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