Whirlpool

Okay, just first the gear im using, I have a wifi card with detacheable antennae (easy to take apart), and another card with non-detacheable antennae (which ive managed to solder a cable onto the board where the antennae sends its signal without ruining the card with an electric soldering iron).

Non I've got one of those portable APs from ASUS, the mini ones, which I've rigged up a battery box for using 4x 1.2v AA rechargeables (also works with a third-party/generic BP511A battery (7.4v) so its pretty tolerant).

Anyway this thing is great, been thinking about soldering onto this for amping too..

Anyway my basic premise is that I want to put gain on the signal coming in (receive) and the signal going out (transmit).

Now here is how I want to rig it up -
www.photodan.com.au/samp.jpg

In case anyone is curious as to the circuit, this is it (sorry about image quality, the lens on my camera atm is a bit crap) -
www.photodan.com.au/sampcircuit.jpg

It has a specified power output of 1W per channel (8 ohms, Vcc = 9V), 39 decibel gain.

Already got the parts, just want tips or suggestions, and any idea if this will actually work (i dont see any reason why it wouldnt..).

If all goes well I'll design my own circuit, use a few boards, and build a basic box well I can plug in, and hook it up to an antennae etc (i know there is a 4W legal maximum, but i'll stick a "volume" control on the out and in signals).

Athiril writes...

In case anyone is curious as to the circuit, this is it (sorry about image quality, the lens on my camera atm is a bit crap) -
www.photodan.com.au/sampcircuit.jpg

In my expert opinion, don't bother. Your circuit will give you no more than 200kHz and quite likely not even anywhere near that. You need a circuit that is suited to amplify in the 2.5GHz region and I can assure you that the schematic by itself indicates that the circuit will never do it, even if you changed the components.

Ah right, been looking at this one too - www.qsl.net/n9zia/wirele...2.4amp-block.png

I just figured that being able to separate the antenna into two sections would allow me to set up more gain on receive past the legal limit (if for some reason i wanted to) over the transmission limit.

Im assuming the IC is not suited for the job?

Though I've got a two NPN and a PNP transistor floating arround I wanted to play with too.

Athiril writes...

Anyway my basic premise is that I want to put gain on the signal coming in (receive) and the signal going out (transmit)

Don't even think of going down the path you have described.The commercially available T/R amplifiers for WiFi have sophisticated switching between transmit and receive that are impossible for a one off design to emulate. Not only this, the required circuitry for receive and transmit amps at 2.4GHz, to improve what you already have, is not able to be constructed by a hobbyist.

Sorry I dont need naysayers, saying dont attempt it.

In any case, my uncle has been an electrician all his life, and used to play around with ridiculously powerful CB radio amplifiers, so I can get his help on it.

Athiril writes...

Athiril...

Sorry I dont need naysayers, saying dont attempt it.

In any case, my uncle has been an electrician all his life, and used to play around with ridiculously powerful CB radio amplifiers, so I can get his help on it.

Yeah well good luck to you.

Athiril writes...

and any idea if this will actually work (i dont see any reason why it wouldnt..).

I can't see this working well. It's an amplifier designed for low bandwidth signals. If it did do something other than produce lots of smoke, who knows how much interference you will pump out into the neighbours equipment. Does this opinion make me a naysayer? ;-)

Athiril writes...

In any case, my uncle has been an electrician all his life, and used to play around with ridiculously powerful CB radio amplifiers, so I can get his help on it.

OK, from memory CB is at 27MHz, UHF CB is around the 470MHz mark -- could be wrong, those number seem to ring a bell though.

The amplifiers required for 2.4GHz (that's 2400 Mega Hertz) are of a completely different type to that required for CB. Once you get up into those frequencies the way RF and transmission lines interacts make things very interesting. What you will find is that most amplifiers for these type of frequencies are built into the transmit/receive stages of the gear, and most of the amplification is done a lower, intermediate frequency before being up/down mixed for the final amplification stage.

Have a crack if you feel you must, but just know it will probably involve quite a bit of theory before you get a decent design, and trying to directly amplify the output/input of your wifi card will prove difficult.

