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Re: [FT897] high noise floor

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  • Nacho
    Hello. Well, I think that noise floor and s-meter are different problems. Noise floor could be measured without antenna, or with a signal generator, injecting
    Message 1 of 12 , Jan 31, 2006
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      Hello.

      Well, I think that noise floor and s-meter are different problems.
      Noise floor could be measured without antenna, or with a signal
      generator, injecting a very faint signal and measuring the audio
      output in a spectrum analyzer.

      I also find the S-meter very easy to overload. Sorry to mention
      another transceiver, but for example, my TS-50 has 30 segments in the
      S-meter, and the last 10 or so are from 9 to 9+60. I never have seen
      it completely fill (in SSB). When my neighbour was transmitting, I got
      9+50, but not 9+60.

      In any case, with a decent antenna, there is a lot of noise in HF
      bands, specially in lower bands, so noise floor in those bands isn't a
      real problem, I think. It may be in higher HF bands (10m in closed
      band conditions, for example, is similar to VHF), and of course, in
      VHF and UHF.

      Of course this is my humble opinion :)

      Regards.

      2006/1/31, Mark Vaughan <mark@...>:
      > I have been wondering this as well. My 857 isn't too bad but that's compared
      > to my older radios, plus there are many other associated factors, like the
      > poor linearity and accuracy of the FT857/ 897 meters which will need
      > calibrating using a good calibrated frequency source.
      >
      > If you look up various mods for the FT847 which is similar in some areas you
      > will find that Yaesu used rather noisy switching diodes in the RX section,
      > these can be changed for lower noise ones with major improvement. Yaesu even
      > offer the mod for the 847 in the UK
      >
      > I haven't investigated this with the 857 but it may be relevant.
      >
      >
    • bobmayerau
      Mike, Do to the time difference between W0 and VK2 I am a bit late in coming to this thread. Many others have replied so I ll try not do duplicate their
      Message 2 of 12 , Feb 1, 2006
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        Mike,

        Do to the time difference between W0 and VK2 I am a bit late in
        coming to this thread. Many others have replied so I'll try not do
        duplicate their comments. First, what you are describing is not a
        high receiver noise floor. The receiver noise floor is the
        equivalent input noise when the input is terminated with a 50 Ohm
        dummy load. Since you are using an antenna what you are actually
        measuring is the level of man made and atmospheric noise. This is
        not the receiver noise floor. The noise floor of the FT897 is really
        quite good.

        The S meter reading on the noise from your antenna is a function of
        the receiver's gain and AGC characteristic. On my 897, and I am
        assuming it is typical, the S meter reading is very far from the
        conventional 50 uV at S9 and 6 dB per S unit. It reads S9 at 39 uV
        which is reasonable, but S1 to S7 requires only a 6 dB change in
        input level or approximately 1 dB per S unit. The meter always shows
        several S units on noise for all bands below 15 metres and even weak
        signal show S6. This allows me to give flattering reports to DX and
        QRP stations. I also tell them that I have a high noise level.

        My 897 may be a bad example, but in my experience the 897 S meter is
        no worse than other HF rigs I have owned over the last 40 years.
        They are all read S9 at 50 uV because that's how they are
        calibrated. Above and below that point they are only useful as a
        relative strength indicator.

        If, you are disturbed by the high meter reading and/or noise, try
        adjusting the IF gain as suggested by Perry WK9L or use the
        attenuator. I am content to use my 897 as it is, the most fun in a
        single piece of radio gear ever!

        73, Bob VK2BMU
        - In FT897@yahoogroups.com, "worsr" <worsr@c...> wrote:
        >
        > My FT-897 seems to have a higher noise floor than any of my other
        radios on H.F. Today on 20M, my TS-850, Jupiter and IC-746 all
        were showing approx. S-5 noise level. The FT-897 was showing an S-9
        level, however. This was on the same antennas. The outboard LDG
        meter shows the same S meter as the rig on the FT-897. The peak
        signal strength on the stronger stations seem to be about the same
        on all my rigs. I have the IPO disabled on the FT-897.
        Additionally, I have determined this problem is not power supply
        related.
        >
        > Has anyone else noted this with this radio?
        >
        > Thanks in advance,
        >
        > --Mike, W0RSR
        >
        > [Non-text portions of this message have been removed]
        >
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