Hi Greg,
I think it has to do with preselection and dynamic range.
Most inexpensive (don't want to call them "cheap") SDR receivers for
HF suffer due to strong broadcasters somewhere in the HF/MF bands (so
the built-in preselection in your Omni helps) and can get overloaded
by in-band signals as well (so the built-in attenuator and part of the
AGC chain protects the SDR receivers as well, provided that the AGC
drives more than just the IF circuits).
I have a RTL-SDR dongle sampling the 9 MHz IF in a Corsair II, in
direct sampling mode, just before the roofing filters. I can see more
than 300 kHz at a given time, which is more than enough for my
purposes. If you need to "see" the entire HF spectrum then it is a
completely different story.
73,
Carlos VK1EA
On 8/31/18, Greg S via TenTec <tentec@contesting.com> wrote:
> Yes, but it can tune much HIGHER. Just so limiting using it as an I. F.
> Monitor only, in my eyes.
> Strokes for folks, I guess.
> Good luck getting it all sorted out.
> Greg, KC8HXO
> --------------------------------------------
> On Thu, 8/30/18, Bob McGraw K4TAX <rmcgraw@blomand.net> wrote:
>
> Subject: Re: [TenTec] TT omni vii if port problems
> To: tentec@contesting.com
> Date: Thursday, August 30, 2018, 6:39 PM
>
> Largely because the dongle being
> used does not tune below or have
> adequate
> sensitivity below about 20 to 25 MHz. The IF in the
> Omni VII
> is about 70 MHz.
>
> 73
>
> Bob, K4TAX
>
>
> On 8/30/2018 3:31 PM, Greg S via TenTec
> wrote:
> > I highly recommend this mod, to
> allow full use of the SDR. Not sure why anyone would use the
> I.F. these days, honestly.
> > Greg,
> KC8HXO
> >
> --------------------------------------------
> > On Thu, 8/30/18, Bob McGraw K4TAX <rmcgraw@blomand.net>
> wrote:
> >
> > Subject:
> Re: [TenTec] TT omni vii if port problems
> > To: tentec@contesting.com
> > Date: Thursday, August 30, 2018, 12:59
> PM
> >
> > Do you
> have any application
> > associated with
> the device controlling the
> > radio?
> Also, if you are tuning to a signal
> >
> using the dongle, it may be
> >
> incorrect with
> > regard to frequency
> thus this puts the Omni VII off
> >
> frequency. You may need to perform a
> > Master Reset on the Omni VII.
> > There are
> > known
> some software applications which do shift the VFO,
> > although not displayed as such on the
> radio.
> > This will produce and off
> > frequency
> >
> condition.
> >
> >
> I had a a 3
> > Rivers Dongle on my Omni
> VII and it worked OK. The
> >
> software was a major pain in the posterior to
> > get running correctly.
> > Finally I
> > wrote
> it off as a learning experience. I then purchased
> > an
> > SDR Play
> RSP-1 receiver and downloaded
> > free
> HDSDR software. All issues
> >
> resolved
> > and it works great.
> >
> > I also
> > made the mod to the Omni VII for the
> 2nd receiver which I
> > find
> > works even better. With the SDR
> Play
> > I can see signals on the
> entire
> > band, thus
> > not limited to the IF bandwidth. That
> works great as
> > well.
> >
> > 73
> >
> > Bob, K4TAX
> >
> >
> > On 8/30/2018 11:17 AM, denton
> > sprague wrote:
> >
> > Hi all…I installed an
> > if port
> output as per 3 rivers TT omni vii dongle
> > instructions to enable me to use a pc
> as a spectrum monitor.
> > it works fine
> on receive but the minute I transmit, am told
> > I am off frequency.
> > > I am thinking of
> > either installing a relay that will
> disconnect the
> > dongle’s if input
> during transmit…
> > >
> > Anyone else have a different work
> around?
> > >
> >
> _______________________________________________
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> > >
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> >
> >
> >
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