C172 Pilot reported radio problems and carburetor ice. When Reporter punched radio it resumed functioning normally.

Narrative

I had filed an IFR flight with FSS for the last of three flights returning home to my base. The earlier flights that day were uneventful; and weather conditions were similar; with AIRMETs for moderate turbulence to 10;000 MSL and scattered reports of icing in clouds; with broken to overcast layers present from about 3500 feet through 8000 MSL with tops of all layers no higher than 10000 MSL and only widely scattered precipitation; mostly rain at the surface with the FL being at 2000 to 3000 MSL along my route of flight. My plan; which worked well for the first two flights; was to avoid clouds as much as practical and fly up to a flight level of 9000 MSL IFR; though for the first flight at one point I asked to fly up to 10000 MSL without any difficulty in terms of significant icing; turbulence; or any carburetor icing. I did experience a little communication issue from my older single Bendix radio just prior to landing during the latter part of the second flight while communicating with Approach; but by the time I was handed off [to] the Tower; both transmission and reception were OK once again. I also had a hand-held radio which I used successfully; albeit with some difficulty; to communicate for this flight. Notably for me; within the last 2 months I have had these radios extensively checked and tuned up at a certified avionics shop. However; after an uneventful departure and flight up to 9000 feet; I found almost simultaneously that I was experiencing difficulty reaching Approach via radio and then also maintaining altitude; despite normal engine temperatures and no overt engine issues. Regarding the former; it was clear that the controller did not hear me while I heard him with difficulty. Unfortunately I was not able to communicate with him better with adjusting the radios; PTT; changing headsets; etc; nor unfortunately with my hand held radio either. I did however at one point successfully communicate that I could no longer maintain 9000 feet due to carburetor icing; and needed a descent to 8000; however after realizing what the engine problem was and applying carburetor heat; I was able to climb back up to 9000 feet; which I announced to him via both hand held and other radio; but do not know whether he heard. He then handed me off to another Approach controller; but was only minimally able to communicate with her on this frequency; and not at all on the frequency I heard her change me to. I tried switching back but was entirely unsuccessful; and unfortunately in the meantime after reaching 9000 feet again I began to sink back down to about 8500 feet once again; because in retrospect I had taken out the carburetor heat too soon (had left in on perhaps 7-8 minutes the first time to regain the altitude to 9000 MSL but not left it on long enough for the sake of speed); and realizing this I reapplied the carburetor heat and within a couple minutes was able to reach 9000 feet again and stay there; and then was able to maintain altitude by keeping it on for at least 10 minutes after this. At that point; in terms of communication; I gave up on ZZZ and successfully reached ZZZ1 Approach; realizing that I was likely in ZZZ1's airspace at that point; and after a few minutes of radio difficulty; punching the radio serendipitously cured all radio transmission difficulties (perhaps it was a physical contact issue affecting the wiring and not the internal aspects of the radio itself; despite the fact that radio did not seem to be falling out of its casing) and I was able to relate the issues to the ZZZ1 controller and had no further communication or carburetor heat issues for the remainder of the flight. I am thankful that my radio seemed to cure itself with a small physical maneuver that I would not have expected would help; that at all times during my issues with maintaining altitude that I had not descended into icing conditions in the clouds (always remaining above the tops) and that I was able thankfully to see any othertraffic that might have been around; and that the carburetor icing issue; while perhaps I could have dealt with it better by a longer initial application of carburetor heat; eventually was solved.