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Tadeusz SP2DKS
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 20.08.2014r. godz. 16.30


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Transverter TS70     Assembly TS70     Amplifier PA70     Kit's, projects and others

Transverter TS70

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   This is a SMT version. TS70 is similar to the version of the through hole TH70. There are several differences between them.
   Firstly, there is no air coils (except the input and generator). Coils - SMD inductors with a quality factor Q = 45 - 60. Tests and measurements SMT iductors are made with the help NWT500, this is very good and cheap solution.
   The figure below shows a block diagram.

General assumptions

   IF frequency is 28MHz. Local oscillator operates with a frequency 42MHz (3th overton). At the input of the transmitter there is 27 dB attenuator. Maximum input power is 5W.

The RX block

   At the input, there are two 1N4148 diodes which prevent overvoltage formation originating from the transmitter. The amplifier contain transistor type MOSFET BF994s. It has good performance. Behind the amplifier is 70MHz bandpass filter. Coils in the filter, are 120nH SMD inductors. Tuning this filter we make over the trimmers. The best tuning filters we can do by analyzer. You can also use the GDM. If we do not have instruments, we can adjust on the maximum strength signal. Behind the filter the signal is attenuated about 6dB. However attenuator has, a special task, adjusts the impedance to the mixer SCM-1. Block IF working with 28MHz band filter and the MSA0886. After the filter the signal goes to the relay TRX.

Local oscillator

   It is built on a low-noise FET transistor J310. Note! Manufacturers use different pin configurations! (See diagram) The extent XO buffer is also built on the transistor J310. The final stage transistor amplifier is the BFQ19 (s). It strengthens the heterodyne signal to about 3.5 - 4V RF. The signal generator is filtered by LPF 45MHz. Provides effective suppression of the second harmonic about 45dB. Capacitors C83 27pF and C84 43pF solder on the "sandwich". The signal passes through the splitter (3 x 18om, 3dB), which matches the impedance of the mixer. BFQ19 transistor is working with quite a big current. It should be spread with heat conductive paste.

The TX block

   The maximum input power of our TRX - is 5W. Therefore, at the beginning of this track is a PI attenuator (about 27dB). There are a few metallic resistors connected in series and in parallel. Each one power of is 2W or 3W, attenuator should be screened. P2 potentiometer allows you to adjust the RF power supplied to the mixer. Mixed signal is amplified by two monolithic MMIC amplifiers. The first type is MSA0735 and second type MSA1105. Each one has a 70MHz bandpass filter. The last two blocks works on transistors BFQ19(s) and BFG591 (or BFG35). Tuning of filters is the same as the receiving block. The last part of the track is a dual-circuit transmission LPF. Attenuates the second harmonic of about 37dB.


   Now you can buy and use a wide range of monolithic MMIC amplifiers. You should always remember about the value of the resistor in supply circuit. Accurately described in its documentation. The resistors are size 1206, capacitors 0805. The exception is C70 - 1206 The plate is one-sided plated with solder mask.

Any comments - please send e-mail:      sp2dmb(at)

Videos on youtube - copy link:

Transverter TH70:

Transverter TS70:

Final test:

Component list TS70

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Transverter TS70       Assembly TS70       Amplifier PA70

73 de Peter SP2DMB