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Old 10-27-2017, 02:26 PM
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wa2ise wa2ise is offline
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Join Date: Dec 2002
Location: USA
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Modified TV modulator on channel 6

Another TV modulator (Archer 15-1273 C2S7QZ) moved to channel 6 (a little off, but that's what "fine tuning" is for) Used a 82.7MHz crystal I salvaged from a flip phone. 550 KHz low, but TV sets handle it fine. This replaced a 2 channel SAW resonator.

I tried using a second crystal so I could have channel 5, but as it's not completely switched out of the oscillator circuit, it created noise on the selected channel. So I went with only one crystal and thus one channel.

I also changed an attenuation resistor (was 680 ohms, now 33 ohms) to get about 13dB more signal strength. So I could split the RF signal to multiple sets if I want and have decent signal to noise. You could do this without changing the crystal.

I also changed the half wave rectifier diode with a bridge, so the transformer doesn't end up with DC current bias (tends to cause core saturation).
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File Type: jpg archer-rf-mod-ch6.jpg (139.6 KB, 100 views)
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Last edited by wa2ise; 10-27-2017 at 02:33 PM.
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