When it is better to try ( or avoid) a sked EME on 50 MHz?

·        Avoid the days just before or after the apogee

When the Moon is at his perigee the signal we potentially receive is about 2.2 db stronger than the one we get when the Moon is at the apogee (the average signal loss on 50 Mhz EME path is around 242 db). So it is preferable to set up a sked during days around the perigee. Moonsked is capable display in real time the exstimated degradation of the signal due to the distance of the Moon from the Earth.

·        Avoid days with high cosmic noise behind the Moon

During the monthly trip, the Moon crosses zones of the space with a high noise level which, naturally, seriously interferes with the very weak moonbounced signal we are waiting for. So it is very important to avoid sked during this period. Nova for Windows and Traker have a very usefull option to calculate the cosmic noise level for every day of the month.

·        Avoid days and time with potential ionosferic propagation

At 50 MHz it is quite easy to run across ionosferic propagation (TEP, F2, ES ...). If this is the optimum for people who use these reflections to get a good qso or an excellent dx, for radio-hams who want to try EME these phenomenons are absolutly negative because they absorb or scatter the signal that, in this case, can't reach the surface of the Moon with the power needed to be bounced. That's the reason why we must avoid running sked when our antennas will beam zones potentially involved in these ionosferic situations.

·        It is very useful to run a sked just after rained

I experimented that running skeds just after the rain it was absolutly profitable. The wet ground, infact, increases his capability to reflect the wave radio and ground-gain, naturally if you are not elevating the antennas, results stronger than when the ground is dry. The problem is that usually it is difficult to forecast rain (at least here in Italy!).

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Due to the very weak signals we can receive off the Moon, it could be very useful to try a sked when the propagation condition is theoretically good.

W5LUU releases every year an useful table were you can easily find the good days for a try. Here is listed the condition for 144 and 432 Mhz, but we can use it for 50 Mhz prediction also.

