Pilot reported a brief loss of radio contact with C90 TRACON and suspected ATC transmitters in the area are intermittent.

Narrative

Earlier today; I had a brief loss of radio contact with Chicago Approach. Although safety wasn't compromised; I think it may be useful to report this area of poor radio contact. I had just checked on with Chicago Approach on 120.55. We were IFR; and flying at 4000' about 10 miles north / northeast of DKB. After checking on with the Controller on 120.55; he gave us a vector of 060; which we read back and complied with. The Controller was audible but only faintly. The audio wasn't bad enough where I thought I should turn off squelch; which proved to be a mistake.Looking at my flight data log; I can see that we were on this heading for about 2 minutes; and heard nothing at all on the radio. I then heard; simultaneously on 120.55 and guard; which I always monitor on com2; the Controller calling us and asking us to contact him on 120.55. I replied right away; since I could now hear him; and he did a radio check and then gave us a further clearance to an IAF. He sounded irritated; so my assumption is he had called me several times on 120.55; but I didn't hear any of that. Only until he called on guard could I hear him. My com radios are about 1.5 years old and have been heavily used; and work very well. I strongly believe this is not an aircraft problem; and instead shows an area of spotty coverage on Chicago Approach frequency 120.55. If this issue can't be resolved at the radio hardware level for ATC; then Controllers should be aware that 120.55 is spotty about 10 north / northeast of DKB at 4000'.