UmTRX preselector frontend updae

Andrey Sviyazov andreysviyaz at gmail.com
Fri Aug 24 13:27:19 UTC 2012


Hi all!

> As far as I understand, the IF frequency should be 360 MHz as the UmSEL
> uses
> > the TB0130A IF SAW filter. Its center frequency is 360 MHz.
>

Yes, IF freq can be 360MHz (TB0130A) or 400MHz (TB0448A), matching
components there is for both variants (C32/C38, C46/C51).


> > By the way, why do you say it would be a problem if IF was above 380 MHz
> ?
> > Because of interferences ? In this case, would it still be problem if we
> > install the UmTRX + UmSEL boards inside an enclosure ?
>
> Well, the original question was from Harald, but the concern was with
> interference, yes.
>
I thought about these well known problems like strong mirror (image) freq's
with their interfer's, direct passthrough, LO-ANT emission and so on.
So, month ago I made measures of RF SAW filter TA1003A (see pics here).
Actually, I chose quite typical method - additional highpass filter  (Z6 -
HFCN-740+).
I hope it can help to avoid most of those low-frequencies problems.
It will be much better if Taiyo Yuden RF filters would be used (those
filters also known as Fujitsu brand).


> I think it depends on the type of enclosure we use. Andrey should be
> able to comment here.
>
Yes, of course, tower-mounted enclosures should be not only IP65, but also
EMI isolated.

Best regards,
Andrey Sviyazov.
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