Re: Réf. : Re: Re: 5.7 GHz PAs


Mark GM4ISM
 

Francois, all
I believe that all WiFi systems employ OFDM modulation schemes.
This is a multi carrier  modulation with an inherent requirement for linearity in any amplifiers.
 
Because of the multi-carrier nature of the signal,  any amplifier must be able to handle, to some extent, the elevated peak voltages associated with this.  The crest factor of an OFDM signal is regarded as 10dB.  For practical amplifiers you don’t need to necessarily rate them at 10 times the wanted power out.  Depending on the  tolerance to  intermodulation product errors, you may get away with rating the amplifier  with 6dB headroom (more or less)  I suspect these amps have less headroom, but because the  peak voltages are statistically distributed, the error rate probably doesn't increase too much, and given the robust nature of Wifi, you get away with it ( or the user  doesn't notice that the error rate has gone up)
 
 
This is probably how is reported that you can get 4W out of these amplifiers, which i presume was measured  somewhere about the 1dB Compression point, ie satisfactory for  SSB
 
At the rated 2.5W, it will almost certainly be really quite linear and below the 1dB compression point.
 
They do indeed look like good value.
I am tempted to get one to play with myself.
Regards
Mark GM4ISM
 
 
 
 

Sent: Sunday, August 07, 2016 10:28 AM
Subject: Réf. : Re: [ukmicrowaves] Re: 5.7 GHz PAs
 
 

looking via google to "txpa58002w5" it is possible to see a lot of discussions ..
seems that the SMA plug are REVERSE (RPA)
so we need either to plug an adaptator or change the plug  (is it easy, I don't know)
about the polarisation, I don't see if this PA is compatible with SSB signal
but for the price, it is nice
Francois F1CHF
 
 
 
 
-------Message original-------
 
Date : 08/07/16 10:14:18
Sujet : Re: [ukmicrowaves] Re: 5.7 GHz PAs
 
 

Hi Gus,
Well indeed this was one avenue and you have confirmed >4 watts, i think i will try this and then i might fight with some internally matched devices for the 7.5 GHz band.
Thanks
Geoff
GI0GDP
 
 
 


On Sunday, 7 August 2016, 0:23, "gus_452000@... [ukmicrowaves]" wrote:


 
Might not be 100% suitable for your needs, BUT have you thought of something like this, mine does 4.2W, not perfect but cheap enough, perhaps worth a try for your needs or to start with, there on Ebay (other sites are available), might be worth a try to see how they perform, part number 112048942890, you probably might need some more filtering on the output!
regards
Gus M0IKB
 


 

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