Tuesday, February 21, 2017

Aligned receiver section, preparing to do transmitter alignment of HW-100


I wrapped up the conversion to using the DDS VFO, powered up and confirmed that the unit is tuning properly. I haven't confirmed that the output is free of coupled frequencies through the cable that joins the DDS to the VFO, but at some point before operating on the air I will hook this to a spectrum analyzer and look at the output of the VFO. 

I proceeded through the receiver alignment, using the 100KHz built in calibration oscillator. All this assumes that the oscillator itself is right on frequency. There is a procedure to follow to validate this, which will be my next move.

I had a plastic project box that I initially though I would use to mount the DDS, but it is too small and not shielded, both are a problem. I am looking for a larger metal project box which I can install my DDS VFO and its LCD screen. It will sit atop or alongside the HW-100 rig.

I notice that there are minor differences in the frequency that the 100KHz signal peaks as I switch through the bands - this indicates that the crystal oscillators for the final frequencies that are mixed with the IF are a bit off their nominal values, each differently. There are trimmer capacitors on those crystals, I believe, which would allow me to get this spot on to the desired frequency. All that REQUIRES that I can trust the 100KHz calibration frequency, making that tuneup a priority.

I have about ten feet of wire stuck into the antenna jack and sprawling across the floor. Not much of an antenna but I was able to find some CW (Morse Code) going on in the 15 meter band. I need a really strong, i.e. local, signal to hear anything without a proper antenna, but at least I have reception, tuning and so forth. 

My dummy load arrived by early evening, however I still couldn't move on to aligning the transmitter section of the transceiver. I didn't have a morse key or a microphone with PTT yet, thus no way to trigger the transmitter. 

No comments:

Post a Comment