This is an older thread but I will post to it because I have firsthand experience with the H501x Tecsun receiver, which I would caution folks about buying at this time. The reason for the caution is the series of issues I encountered with my unit, some of which are outright deal killing in impact to the radio.
In SSB the radio I received exhibits zero stability, specifically you can zero beat the radio all you wish too, but once tuned to another frequency, or band, your radios zero beat is gone to, you cannot zero beat the 501x across frequencies, at least on my sample! I zero beat mine repeatedly on wwv and chu, only to immediately lose zero toggling back and forth from LSB to USB, they cannot be zeroed! This translated into the MW bands too, where zero beating the radio in ssb, then trying to listen in to strong MW stations in ssb results in need to re-zero the radio, again and again! While the H501x is superb at SSB demodulating, don't expect it to maintain zero from frequency to frequency, I would love to hear from others about this, again this is based upon my sample.
Do keep in mind my PL880, which is half the price of the H501x, and half its size, it was zero beat once, that beaing the day when I bought it, and it has stubbornly maintained that zero across all SSB and MW ever since! After zero beating the H501x extensively, its customary to turn it back on after powering it down, to discover your as much as 100 to as much as 180 hz away from zero, in other words, totally garbled and out of tune, like you would be with a radio like the old Yacht Boy 400's, or the original 909's from Sangean, both of which cannot be zero beat, simply tuned and fine tuned upon each new frequency, and never can achieve, or could hope to achieve the stability required for ECSS!
Synch, you'll hear from the shills that synch just doesn't sound right on the H501x, well thats true, because the SSB is never zeroed whilst using the synch! On my sample, the synch works great, tenaciously holding down the signal, the problem is not the synch, its the SSB which is not zeroed and never will be due to whatever firmware issue it is preventing it! This issue is a deal killer on it own!
Battery consumption, on my sample is appalling, having fully charged up the two included tecsun 18650 cells, one was totally drained after just a several hour evening try out period, and the radio will power itself down swiftly upon alerting you of the low battery! This is completely unacceptable performance, again using the superb PL880 as our benchmark, that radio runs on its single 18650 cell for weeks, even months if it sees little use, but three to five days with heavy usage being common.
This is based upon both units being run absent the backlights, however there was a further nasty surprise in store, upon seeing the battery fully depleted, I inserted a new fully charged Olight 3200 mah 18650 cell at the end of that evening session. Upon firing the radio back up the next day I was greeted by a low battery warning, then the swift powering down of the radio!
Removing the Olight 18650 from the tecsun radio, again which turned itself off due to lack of power, I was worried the radio was literally engaged in epic bleed down, however upon inserting that Olight 19650 into charger it was revealed to be fully charged! If this proves a common occurrence its gonna be a real problem on a radio that only can be powered via an 18650 cell, the included tecsun battery may be crappy, but the Olights are not, and if the radio refuses to accept them then we have us a definite deal killer!
Frequency and firmware glitches occur, the radio will suddenly drop out of frequency on its own, which is pretty damn peculiar on a digital tuning radio, touching some buttons such as the button to turn off the synch/ssb mode introduce strange things to take place on the sets display, the kind of things that remind of firmware issues!
The bass and treble are virtually meaningless, they work(barely)on FM, I seem to notice no other effect while in the other bands!
The Tecsun H501x is potentially a great radio, like the 909X I really want to like it, but just like the 909X it(my sample anyway)comes with significant shortcomings, several of which such as the inherent instability of its ssb function, are do not buy red flags, the little PL880 is absolutely stellar in ssb, I use it extensively for ecss, its stability proven now over two years of ownership, it absolutely crushes the H501x based upon my first week experimenting with the latter.......