25mW Tx with TSA6057 PLL

[1608cc]

My first exciter with PLL Seiler oscillator on BF240, then BF960 buffer amp, and BFR91 final stage. Output power is 25mW @ 50ohms. PLL is old philips I2C controlled TSA6057. Programming via Attiny13 with memory of 4 various freq.

1.jpg

2.jpg

schematic.png

TX 25mW.zip

[Bton-FM]

Nice work 1608cc! I like how you’ve included a screen between the PLL section and the oscillator.

I also use an ATtiny in my board, but an SMD version. So far I’ve written code for the TSA5511, MC145170, LMX2306 and SAA1057. I need to test the last two out but my TSA5511 code and MC145170 code both work fine.

PICs are nice and powerful, but expensive! You don’t need a powerful MCU for controlling PLLs, it’s a simple task.

[Zozo]

That's great work 1608cc, the construction is so neat and tidy. I would like to have a go at building this soon.

I've never used the TSA6057 before or an ATtiny, so this will be all new to me.

EDIT Sorry if this is a bit cheeky to ask, But is it possible for you to share the Gerber Files? I have no way of etching boards at home now, and I like to avoid using such chemicals

[sinus trouble]

Excellent work 1068cc

Very tidy and a great vintage look!

It seems both of your varicaps are fed from the control voltage loop? Do you achieve a better tuning range that way, and does it compromise your audio in any way?

[1608cc]

Nice work 1608cc! I like how you’ve included a screen between the PLL section and the oscillator.

I also use an ATtiny in my board, but an SMD version. So far I’ve written code for the TSA5511, MC145170, LMX2306 and SAA1057. I need to test the last two out but my TSA5511 code and MC145170 code both work fine.

PICs are nice and powerful, but expensive! You don’t need a powerful MCU for controlling PLLs, it’s a simple task.

I don't need LCD and 256kB uC - small microcontroller with 8 pins do same job , especially if the the frequency doesn't change 10 times per minute - dip sw is enough. I use AVRs, because they are much cheaper than PICs. Also programmer isn't costful, and there are way more tutorials for avr's. Whats weird 99% RDS encoders are based on PICs I have some 5511 and 1057 too so I will use them in next projects. TSA6057 is fine, but on the high charge pump current (450uA) there is lot of noise produced. On the low 5uA everything is OK. SAA1057 should be better choice (it was originally purposed for this project) because has more charge pump current values to choose.

EDIT Sorry if this is a bit cheeky to ask, But is it possible for you to share the Gerber Files? I have no way of etching boards at home now, and I like to avoid using such chemicals

sure, I will attach gerbers when I get access to my PC

It seems both of your varicaps are fed from the control voltage loop? Do you achieve a better tuning range that way, and does it compromise your audio in any way?

Modulation circuit design (these two varicaps and LC filter at the top) is coming from factory transmitter. It give really clean sound without noise, and ensure same loud on 88 and 108. I checked and with values from my schematic it allow to tune from 60MHz to 120MHz (0-12V), so lets guess what will happen if we will use full 30V varicap voltage I also noticed that BFR final stage can very easly start interferencing (you will hear cyclical popping in audio) - probably to much gain, additional wall between its base and collector can help, or decrease 1k resistor in its collector

[sinus trouble]

Yeh it may just be me? The higher frequencies of my audio seem to roll off relative to the loop voltage or bias of the varicap?

If the voltage is too low? The sound is loud and crisp! If too high? The sound is dull! I dunno what it is but the sweet spot seems to be around 3 - 4V?

[1608cc]

I think 3V is safe border - under that voltage varicaps behave very nonlinear, and on lower voltages there is more noise produced. Mine is ~5V at 90 MHz. Also see, that input voltage in this modulation circuit can't be higher than tune voltage, because then first varicap will start conducting as normal diode, so these ~ 3V margin should be kept to avoid that.

Gerbers :

Tx.zip

[Zozo]

Thank you 1608cc, It's a very interesting project you've put together and I will enjoy building it. I will need to source and buy all the components first, before I get the PCB made.

[radium98]

such a good work

[MiXiN]

Very nice.

Some cracking work being done on here at the moment, presumably because of lockdown & heaps of spare time.

Keep up the good work.

[Gigahertz]

Thanks for sharing 1608cc!

Decided to order some boards and give it a try. Also give me some expericence with programming!

[1608cc]

Thanks for sharing 1608cc!

Decided to order some boards and give it a try. Also give me some expericence with programming!

[1608cc]

I changed soft a bit - PLL current value is read from eeprom (00 is LOW, the rest values from range 01 to FF is HIGH), all 3 dip switches set frequency - there are 8 presets available now. SW in attachment

config.jpg

sw v1.1.zip