60 meter 5 Watt PA

I have decided to change the plans for the power amplifier.
The 45 Watt amplifier may not be enough. I need 100 watt. So I will make a 5Watt amplifier and boost that signal to 100 Watts using an external amplifier.

The following amplifier will be build. I have designed it using SIMetrix. It should be able to generate 8 Watts. I hope it performs well.

Wiring modules

The cw/multi function board has been build in. Most connections to other modules are made.
Now I have:

• CW Sidetone,
• PTT switch
• TX/RX are displayed on the display.
• S meter circuit works although I have a used a led as S indicator. The brighter it is the stronger the signal strength.
• CW semi break in

The circuit to disable the bfo while transmitting CW has been made but is not wired to the modules.
Without this functionality the suppressed bfo out of the mixer would be present in the output signal.

Receiver is ready it seems to work fine. A better speaker would improve audio quality though. I may replace the small speaker by a bigger one. I could also make a connection for an external speaker.

Things to do:

• Make the power amplifier including ALC and low pass filter
• Make a CW unit to be able to TX in CW mode.
• Make a better audio filter for CW and SSB

Speech processor

A speech processor would help to cut through the QRM. So I build one.
It is a complex unit. It contains a small 12 MHz ssb transmitter and receiver for 12 MHz.
The signal out of this small SSB transceiver is limited by two diodes connected anti parallel.
Then the signal is filtered by a xtal filter that contains a single xtal. This filtered signal is detected by the SSB receiver. This results in compressed audio.

Clipping could be done on the audio signal but then only a little clipping can be done. The audio sounds distorted when more clipping is done. When clipping the SSB signal much more clipping can be done with good signal quality.

I took some ideas form the dsb clipper designed by PA0FRI. My processor makes real SSB instead. It also has a second xtal filter.

The compressed signal sounds good.

60 meter transceiver CW/multifunction board

I made a PCB with some CW functionality. And some generic functionality
It is build on a breadboards pcb with a lot of holes in it.
The functions So far:
-CW semi break in.
-CW sidetone
-TX/RX switching
-S meter circuit.
-An output when CM mode is selected and TX is working.

The board has space for more functionality. Maybe for the future

60 meter trx audio

I made the audio amplifier for the transceiver. It uses a LM386 as amplifier.
In front of this amplifier I have added several RC filters with buffers between them.
It works, Although the suppression of signal above 3 KHz could be better.

The circuits were build in a tin box. I still has room for a CW audio filter or a better audio filter for speech I may add that later.

The speaker that I use is small. Sound is way better when a bigger one is used. I have tested this. So I may replace it.An improvement could be the mounting of the small speaker. Now I have a acoustic short circuit.

The speaker is thin. I was able to mound it on the front of the radio. Then the cover was placed over it . This way I did not have to drill holes in the stainless steel of the front.
Unfortunately volume is low with this setup because of the acoustic short circuit.

60 meter transceiver concept

This is the concept of the transceiver

TX/RX switching is done by switching LO and BFO to the mixers.
AGC and ALC can be done with a single IF amp.
Note that it has 2 bandpass filters for 5.4 MHz. It could be done with a single filter and two relays.

Most items have been  I still need to build:
Speech Compressor.
Diver for the PA.
Lowpass filter 5.5 MHz.
Audio power amplifier (not in drawing).
CW unit  ( Not in drawing).

I can receive and transmit using a signal generator a LO and another generator as audio source. Now it is time to build the DDS unit and the microprocessor board together. Then I have a working LO.
After that I can add the audio amplifier. Then the receiver should be working.

The PA has been assembled except for the power transistors. I bought the kit on ebay. It should be able to deliver 45 Watts.

60 meter transceiver amplifier and agc

The unit that provides 5 mili watt on 8 MHz and 13.350 -13.450 MHz is working. It is connected to the main board. The 13 MHz signal comes out of a signal generator. Later the signal generator will be replaced by a DDS board.

On the main board I have build the amplifier for the tiny 5.4 MHz signal out of the mixer. I can get 5-10 milli Watt out of it. That is enough for now.
In receive mode I can get 8V pp audio with 2 uV 5.4 MHz signal input. This signal is rectified and used for the AGC. It works, from 2uV to 30 mV the signal level of the audio is constant. I cannot get more than 30 mV from the generator.
The time constants for the AGC must be improved though. I want fast attack and slow release.
So some more experiments are. needed.