1w Driver Amp

Failure is always an option 🙂

So, i need a 1w driver amp to drive a pair of IRF510’s in a 10W final PA. Having played with a number of my own designs, and failed miserably, i decided that it was time to borrow from others something that is known to work. The following is the amp chain from The Beach 40 by VK3YE Peter Parker.

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I first laid out the board in Sprint Layout.

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I then routed the board out on the CNC machine.

 

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Then built the board and proceeded to smoke test it.

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I have an obvious clipping issue because of 2 much gain in the 2nd stage where i reversed the bias and gain resistors by mistake, a quick fix on those should fix that ugly waveform. I also do not need almost 3w, I only need 1w, so i will also be increasing the gain resistors to bring the output back closer to the 1w i need. All in all, a successful experiment.

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So after tinkering with the gain on the first stage, i have the thing looking nice and clean and giving 0.8w, smack bang in the middle of the 0.5 to 1w drive the final amp requires.

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VKFF Honor Roll 150

VK4FFAB VKFF Hunter Honour Roll 150

 

This is the latest award i have received for VKFF/WWFF programs for working 150 different parks. Which for a Queensland based F-Call is a fair achievement. To add a little perspective, at the time i writing i am ranked 30th in VK all time rankings, 3th highest Qld’er behind big gun Rick VK4RF and Rob VK4AAC who is portable in VK5, and 3rd highest ranked F-Call behind Amanda VK3FQSO and Adrian VK5FANA, both of whom are much closer to the action than I am. So i am certainly punching above my weight here when it comes to VKFF.

Thanks as always goes to all the park activators for without whom there is no program and to Paul Simmons for his tireless work as national co-ordinator and passionate activator extraordinary. Thanks guys. 73 and 44.

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QSL Cards

 

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I don’t normally comment on qsl cards, but this one deserves mention, its an SWL report from a Russian Short Wave Listener with a very accurate report from a CW QSO i had with Ton PA1CC on 15m tonight. You don’t see a lot of SWL reports, but they are really nice when you do get them.

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100 DXCC Entities Worked

I was first licensed on 25 September 2014, a little over 18 months ago at the time of writing this. And from the very beginning i was hooked on chasing DX and with contests. A few weeks after being on the air, in October was the 2014 Oceania DX Contest, over about 6 hours, i worked 30 different countries, I was hooked.
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A little later i found out about CQ WW Contest, John Moyle Field Day and the WWFF/VKFF and VK5 Parks programs and I started to set myself some goals for what I would like to achieve while on my F Call. For those who read this, who dont know anything about the F-Call license, it is a rather restricted license, SSB, CW and FM modes only, 80, 40, 15 , 10, 2m and 70cm only and the worst part of it 10w only.

But being limited in what i can use was never going to stop me, i got that taste for DX and i was not going to upgrade my license till I had worked 100 DXCC entities. Doing so without 20m or reasonable power was going to be a challenge, but not impossible, and today i achieved one of last goals on my list, 100 DXCC.

Now, most are not confirmed, I think only about 70 of them are confirmed across LOTW, Club Log, EQsl and Paper, but I am not concerned with confirmation, just the knowledge that I have worked all these places is more than enough for me. All that now remains on my goals list, is to put in a proper effort at being the top placed F-Call in my division at John Moyle Field Day this year and then sit the licence upgrade, get 20m and start on the next 100 DXCC.

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73 and thank you to all the dx stations in my log.

 

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Arduino CW Memory Keyboard

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This project is based on the code found in the book Arduino for Ham Radio Book” By Glen Popiel, KW5GP   I have not reinvented the wheel here or anything, but i have improved on and made fully usable this code. Its a CW keyboard with memory keying, it keys the straight key input on your radio using a relay to replace the straight key. This is obviously low voltage negative keying, and not suitable for old high voltage value systems etc.

So the changes i made have done added the following, firstly to make the default key speed to not be over ridden, currently this is set as 10wpm in code. Next i added in changing the key speed using the page up and down keys. Its very useful to be able to change your key speed to suit the person you are cw’ing with. Next i fixed an issue with the macros keying at a speed other than the current set keying speed. I also make it default to keying mode, not beeping mode. The software had 2 modes, keying the radio and beeping a buzzer for practice i guess, well it kind of seems redundant to key a buzzer with a keyboard when a radio has side tone already and i cannot see much practice value in keying a buzzer with a keyboard, its not really going to help you get better as cw operator.

