G4WGT ROS MF1 137 kHz recu par F5WK !!!

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F4DTL
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G4WGT ROS MF1 137 kHz recu par F5WK !!!

Message par F4DTL » 20 juin 2010, 02:34

Hi LF,

Tonight I will be running a test beacon using ROS data software in ROS MF-1 mode.
The frequency to be used is carrier at 137.500 kHz, dial set at 136.500 kHz USB.
Tx periods will be 3 minutes, also listening for replies or calls between beacon Tx periods.
ROS software & manual is available at :-

http://rosmodem.wordpress.com/

Reports very welcome.
73
Gary - G4WGT - IO83QO.

F4DTL
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Re: G4WGT ROS MF1 137 kHz recu par F5WK !!!

Message par F4DTL » 20 juin 2010, 02:34

Hi Gary,

Not even a faint trace on a QRSS3 spectrum but:

> RX1: 19:23 @ 5.9 Hz: 9 <STOP> -37 dB
> RX1: 19:28 @ 5.4 Hz: O4WGT <STOP> -34 dB
> RX1: 19:33 @ 5.4 Hz: G4WGT <STOP> -31 dB

73,
Michel - F5WK JN18HP

F4DTL
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Re: G4WGT ROS MF1 137 kHz recu par F5WK !!!

Message par F4DTL » 20 juin 2010, 02:37

400 miles with 150mW on LF Band!!
19 June, 2010 by José Alberto Nieto Ros
¡¡Amazing!!

Jose

150 mW erp on 137 KHz , 400 miles into France MF-1 .. not bad eh ?

G..

————————————————–
From: “Michel F5WK” <f5wk@mterrier.net>
Sent: Saturday, June 19, 2010 8:36 PM
To: <rsgb_lf_group@blacksheep.org>
Subject: Re: LF: 137.500 kHz ROS beacon

>
> Hi Gary,
>
> Not even a faint trace on a QRSS3 spectrum but:
>
>> RX1: 19:23 @ 5.9 Hz: 9 <STOP> -37 dB
>> RX1: 19:28 @ 5.4 Hz: O4WGT <STOP> -34 dB
>> RX1: 19:33 @ 5.4 Hz: G4WGT <STOP> -31 dB
>
> 73,
>
> Michel – F5WK JN18HP

F4DTL
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Messages : 1553
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Re: G4WGT ROS MF1 137 kHz recu par F5WK !!!

Message par F4DTL » 20 juin 2010, 03:07

Image

F4DTL
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Re: G4WGT ROS MF1 137 kHz recu par F5WK !!!

Message par F4DTL » 20 juin 2010, 12:14

Hi LF,
Having successfully bench & on-air tested a x2 harmonic amplifier method of driving my G0MRF Class D LF transmitter, I ran a beacon last night (Saturday 19th) on 137.500 kHz.
An extract from my previous e-mail description is shown at the end.

Using the equipment & method described below, the ERP from my 12 metre vertical antenna was around 150mW. The mode was ROS MF-1, 100 Hz bandwidth.
I received the following report from Michel, F5WK in JN18HP, a distance of 410 miles (661 kilometres) in daylight.

>> Not even a faint trace on a QRSS3 spectrum but:

>> RX1: 19:23 @ 5.9 Hz: 9 <STOP> -37 dB
>> RX1: 19:28 @ 5.4 Hz: O4WGT <STOP> -34 dB
>> RX1: 19:33 @ 5.4 Hz: G4WGT <STOP> -31 dB


The x2 harmonic low level amplifier is a simple way of driving a Class D type of transmitter which employs a divide by 2 drive chain. My limitation with multi tone drive is that my DDS VFO will only produce 2 frequencies ie. the main frequency & a CW/Rx offset which has previously limited me to 2 tones as with RTTY & DFCW modes.
Please bear in mind that it will not be suitable for modes like PSK were tones are transmitted simultaneously.
At the moment the 2 small PCB's are precariously lying on the desk, when I have cased them I will publish the circuit & pictures.

73
Gary - G4WGT.

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Driving a class D transmitter, the software method ...

Message par f5wk » 20 juin 2010, 20:32

The x2 harmonic low level amplifier is a simple way of driving a Class D type of transmitter which employs a divide by 2 drive chain. My limitation with multi tone drive is that my DDS VFO will only produce 2 frequencies ie. the main frequency & a CW/Rx offset which has previously limited me to 2 tones as with RTTY & DFCW modes.
Please bear in mind that it will not be suitable for modes like PSK were tones are transmitted simultaneously.
There is another way to drive a Class D transmitter, which was recently developed by Jose Nieto and myself.
The same limitation as above still applies.

The idea was based on an existing WSPR high power transmitter. There is not much difference between ROS and WSPR, both generate one unique frequency (audio tone) at a time, therefore it's just a matter of loading a DDS register with the correct FTW (Frequency Tuning Word) at the correct pace.

I asked ROS's author to write the audio frequency to a COM port, thus avoiding the need to measure the audio frequency (I quickly gave up this idea) We ended with a fairly simple communication protocol where frequency values are sent in ASCII.

The ROS data is sent to a Windows GUI program which calculates the 32 bit FTW, depending on the TX frequency, and finally sends the FTW to a 16F628 PICmicro controller using another COM port. The PIC handles the received messages and performs the specific routines to load the AD9851 DDS registers and switch the transmitter back and forth. The hardware already exists at F4DTL and a few other stations.
LF200_ROS_diagram.pdf
Communication diagram between ROS and the LF200 transmitter
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