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Baofeng ptt circuit

Posted by Dave : My laptop soundcard doesn't work very well, so I wanted to use a cheap USB soundcard.

baofeng ptt circuit

The USB soundcard I have only provides a microphone input and not a line-level input. As a result, the received signal level going to the soundcard had to be very low of the order of a few 10's of mV. The Baofeng radios are not very good at providing this low signal level because the only audio output on the radio is intended to drive a speaker with audio levels of a volt or two. Adjusting the speaker audio level to match the mic input via the Baofeng audio control was very tricky due to the sensitivity of the soundcard.

I needed to be able to adjust the audio output of the radio with a reasonable margin for error. The Baofeng's VOX mode is notoriously slow to drop out, hanging on for a few seconds in most cases. Looking around, I found several possible solutions, but none was a complete soundcard interface for the Baofeng UV5R. My soundcard interface is shown below click the thumbnail for a larger version.

The transmit audio circuit uses a audio isolation transformer to isolate the Baofeng 3. Careful initial tuning of the deviation by setting R2 is required in order for your signals to be reliably copied by others. When the serial port RTS line goes high, the LED turns on and pulls the collector of the optocoupler low, shorting the sleeve of the 3.

The receive audio circuit includes capacitor C1 to block any DC voltage from the soundcard usually used for powering electret microphones.

Resistor R4 is chosen to attenuate the audio signal from the Baofeng speaker 2. Assuming a typical soundcard microphone input impedance of 15 kOhms, a value of 82 kOhms attenuates the voltage by a factor of a approximately 6. Using this value of R4, together with a soundcard mic gain setting of between 7 and 10 in alsamixer, I obtained reliable reception with the Baofeng audio knob set anywhere between the 6 and 9 oclock positions.

I also added a header J1-J2 which can be shorted to bypass R4 if I want to switch to a soundcard with a line input instead of a mic input. I would also note that this interface could be used with a hardware packet TNC. Tags: baofeng, packet radio, ardop, direwolf. Comments Post a comment Name required :.

Type "red" without quotes here:. All rights reserved unless otherwise specified. This site is produced using the Haggis static site generator.BaoFeng radios are designed to be affordable radios for licensed amateur radio enthusiasts and commercial users schools, hospitals, municipalities, and many more.

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Our firmware is months ahead of any other storefront. What are BaoFeng Radios?Svxlink is a powerful software program that can be used as a repeater controller, a simplex link.

Supports networked multiple receivers and transmitters. It also has an Echolink module. Echolink is a popular system that allows two or more nodes to connect over the internet.

I wont discuss the installation or setup of Svxlink as that is covered many times. During my research time and time again I found reference to a hardware modification for the UV5R where you solder a wire to pin 2 of the audio amplifier in the UV5R.

This mod which connects to that supply Vcc was fairly easy and can be found here. However I noticed on the schematic of the UV5R that there is no dc blocking capacitor on output to the speaker and external speaker jack.

The output goes to about 3 volts when the amplifier is enabled. To zero when no signal is received. Why then do I need to open the case? It is not necessary. Note the connection from pin 1 to the external speaker jack. Seems like a poor design to me to keep the internal speaker inline?

I wont go into the point of C and R in series with ground connect at each end? At least their is 3 volts on the external speaker output when a signal is present…I can work with that!! Here is the interface I built which works fine. I decided to use 2 isolation transformers for the audio to minimize hum. There are three adjustments. I made that variable so it can be used on other systems if desired.

Hard to tell as I purchased the parts in lots of 10 or more. Was a cheap chinese usb soundcard dongle. Bought off amazon. Are the values for R2 and R4 correct? Can you make the image of the circuit and the writing next to it bigger, when I make the screen bigger on my end, it all get very blurry.

Baofeng: On-Board Mic vs. Speaker Mic vs. Clip-on Mic

It is what I am using. Though I suspect for reliable operation ohms might be better at 3. I just visually reverified that the 1k value is what I am using. That would be great and easier to see. Please add a pcb file, thnx. Let me say again that this project was simply built on a breadboard.

