Return-Path: Received: (qmail 17704 invoked from network); 30 Jul 2002 12:35:59 -0000 Received: from warrior.services.quay.plus.net (212.159.14.227) by mailstore with SMTP; 30 Jul 2002 12:35:59 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: (qmail 3175 invoked from network); 30 Jul 2002 12:36:01 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from post.thorcom.com (193.82.116.70) by warrior.services.quay.plus.net with SMTP; 30 Jul 2002 12:36:01 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 17ZW94-0004ud-00 for rsgb_lf_group-outgoing@blacksheep.org; Tue, 30 Jul 2002 13:30:34 +0100 Received: from relay.dera.gov.uk ([192.5.29.49]) by post.thorcom.com with smtp (Exim 3.33 #2) id 17ZW93-0004uY-00 for rsgb_lf_group@blacksheep.org; Tue, 30 Jul 2002 13:30:33 +0100 Received: (qmail 1355 invoked from network); 30 Jul 2002 13:30:32 +0100 Received: from butterfly.mod.uk (HELO warlock.dstl.gov.uk) (192.5.29.10) by relay.dera.gov.uk with SMTP; 30 Jul 2002 13:30:32 +0100 Message-ID: <7D653C9C42F5D411A27C00508BF8803DCB9B50@mail.dstl.gov.uk> From: "Talbot Andrew" To: "LF Group \(E-mail\)" Subject: LF: Re: Power of Donebach 153kHz TX Date: Tue, 30 Jul 2002 13:30:07 +0100 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2653.19) Content-Type: multipart/mixed; boundary="------------060802090007080603070302" Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: This is a multi-part message in MIME format. --------------060802090007080603070302 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit I've just made a check of both Droitwich and Donebach transmissions using the WatKins Johnson WJ-8711 receiver here at work. Using the narrowest IF bandwidth of 56Hz, setting manual gain control, and monitoring the output tone using Gram on its widest setting I cannot detect any variation in carrier level with modulation on either of the two transmitters. The level meter, which indicates actual signal level, accurately calibrated in dBm, also shows no significant variation with modulation. There is perhaps 1dB of variation on Donebach ( due to fading ?) and nothing on Droitwich. I'm very sure (read 99.9% certain) Droitwich has no amplitude modulation - viewing it on a vectorscope in the past shows only the phase variation. So perhaps you are seeing some secondary effects introduced by the receiver ? Andy G4JNT >I am pretty sure Donebach uses some form of controlled carrier modulation, >apart from the phase modulation mentioned by Walter. >Our Dutch MF transmittters at 747kHz and 1008kHz are also made by >Telefunken (400kW at daytime). The 747kHz transmitter uses controlled >carrier to save power and expenses; the 1008kHz one does not. The carrier >at 747kHz, as measured by the SPM-12 at 25Hz bandwidth, shows the same kind >of fluctuations as the Donebach one, the 1008kHz carrier is steady. R>emarkable is Droitwich at 198kHz. There the carrier goes downward during >modulation! "This e-mail is intended for the recipient only. If you are not the intended recipient you must not use, disclose, distribute, copy, print, or rely upon this e-mail. If an addressing or transmission error has misdirected this e-mail, please notify the author by replying to this e-mail." "Recipients should note that all e-mail traffic on MOD systems is subject to monitoring and auditing." --------------060802090007080603070302 Content-Type: text/html; charset=windows-1252; name="ATT00001.htm" Content-Transfer-Encoding: 8bit Content-Disposition: inline; filename="ATT00001.htm" Dear Walter & the LF-Group,

Today I tried to measure the field strength of Donebach at 153kHz again.

I am pretty sure Donebach uses some form of controlled carrier modulation, apart from the phase modulation mentioned by Walter.

