives you a 30 dB advantage over a regular ATSC receiver
                      > > > > > that must use a 6 MHz bandwidth.
                      > > > > >
                      > > > > > Ron W6RZ
                      > > > > >
                      > > > > > On 1/21/2013 12:10 PM, Bookcollector wrote:
                      > > > > > >
                      > > > > > > Thanks for the info. KOFY is doing an excellent job of keeping
                      > > their
                      > > > > > > signal in the horizontal plane over a 110 mile path. It sometimes
                      > > > > > > fades but is the most consistent of the Sutro transmitters at my
                      > > > > > > location (38.489/-120.589).
                      > > > > > >
                      > > > > > > Channel 7 is stronger today and the rapid fading is less
                      > > obvious. It
                      > > > > > > almost sounds like the signal is coming through an Altamont
                      > > Pass wind
                      > > > > > > mill.
                      > > > > > >
                      > > > > > > I adjusted the contrast on the waterfall and now I see
                      > > carriers that
                      > > > > > > are just above the noise on 15 and 31. I think 15 is Reno PBS. I
                      > > > > > > notice that the channel 47 I am seeing is about 30khz high with
                      > > > > > > carrier on 668.313. Or maybe I'm just seeing the offset today
                      > > and not
                      > > > > > > the carrier. I think that is 68 in Novato and its one of the
                      > > > > strongest
                      > > > > > > stations I receive on the horizontal antenna.
                      > > > > > >
                      > > > > > > Do tuners have an AFC that makes a small difference in ATSC
                      > > carrier
                      > > > > > > frequency immaterial?
                      > > > > > >
                      > > > > > > I ordered a cable to interface my 91XG antenna to the dongle.
                      > > It will
                      > > > > > > be interesting to see what level of quieting is needed to
                      > > receive a
                      > > > > > > signal.
                      > > > > > > Ernie
                      > > > > > > W6KAP
                      > > > > > >
                      > > > > >



                    • Ron Economos
                      Thanks. Ron
                      Message 10 of 16 , Jan 23, 2013
                      • 0 Attachment
                        Thanks.

                        Ron

                        On 1/23/2013 5:25 PM, Ernest L. Kapphahn wrote:
                         

                        Select "original" to view the full screen.
                        Ernie


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