The comparisons were done with the receiver preamps in the OFF, preamp1 and preamp2 settings. This was also the case even on the noisiest of bands including 80/160mtrs in the late evenings while pulling out the weakest signals I could find. What I had found was that the receiver sensitivity of each rig was practically equally sensitive. Many hours were spent comparing the IC-7700 to the IC-775 on the higher 10-20mtr bands in search of the weakest signals. However, the horse race could get tight if I were to opt for one of those 125 Hz, 455 kHz IF, CW 8-pole filters by Inrad to place inside the IC-775DSP. My consensus is that the IC-7700 has more capability in selectivity due to these selectable narrower bandwidths down to 50 Hz, but without noticeable receiver desense. I found no audible attenuation from filtering of even the weakest signals, even on the higher 10-15mtr bands where the noise floor was very low and quiet with preamp2 engaged. These observations included repeated deep scrutiny of the weak signals to make sure the classic desense issue was not evident as typically found in older generation DSP only rigs where close in signals became severely desensitized due to poor blocking dynamic range. I discovered that the IC-7700 is more capable in selectivity verses the IC-775. The IC-7700 can also go down to a bandwidth of only 50 Hz this is where the upper hand comes in.
To get the interfering CW signal out the IC-775 pass band, you had to be 200 Hz or greater from the QRM signal, while the IC-7700 could give you an additional 100-125 Hz of playground next to that big signal. If the IC-7700 had the shape of the filter set to “soft”, the IC-775 did a better job but when the IC-7700 had the shape of the filter set to “sharp”, the IC-7700 was slightly more selective. What I had found was that both rigs performed almost equally when the filter bandwidth of the IC-7700 was set to the same 250 Hz bandwidth of the IC-775 narrow filter. These are the basic metrics (in my opinion) in a receiver that can make or brake getting that weak one in the log while fighting big signal QRM. I frequently looked for the perfect recipe for receiver comparisons by searching for those situations where a very weak DX signals fell within 100-200 Hz of those bigger S9+30dB and greater signals. S9+30dB and greater CW signals were hunted down on all bands with an emphasis on 80/160mtrs. The high pass and low pass receive audio filters were set on the IC-7700 to match the widest settings of those in the IC-775 during my observations. Please note, there is one CW filter spot empty on the IC-775 which is the place holder for another 250 Hz filter in the 9 MHz I.F. The IC-7700 was put to the test against my old IC-775DSP that has the stock cascaded 500 Hz CW filters for the 9 MHz and 455 kHz, and an optional 250 Hz filter by Inrad for the 455 kHz I.F. Since I perform testing, validation, and benchmarking of electrical and mechanical components as a test engineer, and am analytical by nature, I can easily state things like I see them and give a non-biased observation even though it was a lot of ‘my’ hard earned money spent. Before a rig review, it’s nice to hear that the new owner gave some time and attention in performing real A-B comparisons to old shack benchmarks that have been used to for many years. Sometimes we hams fall victim to a “wow” trap when we first get a new rig, just dying to put a review out instead of waiting a while and then giving a more non-biased observation once the new rig’s been in the shack for a while. Previously owned rigs include Icom IC-735, 746, 751, 751A, 765, and 775DSP along with a short term in-shack usage of an IC-781 and Yaesu FT-1000MP. I am not a phone op, and am as rare on phone as P5 North Korea is on all the bands, so my review may not help those who favor operating phone. I’ve been an avid, all band, CW DXer for 22 years with emphasis on 160mtrs while also operating in the CQWW-CW, ARLDX-CW, and other contests. Please note that there are many other apparent qualities of the IC-7700 in regards to phone and digital modes of operation but which go beyond the scope of this review and commentary. My objective is to point out some of the main characteristics that I have observed on the IC-7700. This review of the Icom IC-7700 is essentially a benchmark comparison to my Icom IC-775DSP, which has served me well as the main rig for the last 10 years. This review was written by Bob WB8B and is placed here by permission.