Wireless headphones-I have schematics-why dont the

[Anonymous]

manufacturers sell wireless headphones? f anyone wants the schematics email me.Chuck

 

[Anonymous]

Hello Chuck,
I'll take a print of the schematics. Let me know if you need postage. Or if you can. E-mail them to me.
About 6 years ago. Radio Shack had a very small powerful wiresless transmiter. They pulled them off of the shelf because they had too much output. I managed to talk the Manager into selling one under the table.
I mounted it inside my XLT control box with a switch on the outside. Boy! was it great! It would transmit to a FM headset. One day my car was rear ended and three of my best detectors were crushed. Since then. I have tried other transmiters, but none have ever come close to that radio shack unit in both strenght and lightness.
Take care,
Paul

 

[Anonymous]

Chuck,
the main problem seems to be the Headphone transmitters rf causing interferance with the detectors sensitive rx.
Iv'e experimented with different fm designs and frequencies from sw to uhf and most detectors running at full sensitivity are affected by the RF signal of the transmitter causing falses, the best system is using an infra red beam like the TV remotes use but it neads a lot of power to combat the sun and an uninterupted line of sight between sensors, im working on other ideas using high gain audio but thats presently picking up the output pulse from the search head.
regards Rob

 

[Anonymous]

Rob, You must have been using too much power. I used a SAW based oscillator at 433.92MHz which used pulse width modulated audio and it worked fine. SAW based transmit and receive modules are available from RF Monolithics at www.rfm.com. They are available on frequencies from 303MHz to 916.5MHz. The transmitters and receivers are really tiny and operate from 3.00 Volts. The power output is down in the microwatts. All you need is a small length of wire for use as the antenna on each module. For a PI to pick up RF, the RF is most likely being rectified by the back to back protection diodes at the amplifier input. You would need a lot more strength than an RFM transmitter for that to happen. Many illegal FM microphone circuits I have seen were running as much as 100mW. This would cause a problem, Dave. * * *

 

[Anonymous]

Dave,
Thanks very much for your info, I havent tried 916Mhz or higher as yet,
Individual detectors could be screened sufficiantly to operate ok without interferance, But i was aiming to design a general purpose cordless headphone adaptor to fit any kind of detector on the market (hopefully not using rf), im playing with vlf re-radiated audio at present but its a job to get the signal to noise ratio to acceptable levels, still have other ideas to try when time allows.
Regards Rob.

 

[Anonymous]

Been sold in the U.K. for years as well as a detector that transmits from coil to control box.I adapted a kids pair of transmitters that cost