Super Simple Way to do FLDIGI with the Baofeng HT

Had to "experiment" with a super-simple Baofeng HT FLDIGI station.  Thanks for the generosity of Scott KD5NJR for letting me try out my idea on his HT pair.

The Baofeng HTs have a 2.5 mm female connector for audio output (speaker) and a 3.5 mm female connector for microphone.  The two connectors are designed to be plugged into a "remote" mic that can be placed on your shirt or belt buckle.

3.5 mm is the standard "1/8 inch" audio connector size that we use for consumer electronics, such as MP3 players.  It is also the size used by most computer sound cards for either microphone or audio out.  2.5 mm is a non-standard size and is typically only used on cell phones.

I used two male to male adapters to complete the connection between the Baofeng HT and a SYBA sound card.  One is a 3.5 mm to 3.5 mm adapter.  The other is a 2.5 mm to 3.5 mm adapter, which can easily be found on Amazon.com.  It is important to note that both adapters are 3-pole (meaning there are three sections, two black rings).  Four pole adapters will not work with the Baofeng.

You end up connecting the 2.5 mm Baofeng connection (audio out) to your sound card microphone or line-in connection.  The 3.5 mm Baofeng connection (microphone) is connected to your sound card audio out or speaker connection.

All of this completes the plumbing, but what about push-to-talk?  That is the easiest, as Baofeng includes a "VOX" function that will key the transmitter whenever a certain audio level is detected on the microphone.  All you need to do is turn the VOX function and set the VOX level to a comfortable speaking level.  Test by speaking into the HT and adjusting accordingly.

After you get everything plugged in, start adjusting your sound card microphone and audio out levels.  Be careful not to overdrive the output, or you will get a distorted waterfall.  Same will be true if the microphone level is too high.  If you go too low, the PTT won't engage or you won't see another station's signal on your waterfall.  Always helps to have another friend that is running FLDIGI to start making the correct adjustments.

Typically I like to put an audio isolation transformer between the radio and the sound card, but this "shortcut" method will get you on the air.  Since you are running FM, there is a little more forgiveness in the waterfall, as you will not be knocking off other stations like you would on SSB.  Still, a highly distorted signal will not be copiable and will be hard on other station's ears, so try to get as close as possible to the ideal waterfall.

I ran all the way up to BPSK-1000 with good success between the two Baofeng HTs with this simple setup.

Baofeng 888 series HT connected to SYBA sound card using
male to male adapters (3.5 mm to 3.5 mm and 2.5 mm to 3.5 mm)