Recently I decided to join this interesting project and purchased semi KIT from Sunil – VU3SUA. Kit consists of all three boards – exciter, LPF and BPF and parts for the exciter board. Multiband concept of the BITX transceiver has been developed by Andy – G6LBQ. Further I purchased toko inductors from Spectrum Communications – UK and PA0KLT Si-570 VFO kit from sdr-kits.net.
Here is how it looked in the begining:
Some hard to find parts as double balanced mixerADE-1 I supplied from ebay.co.uk and other internet sites.
Si-570 is excellent chip and gives pretty much signal at the output… so it must be conditioned to suit 7dbm level requirement for diode DBM mixer ADE-1. Also suitable low pass filter should be added in order to achieve good sinusoidal signal. As seen on the photos I used an old KVG 2.4kHz crystal filter XF-9B with carrier crystals.
As seen on the photos I placed some tin shields between the stages of the exciter board and some additional grounding on the bottom side. This and placing low pass filter on BFO output completely cured so called BIRDIES problem. Also this improved carrier attenuation on transmit.