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Date: Fri, 11 Dec 2009 13:51:54 +0000 (GMT)
From: ALAN MELIA <alan.melia@btinternet.com>
To: rsgb_lf_group@blacksheep.org
In-Reply-To: <38A51B74B884D74083D7950AD0DD85E828AC15@File-Server-HST.hst.e-technik.tu-darmstadt.de>
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Subject: Re: AW: LF: "Gain" between qrss3 and qrss10?
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Hi Johan some off air tests done between Dave G3YXM and myself seemed to=
 confirm those theoretical figures quite nicely. Posibly still on Dave's=
 web site. I believe others have found the same too. Lyle Kohler K0LR (?)=
 did some similar tests in the States which used to be on his web site.

Alan G3NYK

--- On Fri, 11/12/09, Stefan Sch=E4fer <schaefer@hst.tu-darmstadt.de> wrot=
e:

> From: Stefan Sch=E4fer <schaefer@hst.tu-darmstadt.de>
> Subject: AW: LF: "Gain" between qrss3 and qrss10?
> To: rsgb_lf_group@blacksheep.org
> Date: Friday, 11 December, 2009, 13:18
> Thanks Johan for the qualified
> answer!
> With the receiver bandwidth, do you mean the bandwidth of
> e.g. the argo programm or of the real receiver, say the
> ic706?
> I use a K2 with a bandwidth of 50Hz (not very sharp edges),
> which is relatively norrow compared to the most standard CW
> filters in standard HF-TRXs. Since I can=B4t reduce it even
> more and the others as well, it would be no advantage to
> reduce the speed. So I think you mean the bandwidth of e.g.
> argo? Right?
> Tnx!=20
> Stefan/DK7FC =20
>=20
> -----Urspr=FCngliche Nachricht-----
> Von: owner-rsgb_lf_group@blacksheep.org
> [mailto:owner-rsgb_lf_group@blacksheep.org]
> Im Auftrag von Johan H. Bodin
> Gesendet: Freitag, 11. Dezember 2009 13:55
> An: rsgb_lf_group@blacksheep.org
> Betreff: Re: LF: "Gain" between qrss3 and qrss10?
>=20
> Hi Stefan,
>=20
> > Or isn't it possible to give such a relation?
>=20
> Yes, it is not only possible, it is in fact quite simple:
> When the speed is reduced by a factor K, the information
> bandwidth is
> also reduced by the same factor. This allows you to use a
> receiver
> bandwidth which is K times narrower without missing any
> information. The
> nice thing is that the noise power passing through this
> bandwidth is
> also K times smaller - The S/N ratio has improved K times
> (or 10*log(K)
> dB if you prefer). In other words, you can reduce the TX
> power by the
> same factor K and still enjoy the same SNR (if RX BW is is
> also made K
> timer narrower).
>=20
> In visually received QRSS, the receiver bandwidth is equal
> to the RBW,
> the "resolution bandwidth", which is approximately equal to
> the FFT bin
> width (one pixel on Argo).
>=20
> QRSS30 is 10dB more efficient than QRSS3, in theory at
> least.
>=20
> 73
> Johan SM6LKM
>=20
> ----
>=20
> Stefan Sch=E4fer wrote:
> > Dear LF,=20
> > Does anybody know about the "gain" between QRSS3 and
> QRSS10 or QRSS30? I mean, if the noise in both cases is
> equal, how much can I reduce my tx pwr when switching from
> qrss3 to qrss10? Or isn't it possible to give such a
> relation?
> > And: Was there ever a TA QSO in QRSS3?
> > I am new on the reflector, sri ;-)
> >=20
> > Stefan / DK7FC
> >=20
> >=20
>=20
>=20
>=20