The developers are testing this currently since it's a critical problem.
AF does not work properly
jamar
Добавлю, что при достижении на работающей частоте критического минимума уровня сигала (триггер для перехода на AF), нужно отсортировать список AF по силе сигнала (от лучшего к меньшему), и затем начинать сравнивать на них PI. Т.к. в зоне может оказаться пересечение нескольких частот одной станции, и не всегда сильнейшая будет в начале списка AF передающихся от станции.
VladOst
You're right. The 7708 chip should be able to tune frequencies fast enough to scan for signal strenght with barely noticeable dropouts. And I guess it's maybe already done this way, but as I said, sometimes wrong frequencies appears on AF list from previously listened station. And some stations broadcasts AF list of their whole network, so there is possibility, that some frequency in the AF table might be in use by another station in particular area. That's why the check for correct PI is really importat and if it differs from PI of currently listened station, don't check that frequency again and try another one.
Today I was driving from my client between two cities, listened to some station and when the signal drops under level where AF kicks in, it starts trying a frequency with stronger signal, but from completely different station. And it kept trying it for at least minutes, cycling between station I was listening to and the different station within 1 second interval, forcing me to switch to another station, because it was sooo annoying ;-)
jamar What can I say is that the devs are working on it. But with this Chinese New Year holiday things might get delayed a bit.
Thank you for your tips, with more tips and people the developers can improve AF
jamar
Я работаю техническим директором на крупной сетевой радиостанции в России, и прекрасно знаю, как работает RDS 
К сожалению, в России нет стандартизации по присвоению PI радиостанциям (не знаю, как в Европе и других странах). Из-за этого может случиться так, что если разные радиостанции в соседних (или даже одном) регионах не договорятся, то могут использовать один и тот же PI 
Приходится выезжать на полевые испытания, искать такие станции, и вести с ними переговоры о смене PI. К тому же PI иногда бывает принимается с ошибкой, и "совпадает" с чужим значением (бывает редко, но бывает).
Т.ч. ложное срабатывание AF не всегда является виной радиоприёмника. Поэтому мы рекомендуем своим слушателям отключать AF в зоне города или уверенного приёма, и пользоваться этой функцией, только если не знаете точной частоты передачи любимой станции на дальнем пути.
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VladOst I understand that, but why can navradio read an alternative frequency or radio on the Mediatek Helio P65 processor at a given time. The problem is with sensitivity, it happens both ways. It searches and cannot return to the previous frequency or in the other direction it does not want to detect an alternative frequency. It also happens that the station disappears, there is no alternative frequency, the radio starts to receive worse when AF is turned on. However, the best AF has a radio on the mediatek helio p65 processor, there the radio and alternative frequencies are received flawlessly. So it's not the radio station's problem since the AF works perfectly on the Mediatek Helio P65
MihaiFlorin
No problem, I'll be of course patiently waiting. The most important thing is that the developers knows about this problem and are willing to make some fixes and adjustment. But of course let them enjoy the upcoming holidays ;-)
VladOst
Okay, fair enough ;-) Anyway, here in Czechia are PI codes assigned by state authorities (namely Czech Telecommunication Office), so PI conflicts really shouldn't happen. Of course, errors in reception and false PI decoding can happen, but I'm not sure what's the probability of this error, since RDS has some sort of CRC error checking and PI is transmitted in every RDS data group, so checking it's correctness by receiving it twice should't take longer than 200ms, if I'm not mistaken.
On the other hand, I think I've never experienced problems with wrong AF switching with OEM headunits or with car radios from known brands over the years, so I really think this is a problem of Dudu7/FYT headunits...
jamar Believe me, they know.
20 days later
I want to calm everyone down, developers are working on improving AF in dudu radios. They realize that the topic needs to be improved.
wybitny2 I don't want to say "I told you so" 
MihaiFlorin I only confirmed what you wrote
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The radio in dudu7 generally works very badly. the receiver sensitivity is worse than radios from the 80s/90s, AF doesn't work at all for me, TA can't be turned on... Generally, the radio in DUDU7 is like a simple receiver, which you can buy in a supermarket for a few dollars... This is not what you would expect from probably the most expensive station
rafisz
Hi, I can't fully confirm that. The sensitivity seems to be on the same level as it was with original headunit I had in my car. I just needed to add power injector for active antena (original headunit had it built-in). What can I say is that Dudu7 (and this seems to be true for all chinese headunits I had my hands on) is much more sensitive for picking up EMI interferrence. I've partially fixed it by adding EMI filter on power line, now I'm trying to find a way how to filter noise picked up from USB connected DVR (Dudu 2k). But otherwise sensitivity is fine.
AF problems were discussed here (and in the ver 3.6 announcement thread) previously, it sort-of works sometimes, but it's far from ideal. The TP function is completely broken, you're right. So let the devs finish and fine-tune the AF function and then maybe they will correctly implement TP handling. And then maybe Radiotext+, and then, well, the sky's the limit ;-)
We will probably receive test version of improved radio app until the end of next week.
jamar
I installed DUDU7 in a Honda Accord 8th gen EU and I compare it to the original unit. In the Accord, no additional antenna equipment is needed, a regular Honda-ISO adapter is enough. The antenna amplifier is powered by a separate cable. The original Accord radio is much better than DUDU, which irritates me a lot. Where the original played cleanly, Dudu often hisses. On a long trip, you can forget about listening to radio stations or hearing traffic reports. I hope that after the corrections it will finally start working properly, the sensitivity probably cannot be improved, but maybe the rest will be OK...
rafisz
Well, that's weird, I don't have such experience. In my car - Toyota Proace City Verso (but it's actually made by PSA - same as Peugeot Rifter/Citroen Berlingo) - original headunit (actually made by Bosch) had comparable reception. And also in other cars I drove ocassionally the reception seems to be not so much different. The frequency switching is of course much better...
Other thing is that OEM headunits often uses two independent tuners where one of them is constantly scanning for another usable frequencies in the background, so the radio always knows about available frequencies and can quickly switch between them without any noticeable interruption. We can't expect this level of functionality in Dudu, since it has only one tuner, but the TDA7708 should be fast enough to make AF switchig work reasonably well. We'll see...