Recent Posts

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1
Firmware / 1.097
« Last post by G3EJS on August 26, 2018, 08:30:39 AM »
rename to hex instead of txt
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Firmware / TJC 2.8 firmware
« Last post by G3EJS on August 25, 2018, 09:15:58 AM »
These are the latest I can find
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General Chat / Power variations between bands
« Last post by G3EJS on June 01, 2018, 04:37:28 PM »
Maybe it is not the "driver to output" that is the main power problem.
I have tried various ways of making T10, and various devices for Q92, 93, 96 and 97, some were better than others, but one thing remained constant, and that was the relative different power levels, ie 3.5 high, 7 lower than 3.5, 14 higher than 7, 21 much lower than 14, then 24 and 28 higher than 21.
Doesn't matter what I changed, or what the actual output was, this trend was constant.

I measured on the hot side of C200 and C204, and the trend is exactly the same.
Measuring the CLK2 level at R100 shows it is constant across all bands.
Tests were om CW, so the preceding circuits had no effect.
The only thing between the CLK2 level and C204 is the T1/T2 mixer circuit, so I suggest this is where the major power variations are originating. (I did not isolate the LPF from the output of T2, so that may come into the picture)
I would expect a smoother decline in power from 3.5 to 28 as the gain pf the amplifiers declined as the frequency rises.
I'm also thinking of increasing the values of R97 and R98 to 100Ω or even a bit more. (may make no difference, as)
Critical comments welcome :)
4
Building / PIC circuit for pop eliminator
« Last post by G3EJS on May 28, 2018, 05:03:38 AM »
Have drawn the circuit for any one interested.
Hex code is in a previous post


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Firmware / Re: Is there a best?
« Last post by G3EJS on April 30, 2018, 05:53:52 PM »
After lots of changing between different flavours, I have decided for my use the    KD8CEC  firmware leaves the others far behind.


It has gone exactly the direction I had hoped for, though I admit I have no interest in using the [size=0px]µBITX[/size][/color] for WSPR.
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Building / Re: Pop eliminator
« Last post by G3EJS on April 29, 2018, 12:40:32 PM »
All worked very well, so built it all on one board, and added a meter driver and an audio amp on the end to take it to the level neede for the amp module I will use.


Will have to wait for next weekend to try it out :)







7
Building / Re: Pop eliminator
« Last post by G3EJS on April 29, 2018, 05:02:57 AM »
Pop / click totally gone.


Slight change, I tried different AGC circuits, and decided the one with the LED>LDR did the best job overall, so I combined the mute with the AGC.


Once I have finished, I will put all the small PCBs onto one larger one to eliminate some of the wire.


8
Building / S meter
« Last post by G3EJS on April 25, 2018, 04:07:46 PM »
After a lot of deliberation, I have decided to use LED bar displays for the S Meter, forward and reverse power.


I wanted to avoid them as they do add considerably to the RX current draw.


However, after reading how people found the S meter readings were too mean on low signals, and too generous on strong signals, it is evident that a log scale would give a more meaningful display.


Too complex to do it well with a moving coil meter, but easy with an LED display.


If I build one up for portable use, will think again then. Maybe use the one on the LCD display, which I am not keen to do at the moment.


Will post pictures at the weekend if I get chance to connect it all up.



9
Building / Pop eliminator
« Last post by G3EJS on April 22, 2018, 01:51:06 PM »
Decided to try a different approach.


Using a PIC to sequence the mute of the RX and change to TX


The PIC responds to the PTT going low by muting the audio amp, and 100ms later, passing the PTT low state to the raduino.
When the PTT is released, it stops the PTT to the raduino, then 100ms later un-mutes the AF amp.


On the breadboard version, it was a silent transition.


Made some boards this morning, this time I remembered to duplicate them and make more than one, saves setting up a second time.









The hole drilling is one of the best things about the CNC router making the boards :)









The almost finished boards, decided to make the different functions on separate boards, and the AGC board will probably function as the mute circuit later. (The top of the resistor nearest the chip is wrong! It should go to the +ve rail, not -ve, see the photos of the larger board on later posts)







Hex file for 12F629 attached
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Building / SWR bridge
« Last post by G3EJS on April 12, 2018, 11:23:51 AM »
Made one this morning, decided to make provision for ALC and protection circuits, not in use at the moment, but if I upgrade the finals, it will save having to design the board again.


It's the same design as the one in my Russian linear, just smaller!






The CNC router makes boards quickly and cleanly  :)













The finished bridge
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