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SPE EXPERT 1K-FA linear amplifier review | Radioaficion Ham Radio

SPE EXPERT 1K-FA linear amplifier review

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SPE EXPERT 1K-FA solid state linear amplifier SPE-1K-FA_Schematics.pdf

Operational Description

The SPE EXPERT 1K-FA solid state linear amplifier is small, powerful and completely automatic, it covers the radio amateur band range from 1.8 MHz to 50 MHz, it provides 900W (700W in 50 Mhz) output power with 60W input tipically. All operating conditions (frequency, antenna and tuner) may be controlled from the transceiver.

The linear amplifier has two inputs (INPUT 1, INPUT 2) to which it is possible to connect two transceivers of any brand or type. These inputs are selected with the [INPUT] key. It can manage up to four antennas (ANT 1, ANT 2, ANT 3, ANT 4).  The amplifier selects antennas automatically when they have been programmed.

The amplifier is composed of three push-pull of MRF150 (mosfets) in class AB paralleled with a passive combiner.

The modern transceivers have CAT control, thanks  to this link the linear  amplifier detects the operating frequency of the transceiver and then automatically changes band, antenna and automatic tuner.

The power supply unit of the SPE Expert 1K-FA has two blocks with two separate power transformers. The first block has regulated and  protected voltages, and powers all the electronic circuits for command and control.

The second block powers only the PA. It has a toroidal transformer with a low magnetic field to avoid disturbances to nearby equipment. The output voltages are 44 Vdc  (on Full-power mode) and 30 Vdc (on Half-power mode), regulated with SCRs that also provide ‘soft start’ on switch-on.

The amplifier has an automatic tuner that handles load mismatches up to 3:1 VSWR (2,5:1 for 50MHz). The circuit used is a PI – L network with excellent harmonic suppression. The amplifier contains a look-up table with  the permitted amateur bands only (the continous coverage is inhibited) .  For tuner management, antenna data and other working data are stored. Every band has a sub-band set, and for each of those, data related to the antenna and auto-ATU tuning is stored.

The CAT and the frequency counter detect the operating frequency and the correct sub-band. Thanks to the stored data, the tuner and the antenna are automatically set correctly. In the US version, operation on the 12 m and 10 m bands has been inhibited following FCC regulations.  Setting of the match data to write in the tables is performed automatically by pressing the [TUNE]  key The system will then find the correct match for minimum SWR.

The SPE 1K-FA has a sophisticated protection system that constantly controls the amplifier’s most
important parameters. These parameters are:
Temperature of the heatsink; max. / min. voltage on the PA; max. PA current; SWR; reflected power; max voltage RF on the tuner; input power; power combiner balance.


The protection system is effected in two different ways:
1) Through hardware circuits to guarantee  minimum intervention time.
2) Through software, with one of the two CPU’s, to guarantee the maximum precision.

The two results are always compared, every difference produces a protection trip and consequent alarm.


Tuning Procedure

TUNER
The amplifier has an automatic tuner that handles load mismatches up to 3:1 VSWR (2,5:1 for 50MHz). The circuit used is a PI – L network with excellent harmonic suppression. The amplifier contains a look-up table with all the permitted bands. For tuner management, antenna data and other working data are stored. Every band has a sub-band set, and for each of those, data related to the antenna and auto-ATU tuning is stored.

The CAT and the frequency counter detect the operating frequency and the correct sub-band. Thanks to the stored data, the tuner and the antenna are automatically set correctly. For every input there is a different table. If two exciters are connected at the same time, each exciter can have different configurations.

It is possible to use the two different tables when the amplifier operates at two different locations.

In fact it is possible to use the INPUT 1 at one and INPUT 2 on the other. In this way repeated reprogrammings are not needed  In the US version, operation on the 12 m and 10 m bands has been inhibited following FCC regulations. Authorized 12/10m  operation of the amplifier by licensed radio amateurs will be enabled by the dealer there in accordance with current rules.  The auto-tuner and antenna selection via the amplifier are still enabled even in 12/10m inhibited units.

All auto-tuner functions remain, on standby, whilst using the transceiver only. Setting of the match data to write in the tables is performed automatically by pressing the [TUNE]  key The system will then find the correct match for minimum SWR. To achieve a better match than that achieved with the automatic tune routine  (most unlikely) it is possible to set the tuning manually by using the keys [◄ C], [C ►], [◄ L],  [L ►].

When manual tuning has been performed, it is possible to read the tuning  value, the working frequency and the associated sub-band on the appropriate screen page. Both the types of tuning are always effected in “STANDBY“ state.

NOTE:  The tuner, like all analog circuits, introduces a loss (0,8 dB max.) that may vary with tuning
conditions.The power meter of the amplifier does not show this loss as the power is measured at the tuner input where the load resistance is always constant (50 ohm).

NOTE:  ATTENTION, When the amplifier is on  the ‘STANDBY’ or ‘OPERATE’ modes, always disable the
automatic tuner in your transceiver.


Use of Automatic Tuner
To complete the programming it is necessary to match the antennas to the  amplifier  by operating  “TUNE“ (read the “TUNER“ chapter of this manual). We recommend you to select each band (with available antenna) and then program the tuner for the sub-bands within which you will operate.  Refer to the table in section  18 of the manual to select the  appropriate sub-bands for your operating preferences.  

Progress as follows:

  • 1) Find the central frequency of the sub-band to tune in the table (refer to section 18 of the manual) and set the transceiver to that frequency.
  • 2) Press the [TUNE] key.
  • 3) Set your transceiver to transmit a continuous tone in RTTY or CW. The procedure for automatic tuning will start and then  it will stop when SWR is at a minimum. Sometimes it is possible to improve tuning by pressing the [TUNE] key  again.
  • 4) Repeat the previous steps for all bands and sub-bands you want.


NOTE:   If the ALC link is not used, it is preferable to reduce the transceiver power to about 50 Watts during
this operation.

NOTE:  As a default, the table is programmed for standard 50 ohm out. If, for a band, you want to reset to
default programming,progress as follows:    

  • - Go to the “ANTENNA“ menu page  and set this band to “NONE“,  then exit from that page.
  • - Go to the “ANTENNA“ menu page again, assign the appropriate antenna  to this band, then exit

from that page. The programming will be reset for 50 ohm output.

Donwload SPE 1K-FA Block Diagram

Donwload SPE 1K-FA Schematics

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