Perfect module (D751749ZHH)

[Serg l]

Thanks for looking into this. I was trying to figure this out by looking at
the pictures, and it appeared to me that there is an unpopulated RX3.

I think it is pretty minor modification for an experienced tech, so it can
be converted to region specific bands as needed.



On Tue, May 28, 2019 at 10:50 PM Mychaela Falconia <
mychaela.falconia at gmail.com> wrote:

> Serg wrote:
>
> > Seems like nice module, I see that it has at least 3 variants A/B/C,
> could
> > not find a good document in English what is the difference.
>
> It can be seen from Songbosi's huawei.jpg picture that the B version
> is Calypso-based, whereas the C version is LoCosto-based.  Back in 2013
> I made the decision to base my work on the Calypso chipset rather than
> LoCosto, and this decision is now enshrined in the FreeCalypso project
> name - and I am not switching.
>
> If Serg or anyone else feels like playing with LoCosto, you are on
> your own.
>
> > Also seems like it has dual band SAW filters installed in B version, so
> > additional components need to be installed in order to make it tri-band
> and
> > following the re-calibration process executed.
>
> Looking at Songbosi's huawei3.jpg picture (detailed view of the
> component side of the board), it can be seen that the board CANNOT be
> modified from dual-band to triband.  One can remove DCS band support
> and add PCS band support in its place, but it is not possible to have
> DCS and PCS on the same board without redesigning the PCB.  The antenna
> switch only has two Rx paths coming out of it, not 3, and as you can
> see in the photo, each goes through what looks like a series capacitor
> acting as a high-pass filter.  The layout is done in such a way that
> the series capacitor for the high band Rx path can be populated in one
> way for DCS and in another way for PCS, but you still can't have both
> at the same time with this PCB design.
>
> To Songbosi: for my experimentation purposes I don't mind getting a
> dual-band modem module without PCS band support: even though I am
> located in USA-occupied California, I won't be operating the modem on
> live airwaves here, instead I do all GSM RF testing on my CMU200
> instrument, and with that instrument I can operate in any band in my
> lab.  I would indeed be interested in getting a few of these modules
> for experimentation and further reverse engineering, and Songbosi's
> asking price is very cheap, but I would really need a breakout board
> for the interface connector.
>
> M~
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