Icom IC-9700 and 10 MHz GPSDO lock

Many people are confused about the 10 MHz reference lock input on the IC-9700. And so was I. While all of us expected the VCXO was locked to the 10 MHz input (which in most cases will be locked to a GPSDO) it isn’t. Unlike the new IC-7610, which is locked, the 10 MHz input on the IC-9700 can only be used to calibrate the transceivers’ VCXO. And even this doesn’t seem to be most accurate.

According Rex (VK7MO) tests, he had a 4 Hz error on 144 MHz, a 40 Hz error on 1296 MHz. Icom has work to do to fix this (and the ALC / Power Overshoot) error. A fix could be a (more) permanent lock/sync, but a fix could also be made in the fan controller, since the temperature is directly involved with the IC-9700’s drift.

People using the IC-9700 for FM (repeaters), satellite, FT8, etc. should not worry. People using the IC-9700 for weak-signal modes and EME should, and not putting the old locked IC-910(0) or TS-2000 on sale, yet.

IC-9700 receiving from a GPSDO signal source. RX only but with case temperature above 30 degrees so the fan turns on and off.

1 comment

    • dfIas on 18/04/2019 at 09:43
    • Reply

    Discussed already several times, but is there anybody knowing the native oscillator frequency to look for an OCXO with custom frequency, e.g. Vectron OX-175? The drift is such big that it is no good idea to hook up this badly designed VCXO directly, even with additional thermal insulation. However, the latter is not easy to do as this big copper block near the fan seems to be the shealding of it and is well conducted to the PCB on the sides. There is also another small oscillator visible at another place that is probably not the main one. 73

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