Dear Rik,

thank You for your contribution. Especially your last sentence is interesting for me because this may explain the success of MF-stations operating close to the coast.

Another example for exceptionally high antennas on MF for me is DI2AM, located on a museum ship in the harbour of Rostock. I have been informed that the antenna has been put up between two masts of 30 meter in height. Other favourable conditions are the low ground loss onboard of a ship and also the vicinity of water, of course. 

In general I do not have any objections to Finbar's setup; it shows that effective MF antennas can be built up on a rather small area.

But I am not yet convinced that height of MF antennas should not matter, and I will continue to observe the scenery.

OK?

73 Ha-Jo, DJ1ZB


  "Rik Strobbe" <[email protected]> schrieb:

Dear HaJo,

But in general I feel that antenna height should not be disregarded. Even with equal ERP sky waves may develop better from higher aerials.

HW?

I guess that the only cause that 2 antennas fed with the same ERP produce different signals is a difference in the (vertical) radiation pattern, ie. the takeoff angle.

I simulated a 30m, 10m and 3m vertical (at 502kHz) with mmana_gal and found only very small differences: from 18.2 degrees for the 30m vertical to 18.6 degrees for the 3m vertical. This for a uniform ground with a conductivity of 10mS/m.

Making the ground poor (1mS/m) results in a takeoff angle of about 26 degrees (+/- a few tenths depending on the height).

Increasing the conductivity to 100mS/m reduces the takeoff angle to 12-13 degrees.

73, Rik  ON7YD - OR7T

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