Hello, I'll comment some of Dick's comments right away.
I was not at all talking about skywave (which we prefer
to call ionospheric wave). Ground wave is an observable
and measurable resultant of direct wave, space wave,
surface wave, subsurface wave etc. It is the component
we measure at the ground level and some height above
ground level. It is GW anyway and we have a number of
programmes to calculate this practicable component, as
we have to live with it at ground level and up to some
1 km or more. We have made numerous flight measurements
to testify the effects of so called height gain up to
some 10000 feet, the height effect is negligible.
Curves in CCIR Recs are just curves resembling some of
the programs I mentioned. Some of them are more useful
for fligh measurements and some for other purposes.
Sky wave or ionosperic wave or component is in its
own category making living during darkness awful, as
old generation pilots and navigators can tell.
Dick, I'll snail mail you one document describing
DGPS beacon flight measurements in 1995 and 1996.
In the reference list are the best documents available,
Nominal flight height in beacon measurements is 100 m
(AGL) at least outside towns etc. 73 de Vaino
At 12:43 28.10.1999 +0200, you wrote:
To All from PA0SE,
It is interesting that the Millington method used by that Vaino to calculate
Reino's power seems to produce more realistic results than the CCIR
Recommendation 386-7. Why is that so?
Is the Millington method newer than the CCIR method? What is it like?
Perhaps Vaino can tell us a bit more about it.
As I see it the CCIR curves and presumably the Millington method produce a
relation between the power fed to the antenna and the field strength of the
ground wave (surface wave).
Using an aircraft obviously measures the field strength of the sky wave.
This makes sense as it is the skywave that is used by an aircraft
approaching a locator (part of an Instrument Landing System). But the CCIR
curves and presumably the Millington method cannot be used for this
situation I think. How the power radiated by a locator can be found from
measurements using an aircraft is not clear to me.
From Vaino's figures for locators it seems that the power in the sky wave
is very much higher than in the surface wave.
The 500 W TX power and a top loaded antenna of 14 m as quoted by Vaino for
Finnish NDB/locator beacons is not unlike the situation at several amateur
stations in our LF-band. But they certainly do not radiate 8 - 15 W in their
ground wave! The somewhat higher frequency of the beacons, resulting in a
higher radiation resistance, cannot explain the difference.
73, Dick, PA0SE
Vaino wrote:
Hi folks,
This is just a comment. I recently wrote a short story
for the Finnish SRAL magazine about Field strength
measurements - which we have been doing for over 40 yrs.
We have been flight measuring most Finnish NDB/Locator
beacons and all Finnish and Swedish DGPS beacons.
Most powerful I've ever seen in N. Europe is Tallinn
"LK" 386 kHz radiating abt 30 W. Of 105 Finnish NDB
/Locators most (Tx=500W) radiate between 8-12 W,
some even 15 W, using a 14 m high top loaded monopole.
I made some EMRP calculations for OH1TN who is located
152 km from my place. Can hear him daily as ground wave.
For 136 kHz sigma I use 0.5 mS/m, for 300 kHz 1 mS/m.
Reino's EMRP can be anything between 10 mW and 50 mW.
Hope some day we can make some real field measurements.
I have at home an old Anritsu Field strength meter but
its sensitivity / selectivity is not good enough.
Can only estimate that his real Fs is less than 10 dBuV/m.
---------------------------------------------------------
GROUND WAVE FIELD-STRENGHT, MILLINGTON METHOD
OH1TN -> OH2LX, Ground distance = 152 km
FIELD-STRENGTH DB ABOVE 1 MICROVOLT/METER
EPS =10.0 SIGMA = .5 mS/m FREQ = 136. kHz POWER = .05 W
DIST. (KM) F-S (DBU)
1.0 66.3
2.0 60.2
3.0 56.5
4.0 53.9
5.0 51.9
6.0 50.2
7.0 48.8
8.0 47.5
9.0 46.4
10.0 45.4
30.0 33.9
50.0 27.2
70.0 22.6
90.0 18.8
110.0 15.7
130.0 12.8
150.0 10.2
170.0 7.8
190.0 5.6
210.0 3.5
END OF CIRCUIT
------------------------------------------------------------
----------------------------------------------------------
V.K.Lehtoranta, OH2LX, POBox 50, FIN-05401 Jokela, Finland
------ Tel: +358-9-4173965 ---- Fax: +358-9-4173961 ------
E-mail: [email protected] - alias: [email protected] & [email protected]
----------------------------------------------------------
V.K.Lehtoranta, OH2LX, POBox 50, FIN-05401 Jokela, Finland
------ Tel: +358-9-4173965 ---- Fax: +358-9-4173961 ------
E-mail: [email protected] - alias: [email protected] & [email protected]
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