fm transmitter

[nay27uk]

Nay27uk,

I am wondering what country you are in. The basic design here is a 5W transmitter. The one most of use are building omits the final transistor to keep the total gain down to below 1W. In the US, even a 1W xmitter can get you in real trouble! A 5W will most certainly get you in serious trouble.

Cheers,
Chris

I am in the UK m8 thanks for the concern though

[radium98]

Hello i know that is an old thread BUT i have just done the tx pira transmitter and i need little help please what software do i need to open the .asm file and change the start up name and recompile to .hex file thank you and merry chritmas in advance for this year 2016

[radium98]

can you send me correct pcb size of stereo encoder pira.cz

[ukewarrior]

I'm not sure I understand this question.
Have you built the unit or are getting ready to build it?

Did you get an answer to your asm question?

can you send me correct pcb size of stereo encoder pira.cz

[g2ktcf]

can you send me correct pcb size of stereo encoder pira.cz

The size of the pcb is in the file you get from pira. I have etched this board but never built the unit. The pdf works just fine when printed to actual dimensions.

[radium98]

there is no pdf file size but i have resised it on irfanview 134 mm and 67.8 mm aspect ratio .can anyone change to me the hex file for transmitter pira start up i want to put my station name REVE FM

merry christmas and happy new year

[mictester]

Good info DMC...
A Dipole is a very simple yet effective antenna. Technically called a Half Wave antenna where the radiating element is 1/4 wave and the ground plane is 1/4 wave(typical 3db gain)

Sorry to be picky, but the first part of the above is correct, but the dipole only has "gain" over an isotropic aerial - which only exists in theory! The dipole exhibits 0dB gain, as it's used as the reference point for all real antennas with actual gain! Therefore your 125mW into a dipole will be (neglecting slight losses) 125mW radiated.

Other aerials that don't show gain over a dipole include the quarter-wave ground plane type.

In the Real World™ you'll find that you'll incur some losses. Your antenna feeder will be (slightly) resistive and will show capacitance between the centre conductor and the braid - both will incur losses (which increase as the feeder length increases, of course). Also, your dipole will present a symmetrical load of about 72Ω (if it's the right length), so you're going to have to make your asymmetrical feeder into a balanced feed to properly match your dipole. This can be achieved most easily by means of a "Pawsey Stub" or (trickier) a quarter-wave phasing loop. Other feed options include the "Gamma Match" which works very well but makes the antenna more complicated.

My favourite approach for very low power FM installations (I used to install lots of Drive-In cinema systems) was to use TV coax (the 75Ω characteristic, brown-sleeved stuff available in any hardware store), and a Balun (actually an "Un-bal" because we're going the other way!), made from a ferrite bead with (typically) six turns bifilar for the two windings. This works very efficiently with a dipole up to about a Watt.

One little transmitter I worked on was a small phase-locked loop design, with a pair of identical ¼Watt output stages driven in phase opposition, and connected directly to the antenna elements, so eliminating losses and matching issues. The little transmitter was housed in a small waterproof diecast box, and it was fed DC power and modulation signals up a multi-core flex from the ground below. The box was equipped with a clamp to allow it to be attached easily to a mast / boom arm arrangement. The antenna elements had telescopic ends, and the manufacturers provided a calibration chart of antenna length against operating frequency! This little device could be set to any frequency from 76 to 108 MHz in 100kHz steps, so could cover both the Japanese and European / American ranges of frequency.

[rigmo]

https://web.facebook.com/k19radio/po...acp5dKYJ4EaYtl

Pira PLL 5W transmitter review 2023
A review of the famous Pira PLL 5W transmitter in 2023. Since there is no detailed analysis from that time, we conclude that it was certainly never possible to have 7W of pure signal. We measured pure 5W at 14V, and that is the best that can be achieved for a pure signal that "does not need" after LPF. However, we had to make some changes to the basic circuit to achieve this.
Of course it is possible to reach 7W 8W but with enormes of spurs and harmonics.