Question about pixie transceiver

[obrien135]

Hello,

Does anybody know what kind of antenna the pixie transceiver would use, and what impedance?

George

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actually, I figured out that at 80M the output Z is 50 ohms. So that answers my question. The one I built had an output Z of 50 ohms, but I had to go with a lower power resister so I had to raise it to 150 ohms. Maybe if put a transformer to match the inpedance to the 50 ohm antenna it would transmit more clearly.

George

 

[vfone]

There is no dedicated antenna for pixie transceiver. Use the best antenna you have. The best antenna match is the PI match (covering wide range of impedances), which actually this mini-transceiver is using.

 

[obrien135]

I think the garbled transmissions are caused by noise from the power supply getting into the modulation amp. The supply measures about 30VRMS when nothing is hooked up. Is it better to use a linear supply? I think this one is a switcher.

George

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will an LM7812 circuit work well enough?

 

[jiripolivka]

I think the garbled transmissions are caused by noise from the power supply getting into the modulation amp. The supply measures about 30VRMS when nothing is hooked up. Is it better to use a linear supply? I think this one is a switcher.

George

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will an LM7812 circuit work well enough?

Switching power supplies cause many bad problems like in your case. Good switchers with a nominal load generate 100 mV to 1 V p-p which is easy to filter out.
The 7812 is good to regulate the output voltage but often cannot suppress the input-voltage transients like yours,. I would recommend a good filter first (RC or LC, use 10 nF ceramic in parallel with >100 uF) with the 7812 afterwards. If possible, add a load resistor before the 7812 to reduce the spurs.