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No pcb layout is available. Your audio circuits have blocking capacitors on both sides of the transformers; is that not redundant? I was thinking that any DC bias is removed on the input side, and only audio AC is presented on the output of the transformer. Therefore, no DC block should be necessary on the output side of the transformers. If the caps are more for filtering, I would think that this would provide the same frequency range on either side of a winding, so still one is redundant.

Any ideas?But your design does much better PPT Since it's been two years since the last post, have you been able to build up a board and test it out? If so, are pcbs available? Saturday, May 20, Baofeng-RPi interface.

There's a lot of information out there and I ran across a post from N1GYwhich describes in great detail how the wiring works. Please check out his page for a detailed description. So I decided to build my own interface board and to document it here.

Here's a 3D render of what the final design is:. Although the connector pinout for the Baofeng is documented pretty well, here's again what it looks like. Fortunately, there is a high impedance potential between the two - about 3.

I wired it as a monostable multivibrator with a 5. As soon as we provide power to the trigger line C1 gives us just enough delay for the chip to turn on before the trigger signal is provided. APRS packets are sent in short bursts, so this should be plenty even if the radio has a slight delay.

Again, checking the absolute maximums confirm that we can use it for this project. I would normally calculate the current requirements for the whole circuit with a circuit simulation tool, but since it's just a hobby project I'll simply breadboard it and measure what the current requirements are.

It turned out that we need to switch 3. We'll play it safe and pick a standard 4. We need to make sure we don't exceed the limits for the current the RPi can source and sink, so let's do the math real quick: We have a 0. No problem. All that's left now is to connect the audio lines: radio microphone to sound card speaker, and sound card microphone to the radio speaker.

We are going to isolate the audio signals with a audio transformer, which lets the audio signals pass through unmodified while at the same time blocking DC voltage. An added benefit is that audio transformers have a limited frequency response and therefore block out RF interference RFI. So it is only responsive to audio signals - exactly what we want. The PCB design process starts for me with choosing a proper enclosure.

This way I know what the board size is and where external connectors are located. For this project, I needed something small the circuit doesn't take any room at allbut also large enough to fit the relatively large audio transformers - and of course all my external connectors.

baofeng ptt circuit

I went with the Hammond CF Most manufacturers nowadays have 3D models of their parts available online, and putting together a 3D model of the entire board goes a long way in avoiding problems later.

A view like the one here allows to see if everything fits and lines up:. For cost reasons, I wanted to go with a two-layer board.

Keeping digital and analog portions separate from each other, having separate grounds, using large ground planes and using wider traces for analog signals should help. Smaller traces would reduce the noise on these lines but in effect turn them into a large capacitor - not good. I also kept the two transformers at right angles to each other to avoid mutual inductance.

I will ship the design files off to Oshpark and it's going to take a little to get them back.You can find them by searching here. Although the radio supports PTT keying, you have to take care to wire it correctly.

After a quick search, I found this better image of the pinout:. Going off this, you can see that the 3. You can also see that the grounds are on the 2. This should also work for all 2-pin cable compatible radios from other manufacturers, as long as they use the same pin out. The rest of this article will give you a working setup, but will key PTT for the bottom display only.

The top display is keyed using the tip of the 3. See this page on miklor. This left me with 4 conductors, of which I only needed three. I wired the RTS, DTR, and digital ground to a DB-9 female connector, with a little bit of electrical tape to keep the cable shield from causing any problems.

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Then wire the connections to and from PC audio in the usual manner. On the Easy Digi the polarity is not marked, but if you follow the wiring diagrams included, you will see the two negatives are in the center, and the positives are on the outside.

I marked them myself with a silver marker to help during assembly.

