Collins 75A-4 Receiver

Collins 75A-4 Performance Test

Collins 75A-4


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

80 meters	-141 dBm	102 dB	79 dB
40 meters	-141 dBm	100 dB	77 dB
20 meters	-141 dBm	98 dB	75 dB

AM Audio S/N: 48 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

-3 dB

-1 dB

0 dB

-1 dB

-12 dB

-44 dB

-46 dB

-48 dB

AM Audio Distortion:



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

30%	4.5%	1.4%	1.0%	1.0%	1.0%	0.9%	1.0%
50%	3.2%	1.0%	0.8%	0.8%	0.8%	0.8%	0.7%
70%	2.8%	0.7%	0.7%	0.7%	0.7%	0.8%	0.7%
90%	5.0%	4.0%	4.5%	5.0%	4.5%	2.8%	1.2%
100%	8.9%	7.1%	7.9%	7.9%	7.1%	5.6%	2.0%

Notes: Maximum i-f bandwidth is about 6 kHz @ -6 dB with the stock Collins AM filter.

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.