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Re: [softrock40] Re: V9.0 over powered by an AM signal

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  • Sid Boyce
    Why I suspected the broadcast station eventually was when the guys Stateside reported the same problem using top of the range commercial rigs and only 40m was
    Message 1 of 14 , Apr 29, 2010
      Why I suspected the broadcast station eventually was when the guys
      Stateside reported the same problem using top of the range commercial
      rigs and only 40m was affected. There were also similarly strong signals
      above 7.200 that didn't cause breakthrough.
      I haven't looked at the characteristics for Tony's SR v6.3 BPF to guage
      whether I should have expected 20m to be somewhat affected. I am using
      the Lightning Bolt 2-el for Quad 20/17/15/12/10 and for RX on 40m.
      I'm well aware of the harmonic problem - I got the fright of my life
      when a fellow member of our RAF club back in late 1965 asked who was
      G3VBV and said he heard me at home on 80m CW at the weekend. I only
      transmitted on topband and checking the transmitter I found a loose
      earth screw.
      I never tried it, but I read about using a rusted nail as a diode in
      crystal sets. I tried a blob of mercury on a piece of metal with a bit
      of wire in contact with the mercury as the other electrode, but that
      diode arrangement didn't work.
      73 ... Sid.

      On 28/04/10 22:44, Graeme wrote:
      > The problem is likely to be straight out audio rectification of the
      > local broadcast signal. The "diode" may be the softrock mixer where
      > traditionally in direct conversion receivers this usually happened but
      > it can be in anything which can cause intermodulation like a dirty
      > joint, (not to be confused with a Cairo hellhole) or a diode
      > deliberately connected to the ant like in RF power monitor or a 1001
      > obscure things. I once tracked out a source of intermod which turned out
      > to be that the climbing rungs screwed into the side of a 60 ft wooden
      > pole had rusted into the wood and formed a diode. Removing them and
      > regalvanising them, cleaning the holes in the pole fixed the problem.
      > These things can be pretty obscure.
      > 73 Graeme ZL2APV
      > --- In softrock40@yahoogroups.com <mailto:softrock40%40yahoogroups.com>,
      > Sid Boyce <sboyce@...> wrote:
      >> On 27/04/10 04:52, Donald L. wrote:
      >> >
      >> >
      >> > On some, but not all, evenings in the last two weeks 40 meter reception
      >> > with my V9.0 is masked by a strong signal that covers the full 48 kHz
      >> > spectrum displayed by Quisk. the AM signal is centered on the local
      >> > oscillator regardless of tuning in the 40 meter band.
      >> >
      >> Same here in the UK on the SR63ng and I heard a couple of guys in the
      >> USA complaining of the same thing a few days ago. The SR63ng is uncased,
      >> but those guys were using commercial rigs.
      >> It comes up for quite a while and disappears. I did hear it very briefly
      >> on the SR v6.3 last night.
      >> > The signal is actually at 7315 kHz. Quisk reports its strength as S9+35.
      >> > It has never reported a ham signal above S7.
      >> >
      >> Same with quisk this end, it makes the band unusable.
      >> > Do I have a shielding problem? The signal must come in on the antenna
      >> > and jump to the op amps. Mixing with the LO does not seem to be taking
      >> > place. Maybe the conditions are beyond the V9.0's capabilities.
      >> > Don
      >> >
      >> It has to be that broadcast station splattering the band as there are
      >> other stations out of band on 7MHz that do not cause the problem with
      >> similar strong signals reaching the antenna.
      >> 73 ... Sid.
      >> --

      Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
      Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
      Specialist, Cricket Coach
      Microsoft Windows Free Zone - Linux used for all Computing Tasks
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