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UV-B5  UV-B6
 
Operation on 220MHz
 
OTA and Lab Tests
 
John K3NXU and Jim W6YXY
 

 
Periodically, the question arises regarding potential of converting the UV-B5/B6 series  for operation on the 220MHz band. Below are the results of this conversion, both in a lab environment and Over-the-Air.
 
 
Intended Operation Range
 

As you're probably already aware, the specified range of this radio is 136-174 and 400-480.  Using CHIRP software, you are allowed you to extend the Frequency Entry range to 128-270 and 400-520MHz.  The question that remains is the actual operating capability within that range.
 
 
Testing of the Extended Range

Test 1 - Over-the-Air
 
This was run using my Baofeng UV82X and my UVB6 test radio.
The Power Levels were verified as UV82= 4.2W, UVB6=2.5W (using Telewave 44A). All tests were run using the same Workman 220-10 antenna on both so there was no advantage of one over the other.

The test repeater was approximately 10 miles away.
The signal with the UV82X was nearly Full Quiet on both RX and TX.
When I switched to the converted UVB6, both RX and TX were extremely noisy, where there should have been only a slight difference at best. (2 db)

I checked the UVB6 on a frequency counter to confirm my suspicion.
With the UVB6 set to 223.5MHz, the counter immediately locked up on 447.0MHz.
 
My testing showed the internal filtering prevents reliable 220 operation. Although a few hundreds mW were on 223.5MHz, the greater majority of signal was on 447.0 MHz, not the intended frequency.  For this reason, rather than radiate interference on another band, I personally elected not to use mine on 220MHz.
 
 
Test 2 - The Lab
 
In another series of tests run by Jim Keller W6YXY, a similar UV-B5 was altered to accept 220MHz programming. He had taken his to a lab to see what things looked like on a spectrum analyzer.

When transmitting a signal on 220MHz, the display showed one main spike, which was the intended frequency, and quite a few little spikes (spurs) around it.  When he looked at the first harmonic in the 440MHz band there was only one single spike that was much stronger than the fundamental frequency signal.

His initial thought was it would be cool to use the radio on 220MHz but, after the tests decided he wouldn't be doing it based on these test results.

Below are the Spectral Plots for these tests.
 
Baofeng Spectral Plots on 220

 
Conclusion
 
Tests shows that 220MHz operation is not recommended with a UVB5/B6.  The internal filtering is doing exactly what it was intended to do.  Suppress unwanted RF outside its intended operation range to avoid unlawful interference.  It would be a lot cheaper to buy a radio intended for 220MHz than pay an FCC fine due to interference.

The results above indicate that the UVB5/B6 was not designed to be a tri-band radio.

The only currently available Baofeng for 220MHz operation is the UV-82X. This radio has the same characteristics of the UV-82, with a factory specified range of 136-174 and 220-260MHz.
 

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