fm transmitter

[wvengineer]

Has anyone ever tried to build any of the designs over at at Pira. I know alot of members here are using the mini rds module that they sell and i will probally jump on the next group buy to snag one...

Pira CZ PLL FM Transmitter
http://pira.cz/entx4.htm

Pira CZ Compressor/Limiter/Clipper for FM broadcasting http://pira.cz/hyperlme.htm

Pira CZ Stereo Encoder for FM broadcasting: http://pira.cz/eng/stk2en.htm



I do know the 5watt or 1watt transmitter will not pass fcc part 15 because the power output radiated even with a simple vertical antenna will beyond the limits allowed but i am hoping to tweak its power output..

I currently have all the boards etched to make each pcb and most of the parts. I will have to take pictures of each... I was just curious of anyone has purchased one of his ready built transmitters

I have access to a oscilloscope and a spectrum analyzer once i have everything built...


:shock:

 

[ukewarrior]

When I look at the pira FM transmitter, I don't see a typical stereo input connector for the audio.
I'm assuming you need a stereo encoder?
Would something like this work?

 

[wvengineer]

from a quick look at the block diagram... id say no... even though its baseband encoded the pilot frequency for stereo rides on 19 Khz where the audio gets modulated... there is a subcarrier that resides at 38 kHz for stereo seperation

and if you add rds into the mix then you really have to pay attention to RDS deviation: 3.4 kHz

the diagram you supplied would not provide the necessary encoding for stereo fm, that one
more for baseband encoding the audio onto a video cable which is used widely in television broadcasting......




another one that would work with the transmitter is the one explained athttp://electronics-diy.com/stereo_encoder.php using the NJM2035 ic but that is is getting harder to come by

or another route is micromax-stereo-encoder

but I still want to use the ones over at pira.cz i will let you know how it comes all together
once i get all the parts to complete it...

 

[wvengineer]

I finally had a chance to take some photos of my progress....

I have ordered supplies from a few manufactures

90% of the stuff had been ordered from mouser...

The ferrite core (BN-61-202) had to be ordered from Amidon.
and the RF transistors (2n3553) I ordered from Futurelec.

I Was able to find a TSA5511 on eBay.

The Coils are homemade 20ga enameled magnet wire


I still have to order a 8x2 lcd display and metal enclosures and come up with a low noise power supply with filtering for the transmitter.

 

[wvengineer]

here are the rest of the photos, hit the max limit of 5 on last post.

 

[Wayne J]

This is an interesting project.

 

[Blackbeard]

Tim,

I visited your website and it looks like the project is moving along smoothly and hopefully, successfully. You mentioned over there that you wouldn't recommend the Ramsey or EDM designs for inexperienced guys like me, but would you recommend this particular design?

Finding a low-cost, reliable FM transmitter seems to be a dead end for me right now. I'm not sure about plunking down $50 for one of those Ebay units without knowing how solid they are.

Good luck from another West Virginian.

steve

 

[wvengineer]

No I was saying that the ramsey or the edm would be a good choice for
Anybody that isn't that majorly experienced with RF there is alot better documentation than the one for instance at pira.cz

With all the fancy tools at my grasp. 100 mhz oscilloscope and a
3mhz to 3ghz spectrum analyzer it makes working on some of
the more involved transmitter designs with greater ease

I havent actually added everything on a cost, but as a
ball park id say i have invested at least 70 bucks in all
the parts.

And some of the parts are not so easy to find... I need to post
some new pics....


UPDATE:

The Compressor/ Limiter is working , The stereo Encoder is working , The FM Transmitter works sorta.. I am waiting on an exact 6.4mhz and a 3.2mhz crystals.... from futurlec and from the UK, right now I have a 6.5mhz crystal and I can get the pll to lock when I adjust tune the L1 coil but the frequency stepping is way off... It sounds really really good... The stereo separation is perfect. I have tested the RDS part of the stereo encoder and no
issues...


I had to remove Q3 (2N3553) final output transistor, It gave me about 1.2 watt output. with a dipole at 5 feet above ground I had almost 1/4 mile coverage.... would be great if my display was acres in size. if I had the antenna higher id say I probably could have a coverage area just outside 1- 1.5 miles. I don't think I want a visit from the guys in the white vans so I need to crank the power down...

What I did is made Q2 (BFG135) surface mount rf transistor the
final output which gives me about 150mw rf out.. i still have to play with some resistor values on the output transistor.

at this point I have not ordered any metal enclosures for the transmitter

This is where i am at so far....

 

[wvengineer]

here are some photos of my progress...

