# Noise Figure measurement of a converter / transverter

I recently came across an article Signal level measurement with PowerSDR and external transverters in which Carol (KP4MD) details a set of measurements of a Flex 1500 transceiver and Electraft XV144 transverter.

Carol gives the following table of measurements and calculated results.

Table 1.  Transverter Measurements
Freq
MHz
Noise
Source
ENR (dB)
Noise/10
kHz
Conversion
Gain (dB)
Noise
Figure
(db)
50 Ω expected Noise On Noise Off On-Off (Y)
144 15.2 -134 dBm -118.8 dBm -132.1 dBm 13.3 dB 26.5 2.1
432 15.3 -134 dBm -118.7 dBm -131.7 dBm 13 dB 24.1 2.5

Lets focus on the 144MHz measurements.

These are a measurement of the system (ie Flex 1500 transceiver + Electraft XV144 transverter) and Y factor based calculation of Noise Figure (NF), and note that the Noise ON and Noise Off figures are from the Flex 1500 which has 26.5dB subtracted (a calibration adjustment for expected transverter gain).

This article presents a simulation of a two stage measurement which establishes the NF and Gain of the transverter. The two stage technique is described at Noise Figure Y factor method calculator.

To achieve that, we must determine the NF of the Flex 1500, the ‘instrument’. Since the necessary measurements were not made, for the purposes of this article I will assume that the NF of the instrument is 10dB, that the noise source has an ENR=16dB at the transverter output frequency, and calculate the Noise Off and Noise On powers in the same measurement bandwidth for that scenario. Instrument NoiseOn=-117.0dBm and NoiseOff=-124.0dBm.

For the system measurements, I will add the gain adjustment back in to the Table 1 figures, so DUT NoiseOn=-92.3dBm and NoiseOff=-105.6dBm, and the ENR was given as 15.2dB.

Entering them into Noise Figure Y factor method calculator we have: and the calculated results: The process calculates the Gain and NF of the transverter itself to be 26.3dB and 2.05dB respectively, and the system NF=2.11dB.

These figures depend on my assumption of the NF of the ‘instrument’, and different figures will flow into some differences in the calculated results.