[TenTec] Isolation of diode T/R Switch on Corsair
ken.d.brown at hawaiiantel.net
Sun Jun 7 16:54:47 PDT 2009
> I'm seeing voltages at the RX ANT jack that are 1/1000 of the ANTENNA output voltage on 80 and 40 meters, and only 1/165 at 10 meters. These tests were made using a 50-ohm dummy load connected to the ANTENNA connector.
How are you measuring the voltages? Oscilloscope with 10X probe, 10
Megohm impedance, properly compensated? A poorly compensated scope probe
might explain differences in your measurements on 80/40 versus 10
meters. Even if the compensation of the probe is adjusted properly for
correct voltage division at 3 MHz and at 30 MHz, the capacitive loading
of the probe connected to the circuit under test may have a lot more
effect on 10 Meters than at 80 Meters. Are all of your voltage
measurements above the noise floor of your measuring setup?
Voltage ratio of 1/1000 is power ratio of 1/1,000,000, or 60 dB. That
seems like pretty good isolation to me. Voltage ratio or 1/165 is power
ratio of 1/2275 or 44 dB, which is maybe good enough too.
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