Message-ID: <20080825230616.dj3j5g7woyok4owo@webmail4.kuleuven.be>
Date: Mon, 25 Aug 2008 23:06:16 +0200
From: Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>
To: rsgb_lf_group@blacksheep.org
References: 	<000d01c9052d$6f142c30$0301a8c0@mal769a60aa920><C6D17EC6BC594EC7A5CAAF551968B84E@AGB><003e01c90543$b12bb870$0301a8c0@mal769a60aa920><20080823193946.20d4b66b@sighthound.demon.co.uk><005701c90555$0018bcb0$0301a8c0@mal769a60aa920><9256A09B44B94949B34506B5E7260A84@AGB>
	<20080824233353.muhlmpin3r34kggk@webmail4.kuleuven.be>
	<002401c906de$82e26030$0301a8c0@mal769a60aa920>
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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 =20
humble antennas and locations, including me) is that one can =20
compensate for lower radiation resistance and/or higher losses by =20
increasing TX power. Even near field absorbsion can be compensated by =20
increasing power.
This is true for both 137kHz and 502kHz. On 137kHz the power needed to =20
get 1 W ERP with a small antenna is often in excess of a few kW, so =20
not very realistic (also because of the hight RF voltages). But on =20
502kHz even with a small antenna a few 100 W should do the job. Very =20
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"  =20
> <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"  =20
>>> <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:  =20
>>>> 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    =20
>>> Database: 270.6.7/1628 - Release Date: 8/22/2008 18:32
>>>
>>>
>>>
>
>
>
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>
>
>
> No virus found in this incoming message.
> Checked by AVG - http://www.avg.com
> Version: 8.0.138 / Virus Database: 270.6.7/1629 - Release Date:
> 8/23/2008 1:16 PM



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