These were all minor changes but ones that have made this project to be much more usable. I also simplified the schematic somewhat, pin 12 goes straight to the input on the relay board and the resistors on the LCD are not needed at all.

 

Here is my modified version of the code: CW_Memory_Keyer

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CW Filter Board

So the plan was to add some kind of filtering to the DC Receiver to give some selectivity. Easiest way to achieve that is to use audio filters, of which there are plenty of types that can be used, passive, scaff, active, etc. I settled initially on an fixed width active opamp filter. Further down the track i will change that to scaf capacitance filtering but, i wanted to have this down pat first..

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The filter parameters are shown above. 8th order Chebyshev, 500hz wide, 600hz centre and -40db down at 2k. A fairly aggressive filter which should take out a lot of the adjacent signals and noise.

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The circuit was optimised for low noise, and one of the nice features of doing that makes all your cap values 100nf and a bulk of 5% 100nf is cheap as chips off ebay, leaving only many odd values of resistors to locate.

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Circuit is laid out with R13/14 making a virtual ground for the OP Amp negative voltage rail, a jumper runs from V- to V- to supply the VCC/2 to the negative voltage rail.

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Gerbers were created and converted to G-Code and the circuit mirrored and routed, drilled, cut out and given a coat of board lacquer ready for populating with parts. Board came up rather nice. .

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Buffer Amp, Pre Amp and Mixer

So after the success i had the other night routing bits up, I thought i would have a go at something simple just to wet my feet and ensure i have everything set correct. And i could not be happier with the results. The board i routed is as shown in the picture below, a simple gain stage buffer to bring the DDS upto 7dbm, a SMD mixer and and RF Preamp using a MAR-6 MMIC.

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I am very happy with how this turned out, it just needs a hit with steel wool to remove burs. I think the graver was on the blunt side after being used as heavily as it was last time out, I am not sure on that, but, i will find out soon enough when i make the next board and use a nice new sharp bit.

 

UPDATE:

I have cut and cleaned the board ready for population. Looks even better now 🙂

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CNC Routing Progress Update

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So, after waiting a lone time, things finally arrived from China and i got some new CNC Gravers in my mitts and have been able to do a little more testing to get this business sorted out. I still have an issue with the FR4 board not being flat, they seem to have an arch in them upto 2mm, i try and bend them back flat, but its not the best solution.

In the above picture i am making what amount to ME pads and squares for prototyping with Manhattan construction, rather than waste a whole board, i thought this would be a good way to test things out and ensure i have my settings right and if it fails, running over the same board with different settings would not matter too much, you can see it is already on its 3rd pass over the board. Needed to make changed to settings and g-code.

So what I have is a 0.1mm 30Deg graver a cut depth of 0.15mm, 2 passes 0.05mm offset and i am happy with the track isolation now and should be able to make a usable board with these settings.

All in all, happy with how its going so far, here is a video of the cutting in action.

An hour later and it was done, here is a picture of the finished product, i think i am ready now to make a board that will be part of my projects.

 

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40m Direct Conversion Receiver

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The above picture is a block diagram of the receiver section of the 40m direct conversion transceiver i have been building for some time. There is nothing ground breaking in the design, it is fairly typical fair for a direct conversion receiver, taking elements from many different designs and bringing them all together into, hopefully a cohesive whole.

This is all part of the “5 x 7” CW Transceiver project i started to outline here: “5 x 7 Tranceiver”

A few things have changed with this, especially so in the front end where the original circuit as been totally replaced with something a lot more simple.

Band Pass Filter: The band pass filter is a 7th order Chebyshev 50ohm in and out with 0.1db ripple.

Pre Amp / Mixer:  The pre amp and mixer both use Mini Circuit devices, MAR-6 MMIC for the pre amp and either TUF-1 or ADE-1 for the diode ring mixer.

Local Oscillator:  The LO is an Arduino microprocessor controlled AD9850 DDS VFO.

Buffer Amp:  Is a simple common emitter, common collector, gain buffer stage to take the LO amplitude to 10dbm.

Audio Diplexer:  This diplexer, out of EMRFD starts to narrow up the bandpass and increase gain of the AF.

Active AF Filter:  An active 500hz wide CW filter, 8th order design using a Quad OP Amp.

Audio Amp:  Finally, the audio amp using an op amp pre amp and LM386 driver.

The only things left to actually build are the 3 audio stages and then test it all together and see if or how it well it works. Failure is always an option as they say.

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