3.5MHz 10W SSB transceiver
with 14 transistors
by JF1OZL

In every weekend, I go to the top of the mountain and make local expedition with 50MHz SSB. In week day , after job, I operate 7MHz CW on my shack. But in these days, on the 7MHz , my signal skips out from Japan and I can not contact any station after 10 o*clock. Therefore I decided to make 3.5MHz SSB and CW rigs. I will show you my SSB rig on this page and I will show you CW one on the next page. With each gears, I could contact about ten domestic stations.

Frequency planning
I have about five hundred*s of crystals on my junk box. On these crystals , I have some kind of groups that has the same named frequency. With the same named crystals, I can construct rudder filters and carrier oscillator. On this case I choose seven 9.50923MHz crystals. With six of them I made a filter. Band width of it is adjusted for 2.5kHz by changing the capacitors, by cut and try method. The frequency of the carrier oscillator is adjusted on the upper edge of the pass band of the filter, by changing the capacitor on the gate of the oscillator FET, with cut and try method. See the upper left side of the circuit diagram! Pass band of the filter is from 9.5073 to 9.5107MHz. the carrier frequency is 9.5093MHz. These experiment must be done before beginning to making the transceiver. On this time I could get the prospect to make a 9.5093MHz LSB generator. On the next step, I had to consider how I can convert this 9.5093MHz LSB signal to 3.5MHz LSB signal. Yes I need 6MHz local oscillator. 9.5MHz LSB-6MHzCW=3.5MHzLSB. But 6MHz VXO(variable crystal oscillator) can be changed it's frequency only 12kHz, because VXO can be changed it's frequency about 0.2% of it's oscillating frequency. 6MHz*0.002=12kHz. In Japan , 3.5MHz SSB band is from 3.5025 to 3.5075MHz. It*s band width is 50kHz. Therefore this VXO will be able to cover only a part of the SSB band. I feel it is not good. In order to make big width VXO, I made 16.165MHz VXO. And I made another 10.615MHz crystal oscillator. And I got 6MHz local signal by subtracting these two signals. And by changing oscillating frequency of the OX, I can make two channel of signals. I will put these frequency planning in order as follows.
"Fcar" is carrier frequency,9.5093MHz.
"Fxvo" is XVO frequency, from 16.6036 to 16.5862MHz.
"Fxo1" is first channel frequency, 10.61902.
"Fxo2" is second channel frequency, 10.64902.
Fout1=Fcer-(Fvxo-Fxo1)=3.5249 to 3.5723
Fout2=Fcer-(Fvxo-Fxo2)=3.5549 to 3.6023

Block diagram
transmitting time

 mic--> af amp--> DBM- modulator--> 9.5M Xtal filter--> IF AMP--> DBM- convertor--> 3.5M BPF---> RF-AMP FR-AMP LPF ANT 9.5MHz--> local OSC upside connect upside connect upside connect 16MHZ VXO -------> DBM- mixer------> 6MHz BPF Buffer AMP---> upside connect 10MHz XO -------> upside connect

receiving time

 ANT--> 3.5M BPF---> RF amp--> RF amp--> --> DBM- convertor--> 9.5M Xtal filter--> IF AMP--> DBM- modulator--> af amp--> head phone upside connect 9.5MHz--> local OSC upside connect upside connect 16MHZ VXO -------> DBM- mixer------> 6MHz BPF Buffer AMP---> upside connect 10MHz XO -------> upside connect

