Thank you! That was very informative.

Now it's just a matter of cramming all those wires onto that tiny connector...
--
Darren, W9ZIM

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I posted this a while back. It should tell you what you need to know to figure out the audio jacks. Here is the link.
/g/BITX20/message/24809

After a couple of nerve-wracking hours, my bitx40 fired up and appears to be working as expected!

I haven't connected the speaker/headphone or microphone jacks yet, but it's a promising start.



My only question is, how do I wire up the speaker and headphone jack in such a way that plugging in headphones causes the speaker to mute?
--
Darren, W9ZIM

No complete QSO
I heard what sounded like John or Tom maybe saying Oklahoma something and just Whiskey from someone else.?
Doug
KD9CYF?

my BITX40 arrived today. Ordered on 5 May arrived 29 th May. So 24 days?
Now the fun starts

Adrian VK4KL

I think I am starting to understand why some hams say life is too short for QRP.
I can barely complete a contact with W1LY. But then again 1,471.5 miles is quite a distance for QRP with lots of lightning crashes. He fades in and out and gets more audible later in the evening. Yea, I can hear him fine now, but I can't hear anybody else.
Well, I got the impression he is an expert QRP operator. And should have a long list to post tonight.

Any chance anyone heard my signal, and could comment on the audio quality? I just implemented the Peter Parker improved audio hack. It sounds just a bit better at this end.

By the way I am putting 24 volts into the final, and In-Vee 18 feet at apex.

W1LY with varying strength from 5-5 to 5-9, later in the hour was better than the first half.

I thought I heard someone else calling CQ but could not get the call sign, WA1LAV?

Some broadcast QSB on 7277.?

Phil,

You might already have the answers, but regardless, here's my blog post and vid on this circuit:



FWIW, the first LDR I used from the junk box was 40-400k and did not work. ?I sourced a 4-40k LDR from Jaycar (here in VK) and it worked fine. I didn't even bother to tape it for ambient light penetration. ?Day or night on the bench seemed to make no discernible difference. ?

73 VK3HN

Okay. After reading Peter's explanation, I actually understand. While tweaking the trimmer cap, I can tell there is also a difference in audio signal strength smack in the middle of high to low pitch adjustment. I can hear the difference with this alignment between the BFO crystal and the crystal BP filter as monitored with a WebSDR site. Muffled audio signal in the BITX40 was one of the first problems I ever noticed. I have been waiting a long time for parts to make an amplified electret mic circuit, and don't think I need that anymore.?

Since so many people have had the same complaint, why wasn't the trimmer still on the board? It seems necessary. My board has been needing that adjustment for about 5 months now. I have really got to stop putting these things off.

Thank you for the explanation and the fix Peter. Just in time for BITX40 QSO Night.

If the guy putting things in the wiki is still doing that. Grab his post and put it in there.

I didn't see Peter Parker's post until after my second post.
Cheers.

I am familiar with #define bfo_freq (11998000UL). But this hardware hack acts exactly like the calibration mode in the wire up directions. I used a trimmer instead of ceramics because Peter said he was too lazy to get to the under side of the board. My board is held on by adhesive backed plastic PC board posts. I can pop it off and on anytime without hassle. So it's the same hack, but with ideal hardware.

John Smith write
>I just now performed the Peter Parker improved audio hack with a 10 - 40pf trimmer cap and observed the following.
>Before soldering it on I set it for approx 27pf, and heard a noticeable higher pitched static when I turned it on.
>I tuned in a QSO? and adjusted for optimum tonal quality. This was looking familiar.
>I loaded an WebSDR page and transmitted while adjusting the trimmer cap. I could hear my voice pitch go up
>and down like I was tuning the frequency around. Then I realized how this was looking familiar. It was providing
>the same results as calibrating the frequency offset. The band is currently dead, and I can't tell how much my
>calibrated offset has changed with this BFO tuning hack right now.?Does this make sense to anyone?
>Is this another way of doing the same thing with the calibration function?

The short answer is no. ?While there is interaction between the carrier oscillator frequency (which this mod changes) and the calibration or offset setting in the DDS VFO but they are very different adjustments.?

It is essential to get the relationship between the BFO crystal and the crystal filter bandpass right. ?This ensures punchy audio that's readable when the signal is weak. And people won't be saying your audio is muffled, thin or they have difficulty tuning you in. ?The carrier oscillator setting determines the tx and rx audio bandpass and is more complex than simply being on or off frequency. Set it for optimum transmitted audio and ignore that the frequency display is different on the rig you're aligning and your test receiver. ?The setting that is right for tx audio should also be right for rx audio as the carrier oscillator/BFO and xtal filter are shared.?

Once happy with the audio audio bandpass characteristics you can adjust the offset setting in the DDS to match the BFO frequency so your display lines up with other stations. ?You can usually tell this without any special measuring since most stations on 7 MHz operate on exact multiples of 1kHz. So if all stations are tuned in well when tuning in 1 kHz steps with your DDS you should be right.?

when you made that mods you have changed your BFO-Freq, if you look inside the Raduino schetch you fin this line
?#define bfo_freq (11998000UL)
if you find a counter you will have the right Freq for that line

I just now performed the Peter Parker improved audio hack with a 10 - 40pf trimmer cap and observed the following. Before soldering it on I set it for approx 27pf, and heard a noticeable higher pitched static when I turned it on. I tuned in a QSO? and adjusted for optimum tonal quality. This was looking familiar. I loaded an WebSDR page and transmitted while adjusting the trimmer cap. I could hear my voice pitch go up and down like I was tuning the frequency around. Then I realized how this was looking familiar. It was providing the same results as calibrating the frequency offset. The band is currently dead, and I can't tell how much my calibrated offset has changed with this BFO tuning hack right now.

Does this make sense to anyone? Is this another way of doing the same thing with the calibration function?

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