Thursday, November 12, 2009

5-5.5Mhz VFO Buffer

Now that that the vfo looks nice and works nice....I must found a better variable capacitor, this one only has reduction of 1.5:1, the "rit" pot could help the lack of reduction on the capacitor but I want something nicer... so I will put the assembly on the "finished but no use for the moment" rack.
The output without load is around 1.9V measured with the homebrew rf test probe... ( http://speakyssb.blogspot.com/search/label/RF Probe )

The VFO buffer schematic













Drift from cold start:

video

Not bad hum? Considering the the box isn't closed and there are led's working as varicap's in the circuit.... also no capacitor was chosen for their thermal characteristics, only for their value.

There is some cw in the video background (this vfo was not connected to the radio), I was trying to copy the "no power transmitter" Atlantic crossing (http://soldersmoke.blogspot.com/2009/11/aa1tj-code-talker-on-maine-coast.html) but I guess this transmission was not them...

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