Your best bet here to get better performance is to look into high gain antennas, but as performance increases are gained with better antennas, omni-directional capability goes down.

foxx510 writes...

who knows how much interference you will pump out into the neighbours equipment.

Ooh, forgot about that one ... The ACMA will get very nasty with you too if you end up causing interference, there are standards that specify maximum permitted power output for certain uses/frequencies.

Athiril writes...

Though I've got a two NPN and a PNP transistor floating arround I wanted to play with too.

The transistors will not work at microwave freq. It has nothing to do with being a naysayer. It is physics man. Look up a transistor catalogue for microwave transistors.

No, thats constructive criticism, not destructive.

I'm starting to get the feeling we've taken a bait here....

That helps a bit, my uncle can help me with the designs no prob, i was just giving an example.

In any case, I just wanted to put something simple together first and do a bit of research before hand, before putting something more complex together, as long as I get the concepts I should be right.

I just dont have much of the theoretical knowledge myself, just a lot of time putting stuff together for my uncle and other various things.

I'd rather build something myself than buying it, it would be more satisfying personally, and I would like an active/powered amplifier.

In any case, if anyone knows of resources I can look at for this kinda thing, itd help a lot.

I still don't know if this is serious or not(maybe that gives you some idea of how ambitious this project is), but you will need a spectrum analyzer to make sure you aren't generating harmonics that will be causing interference for others, and you will need a way of measuring your output power to make sure it's legal. To be honest, I'm not sure you are going to get it to the point of transmitting though in the next few years, because it will take that long to learn enough theory to build it. Looks like I am a naysayer.... ;-)

Athiril writes...

In any case, if anyone knows of resources I can look at for this kinda thing, itd help a lot.

Google

Then start searching for home brew surface mount techniques and circuit board fabrication.

Athiril writes...

In any case, if anyone knows of resources I can look at for this kinda thing, itd help a lot.

My dad built marine two-way radios for a living. I worked in the shop. We gave up when the regulations changed for methods of transmission changed. And that is a long time ago and using frequencies that are easy to handle.
Forget working in microwave. You cannot buy components. They come in surface mount reels and you have to buy a min. quantity of a reel. Board layout is critical and mostly these things are not even designed by OEM but the chip manufacturer prepares a design complete with PCB layouts etc.

If you want to do electronics start with simple stuff. You can make an FM microphone or something from a kit with a few transistors. Start small with a design that has a hope of working. DSE is getting out of the kit business so go into the shops when they have specials and buy up what you like. They are cheaper as a kit then buying the components.

Athiril writes...

In any case, I just wanted to put something simple together first and do a bit of research before hand

As a friend of mine just said:

"at microwave frequencies, there is no simple solution before knowing the concepts"

Basically the following video illustrates what you are trying to achieve:

www.youtube.com/watch?v=L2zqTYgcpfg

(No offence intended)

EDIT -- actually a wee bit of offence intended.

Athiril writes...

Sorry I dont need naysayers, saying dont attempt it.

In any case, my uncle has been an electrician all his life, and used to play around with ridiculously powerful CB radio amplifiers, so I can get his help on it.

Do you have a degree in Electronics ? Did you specialise in Microwave Amplifier Design ? Do you know how to layout a PCB to ensure minimal side effects and interference at these frequencies ?

No ? Well I've got the first part and I still wouldn't attempt to do what you are trying. And just because your uncle 'plays' with CB amplifiers it doesn't make him an expert on RF design. Sorry, it's not even RF, it's beyond that. I'll take a dump in the toilet but it doesn't mean I know how to build and design a sewerage system.

Here's a suggestion - take the advice of people on this forum who know a hell of a lot more than you do about this. And don't show yourself to be a prat with comments like "I don't need naysayers".

<rant>I am seriously pissed off reading posts from muppets who only want to hear posts that reinforce their extreme lack of understanding in an area and insult anyone who helpfully informs them that it's not as simple as it looks</rant>

Right, I'm off to get a drink...

Athiril writes...

Sorry I dont need naysayers, saying dont attempt it.

Will this be his response when the feds come knocking at his door?

