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From: "Jose Manuel" <jpradoes@telefonica.net>
To: <rsgb_lf_group@blacksheep.org>
References: <BDEMKFCNLMIILGIFNONNOEBBCEAA.vvkooten@wanadoo.nl>, <002401c77ef4$cb5f7820$0100a8c0@W1KW> <4622289C.10361.1950B29@dave.davesergeant.com> <001f01c77f91$f940afa0$64118351@w4o8m9>
Date: Mon, 16 Apr 2007 00:30:37 +0200
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Subject: Re: LF: [500 kHz] DI2BO has 1.7 mW ERP!
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Hello Jim and Group,

You have mentioned around 0.02uV/m, at the equivalent noise BW of 3sec AR=
GO,=20
for the noise field strength in your location during daytime, can you tel=
l=20
me what level do you have at night? In my noisy urban location the daytim=
e=20
noise is around -20 dB(uV/m) for 1 Hz BW, so I think the true atmospheric=
=20
noise is very far, hi.

73 de Jos=E9, EA1PX


----- Original Message -----=20
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Sunday, April 15, 2007 9:12 PM
Subject: Re: LF: [500 kHz] DI2BO has 1.7 mW ERP!


>
> ----- Original Message -----
> From: "Dave Sergeant" <dave@davesergeant.com>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: Sunday, April 15, 2007 1:29 PM
> Subject: Re: LF: [500 kHz] DI2BO has 1.7 mW ERP!
>
>
>> Thanks for the update Geri, it perhaps shows that all the magic
>> formulas we are using to estimate our ERP are somewhat wide of the
>> mark.
>
> Dear Dave, LF Group,
>
> Not neccesarily - assuming a distance between you and DI2BO of around=20
> 700km,
> an ERP of 1.7mW in a straight line in free space gives a field strength=
 at
> your antenna of about 0.4uV/m, according to the formulas. There will be
> additional losses due to the signal having to be reflected by the
> ionosphere, so the signal might only be 0.1uV/m in practice. My rough
> estimate of the noise level on 500kHz is something like 0.3uV/m in a CW
> bandwidth on a good day, or about 0.02uV/m using Argo in 3s dot mode, s=
o
> there is actually quite a decent margin, providing propagation is
> favourable.
>
>>It also gives me some comfort that my vertical, estimated to
>> have 1% efficiency on a good day, will put out something others can
>> copy. When I have built the transmitter of course, at least I now
>> have my UK NOV.
>
> If your antenna can achieve 1% efficiency, you will only need about 5.5=
W=20
> of
> TX power to achieve the full "legal limit" 100mW ERP, so you should be=20
> able
> to compete on even terms as far as TX signal goes... this is a much eas=
ier
> prospect on 500kHz than 136k, becauase the antenna efficiency for the s=
ame
> bit of wire is about 20 or more times greater than at LF, plus the lowe=
r
> noise level offsets the reduced ERP limit to some extent. On the debit=20
> side,
> higher ground-wave losses can be expected on 500kHz, making signal rang=
e=20
> in
> daylight rather shorter, and as we have all experienced, the faster QSB=
 is
> quite a problem.
>
>>
>> I may have been confusing DJ2BO with DI2AG the other night and was
>> actually listening to AG audible above the noise. Last night SM6BHZ
>> was on, he is incredibly strong here, peaking 599 on the S meter. So
>> I was unable to repeat the test to see if I could hear either by ear
>> as BHZ was a little too close for my 400Hz filter. But will do so
>> tonight or tomorrow.
>
> I think Gus SM6BHZ is running about 10W ERP - truly a big signal in thi=
s
> context!
>
> Cheers, Jim Moritz
> 73 de M0BMU
>
>=20