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The wire up instructions are pretty good down to a certain point.?

When you get to the section of Alignment of the BITX40. Notice #5 is blank. Why it is blank is unknown. But this is where you can adjust R136 (a flat silver trimmer you can adjust with a small blade screwdriver, on the same edge of the board at the PA) to obtain the slightly over 1 amp mentioned in step #6.?

Calibrating the Raduino frequency offset will also require you to download a fixed copy of someone's sketch version found in the files section on the left side if this page. Like mine for example. which has other fixes and tweaks to how it tunes and displays the frequency. Here is a link-?/g/BITX20/files/John_s_Raduino_code_fixed2.ino?Some others may have posted one too with what was important for them to share. Just try to get the one you like from a reliable source. Getting all the libraries in your Arduino IDE for these sketches is likely to give you some compiling errors at first. After that the IDE gives you clues as what to fix. This part could be a whole other section for the newcomer without a working code at the beginning of the build, or when it get's erased like mine did from a shorted wire.

Calibration will get you transmitting on the same frequency as the signal you are hearing. A higher or lower pitched voice means you are not on the same freq. Once you put it in calibration mode you will need to tune around for that signal you were listening to, and adjust the freq until it sounds normal to you. Then turn off the switch, or disconnect the RED wire. Wait for it to indicate SAVED. Then you can reboot it. You can do it again if other frequencies have signals that don't sound like the one you were using to set your calibration. Sometimes others are deliberately not on a 5khz spacing and will sound strange to you if you are expecting them to be on a set freq.

Some folks have had trouble with wiring tuning or volume pots.

The flat diagram near the top of the wire up page-http://www.hfsigs.com/bitx40v3_wireup.html -shows the parts like they are laid out on the table with the shafts pointing up.

With photos like this one-http://www.hfsigs.com/raduino_tuning_pot.jpg - Just hold the pot with the pins facing you, and the shaft facing down. Then follow with Green, Violet, Yellow.And the ceramic cap connects to the same pin as Violet, and Yellow. The two on the right.

Stopping at the 8 pin connector when just only three wires are used slipped past me. I missed the part going to the 5 pin connector, and kept going with wires from the 8 pin set. Fortunately I double checked my work before giving it juice.?

These are my first thoughts on getting people past the first hiccups that seem common in the beginning. As well as that missing #5 instruction that keeps people wondering why they are not getting the expected readings on their meters.?

Are there any more important things to add, or correct?

Next time I'll post about the stereo audio jacks wire up.

Off topic, just feeling my way through on this specan stuff. ?

The AD8310 is spec'd for a maximum input of +/- 2 volts pk-to-pk, or 4 dBV. ?So I'd want at least enough gain after my level 7 mixer to be able to drive the AD8310 to that maximum without having appreciable distortion crop up in the mixer. ? That should give the instrument the 95dB dynamic range available from the AD8310.

More gain than that is a good thing, allows us to see lower level signals. ?Can always use a step attenuator when looking at large signals. ?But at some point the front end is generating enough noise that more gain does not buy anything.

Correct me if I've missed something here.

Should work as expected if you increase the gain of the microphone amp: ?/g/BITX20/message/24437

Assume you raise the signal coming out of the microphone amp by 3dB (double the power). ?Assume the diodes conduct pretty severely on any voice peaks, and reduce them by a factor of 2, so your peak power into the crystal filter is back down to where you started out. ?But the quieter parts of your voice (for those of us that have any) have not been clipped back, and remain at twice the power. ?

This was always tricky when building multiband homebrew, that's why many went for single band design, building up a bank of boxes one for each band.

Good luck Ashhar.

73 Steve

G1KQH

I listened to it. Everything I have read and heard, all are the same. It's great to help being heard through QRN or QRM, There are different ways to do it like audio clipping or RF clipping. And lots of caution about using it poorly, or it amplifies all room noise, or so and so forth.

Bottom line- If you got it, try it. If it helps, great. Otherwise, leave it alone.

I showed the schematic from Allard to someone, and he said the two diodes are shorting the AC signal to ground, and would result in a lower quieter signal.

It's still a mystery to me how that would work. I am going to try out that circuit I posted a link to when I get the transistor it uses. Or maybe sub the part.?

Wow... Impressive, cannot wait for this.

Am following closely the uBitx. Better get space cleared for it.

Thanks Ashhar

Phil-G7BZD

OSHpark is the best I've seen on small runs: ?

For $5 per square inch, you get three double sided boards with soldermask and silk at 6 mil design rules. ?The BItx40 at 4.5x5 inches would cost $5 * 4.5*5 = $112.50, or $37.5 per board. ?But the bidi amps are one square inch each, so could get three of them for a total of $5.

Could go to 0805 or 0603 or 0402 parts to drastically reduce the size of the Bitx40 (or uBitx). ?Take a look at 0201's if you are especially cheap and masochistic, but then you'll want access to a good binocular microscope.

Building for myself, I'd try leaving the extra filters out. ?Use an EFHW wire with a tuned impedance matching circuit. ?Though if mass produced, it really needs an output filter at the amp. ?Perhaps some holes in the board for either one band's worth of L"s and C's, ?or put socket pins into those holes and use plug-in filter boards. ?Can short across those holes with wires and use an external board with relays for a half dozen bands worth of filters, sell that as an option. ?Not too surprising, doubt anybody in the last 70 years has sold something that relies on such balance in a push-pull amp.?

I really have to build a basic spectrum analyzer. ? Perhaps just an Si5351 breakout board, a 50mhz lowpass filter, a level 7 mixer, a?PX1002 86.85mhz SAW filter, an MMIC gain stage, and an AD8310 into a Nano's ADC. ? ?Or do I need more gain stages for this to be useful? ?The PJRC 3.2 ARM has a 16 bit SAR ADC, maybe add a second mixer stage to create audio in the 20 to 50 khz range and analyze that in the ARM using DSP techniques.

Jerry, KE7ER

How many bands will this cover, and does selecting 80m rather than 40m make a difference.

Still very interested.

Phil G7BZD