Our Dutch MF transmittters at 747kHz and 1008kHz are also made by Telefunken (400kW at daytime).  The 747kHz transmitter uses controlled carrier to save power and expenses; the 1008kHz one does not. The carrier at 747kHz, as measured by the SPM-12 at 25Hz bandwidth, shows the same kind of fluctuations as the Donebach one, the 1008kHz carrier is steady.

Remarkable is Droitwich at 198kHz. There the carrier goes downward during modulation!

The varying carrier strength of Donebach makes it difficult to read the meter of the SPM-12. But the instrument has at the back a "DC output"  that is proportional to the measured value (so it is not  DC a purist will remark). I fed that voltage to an oscilloscope and noted the maximum deflection, which also cannot be read  accurately because of the wild jumps of  the deflection with the modulation. I then replaced the loop aerial by a HP606B signal generator, tuned it to 153kHz and adjusted the output to the same deflection. The generator voltage was then 20 microvolt. With a 1 x 1m single turn untuned loop this means the field strength of Donebach is 6.25 microvolt/m. Using the CCIR groundwave curve for "Land" (conductivity 30mS/m; dielectric constant 40) the power of Donebach follows as 200kW EMRP.
The aerial efficiency is given by  Walter as 88%.  This indicates a transmitter power of 200/0.88 = 227kW.
Perhaps, as suggested by Walter, there is only one 250kW transmitter in operation. What with the uncertainties involved and the fact the aerial system is not omnidirectional the 200kw EMRP looks to me like a plausible result, taking into account the uncertainties involved in the process.

As a check I inserted in G4GFQ's groundwave propagation computer program P = 227kW,  efficiency of the transmit aerial 88%, pastoral ground (number 5) and distance 435km. The field strength came out as 5.33 microvolt/m, which differs 1.4dB with my measured value.

73, Dick, PA0SE
 

At 09:10 28-7-02 +0200, you wrote:
Dick, what I forgot yesterday - the efficiency of the Donebach-antenna is quoted as 88% for 153KHz.
73 Walter
 
-----Ursprüngliche Nachricht-----
Von: Walter
An: rsgb_lf_group@blacksheep.org
Gesendet: Samstag, 27. Juli 2002 18:06
Betreff: LF: Re: Power of Donebach 153kHz TX
Dear Dick and All,
    about DLF. During daylight time normal transmitting power is 500KW from 2 transmitters by Telefunken, each 250KW. These power is fed to the northwestern one of the two masts. The southeastern one is coupled by radiation and has a phase shift. This generates a 3dB attenuation to southeast - because of Radio Brasov, Romania, on the same frequency. During the night power is reduced to 250KW, fed to both masts, also with phase shift. So the attenuation increases to 11dB to protect the Brasov-area. I think you get the full radiation. But probably today is only one transmitter in use because of maintenance. Please try next week again. BTW: The carrier is also modulated in phase shift with GPS-correction-data.
73 Walter DJ2LF
 
 
 
-----Ursprüngliche Nachricht-----
Von: Dick Rollema
An: LF-Group
Gesendet: Samstag, 27. Juli 2002 11:03
Betreff: LF: Power of Donebach 153kHz TX
To All from PA0SE,
Sorry to bother you again with a field strength story. But the delete key is within easy reach...

The Deutschlandfunk Donebach transmitter at 153kHz is on again. At 0840 UTC today I measured its field strength as 5.6millivolt/metre.
Using the CCIR groundwave propagation curve that produces plausible results on DCF39 and M0BMU the Effective Monopole Radiated Power (EMRP) comes out as 157kW.

On the Internet I found transmitter power is 500kW. But there are two 363m high aerial masts. This suggests a directive array. As the transmissions are probably not meant for the Netherlands we may get only part of the full blast.

Measuring with the SPM-12 in 25Hz bandwidth the reading moved up and down a bit with the modulation. Perhaps some power (and money) saving controlled carrier system is used. It could also be that some of the lowest modulation frequency components are passed by the 25Hz  I.F. filter. But other BC stations on LF do not show the effect.

73, Dick, PA0SE
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