Sunday, 27 July 2014

ALPS VCO at work

The ALPS VCO 1679C is operational. Power supply and tuning voltage have been connected now. Also a small MMIC, the MSA-0866 from Hewlett Packard has been connected to the output to increase the output level from about 0 dBm to abt. 12 dBm. 
I viewed the spectrum on the SDR receiver and found I could generate a stable signal in the 23 cm band. Here you see a clean signal around 1.256 GHz:

The VCO can be tuned between 1100 and 1350 MHz. I think the long and short term stability are good enough to use the free running VCO for 23 cm ATV transmission. No PLL required !

MSA-0866 data:

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3 comments:

  1. PE1ODJ3 August 2014 at 03:29

    Hi Ron,

    Your estimate of about 20dBm output might be a little optimistic...
    The power gain of the MSA-0886 around 1GHz is 20.5 dB but the maximum output power is only 12.5 dBm at 1 dB compression. That's just under 20 mW.
    If you are looking for a little more power to drive next stages, the ERA-5 might be an option. Slightly less gain (19.5 dB) but around 16 dBm (40 mW) output.
    The 0 dBm output of the ALPS VCO would drive it into full compression so an attenuator is recommended between the VCO and the MMIC.
    This can be a simple Pi- or T-attenuator made with SMD resistors.
    As for the MSA-0886: a 6 dB attenuator would still give you the maximum output power but with less compression and spurious.
    Another benefit of the attennuator is the VCO having a more consistent 50 Ohms load.


    Following your experiments on PI6ZTM with interest...

    Regards, Pieter

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  2. PA2RF3 August 2014 at 23:10

    Hallo Pieter,
    dank voor je goede tips en analyse. Heb je call ook voorbij zien komen op de repeater. De ERA-5 lijkt me een echte aanrader.
    Ja, ik heb denk ergens max. output level en gain van de MSA mmic door elkaar gehaald.
    Het is afgelopen week trouwens wel gelukt om met de ALPS VCO en MSA incl. 1 Watt eindtrapje een redelijk stabiel signaal op PI6ZTM neer te zetten; de Blankaard waar de repeater antennes staan is ong. 6 km van m'n huis verwijderd, dus ik was wel tevreden met het resultaat. Zal binnenkort het schema van m'n bouwsel plaatsen.
    73 Ron PA2RF

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  3. PE1ODJ4 August 2014 at 09:06

    Hoi Ron,

    Mocht je overigens nog meer stuurvermogen nodig hebben dan 40 mW, dan is de GALI-84 van Mini-Circuits misschien iets voor je. Op 1200 MHz een gain van 22 dB en een output van ruim 100 mW.

    Groeten, Pieter

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