[amsat-bb] Re: Very Interesting Radio - Possible Sat Use (maybe not)

Geert Jan de Groot pe1hzg at amsat.org
Fri Jan 13 03:00:24 PST 2012

> I purchased an interesting radio that might be an inexpensive way to
> operate full duplex on the FM sats.
> The radio cost $65 including shipping and all accessories. It runs 2W on
> both 2M and 70cm. It has
> almost all the bells and whistles you would expect on a dual band handi. 99
> memories - tone squelch ...
> http://www.tomdoyle.org/UV-X4.jpg

There have been various postings and publications in QST and Funkamateur
about the brother of this radio, the Baofeng UV-3R, and it's very poor
harmonics filtering on the 2m band. Harmonic suppression was something
like 15-20dB.
I recently measured an UV-3R mark 1 (single frequency on display)
and confirmed that the very poor filtering was indeed the case.

Since these things transmit from 136 - 174 I tuned frequency a bit
and found that suppression is OK at 165 MHz and above, and gets worse
as the frequency goes down. On 136 MHz (on which I don't transmit
except on a dummyload of course), I found that harmonic suppression
was *negative* in some cases. Some of the publications confirm this,
so my measurements are sound and it's not an incidental case.

On request of the owner, I did the "capacitor mod" (adding a capacitor
to the lowpass filter) and found that the suppression was still inacceptable.

I purchased an UV-3R mark 2 (dual frequency on display) and established
that while it was "mark 2", the harmonic suppression was as poor as
a Mark 1 radio. I have not voided the warranty yet on this radio 
to do the capacitor mod on the Mark2 radio, but I'm not hopeful.

While some people claim that "it may pass the specs because the Mk1 radio
comes with separate antennas for VHF and UHF", the mark2 comes with 
a dualband antenna and for sat work, with an Arrow antenna or similar, 
harmonic attenuation of the antenna is nonexistant - we sat hams use 
good antennas!

Mail sent to the manufacturer address in the manual on this issue 
remains unanswered.

The Dutch regs specify '-36 dBm or -60 dBc, whichever is highest'
and this radio doesn't even come close. FCC regs may be less tight,
but I think our transmissions should be to the highest standards
and frankly, this radio doesn't come close.

My conclusion so far is that the thing may be good enough for listening,
but when you want to transmit then this radio is only useful if your
table tips and you need something to remedy that, but not for
making QSO's.

I have not measured the UV-X4 but have been told the internals are
the same - the controls are in the same position, in any case.


Geert Jan PE1HZG

PS: the separate charger does not have any protection circuitry
in it and depends on the protection circuitry in the battary itself
to charge (and protect) a dangerous LiIon cell. 
Personally I would not use this unless I have it in sight and
a way to remove power quickly - these cells are temperamentful 
when overcharged, and the battary protection circuit is not intended 
to replace a correctly designed charger protection circuit..

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