Message-ID: <4F737105.6040609@iup.uni-heidelberg.de>
Date: Wed, 28 Mar 2012 22:13:57 +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: <8CEDA76E04F70F0-1B04-5AAF@webmail-d082.sysops.aol.com> <1332956278.2450.15.camel@gerhard-desktop-acer> <4F7350EA.6080602@freenet.de>
In-Reply-To: <4F7350EA.6080602@freenet.de>
Subject: Re: VLF: DF6NM on 8970.002
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org


Hi Wolf, your last mail came through! So it must be local QRM ;-)

73, Stefan

Am 28.03.2012 19:56, schrieb wolf_dl4yhf:
> Hello Gerhard, Markus, and the group,
>
> This is most likely old hat, and been tried before, but maybe...
>
> Below a certain current density, the discharge into air may be "dark" 
> but still dark enough to produce heat, or even chemical reacions 
> (think about how ozone is produced: a discharge with very low current 
> density).
> I recently visited the local garden store, and those nice giant hollow 
> polished steel spheres caught my eye. May be worth to use two of them 
> as the 'end caps' of the wire antenna, to reduce the field strength at 
> the end of the wires ? These spheres are very light-weight due to 
> their thin walls, only a few hundred grams even for the monster-sized 
> ones.
>
> All the best,
>    Wolf .
>
>
>
> Am 28.03.2012 19:37, schrieb Gerhard Hickl:
>> Hello Markus, VLF!
>>
>> This might be true at least partially. In my setup, I'm observing
>> acoustic noise without the presence of corona discharges. I observed my
>> antenna in the dark, running about 600mA of antenna current. There was
>> no "corona" visible but the noise was clearly heard. Definitely it was
>> not emitted by the loading coil behind the house but I have got the
>> impression, that it was emitted by the ends of the top-load wires. One
>> of those ends is even 50m away from the coil, in my neighbours garden.
>> When walking from my property (where I also have an end of a top-load
>> wire) up to his plot of land, the noise is decreasing and then getting
>> louder again under the end of the wire on his property.
>>
>> In this respect I agree with you. The sound is emitted by the ends of
>> the top-load wires but it doesn't need a corona-discharge to make the
>> antenna "noisy" during transmit.
>>
>> In fact, this behaviour of my antenna is the biggest problem in
>> transmitting during warm summer (spring) days. My neighbour allowed me
>> to use one of his trees as a hook of the top-load so I can't bother him
>> with noise when he's out in the garden.....that's way more than good
>> neighbourhood could bear.
>>
>> The more I would be interested in suppressing this noise by suitable
>> measures.
>>
>> 73
>> OE3GHB
>> Gerhard
>>
>>
>>
>>
>> Am Dienstag, den 27.03.2012, 17:22 -0400 schrieb Markus Vester:
>>> It's a beautiful night! At 20:25, I have started up a straight carrier
>>> on 8970.002 Hz (DHO locked). If all stays well I will leave it on
>>> until after sunrise.
>>>
>>> An interesting observation on the side: In the first few minutes, I
>>> drove the amp up to 400 mA antenna current. A little corona became
>>> visible near the ends of two of the three topload wires - it wasn't
>>> very bright, not unlike 3rd magnitude stars when viewed from the
>>> ground 10 m below. But the 9 kHz sound from antenna itself could be
>>> heard quite loudly, which is a potential cause for neighbourhood
>>> trouble.
>>>
>>> Then I reduced the drive to 350 mA where the corona disappeared
>>> completely. So did the noise, the antenna became absolutely quiet! All
>>> that was left was a little noise from the coil in the dustbin on the
>>> balcony, and the transformer indoors. Thus the predominant cause for a
>>> squeaking antenna must be corona. The fact that it can be heard at 9
>>> rather than 18 kHz demonstrates that the discharge must have an
>>> asymmetric dependence on the voltage polarity.
>>>
>>> At the same time, wideband electrical noise on the nearby LF grabber
>>> antenna went down by 20 dB.
>>>
>>> BTW If you like you can actually read my VLF frequency from an alias
>>> line on the LF TA grabber: It is created by the 24th VLF harmonic,
>>> intermodulating with DCF 77, thus appearing on 24 x 8970.002 - 77500 =
>>> 137780.048 Hz.
>>>
>>> Best regards,
>>> Markus (DF6NM)
>>
>>
>>
>>
>