Small FM transmitter with mp3 player and PA

OwO wrote:
All the design files are at: https://github.com/gabriel-tenma-white/qn8007_fm_tx
There is an S parameter file of the measurement of the PA output matching network: https://github.com/gabriel-tenma-white/qn8007_fm_tx/blob/master/qn8007_fm_tx_2_zl_stock.s1p

Hey. I apologize for my English, I am writing with the help of a google translator.

OwO, I have a question for you. Can you please tell me what documentation did you use when writing this driver https://github.com/gabriel-tenma-white/qn8007_fm_tx/blob/master/sw/qndriver.h?

As I can see there is something in there to control the chip DSP PLL receiver QN8065.

I could not find a complete datasheet for this chip on the Internet. Found a shortened version of the datasheet, but it lacks a description of the control registers of the QN8065.

Can you tell me where you can find detailed documentation for this chip? Or the QN8065 Programming Guide. The complete description of the control registers interests.

I tried to contact the tech support of the chip manufacturer QNxxxx. But, unfortunately, their site has not existed for a long time. Email not responding. It looks like Quantic has disbanded.

Hi super Awesome i get sample 
see
https://www.facebook.com/k19radio/photos/a.2329547933985907/2681796845427679/?type=3&theater&notif_t=page_post_reaction&notif_id=1589402229917221

It looks like this. No new messages.

Can you please send to my secret e-mail address?
british.inteligence.sweden@sm0vpo.com
(Do NOT correct the speling mistake)

BR Harry

Admin wrote:

rigmo wrote:Hi sir
Yes I send you PM 
best regards

Hello Rigmo,
I have just checked and there is no PM for me on this forum.

Did you send it here? Skype? Twitter? Whatsapp? SMS? E-mail?

BR Harry

yes i send two trough  PM icon, i see on my mail box this messages...

rigmo wrote:Hi sir
Yes I send you PM 
best regards

Hello Rigmo,
I have just checked and there is no PM for me on this forum.

Did you send it here? Skype? Twitter? Whatsapp? SMS? E-mail?

BR Harry

Hi sir
Yes I send you PM 
best regards

rigmo wrote:hi sir 
do you sale pcb board?
im specially  interested fo PA stage..

Thank You in Advance 
Best regards

I don't sell stuff, but I have a few of these left. You can PM me a receiving address for a sample.
If there is demand, I might produce some more but after I make some improvements to the design (aux in, more efficient PA, etc). Now is the time to post feature requests.

The PA was my first attempt at class E/F, it does seem to achieve that close to the design frequency (88 - 100 MHz) with 2W out and 60-70% efficiency (can be operated without a heatsink) but at the upper half of the FM band the efficiency and output power worsens. I might experiment with more PA designs and other transistors as well.

All the design files are at: https://github.com/gabriel-tenma-white/qn8007_fm_tx
There is an S parameter file of the measurement of the PA output matching network: https://github.com/gabriel-tenma-white/qn8007_fm_tx/blob/master/qn8007_fm_tx_2_zl_stock.s1p

hi sir 
do you sale pcb board?
im specially  interested fo PA stage..

Thank You in Advance 
Best regards

It's very cheap to ship stuff from here so don't worry about the costs. You can PM me your receiving address. The boards are half assembled (all the 0402/0603 passives are already soldered by a PCBA service). I can also solder on the rest of the parts before shipping if you don't feel like dealing with surface mount soldering (there is a QFN part and some other stuff that requires using hot air).

Hi again OwO,
Thank you very much for the notification. I will check the link and download the files.

"I have some spare PCBs and parts, so if you want one to play with I can mail it to you."
If you could do that I would be very grateful, but please allow me to payfor it.

This is exactly the sort of project I love to work on, in this day and age. When I take on larger projects it seems that all the other commitments I have come in the way. But smaller projects are great as one can see a finished job rather quickly. Also, this particular project is such a high standard that it is really useful.

Very best regards from Harry Lythall- EA/SM0VPO

I've uploaded all the design files and MCU software here: https://github.com/gabriel-tenma-white/qn8007_fm_tx

There is currently no GUI implemented; the board has a footprint for a i2c OLED module but I haven't gotten around to playing with that yet. The UI currently consists of 4 buttons and a LED (more details in the README on github). It will play random songs from the micro SD card, but this can be changed by modifying the code. You can also add RDS by programming the various registers based on the datasheet.

