Re: LF: DCF39 ERP and field strength

[Dick Rollema <dickrollema@casema.nl>]

Hello José,

I found the following results for DCF39,  using the CCIR 
curves:

Sea Water, average salinity, conductivity 5 S/m, dielectric
constant 70, EMRP = 40 kW.

Wet Ground, conductivity 10 mS, dielectric constant 30, EMRP = 40
kW

Land, conductivity 3 mS, dielectric constant 22,  EMRP = 108
kW.

Medium dry ground,  conductivity 1 mS, dielectric constant
15, EMRP = 1364 kW.

1 kW EMRP produces 300 mV/m at 1 km distance.
At 500 km over perfect (flat) ground 1 kW EMRP would produce 300/500 =
0.6 mV/m.
I measure 2078 µV/m. 
Over perfect ground this would correspond to (2078/600) squared x 1 kW =
12 kW EMRP. 

So even over almost perfect conducting sea water there is 10log (40/12) =
5.2 dB  extra path loss. I think this must be refraction loss due
to  the curvature of the earth.  

73, Dick, PA0SE

At 01:00 16-5-06, you wrote:

Hello Dick:
 
 I took a plot, last month, of the transmission of a Spanish colleague, who is in Madrid, at 500 km as well, and the signal level during the day was not stable, varying around 3 or 4 dB; I guess that the D layer reflection for this range is not low.
 
On the other hand, Dick , I think that the mean soil conductivity for your path , in my modest opinion, should be lower than 0.01 S/m, taking into account the conductivity map that can be seen in the Geri´s page.
 
I agree with you that, for this 500 km range, there is high uncertainty in the determination of radiated power.
 
 
73 de José, EA1PX
 
 
 

----- Original Message -----

From: Dick Rollema

To: rsgb_lf_group@blacksheep.org

Sent: Monday, May 15, 2006 2:11 PM

Subject: Re: LF: DCF39 ERP and field strength

Dear Jose,

You wrote:

In the web of Geri, DK8KW, can be seen that DCF39 ERP is 40KW (22KW EMRP), based on measurements made by Geri some years ago. For this radiater power corresponds, at 1800 Km, in function of inverse of distance, 58 dB(uV/m); last nigth I made measurement of 60 dB(uV/m), so I wonder if still DCF39´s power is the same as before, and if the previous theorical field strength, with no reflection loss, can be exceeded some times due to the several propagation factors involved.

I measure the field strength of DCF39 at 2078 microvolt/metre (66.35 dBµV) , as it is always  at daytime.

The distance between my  location and DCF39 is about 500 km. Using the graph for "LAND" (conductivity 0.03 S/m, dielectric constant 40)  in CCIR Recommandation 368-7: GROUND-WAVE PROPAGATION CURVES FOR FREQUENCIES BETWEEN 10 KHz AND MHz I find the power of DCF39 to be 39.8 kW.  This should be rounded to 40 kW of course.  That this agrees so well with the 40 kW mentioned by  Geri is pure coincidence, given the uncertainties involved.

73, Dick, PA0SE

JN22GD