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Likely dead in the water due to too much gate capacitance for use at 7mhz.

Just a quick question, I have not yet blown the IRF510 but I found a few IRF520's in my junk drawer. ?Specs look very similar but current handling is much higher. ?I have not analyzed the schematics but guessing someone here has already substituted the IRF510. ?Is the IRF520 drop in? ?Will i need to make any mods to drive the BitX to higher wattage output?

Thanks.

Not on the air yet but getting close!

?Jerry Gaffke-

I have uploaded the modified sketch and it works great. I can properly tune a freq without fiddling with it to make it stop flicker fluttering. It works the same as the original except for the new tuning stability.

I don't know how there could be a downside, or what the trade off could be. But I think this should be included in the Raduino revision.

This is the whole section I replaced-

? // the tuning knob is at neither extremities, tune the signals as usual

? else if (knob != old_knob){

? ? ?frequency = baseTune + (50l * knob);

? ? ?old_knob = knob;

? ? ?setFrequency(frequency);

? ? ?updateDisplay();

? }

}

This is what I replaced it with, leaving the last one of the three braces "}" in this section of the original Raduino_code. It comes after the last one you see in this snippet.?

 // the tuning knob is at neither extremities, tune the signals as usual
  else if (knob != old_knob){
    static char dir_knob;
    if ( (knob>old_knob) && ((dir_knob==1) || ((knob-old_knob) >5)) ||
         (knob<old_knob) && ((dir_knob==0) || ((old_knob-knob) >5)) )   {
       if (knob>old_knob) {
            dir_knob=1;
            frequency = baseTune + (50l * (knob-5));
       } else {
            dir_knob=0;
            frequency = baseTune + (50l * knob);
       }
       old_knob = knob;
       setFrequency(frequency);
       updateDisplay();
    }
  }

AndyH-

Just incase I didn't say it before, You gotta do this into a dummy load. A mismatched, or high SWR untuned antenna will give you lower readings kinda like the ones you got. If that is the case, lower your settings before testing with the dummy load. Hope it works out for ya.

Should probably add the two 1N4148 diodes from relay K1 pin 12 to ground to prevent damage to Q13 from a nearby TX. Also should add the 100 pf capacitor across L7 in the output filter to reduce the second harmonic.

AL

Correct me if I'm wrong ... didn't you meant to say "The BFO in the transmitter circuit hetrodynes the audio baseband signal with a 12.0 (approx) MHz BFO signal, giving 12 MHz output DSB. ?Then it goes through crystal filter to get rid of the other side band, and then VFO heterodynes 4.8-5 with filtered 12 MHz output,?giving 12+5=17 and 12-5=7 MHz output"

Just got my copy of QST yesterday, didn't have time to read yet. :)

Cheers,

Goran VE6GPO

What is the recommended method for tuning an ATU while protecting the IRF 510? At 7 watts? At 20 watts?

James

What are the minimum hardware and software hacks that a new user should plan to make upon receipt of the standard product?

There are a lot of great ideas out there. What say you?

James

As the "Flutter Fix" topic seems to be getting pretty wide, I thought it would be good to focus a little more closely on the version control issue.

Here's a sample of the header block I use on my code files:

// Name:?? ??? ? ? ? ?? ADS9850DDS.ino
// Author:?? ??? ??????? James M. Lynes, Jr.
// Created:?? ??? ????? February 26, 2015
// Modified By:?? ??? James M. Lynes, Jr.
// Last Modified:?? ?January 31, 2017
// Change Log:?? ??? 2/26/2015 - Program Created
//??????????????????????????? 1/29/2017 - Change Default Frequency, allow tuning via serial terminal
//?? ??? ??? ???????????????? 1/31/2017 - Add Band edge checking, tuning rate change command
//
// Description:?? ??? ?Test Sketch to drive an AD9850 DDS Module
//?? ??? ??? ?? ? ? ? ? ? ? ? Basically a 40 meter VFO
//

Sections could be added for Development Environment, Libraries, Minimum Hardware Requirements, etc.

As individual hardware configurations? vary from the delivered product, the software is unlikely to be plug and play. Good documentation will be important.

James

It would work. ?And might be ok at 5W QRP power levels. ?If the SSB transmitter perfect and your code practice oscillator has a perfect sine wave with shaped rise and fall times at the edges of the dots and dashes, ?then you would be transmitting a clean CW signal. ?But none of that is true, and your transmitted signal could get pretty ugly. ?There are easier and better ways to transmit CW. ?Don Cantrell said he had one method working, injecting 7mhz from a spare Si5351 channel directly into the PA (though I don't think he has addressed key clicks yet). ?There will be others.

Jerry, KE7ER

I think it would be too much trouble for me to add CW unless someone can figure out what Farhan has provided in the code. And just plug a code practice oscillator into the mic jack. Maybe it is already that simple. Like what I was getting at about my CW kit. If others are transmitting a CW tone over SSB none of them will care about a carrier or if it's USB or LSB. Just if they can hear each other.

Would transmitting a CW tone with SSB be illegal? Would anybody know the difference??

It's working now. It was just that I removed the three tokens at the bottom of that section of code. And Jerry said to remove two, like he has in his snippet, and leave the original one after pasting over the original section.

The original Raduino code compiled fine. But it was that mistake that gave me a error somewhere else in the code. And I couldn't make the connection.

When is this Amateur Radio learning gonna stop. It's too deep and wide for one lifetime. Like the carrot says "It's YUGE".

One of the things I noticed about my first audio tests, was that I was off frequency. The Raduino needed to be calibrated to offset the zero beat so I wouldn't sound high pitched.?

You can easily test this by monitoring your signal with another receiver. Then tune your BITX up or down in frequency by one step at a time, and see how it sounds in the receiver.?

If they are not on the same frequency as you they only receive part of your signal. It can sound like Darth Vader one way, or Mickey Mouse the other way.