[Amps] HV MOSFETs for RF

[Jim Thomson]

Date: Mon, 8 May 2017 10:00:51 +0200 (CEST)
From: "sm0aom at telia.com" <sm0aom at telia.com>
To: jtml at vla.com, amps at contesting.com, catherine.james at att.net
Subject: Re: [Amps] HV MOSFETs for RF


<One is the output stages of modern mobile telephony base stations and repeaters for indoor coverage.
<Several of the European type acceptance criteria actually require a -70 dB IM3 suppression in a two-tone test at the +40 dBm PEP level.
<Here, the total adjacent channel suppression is of importance, which also includes phase noise and broadband noise,
<as well as IM products.

<73/
<Karl-Arne
<SM0AOM

##  + 40 dbm  = 10 watts.  10 watts in Class A  would be the simplest way to achieve low IMD products. 
Perhaps Elecraft should think of doing just that with their K3 series of xcvrs. The 10 watt version of the K3
has lousy IMD, and ditto with the 100 watt version of the K3.  I think the 100w version of the K3 uses the
same 10 W stage as a driver.   If you increase the idle current on the K3, the IMD does not improve.

##  Points well taken with Phase noise + broadband noise. 
##  I notice that my yaesu 1000-MP-MKV, when keyed, but no audio applied..mic gain on zero,
is a lot quieter, like by 20 db, when  toggling between DSP method of  ssb generation.....and analog SSB 
generation,using mech + xtal filters. 

##  Analog SSB is 20 db quieter.  This is when listening on a 2nd  MK-V, 2 foot away,  with a 2 foot wire used
for an RX ant, and both xcvrs on the same freq.   With no audio applied, but keyed, I can hear this broadband
hash, while listening and tuning + or – a bit, on the 2nd  MK-V.  The hash drops like a rock, when on analog SSB. 
Moot point though, since nobody can hear it.   Ditto with CXR suppression. 

Jim   VE7RF