R15 serves as part of the stage supply filtering. I would leave it. If you want to remove R16 then be sure to install a 220 ohm resistor in series with the switch or control. That will limit the current. A switch works very well, don't discount the simplicity and utility.

I would recommend that you only do this at this one stage. The others need to provide the proper terminations to the crystal filter. -ND6T

Another AGC idea. ?

Uses an LED & LDR. ?Louder signals brighten the LED which reduces the LDR's value which reduces the volume, so compressing the audio.?

https://www.youtube.com/watch?v=IQ5JEPRiPoM

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Mine hasn't arrived here either yet but in addition to Steve's advice, I would also check that you have a ground connection to the Raduino board.

Bill, VK7MX

Yup. ?So power goes into one terminal of the switch on the volume control from that outside connector, and power goes from the other terminal of that switch to the three places where power is needed: Raduino, PA-Power, Main-Power. ? And all three of those places have ground returns to outside connector. ?(And I don't have mine yet either)

That wire-up page needs a proof-reader.

My unit hasn't arrived yet, but the instructions on the BITX site say:

Solder the orange wire to the DC power switch on the volume control

Sooo, there's a switch on the volume control, one side of that switch has to have the power input and the other side is the switched power, use a meter and to find the switched terminal, then hook your orange wire there.

Hi. This is my first attempt at trying a kit of any kind and I have a question that is probably extremely simple to those who are used to kit building. I ordered and received this Bitx40. The other day I finally got some free time and tried my hand at putting it all together. I've got everything together except the power for the raduino. Instructions say to wire the orange wire to the the power/volume control but this is not giving me power to the raduino. Both rig and pa power is wired to the power input connector and the rig itself turns on and off as it should. Wiring orange wire straight to power input connector does not allow the raduino to turn off by turning rig off. I have tried attaching the orange wire to different pins on the power/volume control with no luck. What am I missing?

Hello,

This email message is a notification to let you know that a file has been uploaded to the Files area of the [email protected] group.

File: Raduino_V1_1.zip

Uploaded By: Steve Robertson

Description:
This is the initial release of the raduino BITX40 sketch that's been modified to work with the Etherkit_Si5351-2.0.1 library. it is untested as my unit has not arrived yet. I have included the compiled hex file if you wish to forgo library installation and compiling and would rather just use XLoader to load the hex directly to the Arduino Nano.

You can access this file at the URL:
/g/BITX20/files/KA0NEB/Raduino_V1_1.zip

Cheers,
The Groups.io Team

That battery should have 12v*7AH = 84 Watt-Hours of power in it. ?Will take at least 84/1.5 = 56 hours of full sunlight perpendicular to the panel to recharge the battery. ?Assuming the rig is 6 Watts at 50% efficiency (so draws 12 Watts), could run the rig for 84/12 = 7 hours of continuous transmitting, perhaps 10 times that for just receive. ?Could deal with your 30 Watt amp as well, for a while.

A starting battery like that is built for occasional high current draw for a few seconds. ?They are not built to be repeatedly discharged. ?So the lead plates are more of a lead foam, for maximum surface area, and disintegrate after the battery is discharged a few times. ?Avoid discharging below 11v or so, and always charge it back up as soon as possible to avoid sulfation. The motorcycle battery will get you started but will wear out with use. ?There are deep-cycle lead acid batteries built to be discharged 1000 times, that is not one of them. ?A lithium-ion battery pack might be a better choice long term. ? I doubt that panel will be worth the bother, though when the sun is out it should at least keep up with the Bitx40 receive current draw.

All near and dear to my heart. ?We're fully off grid, running from an 18 KWh deep cycle lead acid battery bank in the basement and 4400 Watts of solar panels out in the yard.

Jerry, KE7ER

Yes, the bithacks blog explains it fairly well.

Q1 gets powered from 12v through the 10 ohm R15 and the 220 ohm R16, a total of 230 ohms.

Now that you have replaced R15 with 100 ohms, that figure is 100+220 = 320 ohms, which might reduce the gain of Q1 a little bit but likely won't be noticeable.

Here's Don's original post:

??A switch between R15 and R16 will act like a 20 dB attenuator. Or insert a 10 K variable resistor there for continuous control from zero to 17 dB.

So if you remove R16 entirely (or put a switch in series with R16) so Q1 gets no power, you will still get enough signal through the Q1 stage to hear stations but they will be reduced by 20 dB. ?Being able to select between 0 attenuation and 20 db of attenuation might be all you really need

Alternately, you can replace the 220 ohms at R16 with the series combination of the original 220 ohms plus a 10k pot stolen from an old transistor radio volume control. ?Then RF gain will be continuously variable from what it is now to something 17 dB down from that. ?Facing the front of the pot with the pins pointing down, I'd tie the center pin of the pot to the left side pin, and use that as one node into the pot, and of course the free pin of the pot is the other node, ?That way fully counter-clockwise rotation is maximum resistance (10k) and minimum volume.

Reducing RF gain up front like this will keep the first stages of the receiver (the Q1 ?and Q2 amps and the diode ring mixer) from being overloaded by nearby stations. ?Once we get through the crystal filter, all those other stations will be filtered out and no longer a threat. ?

I replaced R15 (10 ohms) with a 100 ohm resistor, but it is still loud.? I will open it up tomorrow and check my work, see if there is a solder bridge or something.

Then I will do this:

Don's got a very nice trick there, and I plan to use it. ?But I needed clarification as well. ?Cutting power to an amp entirely is a rather unusual way to reduce gain.

> A switch between R15 and R16 will act like a 20 dB attenuator. Or insert a 10 K variable resistor there for continuous control from zero to 17 dB.