Additional IC-7700 Receiver Tests: MW Broadcast Band

by Adam Farson, VA7OJ/AB4OJ

At the request of several SWL's whose interest lies in distant medium- and long-wave broadcasters, long-wave NDB's (non-directional beacons) etc., I conducted a few additional receiver tests on my IC-7700.

It should be noted that unlike the IC-756Pro series, the IC-7700 does not insert a pad in the receiver's RF signal path below 1.6 MHz. Preamps 1 and 2 are also available in this range (although DIGI-SEL is disabled.) Thus, I surmised that the IC-7700's receiver performance would be largely undiminished in the LF/MF part of the spectrum. The following tests confirm this.

1. SSB MDS (Minimum Discernible Signal). MDS is defined as the RF input power which yields 3 dB unweighted S/N at the output. The results obtained are comparable to those in the HF range.

Test setup: click here. Initial settings: 1010 kHz USB, 2.4 kHz SSB filter (Sharp), 15 kHz roofing filter, ATT = 0 dB, NR off, NB off, Twin PBT cleared.

Table 1: SSB MDS
MDS at 1010 kHz (dBm)
Preamp SSB 2.4 kHz
Off -121
1 -132
2 -136

 

2. AM Sensitivity.  This is defined as the RF input power which yields 10 dB (S+N)/N  at the output. The test signal is AM, with 30% modulation and a 1 kHz modulating frequency.

Initial settings: 1010 kHz AM, 30% modulation at 1 kHz, 9 kHz AM filter, 15 kHz roofing filter, ATT = 0 dB, NR off, NB off, Twin PBT cleared.

Table 2: AM Sensitivity
Sens. at 1010 kHz (dBm)
Filter 9kHz 6 kHz
Preamp
Off -102 -102
1 -113 -115
2 -117 -117

3. Reciprocal Mixing Noise. Click here for a test description. Reciprocal mixing noise is of interest for medium-wave DX receiver operators, as the receiver's LO phase noise can mix with a strong undesired signal (frequently encountered on the crowded MW band, especially at night) to produce noise in the IF passband. This noise can easily mask a distant station's relatively weak signal.

Initial settings: 1010 kHz USB, 2.4 kHz SSB filter (Sharp), 15 kHz roofing filter, Preamp off, ATT = 0 dB, NR off, NB off, Twin PBT cleared.

Table 3: Recip. Mixing Noise
Recip. Mixing at 1010 kHz (dB)
Offset kHz Roof 15 kHz
2 74
3 78
5 84
10 93
20 101
Copyright © 2008 A. Farson VA7OJ/AB4OJ. All rights reserved. 
Last revised: November 27, 2015

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