High Power Mod for Proxim's Symphony 2.4 GHz FHSS Wireless Ethernet Card 
                          Courtesy of www.gbppr.org

This mod is based on an ISA card labeled "REV19"

Side Note: This device opperates on the shared 2.4 GHz band as a part 15
           device.  It is possible to reclassify its use for Part 97
           (amateur radio) for higher power / high speed RF networking
           applications.  (This may be the future of packet radio, as 
           suggested by TAPR's 900 MHz FHSS radio developments)

There appear to be test points on the card marked:

DIR - direction control ??
AEN - address enable ??
IORD - I/O read ??
IOWR - I/O write ??


The RF power amplifier IC, a 6-pin IC marked with "83A", is an Agilent 
Technologies MGA-83563 running at 3 volts DC, dropped from 5 volts with 
a few resistors.  It's possible to change out those resistors and run 
the IC at 3.6 - 3.9 volts to get more RF power output.  The maximum DC 
voltage for this IC is 4 volts and the maximum RF power output is around 
+23 dBm (200 mW).

The best way to do this would be with another parallel resistor. Adding 
a 22 Ohm resistor in parallel with the four 39 Ohm resistors would bring 
the total resistance to around 6.8 Ohms. This should give you 3.6 VDC 
on the power pin.

Here is the math...

        Vd = Dropping resistor
        V1 = Voltage on the power line
        V2 = Voltage you want V1 dropped to.
        I = Current draw

        Vd = (V1 - V2) / I

        Substituting the Symphony values:

        9.75 = (5 - 3) / I

        I = 2 / 9.75

        I = .205 amps

        Calculate the new value Vd:

        Vd = (5 - 3.6) / .205

        Vd = 6.8 Ohms

        Which is the value of four 39 Ohm resistors and one 22 Ohm in parallel.

        This can also be adapted to other wireless network cards.


You should also remove the Pi-style attenuator pad in the RF input.
This also increases the RF power output a little. Just remove the two 
270 Ohm SMT resistors going to ground and replace the series 18 Ohm 
resistor with a 0 Ohm jumper.

The PIN diode switch is an Agilent Technologies HSMP-3894.

There is also an INA-50311. Probably some sort of buffer amplifier.

The intermediate frequency (IF) receiver is based on the National 
LMX2240. Visit their site for datasheets and application notes.


Tap Points For Transmit/Receive

It's possible to tap the PIN diode bias line to control an external 
amplifier. When looking at the card, locate the PIN diode switch, near 
the antenna output and labeled with "G4A", and tap before the small SMT 
bias resistor. This is a TTL (+5 - 0 volts) indicator of 
transmit/receive and can be extended to control an external power 
amplifier. Measuring RSSI output voltage is also possible by following 
the output of pin 2 on the LMX2240 and measuring the voltage on the 
little solder pad. Refer to the LMX2240 data sheet for more info.