For schematic version 0.3, 12 Dec 1999
This project came about when FP#2, Rick WB6JBM made the comment "we should have a club project to build".
We talked about building a qrp radio that was a bit different. A ten meter rig seemed to fit the bill as
Rick had no 10 meter capabilities :-). I gave the idea a little thought. Doing a vfo rig on 10 is a bit ugly.
So, I thought how about VXO. I looked around and found this odd crystal 8,064 KHz. I'm not sure where it is used,
but it would mix very nicely with a 20 MHz crystal to cover the 10 meter QRP frequency. So I ordered ten 8.064
crystals from radioshack.com (actually manufactured by International Crystal). Built up a little mixer using a
NE602 and bingo; we had coverage from 28,055 to 28,065 and the miniPIG-10 was born.
Output Filter L1,2 C1,3,4,5,12,13
I started out with standard low pass filter values here.
Then I optimised the input and output capacitance for 1 Watt output.
C5 and 13 are for PCB designs only.
RF Volts D1,2 R1 C7
Standard peak voltage detector. Power = E^2 divided by load resistance.
Pin Diode T/R Switch D3,4,5
In receive mode, D3 and D4 are turned on and D5 is turned off.
These diodes exhibit approx. 10 ohm resistance when ON and hiZ whan OFF.
When off, practically speaking, the PIN diodes only have capacitance leakage.
In transmit mode, D3 and D4 are turned off and D5 becomes a 10 ohm shunt to ground.
he ON resistance is a function of the foreward current through the PIN diodes. We could
drive the diode harder and draw more total receive power but the MDS is already 0.05 uVolts.
RF Amplifier Q2 and 4 pole filter
Q2 is a high gain, VERY LOW NOISE rf transistor. We use 4 poles
for filtering out the IF image frequency 11.936 KHz. We do not
need foreign bradcasts coming out of the speaker :-)
Receive Mixer Dev1 SBL-1
This is a HIGH LEVEL DOUBLE BALANCED Diode ring mixer. There are books available
on this mixer circuit. I use it to keep the intermod signals down, should you decide
to take the miniPIG to a multiple transmitter site field day event.
Post Mixer Amp Q9
This cicuit draws about 20 ma.
8.064 Xtal FIlter
IF Amp Dev4 MC1350
Audio Detector Dev5 NE602A
AGC Dev6 LM358
AGC Ref R75 20k
AF Amp Dev7 LM380
Mute Switch Q16 J210
Sidetone Generator Q15 with Twin-T
BFO Q11,12 8.064 X6
BFO Receive Freq C81
BFO Transmit Offset C82
BFO PIN Switch D11,12
VXO Q5,6 20.000 MHz X1
VXO Main tune R5 D6 MV2105
VXO RIT D7 R8 MV2101
VXO PIN Switch D8,9
Xmit Mixer Dev3 SBL-1
Xmit Bandpass Filter L15,18
Buffer Amp Q7,8
Xmit Driver Q4 2N3866
Final Q3 2N3553
6 Volt regulator Dev2 and R42,43 half watt
CAPACITIVE SWITCH PADDLES
11 meter mod