[amsat-bb] FT-991A Transmit Interference

[Paul Andrews]

This is very likely a IM3 issue.  Shielding won't help.  You need to
surpress the IM3 on the 2M output.

I have a torpedo sized cavity filter that knocks down the IM3 by 40 dB and
I see no desense.

GL - 73 - Paul - W2HRO

On Fri, Aug 3, 2018, 12:11 Patrick STODDARD (WD9EWK/VA7EWK) <
amsat-bb at wd9ewk.net> wrote:

> Zach,
>
> The RF shielding isn't over components on the circuit board. The
> inside of the RSP1A's plastic case has metallic paint which serves
> as the shielding. From the same review you cited at:
>
> https://www.rtl-sdr.com/a-review-of-the-sdrplay-rsp1a/
>
> "Like the RSP2 the plastic case is now spray painted with metallic
> paint on the inside. This works almost as well as a full metal
> case to shield from unwanted signals entering directly through the
> PCB, instead of through the antenna. We do still notice some
> leakage making its way in through the coax shield, but it is
> relatively minor with the shielding."
>
> I have used my RSP1A to receive satellite downlinks, and have not
> experienced issues as VA3ASE mentioned. I'm not using an FT-991 or
> FT-991A, but use a variety of other radios (HTs, IC-2730A, FT-817,
> TM-D710G) for the uplink side of my station with the RSP1A and a
> tablet with HDSDR for the downlink.
>
> 73!
>
>
>
>
> Patrick WD9EWK/VA7EWK
> http://www.wd9ewk.net/
> Twitter: @WD9EWK or http://twitter.com/WD9EWK
>
>
>
>
>
> On Fri, Aug 3, 2018 at 3:50 PM, Zach Metzinger <zmetzing at pobox.com> wrote:
>
> > On 8/3/18 10:07 AM, VA3ASE wrote:
> >
> > Zach my understanding is that the RSP1A is still shielded despite the
> >> plastic box, but I actually have access to an RSP2pro in a metal case
> that
> >> I can try out as well. I've never heard of a USB EMI filter before, I'll
> >> look into that. I'm using a quality TrippLite USB cable with molded
> chokes
> >> at each end.
> >>
> >
> > Hello Alex,
> >
> > Based on the pictures shown in the review located at the following URL,
> > there does not appear to be any shielding over any RF component.
> >
> > https://www.rtl-sdr.com/a-review-of-the-sdrplay-rsp1a/
> >
> > --- Zach
> > N0ZGO
> >
> >
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