Comments on CW operation with the IC-7600

by Matt Erickson, KK5DR, 4 May 2009

Today I had a chance to operate more CW on my 7600. I found that it is so good that I can tune to within half the filter bandwidth of an S9 + 20dB CW signal and hear no trace of it - no key clicks, artifacts, etc. It is as if that signal, as close as it is to my tuned frequency, does not even exist.

I tried this with several DSP filter settings. I used 350Hz and at exactly half the filter width tuned offset from the strong signal; that signal went away completely.

At 250Hz BW, I offset the tuning by 125Hz and the signal went away. At 100Hz BW it disappeared at 50Hz offset, and at 50Hz it went away at 25Hz offset. I am able to dig weak signals out of the noise at the same time without the slightest hint of AGC swamping..

If this isn't as good as it gets in the current crop of radios, I don't know what is!

It is some of the very best CW filtering I have ever heard - every bit as good as the 7700. Serious CW operators should not have much to complain about on this radio.

I tried out  the APF in all three of its modes and they all work fine, no problems.

One might say "less is more" on CW (and any other mode for that matter.) Not using the preamps is more important than using them. Unless the distant station is using a radio of the same performance caliber as the 7600, it is unlikely that they will hear you if signals are so weak as to require the use of the pre-amp to copy them.

If one can keep signals to a level that does not use up all the ADC headroom, there will be no problems with the receiver. Most of the time, no preamp is needed on CW, and on the lower frequency bands some level of attenuation will certainly be needed to maintain this control. I can guarantee that no one will ever miss a contact because it was "too weak to copy" if they use this method. With DSP-based radios, less is truly more when speaking about control of the RF front-end.

Refer to "dBm from Heaven"