Construction and typical point
1. Audio amplifier is a normal transformer input and output type push pull amplifier. It is used as a microphone amplifier on it*s transmitting time. It is used as a head phone amplifier on it*s receiving time. On the first side of the output transformer, the six LED is connected. It limits the signal strength of the microphone amplifier under 300mVc-p. In order to avoid distortion, audio signal must be 10dB lower than the carrier signal.
2. On the receiving time , one stage of audio amplifier is pre located before the push pull amplifier. It can offer the enough total gain of the receiver. But when I put the capacitor on the emitter of the transistor this amplifier, the total gain became too much , and my headphone was full of noises.
3. 120 micro henry of micro inductor is used on the souse of the FET of the crystal oscillator. I got 1000 pieces of them on these days. Therefore I decided to use it actively.
4. About crystal filter, please see another page of my home page! The filter on this transceiver has 6dB ripple on it's pass band. But nobody talked about my sound on the 3.5MHz SSB because 3.5MHz SSB band is full of noises.
5. In this machine three DBM( double balanced mixer) are used. All are made with the same parts. 1S1588 switching diodes and FB801 tri-filer transformers are used. 1S1588 is better than 1N60 on these purpose, because the character of the silicon diodes are more uniform than germanium diodes. I measured the carrier suppression of this modulator is better than 40dB.
6. About coils, you can see the name of OZL series and FCZ series. FCZ series are the mane of the coils made and sold by JH1FCZ. OZL series are the name of the coils made by myself imitating the FCZ coils. They are not sold in anywhere in the world. But you can imitate by yourself and you can use in your original gears. Please see how to make them on the another page of my home page.
7. T8 is output transformer of the final radio frequency amplifier. T8 is made with four FB801 ferrite beads and 0.2mm diameter poli-uletanne (enamel) wire. First side of it is winded by one turn. Second side of it is winded with two turns.
8. Idle current of the final amplifier is 0.3A. In a moment of maximum power output, the currect of it becomes 2A. Then the power of it becomes 2A*20V=40W. The RF maximum power is 10W. Therefore the final efficiency is 20%. For our amateurs, that(=20%) is normal numbers. Because input power of the final amplifier is 40W, I needed very big heat sink. The size of it must be twice bigger than my perms.
9. Low pass filter after final amplifier is constructed with single pei filter. The coil of it is winded around the 8mm diameter core bobbin with 0.2mm enamel wire. Only with this simple filter, I did not watch any TVI on my TV. I felt 3.5MHz is far from TV frequency.
10. Push pull wide band amplifier is used as a driver of the converter. It has reason. The IF signal on the IF port of the converter DBM becomes 700mVc-p. Therefore the local oscillator signal must be bigger than 2 volts, to avoid any distortion on this stage. Therefore I used such a high power amplifier on this stage. Unless this office, some unwanted signal occurs on convertor DBM and it will happens some TVI or distortion of your voice signals.
11. I used 1.5D2V slim coxial cables to connect relays and circuits, to avoid unwanted self oscillation.
12. I like relays. I don't like diode switch. But to change the crystal of the oscillator in this machine , I used a diode switch. In this case it works good.
13. I used many 2SC1815 named transistors. It was got by 7 yens per piece. Yes it is very cheap. But I feel this transistor is almighty on lower HF small signals. But only on oscillator, I feel the FET has better activity.
14. You can see, the case is very big. It is second use of my uncompleted FM transceiver. In Japan we have the proverb that bigger is better than too small.
15. In this machine, it has three oscillators on it. Each load of them are not changed from transmitting time to receiving time. Therefore the oscillated frequencies are not changed on it's transmitting time and receiving time. It is very good point of this construction.
16. In this machine , all small circuits are working as common of transmitter and receiver. Therefore the useful 10W SSB transceiver is constructed with only 14 transistors. But this type of construction needs many relays. I used cheap 24 volt relays with 20 volt power voltage from my regulated power supply.
17. The Vcc of final is also driven with this 20 volt. Another circuits are supplied 12 volts by the three legs regulator(7812).
18. I could make contact with all site of Japan by this simple 14 transistor machine.
19. One time I completed this gear unless the final amplifier. In that timing, the output power of this transceiver was 100mW. But I could not make any contact with this machine. I feel the environmental noise will be bigger than my signal in Japan. In Japan the population is very big. And we use many electric instruments on the night. The many electric instruments make many noises. It may be different in your country. You may use this gear without of final amplifier.
20. I bought a pair of 19 meter long vinyl coated wires. I made a dipole antenna with them. I set up it around my house very closely on the wall of my wooden house with bent in some points. Yes it is called bent dipole. I can not buy the 40 meter long garden , because I am only an employee of machine company. Full size dipole can be used only farmer or president of the company in Japan. HIHI
21. From many hand builder living in abroad, untill now, I received many request to teach them the character of the transistors used on my home page. Therefore I will show you them below.

2SC1815 : Usage=AF,Type=Si Epi,maker Toshiba,Vcbo=60V,Ic max=150mA,Pc=400mW,ft>80MHz,hfe=100
2SC2043: Usage=RF PA,Type=Si Epi,maker Fujitu,Vcbo=60V,Ic max=8A,Pc=25W,ft=220MHz,hfe=500
2SK241 : Usage=FM VHF,Type=Mos,Maker Toshiba,Vdssmax=20,Idmax=30mA,Pd=200mW,Idss=5mA,gm=10mS
2SK192 : Usage=FM VHF RF,Type=J,Maker Toshiba,Idmax=10mA,Pd=200mW,Idss=10mA,gm=7mS

Operatin in my shack

 date time(Japan time) call sign his RS my RS his city name distance(km from my house) 14Nov98 1535 JS1DEH 55 55 Kanuma city 65 " 1701 JO1LHC 59 59QRN Sano city 65 " 1835 JH0TFD 59 59 Shimotagaigun/Nagano 190 " 1855 JI2VIF 59 57 Inabegun/Mie 350 15Nov98 2055 JR1KJU 59 59 Niiharigun-Kasumigaura,town 10 " 2218 JH7DMM 59 59 Futabagun 170 16Nov98 2150 JA2VA 59 18 ? unknown " 2225 JA1VGU 59 39 Inbagun,motono,village 38 18Nov98 2107 JA0PE 59 49 Kitakanbaragun 220 " 2150 JQ2LYP 59 59 Hizai city/Mie 380 19Nov98 2307 JR3GAL 59 59QRN Kusatsu city/Siga 400

12Feb2000***My internet friend YB0AH prezented these re paint. Thanks!

Original documentation and schematic: http://www.intio.or.jp/jf10zl/index.html

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