68814Re: [softrock40] Re: Hardrock 50 driver amp relay question
- Sep 20, 2012We 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:
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.
--- In firstname.lastname@example.org, John Williams <KE5SSH@...> wrote:
> Hi Jim,
> Can you explain the bias switching?
-- John Williams KE5SSH - ham since 2007 WQKA523 - GMRS for family use on the farm
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