1. Purpose of the measurement

The purpose of this test was to determine whether the nine VE6WZ element preamplifiers used in the YCCC 9RX circle array are sufficiently matched. In a phased receiving array, equal gain, equal phase response and equal DC behaviour are essential. A single deviating preamplifier can disturb the intended amplitude distribution and may reduce front-to-back ratio, null depth and repeatability of the directional pattern.

This was a comparative production-style test. All nine preamplifiers were measured with the same cables, the same Bias-T, the same supply voltage, the same VNA source and the same oscilloscope settings.

2. Test equipment

DG8SAQ VNWA V2 used as a stable RF signal source.

Calibrated 

RTC1002 digital oscilloscope.

Calibrated Rohde & Schwarz FSH8

Calibrated Fluke multimeter for supply-voltage verification.

Bias-T used for simultaneous RF extraction and DC supply.

Identical coaxial cables and connections for all nine preamplifiers.

Nine VE6WZ/YCCC element preamplifiers from the same 9RX array.

3. Test setup

The VNA output was connected to the terminal normally used for the RX vertical element. The preamplifier output was connected through its normal coaxial path to the Bias-T. The RF port of the Bias-T was connected to channel 1 of the RTC1002. Channel 2 monitored the VNA input signal.

CH2 = VNA input signal    |    CH1 = preamplifier output signal

The Bias-T supply voltage was 14.07 V, verified with a calibrated Fluke meter. The test frequency was approximately 1.795 MHz, within the 160-metre band.

Figure 1 – Basic test setup: input signal and amplified output signal on the RTC1002.

The preamplifiers invert the signal, so CH1 and CH2 are approximately 180 degrees out of phase. This absolute inversion is not a problem for the array as long as all nine amplifiers behave identically.

4. DC verification

Before applying an RF signal, the current consumption of every preamplifier was measured. All nine units drew exactly 34 mA at 14.07 V. This is a strong indication that the supply sections, relays, active devices and bias networks are operating consistently.

5. RF amplitude measurement

For each preamplifier, the peak-to-peak input and output voltages were measured. Voltage gain was calculated as:

Gain (dB) = 20 × log10(Vout / Vin)

Because the VNA input voltage varied slightly between 18.4 and 18.8 mVpp, each gain value was calculated from the actual measured input and output voltage. This provides a fairer comparison than output voltage alone.

6. Statistical summary

A total gain spread of only 0.30 dB is excellent for a home-built nine-element receiving array. The highest- and lowest-gain units remain very close together, with no clear outlier.

7. Representative measurement examples

The following oscilloscope captures are representative examples from the nine-unit test series. They show both the amplitude relationship and the approximately 180-degree phase inversion.

8. Phase interpretation

The oscilloscope indicated phase differences generally in the 175–178 degree range. This confirms that the preamplifiers invert the signal by nearly 180 degrees. The oscilloscope's automatic phase measurement is not the most accurate method for resolving one- or two-degree differences at these low input amplitudes. The result is therefore best interpreted as confirmation that all nine units have the same polarity and approximately the same phase response. No reversed or obviously abnormal unit was identified.

9. Measurement uncertainty and limitations

This was a relative comparison; absolute fixture gain calibration was not the primary objective.

The oscilloscope Vpp reading has a resolution of several millivolts in this setup.

Automatic oscilloscope phase readings are less precise than a calibrated two-port S21 phase measurement.

The test was performed near 1.795 MHz. Matching at 80 and 40 metres was not separately verified.

The laboratory source is not identical to the impedance of a real high-impedance RX vertical, but the comparison remains valid because the same fixture was used for all units.

10. Technical conclusion

Based on this measurement series, all nine VE6WZ element preamplifiers can be considered electrically healthy and well matched. They show identical DC current, nearly identical RF gain and the same inverting phase behaviour. Average gain is approximately 19.15 dB, with a maximum unit-to-unit spread of only 0.30 dB.

FINAL ASSESSMENT: all nine preamplifiers are suitable for use in the 9RX array.