----- Original Message -----
From: "Dave Sergeant" <[email protected]>
To: <[email protected]>
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 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, so
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 5.5W of
TX power to achieve the full "legal limit" 100mW ERP, so you should be able
to compete on even terms as far as TX signal goes... this is a much easier
prospect on 500kHz than 136k, becauase the antenna efficiency for the same
bit of wire is about 20 or more times greater than at LF, plus the lower
noise level offsets the reduced ERP limit to some extent. On the debit side,
higher ground-wave losses can be expected on 500kHz, making signal range 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 this
context!
Cheers, Jim Moritz
73 de M0BMU
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