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Saturday, June 13, 2015

SolderSmoke Podcast 177 Bicoastal Termination Insensitivity Unphased by Phase Noise

SolderSmoke Podcast #177 is available:
13 June 2015
-- Bench Reports:  Bicoastal Bilateral Success:  A Tale of Two Tias
    Only 3 TIA rigs in the world?  It depends...
    Relay improvements in the BITX Builds
    Straightening out amp problems
    The many uses of copper foil
    No phase noise or bleed-over troubles
    Plug-in filters
    Adjusting TIA amp gain on RX and TX (too much is not good!)
    Getting the BITX to work with the CCI amp
    Allison wisely prescribes 3 db pads 
    Curing hum by moving the power supply (duh!)
-- Farhan's New Minima -- Crying out for an Si5351?
-- Mike KL7R's Web Site is Back (thanks to W8NSA)
-- SolderLex: Rigs or Radios?  We go with Rigs
-- A ham rite of passage:  Build a Dipole!
-- What does your shack look like at the end of a project?
    The CORRECT pronunciation of Belthorn
    Multiplication and Division by 4
    W8NSA, Vietnam, a Transoceanic and a 9V Battery 


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  1. The pile of rigs that didn't work... was always small because
    I'd work to make them work. The result is everything in the
    didn't work pile was so chronically bad to be labeled as failed in every way.

    Packaging... I start with one of two things, the box, or an idea. Usually the idea leads to a box then a build. Result
    was a radio that was built up one side and down the other
    to fit the available space. But when it comes to heat (finals)
    is space and heatsinks are a must.

    MMICS, not all are termination insensitive. As me how I know. People have used them to build rigs and parts of rigs.

    Resistance is futile. Except when its constructive. ;)

    TIA, and impedance matching... There might be a story there. In one case the amplifier will present impedances
    that are known to facilitate designing for coupling. The other
    case the impedance is unknown or divergent but we still need to match or as we all know we waste power or worse
    suffer instability.

    The digi-tia and other bands...any shoudl be possible but
    in general avoid bands that are not twice the filter frequency.
    The other is keep the operating filter at about no mor ethan 10x the filter frequency and if simple bandpass or low pass are to be used stay at 5x so a heath 3395khz filter is used
    that means about 15-18mhz. You can go higher but the band pass filters need to be better. Why? Image responses. You want the IF-LO and IF+LO to be easily filtered and avoid frequencies where known strong signals might occur like the 41 and 49M SW band.

    Phase noise. Its the random change in frequency (FM)
    that occurs. If you divide a signal by N the phase noise will
    reduce by the 10log(N)dB. The classic proof of this is the HP8640 signal generator which is know for low phase

    The Si5351, its phase noise is greater than Si570 BUT its not near horrible as the si570 is very good to start with. The problem of comparing to a near golden standard. If I were building a seriously high performance radio the 5351 is not a consideration then again maybe even the si570. However compared to the average commercial radio the 5351 is still good. The cross talk is a layout problem and with care can be down at the good enough level.

    Building a dipole. One must as its a standard. Everything else will be better or worse so having a standard is an important starting point. Open wire line, the old ones understood signal loss and material cost.

    One thing about radio, its all about the antenna.

    FYI: my shack is a total disaster area. I do clear out waste and useless bits like solder splashes and all but its still chaos. I'm convinced a clean bench is a sign of far from enough projects.

    Have a good one.

  2. The Heathkit DX-100 used 1625 tubes for the modulator and not 811A tubes.
    Lee, w0vt


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