The rds encoder is assembled still have to make the 9pin serial

The stereo encoder is now in an enclosure that i had laying around. had to make the end caps couldn't find the original ones

Still have to enclose the transmitter and the audio limiter.

I finally got the rest of my parts from futurlec that I needed.
so next week I will have to tweak the adjustments.

 

[wvengineer]

Here are 2 more pics with the modified asm on the pic for the LCD display...

big thanks to ukewarrior for hooking me up with some really nice
lcd displays...

have not tried it yet on Henne's dmx analyzer but I see no
issues with these lcd units

 

[ukewarrior]

Thanks for the kind words tim.

I'm curious, is that a 4 bit or and 8 bit data interface you used?

Don't you just love these new LCD backlights where you don't have a screwy negative bias and triimpot. Give it +5v and away you go!

btw... i have about 25 of these units if anyone else has some microcontroller projects. just pm me.

 

[wvengineer]

The hardware for pira's transmitter uses 4 bit. looking at the powertip lcd controller its pretty much the standard HD44780 compatible driver. The one I have for my basic stamp with the serial backpack is the same brand...

yea i didn't use a trim pot for contrast just took it to ground... its perfect..

 

[g2ktcf]

How much do you have invested in this Transmitter???

 

[wvengineer]

I have not really kept a tab but I am some where in the vicinity of 60 to 70 bucks so far. I need to sit down and price it out... when I ordered parts I ordered extras of many things figuring i would always use them for something else...

 

[kiowamike]

I am thinking about diving into this project myself. I was wondering if you could supply a BOM for the mouser parts that you used. Also did you etch your own PCB's or did you order them from their website? If you ordered them, how painful was the process dealing with Euro and such. I look foward to possibly starting this project.
Thanks,
Mike

 

[omzig]

how painful was the process dealing with Euro and such. I look foward to possibly starting this project.
Thanks,
Mike

pira.cz is not painful to deal with at all. Paypal takes care of the currency exchange. You just pay like you would any other Paypal merchant, and Paypal will do the conversion based on the current exchange rate. Now is actually not a bad time to buy from the EU because the Euro is pretty low now. You can calculate the exchange rate here: http://www.xe.com/ucc/

 

[Blackbeard]

Does anyone think this is a project that is too complicated to attempt without all the equipment wvengineer has to calibrate this with? I understand electronics, but would need to work with basic stuff like a VOM, scope and the likes.

Over my head?

steve

 

[wvengineer]

Home etching would be fine.... that is what I did but its single sided only.... having the shield site in the top will allow for tighter RF control and less chance of frequency drift / spurious oscillations.. and from the price that he has for a double sided etched board you really cant go wrong. I etched because I was in the early development stages and didn't want to dump a lot of cash into it.

I followed all the instructions on his site including his procedure for tuning before I used any scope
or analyzer just to see if it can be done with out any special equipment. and you can i only used the
scope and spectrum to confirm... you have to be cautious, the second Harmonic of the FM dial is highly
used by aircraft.. make sure you enclose this puppy in a metal enclosure That is tied to the DC & RF ground.

The function of C17,L5,L4,C16,C10,L3 is its the low pass filter that is suppose to block all frequencies
above 108 Mhz from emanating from the transmitter.






Here is the BOM of parts I have purchased from mouser for this project, there are a few parts that have to be purchased from elsewhere..

Caps
80-C1206C103J5R Qty:12 Desc.: 1206 SMD Ceramic Cap 50volts 10000pF X7R 5%
140-100N2-150J-RC Qty:4 Desc.: Ceramic Disc Capacitors 100V 15pF NPO 5% Tol
140-50N5-330J-RC Qty:3 Desc.: Ceramic Disc Capacitors 50V 33pF NPO 5% Tol
140-50S5-331J-RC Qty:1 Desc.: Ceramic Disc Capacitors 50V 330pF SL 5% Tol
81-RPE5CA470J2P1Z03B Qty:1 Desc.: Monolithic Radial Lead Capacitors 47pF 100volts
59-GYC65000 Qty:1 Desc.: FILMTRIM Plastic Trimmer Capacitors 4.5-65pF 100V 10mm
647-UVR1E471MPD1TD Qty:1 Desc.: Electrolytic Capacitors - 85 Degree 470UF 25V
647-UVR1H100MDD1TD Qty:2 Desc.: Electrolytic Capacitors - 85 Degree 10uF 50V 20%
647-UVR1C101MDD1TD Qty:4 Desc.: Electrolytic Capacitors - 85 Degree 100UF 16V
647-USA1H4R7MDD Qty:1 Desc.: Electrolytic Capacitors - 85 Degree 4.7UF 50V
81-RPE5C1H220J1A1Y02 Qty:1 Desc.: Monolithic Radial Lead Capacitors 22pF 50volts
81-RPER71332K2P1A03B Qty:1 Desc.: Monolithic Radial Lead Capacitors 3300pF 50volts
581-SA105E104MAR Qty:2 Desc.: Axial Ceramic Capacitors 50volts 0.1uF 20% Z5U
581-AR211C103K4R Qty:1 Desc.: Monolithic Capacitors 100volts 0.01uF 10% X8R

