[Amps] HV MOSFETs for RF

[Jim Thomson]

Date: Thu, 11 May 2017 13:49:19 -0400
From: "Paul Christensen" <w9ac at arrl.net>
To: <amps at contesting.com>
Subject: Re: [Amps] HV MOSFETs for RF

>" ##  If you think the 100w  K3s  paltry  -23 dbc  IMD3 is something to write
home about.... go for it.   Ditto with the 400w yaesu FT-9000MPs ?12 dbc
IMD3. "

<<<<For the last two weeks, I've been testing the new ANAN 8000DLE.  Worst-case IMD at 200W is -75 dBc and close to -80 dBc on some bands.  The PSDR mRx result was cross-checked with an Agilent N1996A spectrum analyzer.  The combination <<<<of LDMOS, adaptive pre-distortion and a highly-isolated RF sample path back to the receiver's sampling input all contribute to this extraordinary level of transmitted IMD performance.

<<<<Paul, W9AC 


##  superb xcvr, esp with phase noise through the floor,  plus other features like a .1 PPM TCXO  etc.   Ok, per the ANAN forum folks, the 8000  had a 30 msec latency...which is now down to just 20 msecs.  How do you monitor yourself on headphones,
when on ssb ?     I have found that anything much over 5-7 msecs sounds horrid in the headphones. That would be a deal breaker for myself.  Plan B would be to monitor the audio,  b4 it gets to the xcvr.    Will the 8000 do essb ?   The 8000 needs an outboard box, with a VFO and other common stuff, like the flex offers. 

##  I see they used a pair of SMA  connectors on the xcvr for the..... pure signal pre-distortion jacks.    If the xcvr is used stand alone, with no amp, then a simple U cable is used between the pair of sma connectors.   One sma is the sample from the 200w pa, the 2nd sma is the main input for the pre-distortion scheme.   When a kw linear amp is used, the U link is removed, and the sample comes from the  kw amp.   Apparently the sample cant be more than 0 dbm, and no less than  - 24 dbm.   So you would require a big pad on the output of the kw amp, for the sample.    Dunno what type of cable is required for the sampling, back to the xcvr ?    Can you use a bnc, or something else than a SMA...at the kw amp end ?  

##  A VA2  fellow from quebec has one of the other ANAN xcvrs, with the pre-distortion scheme.    His IMD3 on his pair of 3-500Zs, with pre-distortion  improved to  -52 dbc.   He sampled the output of the 3-500Z amp..pad, then back to the xcvr. Looks like the typ  linear amp can have its  IMD improved a bunch, like  10 - 18+ db.    A  10 to 18+ db improvement.... even on a marginal amp is a win – win.  

##   -75  to –80dbc  IMD is not even in the same ball park  as everything else on the market..and NO class A blast furnace required.    I see the new Flex  1500W  SS amp has a sampled output..to be used with any xcvr that has the pre-distortion scheme.. like the ANAN xcvrs.   The current Flex xcvrs dont have the pre- distortion scheme...yet, but at least they can see the writing on the wall, and provided a sampled output on their 1.5 kw ss amp. 

##  whats needed now is to get current SS and tube amp manufactures to include a sampled output.    Plan B is to just use a T connector on the back of the amp, and tap off the T..into a pad, then into the xcvr.  

Jim  VE7RF