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Re: LF: RE: DLF 153 kHz QRT

To: <[email protected]>
Subject: Re: LF: RE: DLF 153 kHz QRT
From: "Markus Vester" <[email protected]>
Date: Sat, 20 Dec 2014 00:51:01 +0100
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References: <[email protected]> <[email protected]>,<[email protected]> <[email protected]en.be>,<[email protected]> <[email protected]en.be>
Reply-to: [email protected]
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Hi Rik, Stefan,
 
back in 2002, some of us were given the rare opportunity to use the Donebach antenna for one summer afternoon (see emails below). 
 
At the time we also considered trying 8970 Hz there. However, each of the two Donebach antennas is actually a folded coaxial monopole around a grounded central mast. The sleeve consists of a number of wires, run from the mast apex, and paralleled at a feedpoint near the bottom. Unfortunately at VLF, the radiation from upward currents in the sleeve would be almost completely cancelled by downward current in the mast. So we decided not to bother trying a relatively inefficient VLF antenna, but rather make the best of the available time on 137 kHz.
 
After some experimentation with different loading coils, we finally found out that we didn't need any, as the antenna was already perfectly matched on 137 kHz! Operating this 80% efficient radiator on a decent LF transmitter throughout a winter night would surely be a dream.
 
But nevertheless, I have to say I'm really sad to hear that AM broadcast is bound to come to an end.
 
73, Markus (DF6NM)
 

Sent: Friday, December 19, 2014 11:23 PM
Subject: RE: LF: RE: DLF 153 kHz QRT

Hi Stefan,

any chance to use the Donebach antenna on 8.9kHz?

Even at that frequency the radiation resistance might be close to 0.1 Ohm!

73, Rik  ON7YD - OR7T 


Thema: LF: DLF-test
Datum: 26.07.02 19:51:44 (MEZ) - Mitteleurop. Sommerzeit
From: [email protected] (Walter)
To: [email protected] (rsgb)  
Hello to all LF`ers, dear friends,
at first we have to say many many thanks to to all of you, who made QSO´s with us or gave us reports, info and tips by mail or phone. And we should like to thank the officials from RegTP and Deutsche Telekom who allowed us the activity from the DLF-site and gave us every support.
I`ll give a summary.
The first QSO took place at 8.45utc, testing with 1W, 5W and 20W (0.3A antenna current), the last QSO was abt 14.00utc because of an approaching thunderstorm 70Km apart. We made 19 QSO´s, 10 only on 136KHz, 9 duplex 136/7030KHz. We received 7 phone calls, the northernmost from Jan, LA8AK in Kristiansand.
And we got mails from 16 different OM´s with a lot of reports, measurements, tips and comments. The southernmost came from Brian CT1DRP (we are glad to be the first audible signal for you and the friends from Spain).
In the morning Markus matched the antenna with a homemade tuner by using scope and other equipment and got 1,9A antenna current. In the afternoon he connected the antenna directly to the amplifier - and got 2,2A ! One should do the simple things first.
It seems the DLF-antenna is especially made for our band.
Dave, I think your 5W are enough for a QSO. But the Frankfurt-area-noise is very strong - even on 40m. And so was the local noise composed:
The LF`er keying on 136 QSX 7030. In the background other boys of the gang talking. A signal comes from the 40m-transceiver by speaker (headphones forgotten),
not so clear. The LF`er increases volume. The boys increasing their loudness. The LF`er screaming "haltet mal die Klappe", what means "be quiet, please". And then the mobile phone ringing and in the rear of the house a worker with his lawn-mower. I think we need better organisation.
Two LF`ers from Frankfurt visited us, 4 members of the maintenance personnel came along, and even the regional Telekom-boss arrived and asked kindly what happened.
During noon 3 of our group drove around and made some measuring of our fieldstrength. We will calculate and compare with the figures from Dick and Jim. Markus will give another e-mail with more technical and calculating details.
The receiving conditions were bad as expected. We used a tuned loop, but must be better next time ( yes, we hope for a next time). And we will reduce our equipment. It is not necessary to take along 3 complete stations, so much measuring equipment, several boxes with cables, connectors, tools and material for every incident. 2 VW-variants were fullfilled. But now we know more than before.
We had a great event. Thanks for participating.
 
For the group: DF6NM Markus, DL2NDO Ralph, DK3GH Ralph, DL3NDR Roland
 
73 Walter DJ2LF
Thema: LF: Activity from DLF´s 360m mast
Datum: 15.07.02 22:16:09 (MEZ) - Mitteleurop. Sommerzeit
From: [email protected] (Walter)
To: [email protected] (rsgb)  
 

Hello to all LF`ers,
on Wednesday, 24th of July, the 153KHz transmitter of Deutschlandfunk in Donebach (JN49ON, 50Km SSE of Frankfurt) will be off air due to scheduled maintenance. By the friendly cooperation of the site personnel and with consent of the regulation authorities, a small group of German LF amateurs has been granted access to one of the 360m masts between 7:00 and 15:00UTC. With a little luck we might be able to achieve about 30dB more radiation efficiency than at home.

We will probably need some time to work out the impedance matching. After that, we intend to operate preferably in CW and Slow-CW modes. As we expect a rather high noisefloor from the Frankfurt area, we will bring along a tuned loop for receiving, and we will be QRV on 7030KHz in CW as well. If nothing else works, please give us a phone call on+49 174 3692499, or send an email note via the reflector or to [email protected] or [email protected].
Let`s look forward to a successfull day, hopefully without thunderstorms or strong noise.
73
The group: Markus - DF6NM, Walter - DJ2LF, Ralph - DL2NDO, Ralph - DK3GH, Roland - DL3NDR, Franz - DL5NER
 
 
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