The receiver is a single super with an X-tal filter and AGC. The transmitter has an RF output of about 5 Watts. Four times an integrated circuit SA612 and one time an LM386 is used in the design. The frequency range is about 60 KHz. In my transceiver I choosed for a range that stretches from 7.030 to7.090 KHz. This enables me to use the PSK31 frequency (rx only) of 7.035 KHz and also the 40m QRP frequency of 7.090 KHz. Tuning is done with a multiple turn potentiometer although I use a regular one turn potentiometer in my ' Le Forty' without problems. An advantage of a single turn potentiometer is the fact that a quick 40m band scan can be made. A seperate X-tal filter is used for receiver and transmitter. This is rather unusual since in most designs a switchable X-tal filter is used. By using an X-tal frequency of 4,915 MHz this solution could be kept rather cheap. In the transmitters PA endstage two Japanese transistors are used: a 2SC1971 and a 2SC2053.

Circuit diagram of "Le Forty" , by Luc Pistorius F6BQU

The receiver of 'Le Forty' isn't super-sensitive, but it isn't deaf either. Behind this trade-off, there is the design philosophy of Luc; with a QRP-transceiver a good, resonant antenna must be used in order to utilize the small power in an efficient way. Such an antenna may not overload the receivers' input circuitry. And therefore the sensitivity is kept on the low side. In the end, the combination of small power and a receiver producing not too much noise has turned out to be a good one.

My basic version of "Le Forty"

In spite of Luc's description I am surprised by the receiver's sensitivity, being not much less than a regular, commercial type of HF transceiver. Making QRP connections turned out to be far more difficult than when being able to use plenty of RF Watts.Yet, I have been able to make a QSO using a non-resonant longwire antenna with a length of about 14 meters with the South of Belgium where Alain, ON6MG, could hear me on August 29, 2004. My small signal just raise above the QRM-level. According to Alain the quality of the modulation was fine, but strong local QRM spoilt the last part of the QSO. Apart from some local short distance QSOs I did not manage to make any other, regular distance QSO's. It was time to build a longwire antenna tuner to get the antenna resonant, avoiding RF power waste.

Tuning is quite simple. When TX-ing, 'LeForty' provides a remainder of the carrier wave which can be used for the tuning sequence. Place a field strength meter device at the beginning of the wire and control the variable capacitors in a way, the deflection of the meter is the highest. At the begin of a wire antenna the transmitter sees a high impedance; here the voltage will peak.

After having installed this pi-filter between my end-fed one wire antenna in the garden with a 14,1 meter length and LeForty, I found that making QSO's was far more easier, as you can see below:

Take care; We are talking about QRP here (all connections made with less than 5 Watts RF; the electrical power of a bicycles backlight...) and not each CQ results in a succesful QSO. One must take calling half an hour into account in order to make one QSO. And most of these QSOs suffer from hard readibility. But a succesful QRP QSO made with a homebrew transceiver has a certain added value. I think, it is a greater achievement compared to making a QSO using a 150 Watts PEP leaving your commercial set while yelling to your neighbours... But do not forget that the receive capabilities of your counter station really make the succes of your QRP connection.

"Le Forty" is not capable of making PSK31 communication. When changing from TX to RX mode (and vice-versa) the transceiver is not stable enough to cope with the 8 Hz stability limit laid down by PSK31. This requirement is only met after about 2 minutes. By the way, reception of PSK31 signals, after " Le Forty" has been switched on for about 5 minutes, is possible. Do not forget to switch on the AFC in your PSK31 decoding software !

Some practical hints:

• Some PCB's do not provide a connection between contact 3 of IC5 to ground. Make a connection yourself.

• Do not buy an expensive housing (often over 10 euros), but take some time to look in your own junkbox or go to a second hand market or fleemarket. For 2 euro I bought a used dataswitch of which its housing perfectly matched my ideas for a housing for ' Le Forty' .

Outside France and The Netherlands, ' Le Forty ' is also built. Have a look at the picture above. Gabriel, DB5AG also succesfully built the QRP transceiver. On his website at " Transceivers" , Gabriel gives some very useful tips to bring this design to a succesful ending. Have a look at " Links " for Gabriel's Homebrew website.

Twice " Le Forty"; the rig on top is made by PE2ER, Erwin. The set on the floor is my creation. A QSO bridging a 2 meter distance with dummyloads on both TRCVRs was realized September 15, 2004 :-). Luc gave some attention to this first Dutch 40-40 QSO on his website:

"...Nos amis hollandais se sont également lancé dans la réalisation des Forty. Ci-dessus les réalisations de PH0RF et de PE2ER, qui font savoir qu'ils ont réalisé le premier QSO inter-hollandais de Forty à Forty..."

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