From: Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Date: Wed, 1 Dec 2010 09:21:04 +0100
Thread-Topic: LF: MF_Beacon DI2AF is running in WSPR_Mode
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Subject: RE: LF: MF_Beacon DI2AF is running in WSPR_Mode
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Hello Jan,

the coil that troubled me last night is the elevated loading coil. It is=
 at the top of the vertical section and its function is to increase the av=
erage current through the vertical section, and thus the radiation resista=
nce. As it is hanging at the topload wire it causes some "sag" what is not=
 so good. Therefore the coil is contructed for minimal weight. It is wound=
 on a plastic 1 liter "yogourt box" with no additional protection of the=
 wire. Advantage is it's weight (only 190 gram for a 200uH coil with a Q=
 of 180 !). Disadvantage is that it detunes the antenna when wet, but as=
 I do not transmit when raining (due to arcing) and it dries very rapid up=
 there, it is no real problem. But  these days the coil wss covered with=
 a very thin ice layer that detuned the antenna so I had t retune the load=
ing coil at the base. During my QSO with Louis I noticed that the antennac=
urrent was going down. When I pointed the flashlight at the loading coil=
 I saw water dripping of, so the ice was melting (despite an outside temp=
 of -5C).
Reactance of the 200uH coil at 500kHz is 628 Ohm. At a Q of 180 the loss=
 resistance is 3.5 Ohm. Last night I was running 200W out, resulting in an=
 antenna current of 2.2A. The heat production in the loading coil was thus=
 17W during "key down", so about 8W average during my transmission.  And=
 probably the ice lowered the Q, so it there be even more loss. Anyway, it=
 was sufficient melt the ice.

73, Rik  ON7YD

________________________________________
Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.or=
g] namens pa3abk [pa3abk@kpnmail.nl]
Verzonden: woensdag 1 december 2010 0:53
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: Re: LF: MF_Beacon DI2AF is running in WSPR_Mode

Thanks Rik
Some time ago I did the  TS440 mod for removing the 20dB att, but
restored the original situation immediately.
It's useless...  So much shit coming in.

Heard yr QSO this eve with Louis
What a luxery problem... Your antenna coil is producing so much heat it
melt the snow!
Anyway your sigs were vy strong here.

Jan/pa3abk


Op 30-11-2010 9:07, Rik Strobbe schreef:
>
> /I'm using a TS440 which can't switch off the AGC by nature. So
> reduced the gain and turned up the LF gain to get a proper feed for
> the WSPR decoder./
>
> //
>
> Jan,
>
> I am using a Kenwood TS440 too. I find it a very good RX, both on
> 137kHz as 500kHz.
>
> It has by default a 20dB attenuator activated between 500kHz and
> 1.6MHz. But so far I found no need to remove that, as I am using the
> TX antenna (lazy-L, 11m high, 25m long) also for receiving.
>
> For receiving DI2AN's WSPR I used the 10dB extra attenuator and then
> reduced RF gain for a stable s-meter. The soundcard is connected to
> the back audio out connector as, the level there is independent of the
> LF gain.
>
> 73, Rik  ON7YD - OR7T
>