Kth - sdr - kit

6/13/2010 KTH - SDR - KIT Page 29
________________________________________________________________________________
If all the voltages are correct, then continue assembling the remaining parts. Don’t forget to install choke L2!
You don’t have to install C1, because this is for impedance matching to 50Ω only.
Take care of the position of TR1. The pin numbers of TR1 are not correctly written on the PCB. Pin 1 and 3
are changed even as pin 4 and 6. The white dot on TR1 is at pin 1 and is facing to the LT5517.
Install a short RG174 coax cable on the back side of the board, between J2 and C10. See figure 2.5-4
Figure 2.5-4 Components on back side I & Q demodulator.
To adjust the amplification of the op-amps IC2, you can install two 10-turn trimpots P1 and P2 in stead of
the fix resistors R12 and R13. It is now possible to set the amplification for an optimal result compared to
your soundcard or to influence the total gain of the receiver from antenna to soundcard.
You can skip the trimpots and install the fix resistors R12 and R13 if you wish. This setting is good for most
of the standard on board sound chips.
If you decide to use the trimpots, then you have to use an oscilloscope or RMS meter to adjust the I and Q
output exact to the same level. An other possibility is to adjust both trimpots to a desired value by means of
an ohm meter.
Install the SMB connectors on both sides of the board, see figure 2.5-3 and 2.5-4.
___________________________________________________________________________________________________________
Instruction manual KH-SDR wideband receiver Kit No-1021. All rights reserved KTH-SDR-KIT. Software design by PA0RWE.