[Amps] RF-KIT SS AMP

[Jim Thomson]

Date: Wed, 31 May 2017 12:26:24 +0000
From: Jim Monahan <k1px at msn.com>
To: "amps at contesting.com" <amps at contesting.com>
Subject: [Amps] RF-KIT SS AMP


<With all of the discussion recently about SS amps, here
is one that might be worth checking out:

http://rf-kit.de/en/2k_Kit.php

RF-KIT, a firm based in Germany, was exhibiting a legal-limit HF Amplifier Kit at the Hamvention. The unit on display was using two LDMOS power devices and sported a 7" color touchscreen for amplifier control and status. The kit includes everything necessary to build the amplifier except the Raspberry Pi 3 CPU, and three fans. The company's literature states that it can be built in less than a day.

Jim, K1PX

K1PX at msn.com

##  Their website is a bit confusing.  They have 3 versions of this amp,  1.5 kw,  2.5 kw and then the latest is 2+ kw.   Some versions have  6m, the latest version does not appear to have 6m.   The..tuner appears to be of the simple LC type, where the shunt C can be switched to either side of the series coil.   With cap on input side of coil, its a step down in Z.  With cap on output side of coil, its a step up in Z.  Dunno if that will provide for a conjugate match or not. Most auto tuners use a T type, with 2 x caps, and a coil at the midpoint of the caps..to chassis. 

##  They list the power supply as a 50 vdc  @  50A  unit in one place....and a 50 vdc @ 60A  in another place.   How the heck you are supposed to get  2.5 kw output of an amp that only has a 3 kw power supply is beyond me.   You would require a
5 kw power supply to get 2.5 kw out.... assuming 50% eff.   Switching type supplies are not like linear conventional supplies, where you can run em at 50% over for ssb use. 

##  They list the 3rd harmonic attenuation at just 13 db.    I assume this is the raw output..with no LP filter used at all.   20 db down from 2500 watts = 125 watts =  heck of a lot of harmonic content reflected back to the amp output..when a LP filter IS used. And thats just the 3rd harmonic, never mind the 5th and 7th  etc.  

##  they list the TX  IMD  on the 2.5 kw output amp ...when run at only 1.5 kw out..as  just  -30dbc..... which is –30db pep...which is lousy.    If run at 2.5 kw pep out, it would be an imd garbage truck. 

##  The english translation could have been a bit better. 

##  they also list  3 x different  LDMOS  devices that can be used.... plus others. 

##  Typ 120 mm fans can be bought in either a  quiet  65 cfm version or a loud  115 cfm version, etc.   They shoulda just used a  dc version, and made it variable, depending on  heatsink temp. 

##  some of his products need clarification.   It appears that on this latest kit version, the NXP devices are used, fans not included, and the tuner is an option.  LP filters are included.   Power supply is included.  For  aprx  $3200.00  in kit form,it looks like a bargain.  But some aspects of it are a bit confusing.   Per their site, it looks like this latest kit version is all that is now available from them.    Perhaps someone could enlighten us all.  Dunno if this latest version is ready for prime time or not. Last thing I need is high imd on ssb.   If its bad at 1.5 kw out..and  cb quality at 2.5 kw out, it may be useable at  750-1000 w out ? 

Jim   VE7RF