Microcontrolller work

May daily jobs involves programming small processors. So I don't want to program at home.
However the transceiver requires a microcontroller so I did some programming anyway.

Stuff I use
-PIC 16F877 microcontroller running at 20 MHz.
-rotary encoder, LCD and several switches.
-2 x 74164 shift registers to select the band. No more IO pins were available.

Features so far:
-Tune the HF band an 160 Meter. The DDS is used as the LO.
-Basic RIT functionality
-Band selection By pushing a button and rotating the encoder. Band is outputted using the shift registers. They drive a relays using a transistor.
-Mode selection LSB,USB and CW by pushing a button an rotating the encoder. An mode dependent offset is added to the DDS frequency.

Features to implement.
-TX and RX handling like adding RIT offset while receiving. Maybe TX/RX in display.

In this state the controller and DDS should already be usable. I have not used it as a LO yet. I have to make an amplifier and a filter for the DDS output first. The frequencies out of the DDS seem OK.

Now I am working on the lowpass filters.

Some progress

Progress is slow on this one. Besides  did not update this blog regularly.

I did a few things though.
-If strip is working. But it needs some finishing touches, like using varicaps instead of trimmers for the band pass tuning.

-I found an enclosure for it. I bought it from a ham who was quitting the hobby.

-On  ebay I have found cheap AD9850 dds modules. I have bought a few. One of them will be used as synthesize for this project. I know that it is not ideal with respect to phase noise. I can add cleanup oscillators later.












I made a controller for this board using a PIC processor. Now I can generate signals between 0 and 40 MHz

A band pass filter is almost ready. I had top skip 160 meters as it did not fit in the filter enclosure (tin box).

 
 

progress on IF strip

In the last couple of days I added the following features:
-CW TX support.
-AGC fast and slow.
-Noise blanker. It does not include the noise detection though. That will be a separate module. I have to experiment a bit to get a adequate blank pulse.

The CW sidetone may not fit on this module. I could keep the receiver on during CW transmission. That will generate a sideone. I do fear that the receiver will overload though. Maybe I can reduce sensitivity during TX.

Band filter

This is a band filter for 160 to 10 meter. I bought it on Ebay to save time. It saves money too.
It came from the Ukraine. I hope it works as expected.

IF strip

This is the IF strip. Development is still going on. In this stage it can generate a SSB signal.
It can also demodulate SSB. The audio amplifier is working and so is the variable bandwidth IF .
Things to add:
-AGC functionality.
-Noise blanker.
-CW sidetone.
-CW TX support.
Adding a noise blanker will be difficult because of lack of space. The blanker itself will fit. The noise detector may not. I could add a separate noise detector module in another tin box. 

I plan to draw a schematic diagram of it.

Start of blog

In this blog I will describe the designing and building of a HF (QRP) transceiver.
I have already build one some years ago. Now I will try to build a better one.

Next picture shows the old one.

 Some of the features:
-Triple loop pll synthesizer,. 30 Hz steps.
-Controlled by micro controller pic16F84.
-Covers 500 KHz on 80 40 30 20 17 15 12 and 28 MHz.
-Modes usb, lsb, cw
-CW audio filter.
-Power output 8 Watt PEP on 80 meter, 3 Watt  PEP on 10 meter. Power is adjustable.
-AGC 1 speed.
-CW side tone

The new one should have extra features like.
-5 Watt PEP on all bands.
-Coverage of all HF bands including 160 meter.
-Adjustable IF Width.
-RIT.
-Noise blanker for pulse noise.
-Internal power supply.
-AGC different for CW and SSB.