[CW] SAQ Xmas transmission

Thu Jan 3 04:58:49 EST 2013

I received this message from another newsgroup about SAQ and I thought that
the members of this list might enjoy reading it.

Thank you also to Karsten - DL3HRT for asking the right questions.

73

DR

QTC

I wrote a mail to the guys at SAQ asking for details about carrier
suppression and frequency change. I received the following answer:
==================================================================================
Dear Karsten,

I received your mail from Lars Kålland, and I will try to answer your
questions.

The antenna current is keyed by the magnetic amplifier, which mainly
consists of two transductors, which are coils with an iron core, and which
changes their inductance, when the DC in a control winding is changed. The
transductors are electrically a part of the antenna, so when there is a DC
in the control winding, the antenna is out of tune, but a residual carrier
is "leaking" to the antenna. At key-down the DC in the control winding is
broken, the inductance changes and the antenna becomes perfectly tuned. The
residual carrier is reported to be 15-18 dB below ordinary output. Once
upon a time, the magnetic amplifier was guaranteed to transmit 90 wpm and
could even transmit 100 wpm, so the Alexanderson alternator is really  a
high-speed transmitter. Ordinary transmitting speed for telegram traffic to
USA is said to have been about 60 wpm.

The tuning of the Alexanderson transmitter has two different actions. First
of course we tune the antenna to maximum antenna current output. After that
we adjust the load compensation of the speed control to meet the load
variations so that the speed can be kept constant when keying. At the
beginning of the tuning phase the load compensation is in a random
position, so we most often get frequency variations until the compensation
is adjusted. If we adjust the compensation to a certain load and if the
load then changes, the compensation is decreased and we get frequency
variations. This often  happens if the antenna and the antenna coils are
wet when we start. When they dry up, the resonance frequency of the antenna
changes a little, and the load is slightly reduced. This probably happened
during the Christmas transmission.

Best regards,

Ola Hernvall
Webmaster Alexander - Grimeton Veteran Radio's Friends
==================================================================================

This corresponds to my observations. I measured app. 15-16dB carrier
suppression.

Karsten

Am Mittwoch, 2. Januar 2013 03:40:56 UTC+1 schrieb Masesrom:
>
> Wow.  Less than 50% efficiency for CW. And 240kw of heat.  You can boil a
> whale in that water.
>
> Sent from my iPad
>
> On Jan 1, 2013, at 16:33, DL3HRT <han... at t-online.de> wrote:
>
> According to a technical article which I have in front of me the
> Alexanderson alternator is driven by a 440kW motor. RF-power of the
> alternator is 200kW. The stator is cooled by means of water pipes to keep
> the temperature below 90°C.
>
> Am Dienstag, 1. Januar 2013 20:06:14 UTC+1 schrieb Masesrom:
>>
>> I wonder that the efficiency is of that big a device. How warm or hot it
>> may get. ?
>>
>> Sent from my iPad
>>
>> On Jan 1, 2013, at 13:42, DL3HRT <han... at t-online.de> wrote:
>>
>> I made a screenshot with my SDR software from the recording of the tuning
>> procedure. There are two iinteresting things:
>>
>> 1. Under load the frequency goes down app. 20Hz
>> 2. More interesting: SAQ still transmits a weak carrier in the
>> transmitting pauses! I think this is due to the keying technology which
>> they are using (transductor).
>>
>> 73
>>
>> Karsten - DL3HRT
>>
>> Am Dienstag, 1. Januar 2013 19:08:33 UTC+1 schrieb Masesrom:
>>>
>>> It wud be interesting to hear those without the tight audio filters to
>>> discern carrier wobble which I imagine wud occur given the mechanical
>>> aspect of the transmitter.
>>>
>>> Sent from my iPhone
>>>
>>> On Jan 1, 2013, at 9:13 AM, DL3HRT <han... at t-online.de> wrote:
>>>
>>> Hello and the best wishes for the new year to all of you!
>>>
>>> Today I received the prelimary listener report for the SAQ christmas
>>> transmission. The signal was heart in W and VE with very weak signals and
>>> much better in Alaska.
>>>
>>> 73
>>>
>>> Karsten - DL3HRT
>>>
>>> Am Dienstag, 25. Dezember 2012 15:55:23 UTC+1 schrieb DL3HRT:
>>>>
>>>> Hello,
>>>>
>>>> first of all Merry Christmas and a happy new year to all of you!
>>>>
>>>> Because most of you are not able to listen to the SAQ
>>>> xmas-transmissions on 17.2kHz I did some recordings yesterday. There was
>>>> only one transmission atb 08:00 UT this year. Last year they did another on
>>>> later for listeners in the US.
>>>>
>>>> 1. Tuning procedure. You may notice the change in frequency when
>>>> transmitting the carrier.
>>>> --> download MP3<http://www.sam-magnetometer.net/dl3hrt/tmp/SAQ_20121223_074716Z_tuning.mp3>
>>>> 2. Xmas message.
>>>> --> download MP3<http://www.sam-magnetometer.net/dl3hrt/tmp/SAQ_20121224_075912Z_message.mp3>
>>>>
>>>> I used the following rig:
>>>> rx: EKD315 with 100Hz filter
>>>> antenna: PA0RDT - Mini Whip (for location see image)
>>>>
>>>> Link to official SAQ page here <http://www.alexander.n.se/>.
>>>>
>>>> Distance from here to SAQ is 700km. Its always great to hear this old
>>>> transmitter!
>>>>
>>>> 73
>>>>
>>>> Karsten - DL3HRT
>>>>
>>> <SAQ - PRELIMINARY REPORTS OF TRANSMISSION 2012-12-24 CHRISTMAS EVE -
>>> Jan 1st.doc>
>>>
>>> <Screenshot tuning.png>
>>
>>
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