Loading ...
Sorry, an error occurred while loading the content.

68830Re: Hardrock 50 driver amp relay question

Expand Messages
  • jim.veatch@verizon.net
    Sep 21, 2012
    • 0 Attachment
      Hi John,

      On the new driver PCB if you populate Q7 with a 2N2222 or 2N3904 NPN transistor and swap E and C, use a 220 ohm for R209 then the amplifier will key up with 12V applied to PTT in rather than pulling it to ground.

      Another thing to think about with running on low voltage is power output, it's related to Vd squared.

      Po = Vd^2/(2*Zd)

      With a 1:3 T201 winding we're lookng at a Zd = 50/9 = 5.55 ohms

      So at 13.8V the max power is 17.1 watts, at 11V a max of only 11W.

      The actual output is less because the formula doesn't account for various losses around the circuit. With 13.8V I was seeing at least 10W nice and linear as much as 13 or 14W if you don't mind compression (CW, FSK). With 11V these figures will be lower.

      73's
      Jim WA2EUJ

      --- In softrock40@yahoogroups.com, jim.veatch@... wrote:
      >
      > Hi John,
      >
      > Thanks I'll look into S12V for keying the driver. The bias is regulated and shouldn't come out of regulation until the voltage drops below 10V, this could be improved at the cost of an increase of a few mA of idle current. Don't worry about it too much because my experience with these MOSFETs is that they aren't too sensitive to IDQ anyway.
      >
      > 73's
      > Jim WA2EUJ
      >
      > --- In softrock40@yahoogroups.com, John Williams <KE5SSH@> wrote:
      > >
      > > We use a signal called S12V from the softrock that is +12V during ptt...
      > > so I use a npn transistor to invert it. since you are targeting the
      > > softrock might be good to add an unpop'ed section to take S12V directly
      > > into the board.
      > >
      > > Will the bias need to be re-calibrated if the supply is a 12v gell-cell
      > > vs. a 13.8V supply?
      > >
      > > John - ke5ssh
      > >
      > > On 9/20/2012 12:16 PM, jim.veatch@ wrote:
      > > >
      > > > Hi John,
      > > >
      > > > The bias for the MOSFET should be a drain current of 500mA. In my
      > > > experience you can't quite get there with 5V but 400-450 mA seems to
      > > > work fine. In the Hardrock-50 a switched 5V source is supplier to the
      > > > Driver PCB from the AMP PCB via the 'PWR' connector. If you are using
      > > > the Driver PCB as a stand-alone amp you need some external way of
      > > > putting 5V across VR201during TX.
      > > >
      > > > One way to do this is put a 5V zener across Pins 1 and 3 of VR201,
      > > > (actually 5.1V) then add a series 1K resistor (R208) now you can
      > > > supply a switched 12V source (which is what the relay needs too). I
      > > > use a PNP switching transistor 2N3906 or similar which switches the
      > > > 13V on to the relay and bias circuit by pulling it's base to ground
      > > > through a 1K resistor (R209).
      > > >
      > > > I can't remember what like of TX signal the Softrock produces but may
      > > > QRP rigs have an open contact pull ground arrangement for TX that will
      > > > work with this circuitry.
      > > >
      > > > 73's
      > > > Jim WA2EUJ
      > > >
      > > > --- In softrock40@yahoogroups.com
      > > > <mailto:softrock40%40yahoogroups.com>, John Williams <KE5SSH@> wrote:
      > > > >
      > > > > Hi Jim,
      > > > >
      > > > > Can you explain the bias switching?
      > > > >
      > > > > John
      > > > >
      > > >
      > > >
      > >
      > > --
      > >
      > > John Williams
      > >
      > > KE5SSH - ham since 2007
      > > WQKA523 - GMRS for family use on the farm
      > >
      >
    • Show all 11 messages in this topic