Re: LF: VLF Transmissions - G3XIZ - 12th / 13th February

["mal hamilton" <g3kevmal@talktalk.net>]

Chris

Manually cut the carrier, that is what ODL did and so I was absolutely sure it was him that I copied.

For me QRS 600 and longer is too slow to wait for an ID. I shall be looking in QRS 60 -   QRS 3 also like you mention the time OFF is a waste for vy slow speeds.

I am not keen on the mains transformer interface, also antenna resistance of 2000 plus ohms seems a lot.

G3KEV

 

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

From: Chris Osborn

To: rsgb_lf_group@blacksheep.org

Sent: Thursday, February 10, 2011 7:23 PM

Subject: Re: LF: VLF Transmissions - G3XIZ - 12th / 13th February

Mal, Roger, Stefan and group

Thanks for the good wishes.
It will all depend on weather conditions as to whether I can fly the balloons but I shall keep you posted via the reflector.

I can try longer QRSS periods but begrudge the long wasted 'off' times especially if I'm having trouble keeping the balloons aloft.
A compromise would be for me to manually cut the carrier for 5-10 minute periods.

The transmitter feeds the loading coil and aerial via a large step up (mains) transformer.
The TX/ transformer will push its RF power into 2000 - 3000 ohms which is an approximation of the aerial circuit resistance when resonant..
I tried using a 50 ohms TX output and link coupling to the loading coil but without success.

The aerial current should be as before about 0.15 - 0.2 A

73
Chris G3XIZ

---

From: Stefan Schäfer <schaefer@iup.uni-heidelberg.de>
To: rsgb_lf_group@blacksheep.org
Sent: Thu, 10 February, 2011 19:05:02
Subject: Re: LF: VLF Transmissions - G3XIZ - 12th / 13th February

Hi Chris,

I think DFCW-600 or even 2400 is a good compromise between a constant carrier and some ID but 60 is probably to fast. Jim received you in less than 2 mHz if i remember correctly. QRSS60 is to fast for that. Looking forward to your results :-)

73, Stefan

Am 10.02.2011 18:52, schrieb Roger Lapthorn:

Hi Chris,

Very good luck. I'll be looking for you and hoping for success this time.

An email direct and to this group saying when TX starts/ends would be helpful. Don't suppose you can send QRSS60 or similar to help with ID? Have passed the word on to Nick G4IKZ as he is closer to you than me and not sure he subscribes to this list.

73s
Roger G3XBM

On 10 February 2011 14:42, Chris Osborn <g3xiz@yahoo.co.uk> wrote:

LF,

 

I have had permission to transmit on VLF this coming weekend: 12th and 13th February.

Weather permitting I shall try again with my balloon-launched aerial, hopefully about 50m vertical.

 

The frequency will be

 

8.976 66 kHz  (i.e. 10.000 MHz / 1114) and is derived from an oven controlled xtal oscillator.

Hopefully the frequency will be more stable than last time.

If this frequency proves unsuitable I can transmit on 10.000 MHZ / 1112 . .10.000 MHz / 1116  etc.

 

I shall send a continuous carrier as and when conditions permit.

 

My newly built VLF TX is working well and can deliver about 150 watts of RF.

On this occasion I shall be using the original (fairly lossy) loading coil but am presently making a more efficient one.

 

All reports will be most welcome.

 

73

Chris G3XIZ

 

 

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