Understanding Radio Modulations - Presentation

Attaching the PPT of the session I took on 05/06/2021 online.

It takes you through the Radio Modulation on a deeper level especially SSB modulation.

Truly SSB is the most wonderful thing invented in the Radio world in last 100 years.

SSTV image from ISS 15degree pass on 6 Dec 2017 10:30 PM IST

From the space

Image received from the ISS using my handy and SSTV decoder app.

Homebrew Kits

LC Meter

This one is a small useful measuring device which would help you in homebrew projects. Usually it is difficult to find a commercial meter which can measure the range of Inductance and Capacitance that we HAMs need. If you are involved in some RF ameteur radio circuit homebrewing, then this tool would be of a great help as it has been for me. I had been using this circuit constructed on a general pcb (vero board) and using it for past few years. And this had been helpful to me in most of my homebrew projects including BITX20,BITX40,MCHF and many more. So I thought of printing a commercial quality PCB from some fab house here. The PCBs are ready now and below are the photos.

The best thing of having an LC meter in hand is, you could wind the coils on any former or ferrite without worrying about the number of turns or the material. Just wind it on any former and measure it . Also you could measure the capacitance of unknown gang capacitors.

Also I have made available the PCB along with the complete set of components as a kit. For enquiring availability please drop a mail to me at vu3ltb at gmail.com. Fully assembled ones are also available.

Update Jan 2019-
Pics of finished LC Meters in Aluminium Box.

 

The mcHF HF SDR Transceiver - 10

And finally...this is what you get :)

The mcHF HF SDR Transceiver - 10

And finally...this is what you get :)

The mcHF HF SDR Transceiver - 9

The Microphone Mod

Below are the pics of my microphone mod which I did for using it with mcHF.

I had bypassed all the circuitry inside the mic and re-wired it so that the ptt and microphone directly goes to the rig.

The microhone(HM-158L) is typically for VHF handies and came with 2 pin connector. I replaced the connector with a stereo connector which is the connector required for mcHF.

 

 

Made use of the tracks available in the PCB removing the unwanted components.

 

You can see the inbuilt speaker in the center and the mic on to the bottom right in this picture.

Later on, I had removed the inbuilt speaker and moved the Electret mic there, which gave better performance.

The mcHF HF SDR Transceiver - 8

As I said in my previous post, my mcHF had been transmitting with 10W power after installing the new Mitsubishi mosfets. With the current goal met, a new target came into place. 
More POWER :). 

Here is the rear view of my mcHF RF board.

One of the modifications that was being discussed in the mcHF yahoo groups was for the T7 modification(Modification of the output transformer in the PA). 

The existing transformer with 2:3 turns wound on BN43-202 core is not matched and is not efficient as it should be. The turns ratio needs to be 1:4 if you see output transformers in other push-pull amplifiers which use RD16HHF1 as the final mosfets. One solution to this is re-winding the T7 transformer to minimize the flux leakage. There is a proven way to accomplish this task.

Instead of using 1 binocular core, we use 2 and the primary will be wound with wire of maximum thickness. An innovative way of doing this is using the braid of coaxial cable-RG58 for winding the primary. Details of this can be found in mcHF Yahoo groups.

Below is the photo of the modified T7 transformer for the additional power output.

After few mods including the above one, my mcHF is now putting out a decent 15 W on 7 MHz :) .

The mcHF HF SDR Transceiver - 7

It has been quite a long time since I posted anything on this blog. Reason being, investing too much time into mcHF modifications whenever ever possible.

Here is one video of my mcHF on transmit.

Thanks a ton to VU2ELJ for the QSO.

The mcHF HF SDR Transceiver - 6

And finally... the mcHF is transmitting...:)
Both Vimal and myself had ordered the MOSFETs from multiple vendors and one among them reached me last week. I replaced both the IRF510s which I had soldered temporarily with the newly arrived RD16HHF1 mosfets. Connected the SWR/Power meter, dummy load and pressed the PTT and whistled. The meter showed close to 10W in Full power mode and showed almost 5W in 5W power setting.

And now I can say the transceiver is complete. Meanwhile I also re-wired an ICOM microphone to work with my mcHF. Shall post some transmitting videos soon. :)