I'm debugging the Si4732 airband receiver with TA2003 and Si5351a. This is a double super heterodyne. FM broadcasting wavw is coming directly into Si4732. The block diagram is below.
I could receive the FM broadcasting wave. So Si4732 is working well. Airband radio signal is converted into 21.4MHz inermediate frequency and feeds into Si4732. I combined R909 sketch with PU2CLR library.
For this design I use TA2003 is only mixer. There are scarcely the examples for those. I ever assembled R80 V6 radio kit. I asked a certain engineer who assembled R80 V7 kit.
He gave me the information about V7. Sensitivity is so so.
Today I found the reason why TA2003 gain. I mistook the resister value of TA2003 FM-RF-OUT being 10 k ohm. Correct is 1k ohm. The front end coils are not tuned well yet. I shall use nano VNA for trimming.
The new airband radio configured with Si4732&TA2003&Si5351a is depending on R909 design. R909 has TA2003 mixer with Si5351a and TA2003 FM/AM radio. Si4732 shall replace with TA2003 radio.
I asked to produce the PCB for Shinseng PCB supplyer but I missed to check after panelised data which was discarded the solid pattern connection to GND. After then I changed the PCB supplyer for PCBGOGO.
Now I'm debugging but it does not work well. The sketch may be insufficient. To confirm the circuit operation, I diverted the serial port control sketch of PU2CLR library. This one can operate SI4732 and also set the frequency on Si5351a. テストスケッチシリアルポート画面
Type F to FM; A to MW; 1 to All Band (100kHz to 30MHz) Type U to increase and D to decrease the frequency Type S or s to seek station Up or Down Type C or c to set AM 21.4MHz RX Type P or p to set 80.0MHz on Si5351aq Type Q or q to set 139.5MHz on Si5351aq Type + or - to volume Up or Down Type 0 to show current status Type B to change Bandwidth filter Type 4 to 8 (4 to step 1; 5 to step 5kHz; 6 to 10kHz; 7 to 100kHz; 8 to 1000kHz) Type ? to this help.
1.Arduino UNO/pro miniのメモリー限界。特にRAMがOLEDの画面リフレッシュのため。EEPROMへのチャネルメモリーを入れていない。 2.R80 V7回路間違い。LM386の入力#2がDCでは浮いており、DC変動があると低域異常発振をおこし、ノイズを出すようだ。 前段のFM62429のパラメータ変化で起こるみたいである。→2-3間に10k入れたら改善した。 3.OLEDの画素書き込み時にラッシュ電流が流れ電源変動を起こすようだ。→OLEDの接続コネクタ根元に47uF入れたらましになった。 4.Si5351aの周波数補正のパラメーターをそのまま移植してたら、第一第二がそれぞれ5kHzぐらいずれていた。 12.8MHzTXCOで較正して、100Hz以内にしたら、音量・音質が良くなった。 5.ボリューム設定値を14段階の真ん中7ぐらいで聞きやすくするため、MAP関数をトライアンドエラー設定した。 1. I could not install EEPROM related function because of shortage for memory. 2. I found that LM386#2 shall connect the ground via about 10k ohm. Nevertheless LM386 may oscillate at low audio by full swing when DC level moves. 3. OLED comsumes much current when it works refreshing the display. That cause power level change to casue noise. 4. I got Si5351a mojule frequency error by refering 12.8MHz TXCO via the frequency counter. And I set it as a #define XT_CAL_F 10000 roughly. I decreased error within less than 100Hz. 5. To set the central value as 7 of 14 range, I changed map function max as half.
とまあ以上のようなところを修正し、FM1放送も聞けるITMチャンネル対応航空無線ラジオ、OLED表示版”R909OLED”をまとめました。もともと1602A液晶用に窓を開けたケースにとりあえず入れたので、見た目いまいちです。The radio set is below. The case was diverted from 1602A LCD usage.
これでOLED表示のやり方を学んだので、OLEDを活用した機能の盛り込みを検討したいと思っています。 As I got the idea for OLED usage, I would like to utilize this furtherly.
I got CesarSound's VFO sketch on PROJECT HUB and edited it as a RF signal generator. This time furtherly I remodeled for R909 radio. In R909 sketch there is u8g2 library but the display design was 1602 format. I'm thanking CesarSound for providing nice material.
As a result the flash memory size is 87%, and SRAM is 35%(about 700bytes). OLED function is asking about more than 1000bytes on running. I could not incorpolated EEPROM channel memory functions. Insteadly I determined 20 waves for my local station usage. ie: 118.1MHz=ITW(Itami ToWer), 132.4MHz=TSK(Tokyo control SHikoku sector).
Operation rule. Naturally the function status is "0" and the rotary encoder gives increment or decrement by step frequency value. The crick by push button of the rotary encoder brings step frequncy change. To push the function key 1 kicks the function status of "2" and "3". When "2", the rotary encoder gives increment or decrement for the volume level. When "3", the rotary encoder gives increment or decrement for the squelch level. To push the function key 1 calls the pre determined frequency one by one.
When I assembled R909 radio, I found several improved points from R80 V7. As the R909 radio circuit has been improved from R80 V7's, It is useful for who would like to get better performance than R80 V7 . (R909 is an Arduino based FM/AM radio from JasonKits. ) www.tindie.com
1. To avoid parasitic oscillation.
When AM mode selected, the FM IF AMP input node of secondary TA2003's is open at R80_V7. Then I checked #5 AGC voltage on airband channel receiving, and I got about 1V nevertheless being no signal. Its voltage should be several decade mV when no signal.
Mr. RADIO KITS IN JA taught me that AM/FM SW signal manages to turn AM/FM circut inside and there is no need to switch the Am/FM input lterminals outside of TA2003. After I had connected LT10.7#3, AM RF IN#16, and FM IF IN#8, I could seize parasitic oscillation for FM IF amp. So the second relay is avoided at R909.
2. TA2003#5 AGC shall be a stable squelch switching signal source. The original squelch circuit of LMC6482 is detecting modulated sound. I prefer to use the carrier squelch. Therefore I utilize this AGC voltage for S-meter value and the threshold signal for the squelch open/close. R909 is incorpolated AGC signal(#5) instead of unstable demodulated sound squelch.
3. Softly muting on the squelch activated. As R909 is using the FM62429 for mute, the switching noise disappeared.
Inside of the R909 case.
To improve above issues on R80_V7, the R909 radio is working very well.
At this time R909 display is 1602A. OLED display will come sooner.
RADIO KITS IN JAさんからご指摘いただいたのですが、TA2003はFM/AM切り替え信号で内部回路が切り替わるので、外部信号入力では切り替え不要とのことです。なのでAM指定時にリレー切り替えでFM IN入力をオープンにする必要がありません。すなわち、AM信号に切り替え時にFM INをオープンにして寄生発振を起こすようなことは必要ないわけです。なのでLT10.7#3信号をAM RF IN#16とFM IF IN#8につないでいます。FM/AM切り替え信号はTRで切り替え、二番目のリレーは取り去っています。
The sketch has deviated from my 2 nd machine of the Chinese kit remodeled. The rotary encoder and the push switch are used for managing the functions and parameters.
To say nice points for this radio, "Good sensitivity", "Stable", "Cool squelch", "S meter function", " 100 channel memories for AB-AM/FM)", and " Monitor over channel memories".