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.
|MDS at 1010 kHz (dBm)|
|Preamp||SSB 2.4 kHz|
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.
|Sens. at 1010 kHz (dBm)|
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.
|Recip. Mixing at 1010 kHz (dB)|
|Offset kHz||Roof 15 kHz|
Copyright © 2008 A. Farson VA7OJ/AB4OJ. All rights reserved.
Last revised: June 16, 2018