Resistors
71-CCF07-G-10K QTY:6 Desc.: Metal Film Resistors 1/4watt 10Kohms
71-CCF07-G-33K QTY:2 Desc.: Metal Film Resistors 1/4watt 33Kohms
660-MF1/4LCT52R183Gt QTY:2 Desc.: Metal Film Resistors 1/4WATT 18KOHM
660-MF1/4LCT52R180J Qty:1 Desc.: Metal Film Resistors 1/4WATT 18OHM
660-RK73H2BTTD1003F Qty:1 Desc.: 1206 SMD Resistor 1/4watts 100Kohms 1%
660-MF1/4DCT52R33R0F Qty:1 Desc.: Metal Film Resistors 1/4W 33 ohm 1%
271-91-RC Qty:1 Desc.: 1/4W 1% Metal Film Resistors 91ohms
271-4.7K-RC Qty:1 Desc.: 1/4W 1% Metal Film Resistors 4.7Kohms
271-680-RC Qty:5 Desc.: 1/4W 1% Metal Film Resistors 680ohms
271-270-RC Qty:2 Desc.: 1/4W 1% Metal Film Resistors 270ohms
531-PT6KV-5K Qty:1 Desc.: Trimmer Potentiometers 5Kohms 6mm Rnd Top adj

Semi
63-MC78L09ACPG Qty:1 Desc.: Linear Regulators- 9V 100mA Postive
579-PIC16F627A-I/P Qty:1 Desc.: PIC16Fxxx Flash MCUs 1.75KB 224 RAM 16I/O
771-BBY40-T/R Qty:2 Desc.: Diodes - Variable Capacitance VHF VAR CAP 30V
512-BC547BU Qty:1 Desc.: Small Signal Transistors NPN Si Transistor Epitaxial
771-BFG135-T/R Qty:1 Desc.: RF Transistors NPN 150MA 15V 7GHZ
512-BF240 Qty:1 Desc.: Small Signal Transistors NPN RF Transistor
512-KA78L05AZTA Qty:1 Desc.: Linear Regulators- 5V 100mA Postive


Other
523-31-5431-10RFX Qty:3 Desc.: BNC RFX Connectors PC R/A BLHD JCK
511-1N5818 Qty:1 Desc.: Power Schottky Rectifiers Vr/30V Io/1A
70-IRF1-1.0 Qty:1 Desc.: High Current Inductors 1uH 10%
593-VAOL-5LSBY2 Qty:1 Desc.: LEDs Standard Blue Diffused 462nm 1500mcd
688-SKHHLM Qty:2 Desc.: Tactile Switches 6.0x6.0x3.85mm 100g

***************************

These parts have to be ordered from Futurelec
Futurlec
2N3553
crystal 3.2 MHz

These parts have to be found I had luck on ebay
TSA5511

***************************
TR1 - rf ferrite transformer
Amidon Corp BN-61-202 Wideband Multi Aperture Core , Unfortunately they have a 10.00 min order so if you are serious send me a pm, I have 3 extras I would send to 3 ppl. they were only 80 cents each



NOTE: IF you decide to only make this a 150mw transmitter these parts you will NOT need parts list according to pira website http://pira.cz/entx4.htm
Q3: 2N3553 4W RF NPN
L2 - 1uH/815mA choke
C18 - trimmer 50p
R9 - 18 Ohms
L3 - 2.5 turns on 6 mm diameter (4.5 turns if Q3 is 2N3553)
TR1 - rf ferrite transformer



This means the only hard to get parts you will need othr than from mouser will be the tsa5511 chip and either the 3.2 or 6.4 crystal

 

[g2ktcf]

Tim,

What do you think of Blackbeard's comments below? Is this something that we can achieve without all your fancy gizmos?????

Chris

 

[wvengineer]

sorry I was updating my info... yes this can be done with only a
digital voltmeter no special tools are needed.... and works very stable...

now remember the transmitter only takes either mono or a MPX signal in....


That is where I used Pira's stereo encoder to create stereo and inject RDS
also no special tools needed, all parts can be purchased from mouser


give me a little time to make up a bom for that one...

Tim