Tuesday, December 08, 2009

HF transceiver (1)

I am building an HF radio....It's my third atempt! I built (soldered) the "Speaky" but never put it to use, built some modules years ago but never finished them, so it's time now to make one to put on the shack.

I am using mostly parts from the schematic at: www.arrl.org/tis/info/pdf/8912018.pdf - (arrl 14 Mhz transceiver) but converted to multiband.
The vfo part will be a DDS3 from Hands Electronics and the bandpass filters from "Gqrp" design using Toko coils. VFO amp (if neded) will be the one from "Analog Devices" application note AN-557 (a simple 2n3866 amp).

I built the IF strip and it looks that is working nice. I am now testing an BFO cristal switcher so I can have LSB and USB. For now the LSB cristal is just 140Hz away from the correct frequency (8.9995)

In the video the rf generator is around 40cm from the 9Mhz if input. I still have no rf front end done except the first mixer.

There are however some "error's" I found on the schematic:

- On the second sbl-1 (connected to the bfo oscilator) the IF pins are switched , replace 3 and 4 by 5 and 6 and vice versa.
- The caps on the BFO oscillator first transistor should be 47 and not 470, probably something around 33 should work also.
- T6 ref. doesn't have the number of turns for the secondary, I am using 2 for the moment (just testing), on my "not calibrated" power meter gives 0.2v (=~ 1dbm) so I will increase later one.
- I replaced the NEC99532 transistor by an 2N3866, still have to test if it's ok.

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