1 watt 433mhz - 2.4ghz rf amp... from SCRATCH! - Page 3 - RC Groups
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Jul 26, 2013, 03:33 PM
Registered User
Traveled a lot last weeks, was even at "a click distance" from srnet, but timings didn't matched
Long walk... like 5000km in 10 days ?
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Jul 26, 2013, 03:54 PM
Stuart
srnet's Avatar
Quote:
Probably how are you sure you accurate reduced the power by 12dB
Two methods, first the simple expediant of reducing TX power, the RFM22B reduces power in 3dB steps. And as a comparison reducing TX power using precision attenuators,

Quote:
At short distance the Tx leaks can be comparable with antenna power.
Sure, tests (both methods) were done over a distance of 4.4kM.

Quote:
Do you mean you effectively expanded range four times, that is 12dB, right?
Well, thats kind of hard to determine for sure, I would have needed to increase the distance between TX and RX to approx 17km, not very practical.
Last edited by srnet; Jul 26, 2013 at 03:59 PM.
Jul 26, 2013, 04:04 PM
Stuart
srnet's Avatar
Quote:
Originally Posted by dave1993
i get very accurate gain indication by using rssi readings from my transceiver modules. verified and calibrated by the highly technical "long walk" method. fortunately i only have to do that once for each type of module.
I did check the linearity of the RFM22 RSSI reading, its pretty good, when measuring continuous carrier. Unfortunately it does not give consistent reading when taken in the middle of a packet reception. External out of band interferon confuses the RSSI also, in that you can be at the limit of reception, but still see relatively high RSSI readings.
Jul 26, 2013, 07:38 PM
Registered User
Sorry, by not adding noise, I meant that the noise in dB of the first amp does not add directly to the noise in dB of the second amp, not that it does not contribute noise to the system, just that the dB values are not directly added. Whereas the gain in dB of the first amp directly adds to the second amp dB value.
Aug 02, 2013, 07:12 AM
Registered User

Rf2126


Back on topic. I have some RF2126 boards. PM-me if you are interested
Aug 02, 2013, 07:25 AM
RC beginner
what do they cost, costi?
Aug 02, 2013, 07:44 AM
Registered User
Quote:
Originally Posted by dave1993
what do they cost, costi?
I don't know ... $5 is ok? I have 6 pieces available. I also have the 4.7nH smd inductor for 2.4ghz application.
Aug 02, 2013, 08:35 AM
RC beginner
thanks. that sounds like a good price. if it werent for my tiny size requirements and big eu shipping id go for it. for now i must be happy with deadbug. low cost is the advantage but more work. fortunately the power amp is not the best way for me anyway. i did this more as part of my deal with jake. must admit it was useful to boost my 7105 modules up to rfm22b level though.

lna preamp is my preferred method to increase range but im not having good luck with the project atm. im not giving up though.
Aug 02, 2013, 09:16 AM
Registered User
shipping is $4, as a bubbled envelope, with tracking.
Aug 02, 2013, 09:53 AM
Stuart
srnet's Avatar
Quote:
Originally Posted by renatoa
shipping is $4, as a bubbled envelope, with tracking.
I just sent a PCB to the USA in a bubble envelope.

$5.10 to send it, plus $8 if you want it signed for an arrival ................
Aug 02, 2013, 10:04 AM
RC beginner
unfortunately that pushes cost over similar rf2126 boards from ebay. i sent several boards and chips to eu recently and it costs around 6$ (+$12 tracking) for bubble env but only 95 cents for same in business env (<1/4" 6mm).
Aug 02, 2013, 10:31 AM
Registered User
Very cool find. This would be a great add on for my 2.4ghz 9x radio.
Aug 05, 2013, 03:04 PM
Registered User
Would any one in the us be interested in the 2.4ghz one as a kit or complete. I would love to build one but buying all the parts one off isnt very cost effective.
Aug 05, 2013, 03:44 PM
RC beginner
yes, i learned that the hard way. id definitely be interested if its really tiny and the price is right. this deadbug gets old real quick.
Aug 05, 2013, 04:33 PM
FPV addicted
futurebreeze's Avatar
This is the populated board that Costi_n posted above(the bias pot is missing as I am waiting for a proper size one to come from a local part provider). I put the parts and made a few bench tests (Costi_n is the RF guy who has the testing equipment). Connected to a FRSky TX the booster outputs 1W and all the other numbers are like the datasheet states. In fact it is not the first time we use this chip, we have a 19,2km FPV flight with it. The difference is now we have a better PCB (in the past we had problems with cooling the chip).
Costi_n will come up with some graph and charts later.


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