Message-ID: <4E3D54DE.1000202@iup.uni-heidelberg.de>
Date: Sat, 06 Aug 2011 16:51:10 +0200
From: =?UTF-8?B?U3RlZmFuIFNjaMOkZmVy?= <Stefan.Schaefer@iup.uni-heidelberg.de>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3
MIME-Version: 1.0
To: rsgb_lf_group@blacksheep.org
References: <4E3B1BFD.5090807@iup.uni-heidelberg.de> <4E3B2EA3.90003@iup.uni-heidelberg.de> <26D9EBB1476B467E9E02C10B3FACC2C8@PcMinto>
In-Reply-To: <26D9EBB1476B467E9E02C10B3FACC2C8@PcMinto>
Subject: Re: LF: Re: CW sked on 137 friday morning?
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: quoted-printable
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
X-AOL-SCOLL-URL_COUNT: 0  
x-aol-sid: 3039ac1d61854e3d55e40430
X-AOL-IP: 195.171.43.25
X-AOL-SPF: domain : blacksheep.org SPF : none


Hello Minto,

Am 05.08.2011 23:59, schrieb Minto Witteveen:
> Stefan (et al),
> I did listen this morning on 136.8 to see if I could copy you or any=20
> other station, but the results were disappointing: I heard nothing.
Thanks for trying anyway.
Well, i was in QSO mit PA0A who must be close to you, so something must=20
be wrong...
> I have an FT817 and an FT879 as possible receivers. Both are not known=20
> for their superb receive quality but with a 5 pole filter + additional=20
> amplification I got them to work quite reasonable on 500 KHz.
> Both rigs are very bad on LF. Very insensitive and prone to heavy=20
> intermodulation, especially at night.
> So this weekend I build a quick-and-dirty 4 MHz uptransverter with a=20
> SA612. The Yeasu=E2=80=99s are much more sensitive at these frequencies=
. To=20
> keep strong LF and MF stations from causing intermodulation had to add=20
> 7-pole Chebishev filter between a PA0RDT miniwhip and the transverter.=20
> For details see:
> http://www.pa3bca.nl/index.php?option=3Dcom_content&view=3Darticle&id=3D=
23&Itemid=3D17=20
>
Looks good, that page.
> This morning (when there was almost no man-made QRM form TV=E2=80=99s e=
tc)=20
> DCF39 was S9+30dB on the 897. On (4000+) 136.8 the noise was S 5 with=20
> the 2.4 KHz SSB filter, and S1 with the 500 Hz filter.
> Now I know that the FT=E2=80=99s S-meter is not very reliable, especial=
ly from=20
> S1-S9. But between S9 and S9+40 it is =E2=80=9Creasonably=E2=80=9D accu=
rate.
If you use SpecLab for receiving, you directly get the signal level in=20
dB (i.e. dB below full scale of the ADC). Then you can measure the DCF39=20
level and the noise floor level. Meanwhile i am getting DCF39 at 80 dB=20
above noise in 488 mHz with the RX loop.
> As far as I could find out DCF39 generates 50 KW ERP. If Stefan=20
> generates 0.5 Watt ERP (My guestimate)
Should be a few dB more ;-)
> and the distance to my QTH is approximately the same, I would expect=20
> Stefan to be 50 dB weaker. But 50 dB below DCF39 would still be above=20
> the noise floor? So why didn=E2=80=99t I hear him (or for that matter, =
PA0A=20
> who is closer and has 1 Watt ERP).
Maybe the S meter is worse than you think, maybe.
> Before I finish my 1 kW TX I first have to make sure that I will be=20
> able to copy any other station.... :-)
I had the same problems. But i immediately received DF6NM audible. So if=20
you don't even receive PA0A, there seems to be lack of sensitivity.
What happens with the noise floor if you disconnect the PA0RDT? How many=20
dB does the noise floor decrease?
Can you do /p tests?

Don't expect to much activity on LF. But there are new stations coming=20
on the band and you could be one of them and help making the band alie=20
again.

CU there :-)

73, Stefan/DK7FC