[amsat-bb] Protecting SDR

[Paul Stoetzer]

I've used my AirSpy Mini and FCD+ without any protection on the input
without any damage, but your mileage may vary!

73,

Paul, N8HM

On Fri, Jan 11, 2019 at 12:55 PM Rolf Krogstad <rolf.krogstad at gmail.com> wrote:
>
> I use a diplexer, such as the MFJ-916B or equivalent, and it provides
> enough isolation of the 2 meter signal to prevent problems.
>
> Rolf    NR0T
> EN34
>
>
>
> On Fri, Jan 11, 2019, 11:14 AM Ryan Noguchi via AMSAT-BB <amsat-bb at amsat.org
> wrote:
>
> >  Is a transmit/receive switch necessary, or would a simple duplexer
> > suffice? Something like the MFJ-916B offers 55dB or better isolation, and
> > fairly low loss (0.2dB). It's a lot cheaper and more convenient to set up.
> >
> > My SDRPlay RSP1A arrived yesterday and I got it and my FT-857D working
> > with CAT control using SatPC32 last night. I haven't worked a pass with it
> > yet, though; maybe this weekend. The RSP1A is rated for 0dBm continuous,
> > 10dBm momentary. The antenna is a dual-band Elk in the attic on a TV
> > rotator, so there is no benefit of interantenna isolation. If I assume the
> > duplexer's spec value of 55dB isolation, that would attenuate even 250W
> > input down to less than 0dBm, correct? Patrick WD9EWK had commented on the
> > subject of SDR protection in a QRZ.com posting, and has used a duplexer
> > instead of a T/R switch with his SDRPlay SDR:
> > https://forums.qrz.com/index.php?threads/kenwood-ts-2000-in-full-duplex-mode-on-single-coax-line.605225/#post-4613865
> >
> > Would love to know if my math is wrong, if the RSP1A's spec isn't
> > trustworthy, and/or if there are any other considerations that make a
> > transmit/receive switch better (or necessary) than just a duplexer, before
> > I let the magic smoke escape.
> >
> > Thanks and 73, Ryan AI6DO
> >
> >     On Friday, January 11, 2019, 8:31:34 AM PST, saguaroastro <
> > saguaroastro at cox.net> wrote:
> >
> >  Kevin,
> > I've be looking at this. MFJ-1708. There are several versions. So look the
> > up on Hro to compare
> >
> >
> > 73Rick Tejera (K7TEJ)Saguaro Astronomy ClubWww.saguaroastro.orgThunderbird
> > Astronomy ClubWww.w7tbc.org
> >
> > -------- Original message --------From: Kevin Zari <kk4yel at gmail.com>
> > Date: 1/11/19  06:40  (GMT-07:00) To: amsat-bb at amsat.org Subject:
> > [amsat-bb] Protecting SDR
> > For those of you with an SDR dongle, for example the Funcube Pro +,  how
> > do you protect it from not being damaged by TX energy? I’m thinking of
> > hooking mine up to the 70cm antenna in my M2 LEO pack while I TX on the 2m
> > antenna and was afraid I’d overload the SDR. I see folks using them for
> > their RX on linear birds, so I’m just wondering how you have them hooked
> > up.
> > Thanks in advance for your advice.
> >
> > -Kevin (KK4YEL)
> >
> >
> >
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> _______________________________________________
> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. Opinions expressed
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> Not an AMSAT-NA member? Join now to support the amateur satellite program!
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