Re: LF: Re: VLF Transmissions

[Chris Osborn <g3xiz@yahoo.co.uk>]

Hello Mal,

My loading coil's wire is a bit fine.
I started out using 0.35 mm diameter but ran out and my E-bay order for wire didn't arrive in time.
I finished off using 0.2 mm which was all I had in any quantity; it's quite flimsy stuff.

I guess the DL chap was using much heavier gauge wire, which I should have done.

I can actually get over 100 watts of RF into a dummy load and I may push the power up a little.
The Met Office didn't detect my earlier 'effort' at all so I doubt I'll be causing them any QRM - HI !

A condition of the N.O.V. is that I sit by the telephone whilst transmitting . . .in case they tell me to QRT.
I think that occurrence is highly improbable.

73
Chris
G3XIZ

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From: mal hamilton <g3kevmal@talktalk.net>
To: rsgb_lf_group@blacksheep.org
Sent: Mon, 22 November, 2010 18:28:03
Subject: Re: LF: Re: VLF Transmissions



Chris

The coil size seems reasonable for 1.3 mH ind. The DL man was talking about a water butt 3ft wide and 4 ft high for a 300 ft kite, seems odd.

What diam wire are u usinvg.

Your pwr is on the low side for the freq to cover any distance.

will look out for u but I cannot calibrate an accurate freq

de mal/g3kev

 

----- Original Message -----

From: Chris Osborn

To: rsgb_lf_group@blacksheep.org

Sent: Monday, November 22, 2010 5:12 PM

Subject: Re: LF: Re: VLF Transmissions

Hello Mal,

I've wound an air-cored loading coil of about 1.3 H
It's on a wooden frame with hexagonal ends (all yacht varnished) and has a mean diameter of 2 feet.
The winding length is 20 inches and it resonates my 40m inverted 'L' at the correct frequency of 8.97 kHz

I've made a VLF exciter which generates the drive frequency and interfaces with the PC's software.
It uses a 2297 kHz crystal divided by 256 and gives a square wave output for the PA FET's.
I can run CW, QRSS or DFCW with 0.05 Hz shift.

For the TX I've modified my existing 200 watt 500 kHz PA and for matching use an ex-UPS transformer.
The PA seems quite efficient into a 2000 - 3000 ohm resistive load.

I have yet to be picked up beyond the boundary of my own garden so would be over the moon if anyone else can detect my signals.

73 Chris
G3XIZ

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From: mal hamilton <g3kevmal@talktalk.net>
To: rsgb_lf_group@blacksheep.org
Sent: Mon, 22 November, 2010 16:12:15
Subject: LF: Re: VLF Transmissions



Chris

What are u using for a loading coil, amp etc

mal/g3kev

 

----- Original Message -----

From: Chris Osborn

To: LF Group

Sent: Monday, November 22, 2010 3:13 PM

Subject: LF: VLF Transmissions

LF,

I have permission to transmit VLF this evening and details are as follows:-

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DETAILS OF TESTS

 

Loc:         Biggleswade   IO 92 UB 

Time:       Monday 22nd November 2010   20.00 - 22.00 GMT

Freq:        8.9719 kHz

Mode:      QRSS - 10 second dot length / DFCW with 0.05 Hz shift / CW identifier at 5 wpm

Power:     Limited to 20 watts RF output (ERP unknown)

Aer:         40m inverted 'L' at 10 m above ground.


Any reports or comments are welcome.I

Regards,

 

Chris

G3XIZ