High side injection looks a lot better...
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12288 kHz IF high side injection
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A. For an IF of 12288 kHz:
2x the LO will be 34976-35376 kHz
3x the LO will be 52464-53064 kHz. [6 meter ham band]
4x the LO will be 69952-70752 kHz
5x the LO will be 87440-88440? kHz
Analysis (All frequencies in kHz):
1. If I design the transceiver to tune from 5200-5400 , then the LO will be? at 17488-17688. Great!
2. 3rd order product (remixing, 3*LO-tx frequency) due to non exact impedance matching in the TX mixer: Low 52464-5200 =? 47264 High: 53064-5400 = 47664. Great!
3. Closeness of LO to band (for effective filtering) 17488-5200 = 12288. Great!
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9000 kHz IF high side injection:
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A. For an IF of 9000 kHz:
2x the LO will be 28400-28800 kHz [ 10 meter ham band]
3x the LO will be 42600-43200 kHz.
4x the LO will be 56800-57600 kHz
5x the LO will be 71000-72000? kHz
Analysis (All frequencies in kHz):
1. If I design the transceiver to tune from 5200-5400 , then the LO will be? at 14200-14400. Not ideal. [LO in the a good portion of the 20 Meter phone band]
2. 3rd order product (remixing, 3*LO-tx frequency) due to non exact impedance matching in the TX mixer: Low? High: 42600-5200 = 37400. Great!
3. Closeness of LO to band (for effective filtering) 14200-5200 = 9000. Great!
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11059 kHz IF high side injection:
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2x the LO will be 32518-32918
3x the LO will be 48777-49377
4x the LO will be 65036-65836
5x the LO will be 81295-82295
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1. If I design the transceiver to tune from 5200-5400 , then the LO will be? at 16259-16459 . Great!
2. 3rd order product (remixing, 3*LO-tx frequency) due to non exact impedance matching in the TX mixer: Low? High: 48777-5200=43577. Great!
3. Closeness of the LO to the band (for effective filtering) 16259-5200 = 11059. Great!
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11059 kHz wins, but I don't have this crystal on hand. 12288 kHz is probably what I'll use as I know the characteristics of this crystal and the LO leakage on 6 meters isn't a big deal for me.
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Steve
Wa6ZFT
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hwstar