Hi
Measurements as taken on my stock standard ICOM IC-7300 Receiver on 18.11.2021
RX Freq mute Spurious mute Diff
MHz dBm MHz dBm dB
27.033 -128.8 97.000 -31.4 -97.4
28.033 -125.0 96.000 -30.1 -94.9
29.033 -125.7 95.000 -117.8 -7.9
30.033 -126.3 94.000 -109.4 -16.9
31.033 -124.2 93.000 -108.9 -15.3
32.033 -122.5 92.000 -108.1 -14.4
33.033 -125.6 91.000 -112.7 -12.9
34.033 -125.1 90.000 -113.8 -11.3
35.033 -125.0 89.000 -114.1 -10.9
36.033 -125.8 88.000 -116.1 -9.7
37.033 -126.0 87.000 -116.1 -9.9
38.033 -126.0 86.000 -117.2 -8.8
39.033 -126.0 85.000 -117.8 -8.2
40.033 -126.1 84.000 -118.6 -7.5
41.033 -125.8 83.000 -119.1 -6.7
42.033 -125.6 82.000 -119.2 -6.4
43.033 -125.6 81.000 -120.6 -5.0
44.033 -125.6 80.000 -120.5 -5.1
45.033 -126.9 79.000 -121.7 -5.2
46.033 -125.7 78.000 -120.9 -4.8
47.033 -125.9 77.000 -121.1 -4.8
48.033 -125.5 76.000 -121.3 -4.2
49.033 -124.9 75.000 -120.6 -4.3
50.033 -124.9 74.000 -72.0 -52.9
51.033 -125.3 73.000 -81.3 -44.0
52.033 -125.4 72.000 -87.5 -37.9
53.033 -125.4 71.000 -92.7 -32.7
54.033 -125.2 70.000 -123.0 -2.2
55.033 -125.1 69.000 -122.6 -2.5
56.033 -124.5 68.000 -123.1 -1.4
57.033 -124.5 67.000 -123.2 -1.3
58.033 -124.2 66.000 -123.3 -0.9
59.033 -123.7 65.000 -123.2 -0.5
60.033 spurious 64.000 spurious n/a
61.033 -123.7 63.000 -123.7 0.0
FM mode, mute opening used as reference point. Only the listed frequency range was measured. There may be other frequencies.
As can be seen spurious frequency rejection on some frequencies is almost not existent.
Icom specifications only cover the Ham Bands.
On 6M and 4M dedicated RX input filters are used resulting in improved spurious rejection. On the other frequencies (30-50, 54-70MHz) it uses a much simpler one consisting of two parallel tuned circuits across the antenna line connected together by a series resonant circuit. These all are resonant on about 45MHz
It is a good thing analogue CH2 is no longer in service and the Commercial Mid Band no longer has much activity on it.
https://klop.solutions/aliasing-on-the-i...mment-1444
throws some more light on the IC-7300 to explain its behavior.
It would be interesting to know how other SDR receivers out there compare with the IC-7300.
73s
Igor
vk6zfg