```Hello Jim and Group, ```You have mentioned around 0.02uV/m, at the equivalent noise BW of 3sec ARGO, for the noise field strength in your location during daytime, can you tell me what level do you have at night? In my noisy urban location the daytime noise is around -20 dB(uV/m) for 1 Hz BW, so I think the true atmospheric noise is very far, hi. ```73 de José, EA1PX ```----- Original Message ----- From: "James Moritz" <[email protected]> ```To: <[email protected]> Sent: Sunday, April 15, 2007 9:12 PM Subject: Re: LF: [500 kHz] DI2BO has 1.7 mW ERP! ``````----- 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 `````` ```