I4FAF Amateur Radio HF "really" linear,  rugged and trusted,  Tetrode Tube Linear Amplifier experience.

Our HF TX system philosofy has been, since many years, to  have available an amplifier which needs a drive level  (ONLY when necessary) around  50 to 65 watts MAXIMUM  as RF input  level (to get the maximum power available, and legally permitted, from a linear amplifier accessory), or LOWER, for even better IMD, lower  harmonics levels, and for longer equipment  life and enjoiable use of the system with lower heat from the transceiver-exiter finals. To achieve our goals we used a tetrode tube with 50 ohm grid input drive which has also  lower High Voltage Anode requirements, (we used a conservative anode voltage value of about V=2100-2200 under load, or about V=2500-2600 no load obtained with a power supply transformer with a secondary ac value of 1850 V x 1,41 with full wave rectification)  strictly well inside the maximum Voltages specifications of the tube manufacturer for longer tube life, with stabilised-regulated voltages and overdrive protections. I4FAF started to investigate, along with his friend Paolo I4PZP (owner of HAM CENTER SRL in Borgo Nuovo di Pontecchio Marconi (BO), professional Philips glass tetrode tube for Amateur Radio  in 1974 (after a comparative evaluation of the well famous triode 3-500Z or better 3-500ZG, graphite). Now we use a ceramic-metal rugged tetrode tube. Of course do not use more RF output power than reasonably needed to achieve a qso!.  Try first low power: often  it is more enjoiable to get a qso with a lower power level than the maximum you have available. The transceiver needs to be equipped with a good RF output level control, not only in CW or  during tune, but also in SSB to keep always under control the drive level.  Remember to use a good PEP RF Wattmeter to monitor the power output level when operating in phone SSB mode.  A good low pass filter accessory  that attenuates  harmonic further above 30 Mhz  can be of help.  Our experience proves that we have been able to work all the DX, Expeditions and Contests as well with the one 4cx800A version, but as in a nice FERRARI  car, if you have a fine drive control you can run lower power also with a strong and trusted linear ampl. still with benefits and longer equipment life. Remember that  experience in HF amateur radio operations and improvements in the antenna system can often make the real difference.

SRC 800   (1998)   HF Amateur Radio  Linear Amplifier with  one 4CX800A
SRC 2001 (2001)  HF Amateur Radio  Linear Amplifier with  one 4CX800A
SRC 2000 (2000)  HF Amateur Radio  Linear Amplifier with  two 4CX800A


Homebrew unique model for personal knowledge and amateur radio use only)



SRC-800 (one 4CX800A) and SRC-2000 (two 4CX800A)


BLA 1000 - RM Italy -  early Review by IK4AUY 
(.pdf  in italiano)


BLA1000 two tones RF  IMD test  with a newly low IMD  RF coupler design by I4SBX
at 410 pep out      (with  24Wpep RF in, DFreq=1200Hz)

BLA1000 two tones RF  IMD test  with a newly low IMD  RF coupler design by I4SBX
at 550W pep out      (with 2x15W  CW RF tones coupled or 31Wpep RF in, DFreq=1200Hz)

BLA1000 two tones RF  IMD test  with a newly low IMD  RF coupler design by I4SBX
at 700 pep out      (with  50Wpep RF in, DFreq=1200Hz) at 14.2MHz

BLA1000 two tones RF  IMD test  with a newly low IMD  RF coupler design by I4SBX
at 500W pep out      (with 2x15W  CW RF tones coupled or 30Wpep RF in)

above BLA1OOO . same test it looks good: 3 order IMD close to 40dB down at 500W pep out and
it improves further out after 5th order


            BLA 350    
                        (48V Mosfets 2x SD2941-10,
10Watts Pin - 300Watts Pout)                            

KPA500 Elecraft - early review by IK4AUY
(.pdf  in italiano)


Some links about Amateur Radio Manufacturer of Linear Amplifiers with Tetrode Tubes 
ACOM ALPIN100 and 200 by Reimesch Kommunikationssysteme GMBH Alpha Power (see Alpha 99 with 2 x 4CX800A)
Emtron (Australia) DX1b
(one 4cx800A)
Leitner Elettronica (It.) 4CX800A amateur radio linear ampls OM Power
QRO tech  (lin ampl with 4CX800A) Ameritron  
More links  
G3SEK Technical site about control boards for tetrode tubes WA6BOB      a lot of links
  ND2X/5 QRO info, links about low cost tube linear ampl.
4CX800A Svetlana Data Sheet  

HAM CENTER SRL (Borgonuovo di Pontecchio Marconi - Bo) air variable capacitors suited for  linear amplifiers

Some links about Amateur Radio Manufacturer of solid state Mosfets Linear Amplifiers  

BLA1000  RM Italy  (1000W - 50V Mosfets full automatic HF/6M)
manual download        
ICAL Italia      see also  SLB300plus (300W)
SLB500  multi function unit with auto low pass filters

ELECRAFT  KPA500 (500W mosfet HF/6m)     



ICOM (USA)       PW 1 (Marcucci Italy)


YAESU   Quadra System





A beautiful "ensemble" view about HAM CENTER SRL (Bologna - ITALY)
variable capacitors specifically designed for HF RF Power amplifiers with TUBES
My father I4FAF helped I4PZP to develop these rugged mechanical units. 
your right: close detail of specifically designed split section to better tune 10 meters
your left: one more detailed view of split section variable capacitors to improve
10 meters (28 Mhz) amateur band tune (with lower residual capacity).


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(last update Feb 23 - 2012)