HalfD написа: ↑вт яну 03, 2023 8:49 am
Yes, but it has a MONO speaker.
That's a downside for me because I want to hear how each Station's Stereo sounds. (When the Signal is high-enough of course!).
What kind of stereo sound do you expect when the speakers are at an extremely short distance?
The sound through the headphones is quite good,strong,without a trace of distortion and the stereo impression is outstanding!
eggplant886 написа: ↑чет дек 22, 2022 2:06 am
I've made some PCBs for TEF668X/665X chips, I plan to verify the effect of several different circuit components and I would give you some more info on this.
When it comes to measuring the signal strength,TEF has one big flaw.Up to 87dBuV,the signal measurement is almost perfect and there are no deviations compared to the professional version of the field meter,but after that value,the device is not able to accurately measure signals that are stronger than 90dBuV. .
I think this is a hardware problem,it possible to find a solution ?
P.S.
The Chinese portable variant is a solid replacement for the PC variant and I won't go into the differences for now...
ArthurSRB написа: ↑вт яну 03, 2023 11:58 am
When it comes to measuring the signal strength,TEF has one big flaw.Up to 87dBuV,the signal measurement is almost perfect and there are no deviations compared to the professional version of the field meter,but after that value,the device is not able to accurately measure signals that are stronger than 90dBuV. .
I think this is a hardware problem,it possible to find a solution ?
P.S.
The Chinese portable variant is a solid replacement for the PC variant and I won't go into the differences for now...
Hello, ArthurSRB !
According to the manual of the chip, the RF Amp may saturate at the lebel around 88dbuV, the RF AGC starts to work at this level to alleviate the inter-modulation. (RF AGC threshold can be set between 84dBuV to 92 dbuV)
The mismatch propably comes from the saturated RF Amp. Also, the attenuations of several RF AGC steps could probably have some deviations. I don't think it can be fixed as it's an internal hardware problem. And the Lithio/Atomic2 chip is not a signal meter so NXP is probaly aware of this and they don't consider it a problem to be fixed. I don't have professional RF quipments, you can test how the RSSI deviates from the actual value, if different chips behaves quit the same, it's possibly to do some correction in software, but RSSI-dependent weak signal handling inside Lithio/Atomic2 could not be changed but these functions typically not works under such a strong singal.
Is the 'Chinese portable variant' the radio made based on PE5PVB 's work? I have not used it before. I used my own control board and TEF module/ self-made tuners.
eggplant886 написа: ↑съб яну 07, 2023 4:00 am
Hello, ArthurSRB !
According to the manual of the chip, the RF Amp may saturate at the lebel around 88dbuV, the RF AGC starts to work at this level to alleviate the inter-modulation. (RF AGC threshold can be set between 84dBuV to 92 dbuV)
The mismatch propably comes from the saturated RF Amp. Also, the attenuations of several RF AGC steps could probably have some deviations. I don't think it can be fixed as it's an internal hardware problem. And the Lithio/Atomic2 chip is not a signal meter so NXP is probaly aware of this and they don't consider it a problem to be fixed. I don't have professional RF quipments, you can test how the RSSI deviates from the actual value, if different chips behaves quit the same, it's possibly to do some correction in software, but RSSI-dependent weak signal handling inside Lithio/Atomic2 could not be changed but these functions typically not works under such a strong singal.
Hello,
I tested the threshold when intermodulation starts and it roughly matches your information.
I need to measure the FM signal up to 120dBuV,so for that purpose I would add an attenuator to the antenna input (30,40dB),what is the impedance of TEF6686/50,75ohm or maybe it is not defined?
These are extremely high levels in an urban area 300m away from the transmitter: https://files.fm/f/k8js63dwm
The good thing about measuring extremely low signal levels is the noise level,which is -7dBuV with the TEFF6686. With the Chinese receiver,a piece of antenna cable inside the box raised the noise level by about 4 dB,which still does not significantly affect the quality of receiving weak signals.
In the urban area,the level of industrial noise is quite high...where it is low,the TEF6686 gives exceptional results and excellent signal reception is possible below the level of <10dBuV! https://files.fm/f/m88v9nx5y
eggplant886 написа: ↑съб яну 07, 2023 4:00 am
Is the 'Chinese portable variant' the radio made based on PE5PVB 's work?
Yes,both hardware and software have been take over with some minor changes.
ArthurSRB написа: ↑вт яну 10, 2023 12:02 am
Hello,
I tested the threshold when intermodulation starts and it roughly matches your information.
I need to measure the FM signal up to 120dBuV,so for that purpose I would add an attenuator to the antenna input (30,40dB),what is the impedance of TEF6686/50,75ohm or maybe it is not defined?
These are extremely high levels in an urban area 300m away from the transmitter: https://files.fm/f/k8js63dwm
The good thing about measuring extremely low signal levels is the noise level,which is -7dBuV with the TEFF6686. With the Chinese receiver,a piece of antenna cable inside the box raised the noise level by about 4 dB,which still does not significantly affect the quality of receiving weak signals.
In the urban area,the level of industrial noise is quite high...where it is low,the TEF6686 gives exceptional results and excellent signal reception is possible below the level of <10dBuV! https://files.fm/f/m88v9nx5y
Yes,both hardware and software have been take over with some minor changes.