I have some spare PCBs and parts, so if you want one to play with I can mail it to you.

Hello OwO,
I must say that I am really impressed. First the professional approach, the functionality and the first-class project. Now an antenna to go with the 1-Watt transmitter

The only thing I am missing is the control software for programming the chip. I have done some reading after finding datasheets on the web, and I could do as I did with a couple of other chips; use GW-BASIC to config the serial port and then send a file to the serial port. But that will take a lot of time that I don't have at the moment.

The RDS is where the receiver has rollong text in the display. I have had occasion to program a commercial transmitter for a local radio station. This function is available in nearly all car-radios, but people playing with the transmitter usually never get to see the text. It's a bit like not being able to remember your own telephone number.

Anyway, I will look forward to more information, and if you can provide a GUI for the chip, or a link to one, then I will probably build your project myself.

Very best regards, and thank you for an excellent project.

Very best regards from Harry - EA/SM0VPO

The QN8007 supports stereo and RDS; currently I have enabled stereo but haven't gotten around to playing with RDS yet as I don't have a RDS capable receiver. The datasheet states a stereo separation of 40-45dB.

Here are some pics of the antenna I'm building:


The length of the box is 20cm. The main element is made from copper foil in order to reduce losses. The point at which the feed cable is soldered to the foil was experimentally chosen to give the minimum amount of RF going up the cable (measured with a diode probe to the SMA connector outer nut). In power handling tests most of the heating is at the tuning capacitor, so I think the efficiency can still be improved by better electrode design and keeping E fields away from the plastic. The high currents in the copper foil didn't seem to be a problem as it barely got warm at 15W. There is still a problem with arcing at higher powers, but at <=1W it's safe.

Tuning capacitor:

Measured impedance of the antenna:


The design can be adapted to 144MHz for mobile use and efficiency can probably be improved to >80% at this size. The near field hand effect is also quite small, I can put my hand within 5cm of the tuning cap without messing up VSWR too much, so I can imagine it being usable in a backpack with some insulation around it. The next step is to integrate a servo motor and VSWR bridge for automatic tuning so it can adapt to objects in the near field.

Hello OwO,
Thank you very much for this information. It is a very professional project and looks very impressive.
I also like the fact it delivers 1 Watt and it is powered by the USB port.

Does the transmission support full stereo? What is the channel separation?
Does it support any other FM functions, such as RDS? Traffic messaging (TMD? or something like that)?

I will google the chips and see what information I can get. Maybe there is a data-sheet somewhere 

But congratulation on a very nice project. Please let me know as soon as you have the full project info available. You will have another fan 

Very best regards from Harry - EA/SM0VPO
(QRV on 145.500MHz)

This is a project from last year, I wanted to integrate all the components of an FM transmitter setup so that it's not a mess of wires and so that it's portable.
The board is around 4cm x 4cm and contains a QN8007 FM modulator, a DFplayer mp3 player, and a power amplifier using a RQA0009. The maximum output power is around 1W. It's a 4 layer board so not exactly hobbyist friendly, but since I usually put many projects on a big panel the cost is pretty low per project.

Top view (without and with DFplayer soldered):

The RQA0009 is the transistor in the center; the 4 inductors are part of the output matching and lowpass filter. The whole thing is powered from 5V from USB.
Bottom view:

Schematic:

I'm going to be putting the full PCB design files and microcontroller code on a new GitHub account.
I think for the next revision I'm also going to integrate a VSWR meter to make it easy to tune an attached antenna.

After reading about your 20 meter loop antenna I decided to build a scaled down version for VHF. After lots of tweaking and power handling tests, the result is a 15cm diameter single turn magnetic loop antenna in a small cardboard box, with radiation efficiency >50%. I used a small surface mount variable cap for tuning (1-5pF required), but it is quite tedious to tune because you have to use a screwdriver and the tuning is very sensitive. I also tried the gimmick cap but that lowered the Q and resulted in poor radiation efficiency. I looked at your 3d printed tuning cap, but I don't have a 3d printer so I think I'm going to make an attempt using those "mini plastic vise" things available online.