Baofeng Building a Baofeng repeater

[W2NOS]

I got my Technician license in March 2026 with 34 out of 35 correct on the exam. Now I’m attempting to build a repeater from two spare Baofeng UV-5R Mini HT’s, two Abbree AR-805S antennas, a Baofeng PB6 radio case, and a relay cable I got from Amazon. To what frequency should I program each radio so the pair functions as a repeater with the microphone input of one unit set to take audio input from the speaker output of the other through the relay?

 

[mmckenna]

Oh, there's so much more to this than you expect.

But, it's a place to start.
What band are you going to use these on? That matters.
Ham's like to have their repeaters coordinated, so if you have not coordinated with your state/region repeater coordinator, you may want to research the temporary repeater pairs that are often set aside for this sort of thing. Picking random frequencies may not go over well with your local amateurs.

Once you get that sorted out, get the radios programmed, and then realize that your repeater doesn't work due to massive receiver desense, come back and we can talk about repeater controllers, antenna separation and duplexers.

 

[nd5y]

You're wasting your time. It won't work. CCRs like Baofengs don't have COS outputs so whatever cable you wasted your money on won't work properly. It probably uses VOX. That will never work properly. Even if it did the receivers in Baofengs are so bad you will never have enough isolation with two antennas that close together.

As far as what frequencies to use you should check 97.205 for the frequency ranges where repeater operation is allowed, then check your state or regional frequency coordinator for your state/regional band plan.

 

[RFI-EMI-GUY]

Ohh boy.... You would be far better off building a "parrot" aka simplex repeater. Far higher chance of success with minimal expense: Example Argent Data Systems ADS-SR1 ADS-SR1 Simplex Repeater – Argent Data Systems

 

[W2NOS]

I was planning to use either 144 or 440 band for my repeater and it would be one of those lunchbox types so I didn't think it would require coordination.

 

[AutumnInu]

you would probably be better off building a simplex repeater from something like an Icom with stouter isolation. and use something like a Raspberry Pi with a sound card and proper software like PeaterPiPyr and a J pole or something depending on what frequency and band you chose. However, it would be an interesting side project to try and make a functional repeater out of Baofeng parts though! I'd be interested to see the results of that project!

 

[GettingOld]

I got my Technician license in March 2026 with 34 out of 35 correct on the exam. Now I’m attempting to build a repeater from two spare Baofeng UV-5R Mini HT’s, two Abbree AR-805S antennas, a Baofeng PB6 radio case, and a relay cable I got from Amazon. To what frequency should I program each radio so the pair functions as a repeater with the microphone input of one unit set to take audio input from the speaker output of the other through the relay?

The best and shortest answer to your question is.......BAD IDEA!

 

[blueline_308]

Just search YouTube for detailed how to's on what you are attempting. May not be "Ham" quality, but fun to experiment with and learn.

 

[mmckenna]

I was planning to use either 144 or 440 band for my repeater

OK.
On the 2 meter band, standard* repeater offset is 600KHz. Depending on which frequency you pick, your input would either be 600KHz above or 600KHz below the output.

On the 70 centimeter band, standard* repeater offset is 5MHz. That can either be 5MHz above or below depending on the coordinator.

You'll have more room to work and more separation between your frequencies if you do this on the 70cm band.

and it would be one of those lunchbox types so I didn't think it would require coordination.

OK, look at your local bandplans (search on repeater listings for your state) and see if they have any temporary repeater pairs set aside, or 'test' pairs you can use for this.


As for everything else, people are mostly trying to help you. This repeater, as you have it planned, is not going to work well, if at all. The transmitter will be too close to the receiver and it'll overload it, making the repeater deaf and providing range measured in feet or yards. Worst case, transmitting at full power right next to a receiver can damage the receiver. $20 radio, so no big loss, but learn from the mistakes of others.
Lots of TX and RX antenna separation will help a bit, but range is going to be exceedingly short.
The duplexer is the right tool for the job, but those are a complex device and take some good test equipment to set up.

Doing a cross band repeater, as in an input on 2 meter band and an output on 70 centimeters will give you better performance and might actually work well enough to be useful. But, still, keep your TX and RX separated by a few feet to keep from hurting the radio.

This will be a good experiment to learn some new things, but don't expect this to be a long range repeater. This is a hobby, and a place to play, so go for it, but don't expect a miracle out of this setup.





