I spent more quality time with my new DX-R8....
...2) 'Narrow' filter is too narrow for both AM and SSB and even voice is too muffled in this mode. Actually, 'narrow' mode may be used for CW signals only
Correct. Derived from an amateur transceiver, the narrow mode in AM is 2.4khz, and for SSB, it is only 1khz. Too narrow for either - but narrow mode is not really meant to be used on AM or SSB in this rig.
Normally, in cw mode, the standard in the Alinco is 1khz. Nice. Narrow in cw mode get you down to 500hz audio filtering. Perhaps not as nice as a crystal filter, but it does the job for non-contesting situations in cw.
If you need narrow filtering in AM mode, your best bet is to use ECSSB mode. That is, when listening to a broadcast station, switch to either USB or LSB and zero beat - easy to do with the slow tuning knob. Make sure you aren't in a narrow mode here. Start out with your IF shift centered, and tweak if needed after zero beating. Works really well, and I actually prefer doing ECSSB rather than sync detection - which was removed from current R75's.
Adjust your agc for fast or slow depending on conditions.
3) No fast tuning option and manual scanning in SSB mode is too slow
Yep - the fast-tune option is done with the arrow keys. Select your desired step, and hold either up or down (make sure that Key-Repeat is active in the menu). Fine tune with knob. I'm a vfo-guy myself, so this is taking a little getting used to. Alinco is kind of forcing me to use the features I paid for.
Scanning on this receiver is pretty comprehensive, although I don't use it for HF much. With the squelch open, you want it slow. If you actually use the squelch, the scan goes pretty fast. Not much use for me on HF, but I could see someone with some great antennas or propagation using it for utility / beacon scanning etc if they are aware of how HF scanning can be a compromise at times. It seems apparent that perhaps GRE had a hand in this - the scanning ability of the R8T/E is the best I've seen - even though I don't use it. Programmable stops, delays, timeouts, priority etc. Kind of wish they had thrown in the VHF airband with all that cool scanning features.
4) I use an 80 ft long wire with 9:1 balun, antenna, 20 ft above the ground in Northern Florida rural area and the receiver is too noisy in this environment. I can hear USA amateurs only on 80 and 40 meter bands and the sound is far from perfection.
Just make sure that you don't have the preamp on - especially on the low bands. Since the preamp toggles along with the rf-attenuator, this might be something you can miss, although +10 on the display signifies the preamp is on. When I first got my R75, I was blowing my ears out running both preamps thinking "man, this radio is hot!". As years went on, I found that I don't use preamps much at all.
AM broadcast stations are in abundance, though, but you may listen them fine with much cheaper radio. My $50 Tecsun-PL210 with a whip antenna performs better in the case.
Ah, maybe you are getting desensed from a nearby broadcast station - not uncommon and this isn't a contesting radio. Perhaps a <1500 khz filter would help in your location. I have the PAR BCST-HPF filter, but luckily I don't need it in my current location.
Don't get me wrong - I love my R75. But if one can put up with the non-adjustable knob step rate (cmon Alinco - do a firmware option for that please!), and some ergonomic things like small buttons for a radio that makes extensive use of them, I think the Alinco DX-R8 makes a fine receiver for the class it is in.