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

SRC 800 (1998) HF Amateur Radio Linear Amplifier with one 4CX800A tetrode tube

SRC-2000 (two 4CX800A tetrode tubes) A lot of work has been made around this one but it looks really rugged and with an impressive amount of controls

SRC-2000 (two 4CX800A tetrode tubes)

 

SRC-2000 (two 4CX800A tetrode tubes)

SRC-2000 (two 4CX800A tetrode tubes)

SRC-2000 (two 4CX800A tetrode tubes) - impressive electronic controls

SRC-2000 (two 4CX800A tetrode tubes) - impressive electronic controls

SRC-2001 (one 4CX800A tetrode tube). This is an improved version after our 1998 experience

SRC-2001 (one 4CX800A Tetrode tube)

SRC-2001 (one 4CX800A tetrode tube)

SRC-2001 (one 4CX800A tetrode tube)

SRC-2001 (one 4CX800A tetrode tube)

SRC-2001 (one 4CX800A tetrode tube)

Ham Center SRL air variable

Ham Center SRL air variable

Ham Center SRL air variable

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

 

 

Now let's see the new BLA600 RM - ITALY 500W out 160 to 6m with pin diode fast antenna relay, with LDMOSFET by Freescale (NXP)

 

official video on youtube by RM Italy here

 

 

 

 

 

 

Now let's see some new Linear Amplifiers with Mosfet devices at around 48V

BLA1000 by RM Italy

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 - RM Italy

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

ST Microelectronics says about SD2941-10 mosfets: The SD2941-10 is a gold metalized N-channel MOS field-effect RF power transistor, intended for use in 50 V dc large signal applications up to 230 MHz. It offers 25% lower R_DS(ON) than the industry standard, with 20% higher P_SAT than ST's SD2931-10 device. The SD2941-10 is housed in the low thermal non-pedestal package, offering 25% lower thermal resistance than the industry standard, thus rendering it the "best-in-class" transistor for ISM applications, where reliability and ruggedness are critical factors.

BLA 350  by  RM Italy (a very early unit)
Pin -Pout test in some bands:

SN. 130911	Power In	Power Out	wattmeter N8LP
Band	W-CW tune	W on 50Ohm dummy Load	LP-100A
160M.	4,5 5,3 6,2 7,2 8,2 9,3	195 235 260 300 350 390
40M	4,4 5,2 6,1 7,1 8,1 9,2	170 205 240 275 300 320
20M	4,2 5 6 6,9 7,9 9 9,8	130 160 180 200 220 240 250
15M	4 4,9 5,7 6,6 7,5 8,5	180 223 260 320 360 370
10M	4,1 4,9 5,7 6,6 7,6 8,6 9,5	170 208 236 260 280 290 300

 

BLA 350 (SN. 130911 - Jan. 2012 - test by IK4AUY)  2T IMD Test with a very low IMD RF Coupler and two CW very clean input signals (input IMD about -50dBc down). Here  are shown the output spectrum  in 4 different bands 160, 20, 15, 10 meters: VERY GOOD

Think about using any transceivers like KX3 Elecraft or TEN-TEC mod 539 Argonaut VI or any other HF transceivers in which you can adjust output power at max 10-12Watt to drive this linear amplifier and you will get out around 250-300 Watts,  or less if you set the driving power lower than maximum, at a very favourable price for each  Watt  ratio.

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

 

 

HLA 305 V 13.8V 250W HF Linear amplifier

RM -ITALY review on HAMRADIOWEB Forum

 

 

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 Amplifiers
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 2 x MRF 157 Mosfets full automatic HF/6M) BLA600 - 500W with LDMosfet ad pin diode fast ant. relay BLA350 (300W - 2x SD2941-10  48V rugged Mosfets)	ELECRAFT  KPA500 (500W mosfet HF/6m)
ACOM	SPE EXPERT 1K-FA - 1.3K- 1.5K - 2K-FA
ICOM (USA)       PW 1 (Marcucci Italy)	ITB ITALAB
YAESU   Quadra System	RF-POWER
Ameritron

 

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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Updated April 14 - 2018