Message-ID: <m10qdyx-0003DhC@fwd04.btx.dtag.de>
Date: Sun, 6 Jun 1999 16:33:03 +0200
To: rsgb_lf_group@blacksheep.org
References: <199906060613_MC2-7851-E8E2@compuserve.com>
Subject: Re: LF: Weekend Report Equipment (2nd trial)
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From: "Hans-Joachim Brandt" <hajo.brandt.dj1zb@t-online.de>
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Reply-To: rsgb_lf_group@blacksheep.org

Dear Geri,

your rallye report reminds me of my my time being a wireless operator on german 
ships in 1956-58. But I had simpler types of transmitters, one big valve in the 
VFO, two of the same type in parallel in the PA, both stages tuned by 
variometers on ceramic forms, ganged by a chain like those from a bicycle . . .

'Geri' Kinzel, DK8KW schrieb:
>
> Hello Lowfers,
>
> After a very succesful weekend looking around for longwave 
> stuff on a fleemarket (some of you say "rally") in Hamburg, I would 
> like to post some interesting equipment news over here today.
>
> I got hold of a complete mediumwave ship transmitter named 
> DEBEG 7121, including full documentation. This "boatanchor" 
> has got a beautiful large variometer inside.

I suppose this variometer will be too small for LF but may be used as the 
variable part of an LF variometer if a fixed coil is added.

> Looking at the schematics, it might be possible to convert it to
>  longwave. Besides the oscillator (chrystals in the range of
>  5 MHz, divided by ten, resulting in seven channels between 
> 410 and 500 kHz), most of the following modules look like
> the broadband stuff we use for LF. Following the oscillator
>  there is a driver stage using BD231/BD230 transistors to
>  achieve an output of about ten watts. This stage is followed by
>  two parallel PA modules using two BDY58 each in push/pull
> configuration. Those modules look very similar to the design
>  G0MRF uses. The output transformer has got three taps to be
> able to configure the system for antenna length between 12m 
> and more than 50m, as stated in the documentation.

For conversion to LF the inductance of the output transformers may be too low
due to the frequency difference! You have to find out.

> The following variometer is simply in series with the longwire 
> antenna, a system that we on LF also typically use. An antenna
> current meter between the PA modules and the variometer
> allows to match the system for best output.
>
> Interesting is the handwritten antenna current for various
>  frequencies that were noted by the ship's radio operator
>  when the unit was still in operation. With the
> main antenna, they achieved antenna currents between
> 6.25 and 7.25 Amperes! Considering the 130 Watts this
> transmitter delivers, this results in a loss resistance of about
> 2.5 Ohms, a value most of us only can dream about
> (I have got losses in the range of 100 Ohms!).

I have losses in the same order.

When with SIEMENS I have met an old engineer who had designed marine 
transmitters with TELEFUNKEN before the second world war. He said that the 
output match for these transmitters were ok under the assumption that all 
transmitter power is dissipated in the loss resistance of the antenna 
variometer. That means: Practically no ground resistance of the ship herself! 

Therefore there is a need to get amateur stations on museum ships etc qrv on LF!
>
> Besides this straighforward transmitter design, the unit
> also contains an AF module to allow to modulate the
> PA with a 730 Hz AF tone to achieve A2 instead of 
> A1. The unit runs on 28 Volt at 18 Amperes max. in A2. 

This has been done much simpler in the old transmitters. Most ships had DC mains 
on board, and therefore a motor-generator converted DC to 220 Volts AC 500 Hz 
(!!). The mains transformer of the transmitters converted this 500 Hz into a 
suitable voltage for the tube heaters and for the plate voltage, and the energy 
to modulate the transmitter for A2 had also been taken from this source.

We have been told that those 500 Hz generators were first used in the spark 
transmitter age, to provide a voltage peak every 1/1000 second for the spark 
gap. When the spark age came to an end in the early twenties the 
motor-generators were still in good shape, and therefore TELEFUNKEN (and 
I suppose other manufactureres too) decided to design the new tube transmitters 
for a 500 Hz supply. 
>
> This transmitter was relatively cheap (80.- DM) and 
> more of them might show up, now, after most of the European
> authorities have decided to stop operation on 500 kHz. It might
> be worth looking for those units. I will keep
> you posted on successes or failures in getting this unit 
> into operation on 136 kHz (btw: has anyone thought about asking
>  for an allocation for the amateur service between 
> 410 and 500 kHz? This might save me from converting
> this transmitter  ;-).
>
YES, I DID, when measuring the ground loss of my LF aerial and calculating its 
radiation resistance! All this would be much more favourable on MF! But on MF I 
would suggest to use a frequency band around 410 kHz, the former direction 
finding frequency, and slightly higher. Because we would get into trouble when 
using the range 454 kHz to 480 kHz where the (final) I.F.s of many receivers are 
situated. 

> The second device I got hold of looks like a giant (60 lbs) 
> synthesized SSB Exiter named "Schlumberger SSB 30".
> No documentation, but this thing produces an output 
> frequency that can be adjusted between 300 Hz and 
> 32 MHz (!) in 1 Hz (!) steps. No documentation, so I have 
> to find out what it does. Maybe an easy way to get an SSB
> (respectively AFSK, PSK31, Hell) signal produced
> on 136 kHz? I will keep you posted.

There will be many applications, also on HF and even higher, but you have to 
find out. But - How long it will take to QSY? This is often a problem with this 
kind of equipment.

73 Ha-Jo, DJ1ZB