Athiril writes...

Anyway my basic premise is that I want to put gain on the signal coming in (receive) and the signal going out (transmit).

That's an awesome idea. You can do that with a directional antenna! I'd recommend you build yourself an antenna instead of an amplifier. It will be just as satisfying, but with the added benefit of being possible for you to do.

It has a specified power output of 1W per channel (8 ohms, Vcc = 9V), 39 decibel gain.

I'm not sure where you're getting 39dB from. For starters, it's not possible to increase the SNR of the receive side through amplification of the received signal - all you'll be doing is amplifying the existing noise, and most likely adding a significant amount of extra noise. If it was this easy to do, then surely all wifi hardware manufacturers would include a receive amplifier built in to the hardware ?
Assuming you're hardware can transmit at 200mW without amplification, a 1W signal represents about a 7dB increase. 10xlog10(1000) - 10xlog10(200) = 7.

Building an antenna with a directional gain > 7dB is easy. Building a 2.4GHz amplifier with a bandwidth of at least 20MHz (many times greater than the bandwidth supported by your stereo amplifier) is (for all practical purposes) impossible.

Sings the "your an Idiot song"

Woo you boosted CB, like thats hard.......not!

27Mhz is easy to boost since its extremely slow.
Oh gheez CB, half duplex audio!

*Rolls eyes*

Wifi is a high frequency, FULL duplex digital signal.

Nothing you build with come close to remotely working.

Reasons Why.

Unable to cope with switching.
Unable to handle the high end frequency.
Unable to cope with the timings. (You will mess up as it requires complex boards.).
A stereo amp only boosts the power levels, since speakers use electric pulses not RF waves!
Speakers also only use between 20hz to 28000Hz band. (28khz).

Wifi is at 2400000000Hz, can you see the huge range difference yet?

All you will do is create noise.
And it just simply won't work.
And the last thing we need is another Wifi nut screaming in the 2400mhz band, its noisy enough as it is.

If you really have to use a amp, then buy one, they aren't costly.
host219.ipowerweb.com/~f...ba6a3eb6ed8f2af6

But you don't need one, and you will easily go over the EIRP.
Normal 60mw AP = 18db, low end directional = 19DB
Total 37 EIRP, add loss from the coaxial and connectors, lets say 1DB.
Means you are sitting at the Limit of 36db or 4watts EIRP.
But a range of up to 30KM LoS.

Another way at looking at it, standard 60mw AP, plus 2DB with the stock antenna, thats a whopping 20DB or 100mw EIRP.

Even if you put a 1 watt amp which is 30DB, on a antenna that weak, you will have a workable range of less then 500m LoS.
Also that system would be highly illegal!

48DB = is about 380watts EIRP.

Also Go over the 36DB limit and your in for some nasty fines.

Get a decent high gained antenna and shush with you. :).

Atheril:

100 marks for willing to tackle a project like this. Too many people these days are afraid of 'cutting their teeth' on electronics projects.

But - you really must listen to the posters above. It is a bit like deciding to build a Maserati as your 1st car, when it should be a go-kart.

If you objective it to
1) Save Money: Buy an amp - don't build it
2) Increase your WiFi range: Buy or build an antenna.
3) Learn Electronics: Choose a less difficult project.

Regards

Rob

As above, forget it.
I did exactly this sort of thing before I retired.
Designed and built numerous 1.5 Ghz, 2.4 Ghz and 12 Ghz amplifiers and low noise receivers.
Its completely beyond the home hobbyist as you need some specialised test gear, namely a Microwave Spectrum Analyser, a Microwave Network Analyser / S parameter Test Set, and a Microwave Noise figure Meter.
If you are still keen to go ahead, then you can buy the above items for around 800K to 1.5M.

mauried writes...

Microwave Spectrum Analyser, a Microwave Network Analyser / S parameter Test Set, and a Microwave Noise figure Meter.

Mmm.... geeky test equipment goodness.

I miss getting my hands on that gear, now all I get is paper shuffling.

sorry, bit off topic, but I do enjoy working on high freq, high power (300KW+) RF gear