* Regarding the use of the term "standard":
"The nice thing about standards is that there are so many to choose from." This is where frequency coordination comes in. Making sure your repeater gets along with all the others. You do not want your repeater output transmitting on the input of another. Playing well with others is part of the hobby. If you are not going to coordinate, then make sure you keep any emissions inside the amateur radio band, and you don't annoy other users. Hams can be a cranky and vengeful lot. You can use different input/output offsets to help your lack of duplexer, but you'll not get enough spacing to make a real difference. For short tests, you'll likely not upset other hams, but if you plan on playing with this long term, make sure you pay close attention to the established band plans and you are not stepping on satellite sub bands, CW, SSB, or other slices of dedicated spectrum.

 

[EAFrizzle]

Some BTech DMR models have a simplex repeater built-in. There's a GMRS HT out there with one as well.

If you're wanting a lunchbox-sized portable repeater that will actually work for you instead of being an experiment, you could use the native crossband repeater in many HTs and mobiles today. (Do any hams use monoband HTs anymore?) This also lets you use simplex frequencies, avoiding any territorial disputes. HT, antenna, external battery, and a box will give you something that's effective for short-range stuff.

 

[prcguy]

I tried a pair of Baofeng UV5Rs as a repeater years ago and it was a miserable failure. I had a flat pack duplexer already working from another repeater and tuned to a good 75dB isolation per spec. I used a 5MHz UHF split and it just could not work.

A typical receiver for a repeater is well shielded and tuned to frequency with some rejection at the transmit frequency. The Baofengs have neither and even with double shielded cables to the duplexer the radios cases have zero shielding and the receivers are pure dog sh*t for use in a repeater. So one failure mode is the duplexer provides adequate isolation but the signal off the antenna, even at a distance will desense the receiver blowing right through the plastic case and render the repeater useless. A Baofeng UV5R is a miracle radio where most of the radio except for audio and RF power amp are on one little IC chip. The miracle is the fact that they even work.

There is no way around this unless you put the radios in a well shielded box but your now left with well shielded dog sh*t. If the antenna is a hundred feet in the air that might reduce the desense but maybe not. But the low loss Heliax type feedline needed to get the antenna well away from the unshielded radios will cost many times what the rest of the repeater cost. Its a no win situation, just get some known radios that work well in repeater service and build it once, build it right. Otherwise be prepared for a lot of wasted time and $$ and hours of frustration with no payoff.

 

[prcguy]

Here is a test you can run to prove the desense problem. Program both your Baofengs for a local UHF repeater with 5MHz split. Key the radio with stock antenna and make sure you can hit the repeater ok. Then turn on the other radio with identical programming maybe 10ft away. Key the repeater with the first radio and see if you can receiver the repeater on the second radio while you are transmitting on the first. My bet is you cant without serious interference being 10ft away from the radio that is transmitting. Putting both radios on a duplexer is going to have the same problem using a flat pack duplexer and/or having the antenna fairly close to the radios.

 

[Smokintbird]

@W2NOS Giving all previous comments their due, an experimenter's opinions might provide a little different perspective. (Keeping in mind that these are more FUN than practical in an emergency)

• Antenna separation
  • Mounting the RECEIVE antenna to TOP of the TRANSMIT antenna with MORE than a wavelength between the two ideally
  • Mounting antennas to OPPOSITE sides of a metal plate or container aids in antenna isolation (bigger metal separator is better)
• Frequency separation
  • Receiving with a single-band radio is BETTER than with a multi-band RX radio (better internal filtering)
  • Physical radio separation is MORE important with lower price radios

I have tried:

• 30cal ammo can repeater - Cheap Chinese TX portable, Used Kenwood single band portable, Cheap "Portable Repeater Cable" with Kenwood plugs, Battery Eliminators for each radio, PL-259 elbows, PL259 antennas, Lithium battery
  • Drilled holes for antenna connectors, so the box could be hoisted into a tree on a hill for a few hours
• Nylon bag repeater - Cheap Chinese TX portable, Used Kenwood single band portable, Cheap "Portable Repeater Cable" with Kenwood plugs, Battery Eliminators for each radio, Dual band J-pole antennas, 200ft+ paracord or similar, Arborist Throw Bag, Lithium battery
  • Tied both j-poles to rope/string with vertical separation giving RX the top spot

Give something a try and see how it works!