After creating "GCA" measurements successfully with PNA-x N5242A rev A.10.64.09, But failed to get GCA handle. The code is listed here:
Type pnaType = Type.GetTypeFromProgID("AgilentPNA835x.Application", "N5242A");
AgilentPNA835x.Application pna= (AgilentPNA835x.Application) Activator.CreateInstance(pnaType);
//create an "Gain Compress" object with measurement "CompOut21" on Channel 1. successfully in next line.
AgilentPNA835x.IMeasurement cust_meas = pna.CreateCustomMeasurementEx(1, "Gain Compression", "CompOut21", 1);
// Get current channel.
AgilentPNA835x.IChannel chan= pna.ActiveChannel;
// to change GCA default settings, need to get GCA handle from IChannel in the next line.
AgilentPNA835x.IGainCompression gca =chan.CustomChannelConfiguration()
The question is : CustomChannelConfiguration() property is not visible for current Channel interface "chan" object though we can find CustomChannelConfiguration propriety of AgilentPNA835x.Channelclass from Object Browser.