National NC-303 Receiver

National NC-303 Receiver
Performance Test

National NC303


Band	MDS	Blocking	Two-tone D.R.
		(20 kHz)	(20 kHz)

80 meters	-139 dBm	110 dB	82 dB
40 meters	-140 dBm	110 dB	86 dB
20 meters	-137 dBm	109 dB	81 dB

AM Audio S/N: 45 dB

AM Audio Frequency Response:

100 Hz

200 Hz

400 Hz

600 Hz

800 Hz

1 kHz

2 kHz

3 kHz

4 kHz

5 kHz

6 kHz

+2 dB

-1 dB

0 dB

-2 dB

-5 dB

-10 dB

-15 dB

-22 dB

AM Audio Distortion:



Mod%	100 Hz	200 Hz	400 Hz	600 Hz	800 Hz	1 kHz	2 kHz

30%	14%	7.1%	3.5%	2.5%	2.0%	1.8%	2.2%
50%	22%	10%	4.0%	2.5%	1.8%	1.6%	2.5%
70%	25%	10%	4.0%	2.8%	2.8%	3.2%	3.5%
90%	32%	11%	7.9%	7.1%	7.1%	7.1%	7.1%
100%	40%	18%	13%	10%	8.9%	8.9%	7.9%

Notes: Maximum i-f bandwidth is about 8 kHz @ -6 dB. Before running the audio frequency response and audio distortion test the tone control was set to 'normal' for flat response as measured through the auxiliary audio input.

AM distortion numbers show the somewhat typical increase at lower audio frequencies - most often caused by the low audio frequencies riding on the AGC line. Also there is the usual increase in audio distortion as the modulation percentage increases. This is due to the detector's inability to cleanly demodulate the higher amplitude levels.

This receiver would probably benefit from a longer agc time constant as did the HRO-60 although no additional measurements were made.