Hello, ArthurSRB !
Sorry for the late reply. According to the manuals provided by NXP. All the DSP receiver chips share the same input stage circuit by now, which orignates from the TEF7000, a high performance low IF front end chip for car radios dating back to 2007.
The input stage has a 300 Ohms differential IC input impedance in parallel to a 9pF capacitance. AGC has seven steps of 6 dB. The input
impedance remains constant for the first five AGC steps. It is reduced for the last two AGC steps.
Here is a picture:
input.png (9.69 KиБ) Видяна 2158 пъти
The FM balun/transformer offers a quasi-symmetrical drive of the FM LNA. The (voltage) gain from antenna input to (symmetrical) FM LNA input is nominal 6dB, denoting that the 75Ω antenna impedance is transformed to a 300Ω source for the FM LNA.
For the single-ended 75Ohms input signal, just connect the output signal from the generator to the Antena input port.
For 50Ohms signal, impedence matching circuit needs to be implemented. You can use several resister for impedence copensation.
About the working temprature, NXP gives the range of -40 to 85°C so -27°C is not a problem.
Последна промяна от eggplant886 на съб яну 14, 2023 5:41 am, променено общо 1 път.
By the way. I connected the baseband signal output port of TEF radio chip to my logic analyzer and captured the baseband data successfully.
After decoding the I2S signal and import it to MATLAB/Simulink, I have made it to demodulate the base band FM signal in Simulink to get the orignal audio. The next steps would be 'De-emphasize, weak-signal handling(high-cut, low-cut, soft-mute, stereo blend, stereo high-blend)'. For the LW/MW/SW band, similar custome demodulation such as SSB can be realized.
I am posting a new thread to share about it after finishing the stereo decoding and de-emphasize.
The IF bandwidth in FM band is around 500KHz, in the AM band is about 30KHz.
This project sounds like 'Teensy convolution SDR' from DD4WH, but here the RF front-end is not self-made. Instead, a high performance compact chip is used.
The RF Amp, RF Mixer, RF Local Osc, RF AGC, IF Amp, IF AGC, IF Filter, IF ADC, I/Q correction are already finished inside the TEF chip. These circuits are designed and tested precisely so it would have a much better performance such as the IP3, sensitivily. Also a lot of time and effort can be saved, since RF circuit is very difficult due to many reasons such as parasitic parameters, test equipment requirement. Here we only need a processor to receive the digital baseband signal and design some algorithms. Hope other people with interests can join.
The baseband digital signal has a dynamic range of 88dB, since it has 14.75 bits accoding to the data captured
TEF6686 does not support baseband output according to NXP. TEF6688 TEF6689 TEF6659 TEF7018 TEF6638 SAF7751 support.
I guess baseband output may be a key-coded feature in TEF6686/6687 just like that in TEF7016, where a security code( known as key-code) needs to be purchased from NXP to enable this feature. I'm now trying brute-force attack on a TEF6687. It may succeed or fail. Or NXP doesn't hide such a feature.
Added signal in dBm when the user is connected to Wi-Fi
Wi-Fi icon rework (now the Wi-Fi icon will show whether you're connected to a network / XDR-GTK separately)
Battery status updates without reboot, if you're not using Wi-Fi
Signal should jump way less when a neighbour frequency is too strong
XDR-GTK graph is now way smoother (similar to XDR F1HD)
A TP indicator has been added next to PTY info
Battery voltage calculation has been recalibrated (bugs may still occur)
A new battery check has been added, which checks if the user has a battery connected or not
The RT is now scrolling
2 new themes (Whiteout & Heaven)
Fixed various graphical glitches
Good so the RT is scrolling now. But where are the preset stations? I use them a lot and in this firmware i don't find them. Battery voltage is gone too.
IMG_20230124_221648.jpg (2.79 MiB) Видяна 1938 пъти
Old (Chinese "stock" fw):
IMG_20230124_190917.jpg (1.58 MiB) Видяна 1937 пъти
п.с. Днес пристигна "ТЕФ-чето" както го наричам, от Алиекспрес. Първите впечатления са ми повече от добри. Единствено ме дразни в стоковата версия на софтуера че радиотекста не скролва и ако е по-дълъг, не го изписва целия. Важното е че има два говорителя и е стерео! ( https://dxing.org/viewtopic.php?p=42770#p42770 )
Everybody has a radio. To listen to a radio is normal. To listen to a radio, that is far away from you is a DARE!
Car LW/MW/FM/DAB+ - Kenwood KDC-BT73DAB / Pioneer X8500DAB + AN-DAB1 DAB+ Antenna Mobile FM/DAB+ - Silvercrest SDRF 10 B1, Denver DAB 42 Mobile DAB+ Antenna - VHF 5-12 YAGI 4F & long 13-element VHF Triax antenna Mobile FM Antenna - Hirschmann Fesa DA 3 UHF Antenna Home - long UHF Triax antenna DVB-T2 Home - Strong 8201 FM Antenna Home - Open Dipole direction Sofia LW/MW/SW/FM Home and Mobile - TEF6686 Tuner+XDR GTK ; RTL-SDR R820T