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LF: Re[2]: LF: RN3AUS 136 khz TX now!

To: [email protected]
Subject: LF: Re[2]: LF: RN3AUS 136 khz TX now!
From: F6CWN <[email protected]>
Date: Fri, 13 Jul 2018 13:37:27 +0000
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Hello Stefan,
A great moment as the radio with a kite antenna!
The story of this kite is quite special (actually there are 2: one of 4m² and another of 6m²), at the beginning it was intended to make manipulations and tests on active payload of satellites, (I am also member of the AMSAT- France).

Pareafter I was contaminated (thank you F6AGR!;-)) by the low bands ...
Having had the chance to retrieve carbon fiber rods for the construction of Ariane 4 (9m long!), We decided to use them to make kites to test our payloads, balloons and satellites (and even to drop sweets in regional events ...!).
In short these machines are only a "tractors"!

During a demonstration (ASTRORADIO 2005, the "small" served as support for an aluminum wire (1.6mm) of ~ 150m to 200m
Some pictures here:

The difficulty of the kite is especially the takeoff in order to capture as soon as possible the good windy zone (not always easy in the middle of June!), But after that it goes ...
I do not speak also of the difficulties to pick up the wire when it falls with the kite in a field of corn! (You have to love the RADIO!)

The problem of the demonstration ASTRORADIO was the reception, we were not the only ones to make the emission and a transmitter of 500W on 14 MHz within 100m of the LF station ... Not simple ... Too bad!

Now, I'm all alone to do LF (and no more young), so it goes slower ...

The main difficulty here (I am in Normandy, near the sea, where there is wind!) Is to find charitable souls able to share my tastes for "curious" things like the LF / VLF. It's long and you have to make concessions, but over time ... It's starting to become concrete!

I have several fields to grow antennas beverage, K9AY, and of course kite! But to this is added some difficulties such as energy and housing that are about to be resolved. Camping in the middle of winter is a bit hard for my old bones ...

On the power stage side, I'm thinking of a power MOS-based amplifier with IXYS IXFH94N30 at liquid-cooled IXYS (water + glycol), with the primary cooler out and the heat up (winter is good sometimes).

The transformers are mounted on welder station ferrites (nominal frequency ~ 100 KHz, a good choice of manufacturers, thanks!) The "high voltage" power supply provided by two 51V 57 A server power supplies (HP EPS120) compatible with a capricious generator! (I think he's allergic to CW!)


       Half a branch of the PWR RF bridge during construction

The MOS (uninsulated, so the Drain) are directly placed on the cold plate which itself is connected to the primary of the transformer. Possible thing with liquid cooling.

There is thus twice this assembly, one by branch and the transformer in the middle, it is more compact!
I will try to find other photographs, now everything is in the box, it is no longer readable so ...
The external cooler is regulated by a turbine, all enslaved by a CTN placed on the radiator (vehicle interior heating radiator recovered in a flea market) Two turbines of 2000 liter per minute at variable speed therefore controlled by a simple PID driven by the CTN.
The turbines (EBM D1G133-BF17-15 40 to 60V DC) are GSM station recovery, their speed control being done by a voltage of 0 to 10V (easy to control so with simple OAP)
My current problem, find a dummy load able to hold the power (I already grilled 2 CANTENA!), The QRSS is naughty!

There is still the problem of the final coil and especially the variometer (mechanical and servocontrol all compatible with a winter weather, rain snow, overloads like the kite on the ground.It must cut the transmission otherwise there is risk to find each other in the television news of the next day under the miscellaneous heading!)
I should preferably use the small kite, the large (6m²) is really too strong, the pulling force is difficult to control even changing the angle of attack, I have already broken several times of the aluminum wire 1.8mm (and find in the middle of the night a kite ground very far in the rain is not compatible with my mood!)

Picture of Ko NL9222 (a very good SWL!)


     In the words of James M0BMU June 18, 2005, our signal at home was more than respectable, it's a good start encouraging!

    To be continued ... And live the LF!

 VY 73'S: Jeff

Le 13/07/2018 à 08:01, DK7FC a écrit :
Hello Jeff,

Am 12.07.2018 22:21, schrieb F6CWN:

It's a pleasure when it works!
My experience balloon and kite (Spountnik loads tests a few years ago, launched since MIR, a great thing too!): Do not use plastic wrapped wire (static electricity, several KV!).
Do not forget a resistance (~ 500 K Ohms 2W) between the antenna and the ground otherwise it is very unpleasant! (Hi!)
I hope to contact you this winter, here I use a kite (6m ²) and aluminum wire (1.6 or 0.8mm diameter). Tests have been done on 160m and it works very well, I hope to reproduce these tests on 136 KHz (QRSS and normal CW), always with a kite (helium and the balloon are too expensive for me).
VY 73 Alex and thank you again for the report.

Great! I'm looking forward to your signal. Some years ago i also worked with kite antennas on LF and VLF. In the first experiments i've built e.g. a J-antenna for 160m, i.e. a 82m vertical wire and a transformer cable to transform to 50 Ohm. A used a call-E PA running 600 W at 160m. The PA worked at 36 V (using 4x IRFP 260N), 3 car batteries switched in series :-) It was all portable and i had CW QSOs with Japan on 160m m at lower power levels :-)
Great great great times!

What type of kite are you using for your experiments?

Good luck to all kite transmitting stations :-)

73, Stefan

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