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For this I used two 3. Next I took a 3. UV series owners onlythis is where you want to connect the tip instead of the shield if you want top display PTT instead of bottom display PTT. Next, I took an Arduino jumper and cut it in half. Put one pin in mic ground, one pin in PTT ground, and twist the free ends together. Tin the twisted end, and solder and snip the excess pin leads. You could use any suitable wire for this jumper. It should end up as shown here:. The radio side of this cable needs to go down to 2.

You can use a 2. All other programs seem to work normally. Example configuration line for DireWolf:. This entry was posted on October 27,pm and is filed under Uncategorized. You can follow any responses to this entry through RSS 2. Both comments and pings are currently closed. Create a free website or blog at WordPress.

Home Disclaimer Contact Me. UV series owners onlythis is where you want to connect the tip instead of the shield if you want top display PTT instead of bottom display PTT Next, I took an Arduino jumper and cut it in half. You should have your board fully assembled now. Follow Blog via Email Enter your email address to follow this blog and receive notifications of new posts by email.

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Post to Cancel. Post was not sent - check your email addresses!Recently, I decided to set up packet radio capability for my station. Adding Winlink email capability seemed like a good thing to do. The RMS gateway station is in a facility a few miles from me, with redundant power and internet backup, and operates on the amateur radio two meter band.

TinyTrak4 with my input level adjust modification. Hooking all this up, I found I could not get a good connection to the gateway. My first thought was that it was low transmit power, but I decided to troubleshoot the entire functionality in a sensible order, and switched to monitoring APRS packet transmissions on Received packet decode was terrible.

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I know from prior experience that some packet decoders are very sensitive to input level, and I spent a lot of time fiddling with this. The first is with an external wired connection. This option is not available for most radios, including the Baofeng, so I was limited to the second and third choices. The third method used by the TT4 is to detect the presence of the tones used to transmit the packet data. I figured that this was because the radio was slow to break squelch, and the beginning of the actual data was getting chopped off.

With the squelch turned off on the radio, I was able to get a few packet decodes. I tried this with the squelch both on and off on the Icom, and had good results both ways.

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The input circuit on the TT4 is worth understanding. The schematic diagram is in the kit manual, which is available here as a PDF document.

The TT4 audio input has a DC blocking capacitor. The choices are 1. This can be seen in the following oscilloscope captures. So in theory, input signals up to 2. This pretty much matches with what I observed while using the Icom. This brings us to the first examination of the receive problem with the Baofeng UV-3R. This is the very lowest volume setting on the Baofeng, one click off of silence. This level should work with the TT4, based on what I was seeing with the Icom.

baofeng ptt circuit

Note that the scales for the traces are different. It takes almost 80 mS before the bias level settles out bottom trace. This could account for why it never decodes successfully when I have squelch enabled, but it sometimes decodes with the squelch off.

I think that it just takes too long to break squelch and settle, and loses the beginning of the packet.

Baofeng interface, now with PTT control

You can see the end of the packet data, then a very short period of low signal at the center of the imagethen noise after the transmitting carrier stops. There are also DC changes from the radio here, and it takes another mS for the input bias to settle. When the squelch is turned off on the Baofeng and audio is output all the time, there are no DC shifts, so it appeared to be only related to squelch operation more on this later.

Differences: 1. Much lower DC bias on the speaker line 2.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. If nothing happens, download GitHub Desktop and try again.

If nothing happens, download Xcode and try again.

Packet radio with Baofeng UV-5R with PTT control

If nothing happens, download the GitHub extension for Visual Studio and try again. This will reduce the amount of time required to send an APRS packet to something not obnoxious such that sending a packet to the repeater on the ISS won't stomp on other sender's transmisisons.

Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up. Branch: master. Find file. Sign in Sign up. Go back. Launching Xcode If nothing happens, download Xcode and try again. Latest commit.

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Latest commit ea3 Mar 6, You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window. Flashed the ATmega16U, it worked, taking a break for a bit. Feb 7, Added some more tasks, reordered some tasks. Updated tasks list. Mar 6,


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