Re: LF: 500khz rtty

[Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>]

Mal,

I am well aware of your large antenna and superb location.

But the nice thing about an ERP limit (at least for those with more  
humble antennas and locations, including me) is that one can  
compensate for lower radiation resistance and/or higher losses by  
increasing TX power. Even near field absorbsion can be compensated by  
increasing power.
This is true for both 137kHz and 502kHz. On 137kHz the power needed to  
get 1 W ERP with a small antenna is often in excess of a few kW, so  
not very realistic (also because of the hight RF voltages). But on  
502kHz even with a small antenna a few 100 W should do the job. Very  
realistic for most.
73, Rik  ON7YD


Quoting mal hamilton <g3kevmal@talktalk.net>:

> Rik
> My advantage is Location. I am only  2 miles from the sea to the East
> across countryside, to my south there is a river, which probably helps
> and I am sorrounded by thousands of hectares of green fields in all the
> other directions. The only obstacle if any is the town of Scarborough
> to my SE.
> Therefore, my transmitted signal has a good take off and the same
> applies on receive. I have maximum advantage with the permitted power.
> Measuring or comparing signals at a distance is impossible, it depends
> how the signal is launched, in an urban environment/middle of a housing
> estate the signal is likely to be attenuated dramatically.
> Air calibration at various distances from the TX is the only reliable
> solution. Hardly worth the effort.
> The German beacons on 505 khz are strong with me during daytime as well
> as night time, and as a matter of interest I can work most EU stations
> on 160 metres daytime when they are active. Antenna on 160 is a one
> wave inv L at over 100 ft vertical, this is one leg of 4 legs for 137
> khz.
> de G3KEV
>
>
> ----- Original Message ----- From: "Rik Strobbe"   
> <Rik.Strobbe@fys.kuleuven.be>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: Sunday, August 24, 2008 10:33 PM
> Subject: Re: LF: 500khz rtty
>
>
> Based on the antenna description given by Mal ("1/4 wave inv L for 500
> khz, 100 ft vertical and rest horizontal") simulation reveals a
> radiation resistance of 5 Ohm and a directivity of 1.5 dBd. This means
> that only 375 mA antenna current is needed to radiate 1 W ERP.
> It is hard to tell from here, but such a big antenna should have a
> loss resistance of 20 Ohm or less. So in the worst case 2.8 Watt TX
> power is needed to get 1 Watt ERP.
>
> I can only dream of such a situation ;-)
>
> 73, Rik  ON7YD - OR7T
>
> > From: "mal hamilton" <g3kevmal@talktalk.net>
> > Sent: Saturday, August 23, 2008 8:18 PM
> > To: <rsgb_lf_group@blacksheep.org>
> > Subject: Re: LF: 500khz rtty
> >
> > > ANYTIME . If you saw the fet in my PA you would'nt bother.
> > > G3KEV
> > >
> > > ----- Original Message ----- From: "John Pumford-Green GM4SLV"   
> > > <gm4slv@sighthound.demon.co.uk>
> > > To: <rsgb_lf_group@blacksheep.org>
> > > Sent: Saturday, August 23, 2008 7:39 PM
> > > Subject: Re: LF: 500khz rtty
> > >
> > >
> > > > On Sat, 23 Aug 2008 18:14:23 +0100
> > > > "mal hamilton" <g3kevmal@talktalk.net> wrote:
> > > >
> > > > > I thought that would be the response from you. Why no ID?
> > > > > I will let OFCOM decide if necessary
> > > > > G3KEV
> > > > Perhaps we could ask them to check your ERP at the same time?
> > > >
> > > >
> > > >
> > > > No virus found in this incoming message.
> > > > Checked by AVG - http://www.avg.com
> > > > Version: 8.0.138 / Virus Database: 270.6.6/1626 - Release Date:   
> > > > 8/21/2008 6:54 PM
> > >
> > >
> > >
> > > No virus found in this incoming message.
> > > Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus     
> > > Database: 270.6.7/1628 - Release Date: 8/22/2008 18:32
>
>
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>
> No virus found in this incoming message.
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> Version: 8.0.138 / Virus Database: 270.6.7/1629 - Release Date:
> 8/23/2008 1:16 PM


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