Signal amplifier

[young]

I am using a HT640 andHT648L and TWS434 and RWS434 for wireless communication, I found the signal is week, so I decided to use a RA07H4047M amplifier to ampilfy the signal. without amplifier, evertthing works fine (my connection is fine so far). then I put the amplifier between HT640 and TWS434. I connected the HT640 output to the input pin pin 1)of RA07H4047M, and add a gain voltage of over3.5V (pin 2), connected VDD (pin 3) to 12V, and output pin(pin 4) to TWS434 input pin, and also connected pin 5 to ground. however, I could not see any data transfer at all. what I might be wrong?

[languer]

You are not really doing this (ouch!, I am pinching myself as I write this).

If I get this right, you system looks as follows:
HT640 -> RA07H4047M -> TWS434 -> Antenna

The RA07H4047M is the MITSUBISHI RF MOSFET MODULE right?

The good thing is you probably have not killed anything. If you are truly using this MITSUBISHI RF MOSFET MODULE the proper connection would be like this:
HT640 -> TWS434 -> RA07H4047M -> Antenna

That is because the output of the HT640 (encoder) is a baseband signal (data) with DC component. The RA07H4047M (amplifier) operates on an AC signal (internal decoupling caps) and is tuned to the 433MHz band (RF). So the amplifier sits in the RF path (between TWS434 output and Antenna).

However, this device can deliver 7W of output power. I do not think the FCC will see this kindly. You say "the signal is weak", by this you mean the RF signal into the receiver? You can try to better the match between the transmitter (TWS434) and the antenna. What is your antenna (in both TX and RX)? The better your antenna, the better your efficiency. The transmitter is usually limited by the FCC. So the better your antenna at both transmitt and receive, and the better your reciever sensitivity, the better the range of your link.

[Guest]

Thank you languer:

yes I am using the MITSUBISHI RF MOSFET MODULE.
I was using a pair of 50-Ohm "Whip" Antennas and another pair of antenna is 14 inch, 22 AWG, insulated antenna wires, they all provide just few feet of communication signal, I tried to adjust the antenna, but \,no much improvement. so I decide using the amplifier that you suggested.

I do mean it is the signal from RF signal into the receiver was weak. how to better match the antenna and transmitter, and what is FCC? thank you.

I will be much appreciated if I could follow you direction to get a success and strong wireless communication!!!

[Mark]

The Federal Communications Commission (FCC) is an independent United States government agency, directly responsible to Congress. The FCC was established by the Communications Act of 1934 and is charged with regulating interstate and international communications by radio, television, wire, satellite and cable. The FCC's jurisdiction covers the 50 states, the District of Columbia, and U.S. possessions.

The FCC is directed by five Commissioners appointed by the President and confirmed by the Senate for 5-year terms, except when filling an unexpired term. The President designates one of the Commissioners to serve as Chairperson. Only three Commissioners may be members of the same political party. None of them can have a financial interest in any Commission-related business.

As the chief executive officer of the Commission, the Chairman delegates management and administrative responsibility to the Managing Director. The Commissioners supervise all FCC activities, delegating responsibilities to staff units and Bureaus.

[young]

Hi languer:

I did as the connection you suggested, like this

HT640 (output pin)->(input pin) TWS434 (antenna output pin)-> (input pin)RA07H4047M (output pin)-> Antenna. at hte beginning I saw light turn on and off and then nothing happened. I checked the 12V power supply to the amplifier, without connection to the amplifier. it is 12V. when I connected to the amplifier, at the begining, it was 12V then it gradually dropped, Does that mean the amplifier was destroyed?

[SherpaDoug]

I would like to add the the FCC in the USA has counterparts in most other countries. There may even be some UN regulations covering areas like international waters that lack local regulation.

In a nutshell, you can't just go spewing RF from an antenna without interfering with other people's equipment. These regulations are our friends, not our enemies as they let us all play together productively.
_________________
The search for better is endless. Instead simply find very good and get the job done.

[young]

I tested resistance between each pin of the amplifier and compared with another new amplifier, they the corresponding resistance between each pair of pin is same, so I think that the amplifier may be good, so whey the voltage dropped and what I might be wrong?

If I paly this 433 RF, do I have to get permission from FCC from a short distance wirless communication?

[young]

I found out, Ibefore I connected amplifier pin 5 to the ground, which the datasheet shown that it goes to ground, when I accidentally disconnected it, the voltage became normal, and the circuit is working, and it clearly shoes that signal has been amplified, because I could received signal at a longer distance. but just a few inches better, which I am not feel good at all. maybe there is really some other thing disturb from better communication. please provide advice!

[SherpaDoug]

[jds-pic]

[young]

Hi jds-pic:

I really appreciate your answers. so far this this the most valuable suggestion and advice that I have ever got for the RF communication.

According to the several suggestion you provided, I really do not need that high power of RF communication. a 100mw will be good enough because I am building a project for indoor data collection, it will be just unidirectional. I believe a 300 meter will be good enough (large factory building).

a 9v battery will be ideal for my project, the size should be very small ( no larger than 2.5 inch by 2.5 inches.

I am sorry to say for all the other question I have to say no.

I will explore the following topic that you adviced:

1. limited or no background in analog RF circuits?
2. transmitter output is so strong that it is saturating the receiver input, which is causing poor performance due to desense
3. antenna match, poor decoupling, and 7W output, you probably have stray RF everywhere on your board.

Sincerely

[jds-pic]

[Guest]

Thank you jds-pic:

so far I have used the

[languer]

Young,

I am glad nothing caught fire . I do believe you do not need the amp (and if you did, then it would probably be easier to go for different modulation, ISM band, or modules).

One of the best places I've found for those modules is here:
http://www.rentron.com/PicBasic/RemoteControl.htm
http://www.rentron.com/ruf-bot.htm

I think you've seen this before, but it never hurts to doublecheck. I have no experience with these modules, but have used similar ones from Radiotronix. With those I have achieved 30-40ft (outdoors, with resistive attenuation/loss in the TX) without much complication.

Laipac has similar modules (most of these LC-modules are based on same design) and have some better performance numbers (i.e. more available data) here:
http://www.laipac.com/easy_434_eng.htm

Basic key points to good RF performance:

Good grounding -> grounds are critical (connections to ground should be kept as short as possible)
Good bypassing -> caps to ground should be placed as close as possible to the pins (again connection to ground as short as possible)
Good antenna match/efficiency -> most of these modules will put about the same output power, the key is to transfer as much of this power from the transmitter to the antenna and from the antenna to the receiver

Many more things come to mind, but hopefully these should get your interest going.

It was also mentioned the application of your wireless link. A simple on/off link is very well served by encoders/decoders (like the HOLTEK type). A link intended to pass some data (i.e. temperature, preassure -> sensors in general) is better suited to a stronger protocol (synchronization bytes, machester coding, etc.).

Feel free to comment on this.

[TooMuchRF]

>In a nutshell, you can't just go spewing RF from an antenna.....

Sure you can - the electrons won't refuse to flow just because it's wrong... It sure would be nice if they didn't flow, but they do.

I see people doing this all the time - some cat in LA sells BIG amps for the ISM bands on ebay all the time. It's wrong to be sure, and is only covering up a poor transmission line or antenna system - but that's how folks fix these problems....