Re: RD16HHF1 in the uBITX #ubitx

K9HZ <bill@...>
 

Well thats a loaded question.  Reflected power just means that the transistor must dissipate the power.  So at infinity SWR, the transistor(s) must be capable of dissipating all of it.  A 50 watt output radio with 50% overall efficiency needs to dissipate 50 watts in heat (input power 100 watts). So you work the problem backwards.  If i want 25 watts out (say PA is 40 % efficient) that means the total input power is 62.5 watts and 62.5-25= 37.5 must be dissipated in heat by the PA device... but that is at perfect SWR.  If the SWR is now 3:1, then since:



At Pf = 25, Pr would be 6.25 so the device needs to dissipate at least 37.5 watts from efficiency and another 6.25 watts in reflected power or 43.75 watts.  When I design TF amps, i use design such that you can transmit into a dead short (must take full reflected) and therefore the device(s) must be capable of dissipating full input power indefinitely. 


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

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email:  bill@...

 


On Feb 4, 2018, at 11:06 PM, Leland Lannoye <wa9aoe@...> wrote:

Bill: 

Sometime ago I read about a transistor that can handle a 65:1 SER. Do you know anything about the device?



Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------
From: K9HZ <bill@...>
Date: 2/4/18 23:25 (GMT-05:00)
Subject: Re: [BITX20] RD16HHF1 in the uBITX #ubitx

Two RD16HHF1 parts replacing the 510’s will do that.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

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Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

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email:  bill@...

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Nick VK4PLN
Sent: Sunday, February 04, 2018 10:06 PM
To: BITX20@groups.io
Subject: [SPAM] Re: [BITX20] RD16HHF1 in the uBITX #ubitx

 

I just wanna be able to output 5-10w on 28mhz.... not 1w... My QTH is pretty remote and without "decent" power, I wont get any contacts on >7mhz...

Might have to seriously consider an FT817, but the price.... lol.

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