W5LUU WEEKEND MOONDATA - 2008 FOR SUNDAYS AT 0000 UTC

Date 2008	Dec. deg.	RA hrs.	144 MHz Temp.K	Range Factor dB	DGRD, dB 144 MHz	DGRD, dB 432 MHz	Moon Phase	CONDITIONS
Jan   06	- 27.7	17.0	905	2.14	8.2	3.8	NM – 2.5d	Very Poor
13	- 2.9	23.1	244	1.15	2.3	1.5		Good
20	28.0	5.7	512	0.53	4.3	1.8	FM – 2.7d	Poor
27	- 2.9	12.0	259	1.77	3.2	2.1		Moderate
Feb.   03	- 28.0	17.6	2227	2.04	11.8	5.6		Very Poor
10	0.9	23.7	247	0.90	2.1	1.3	NM + 2.9d	Good
17	27.6	6.4	407	0.81	4.0	1.8		Moderate
24	- 1.5	12.4	306	1.84	3.8	2.4	FM  + 2.9d	Moderate
Mar    02	- 27.7	18.2	2732	2.01	12.6	6.5		Very Poor
09	5.3	0.3	262	0.61	2.0	1.0	NM + 1.3d	Good but NM on 03/08
16	26.0	7.1	344	0.97	3.3	1.6		Moderate
23	- 10.2	12.9	313	1.99	4.0	2.5	FM + 2.6d	Moderate
30	- 26.8	18.8	1351	2.02	9.7	5.3		Very Poor
Apr   06	9.2	0.8	277	0.38	2.0	0.8	NM  - 3.9h	Good but NM
13	23.4	7.9	229	1.00	2.0	1.2		Good
20	- 13.9	13.5	321	2.14	4.3	2.6	FM  - 9.9h	Poor
27	- 25.1	19.4	654	2.05	6.8	3.7		Very Poor
May   04	12.8	1.3	290	0.29	2.1	0.8	NM  - 1.5d	Good
11	20.1	8.6	186	0.92	1.3	1.0		VERY GOOD
18	- 17.5	14.0	350	2.25	4.7	2.8	FM – 2.1d	Poor
25	- 22.6	20.0	380	2.04	4.8	2.8		Poor
Jun.   01	16.3	1.8	313	0.34	2.4	0.8	NM – 2.8d	Good
08	16.7	9.2	172	0.83	0.9	0.8		EXCELLENT
15	- 20.7	14.6	392	2.29	5.1	3.0	FM  - 3.7d	Poor
22	- 19.5	20.7	337	1.95	4.3	2.5		Poor
29	19.7	2.4	351	0.48	2.9	1.1		Moderate
July   06	13.3	9.7	185	0.81	1.1	0.8	NM  + 2.9d	VERY GOOD
13	- 23.3	15.2	433	2.28	5.5	3.1		Poor
20	- 16.0	21.3	341	1.78	4.1	2.3	FM  + 1.7d	Poor
27	22.9	3.1	364	0.62	3.2	1.3		Moderate
Aug   03	9.8	10.2	193	0.89	1.3	1.0	NM  + 1.4d	V. G. but NM 08/02
10	- 25.3	15.8	493	2.25	5.9	3.2		Very Poor
17	- 12.3	21.9	299	1.56	3.4	2.0	FM  + 2.7h	Moderate
24	25.4	3.9	363	0.69	3.2	1.3		Moderate
31	6.1	10.7	204	1.09	1.7	1.2	NM  + 4.0h	Good but NM
Sept   07	- 26.6	16.4	657	2.24	7.0	3.5		Poor
14	8.6	22.3	252	1.34	2.6	1.7	FM  -  1.4d	Moderate
21	26.9	4.7	430	0.64	3.8	1.5		Moderate
28	2.0	11.3	222	1.35	2.2	1.5	NM  - 1.3d	Good but NM  09/29
Oct.   05	- 27.2	17.0	867	2.26	8.1	3.9		Very Poor
12	- 4.9	22.9	244	1.19	2.4	1.9	FM  -  2.8d	Good
19	27.3	5.5	514	0.47	4.3	1.7		Poor
26	- 2.6	11.8	251	1.59	2.9	1.9	NM – 2.9d	Moderate
Nov   02	- 27.2	17.6	2175	2.31	11.9	5.8		Very Poor
09	- 1.2	23.3	244	1.18	2.4	1.5		Good
16	26.7	6.1	468	0.25	3.7	1.4	FM  + 2.7d	Moderate
23	- 7.2	12.4	303	1.75	3.7	2.3		Moderate
30	-26.6	18.2	2659	2.35	12.0	6.8	NM  + 2.3d	Very Poor
Dec   07	2.9	23.8	249	1.26	2.5	1.6		Good
14	25.5	6.8	385	0.08	2.9	0.9	FM  + 1.3d	Moderate
21	- 11.4	13.0	313	1.79	3.8	2.3		Moderate
28	- 25.3	18.9	1152	2.33	9.3	5.3	NM  + 0.5d	Very Poor and NM

 

• DEC. (deg) : Moon declination north and south ( - ) of the equator. This is cyclical with an average period of 27.212221 days. The maximum monthly declination is also cyclic with a range of 18.15 to 28.72 and a period of about 19 years. Next maximum is in 9/2006.
• RA (hrs) : Right ascension in hours. East-West position of the moon against the sky background. Average period of RA cycle is 27.321662 days but it can vary by a day or so.
• 144 Mhz Temp (K) : 144 Mhz sky (cosmic) noise in direction of moon expressed as temperature.
• Range Factor (dB) : The additional EME path loss, in dB, due to a earth-to-moon separation distance greater than the absolute minimum ( 348,030 km surface-to-surface) Varies from a low (0 to .7 db) at perigee to as much as 2.33 +-0.1 dB at apogee.
• DGRD, (dB): The degradation in EME signal-to-noise, in dB, due to: (1) the excess sky noise temperature, in dB, at the listed position of the moon compared to the lowest cold sky temperature and the system noise temperature (all at the frequency of interest); plus (2) the earth–moon range factor, dBr, for the listed time and date. The tabulated DGRD is referenced to the lowest possible sky noise temperature along the moon path, to a system noise temperature of 80 K at 144 and 60 K at 432, an antenna beam width of ~150 and to the absolute minimum earth-moon (surface-to-surface) distance. The dBr affects DGRD equally at 144 and 432 but, at 432 sky noise effects are lower. During a monthly lunar cycle DGRD can vary up to13 dB on 144 and 8 dB on 432. DGRD varies less with small antennas than with large.
• Moon Phase : Shows new moon (NM) and full moon (FM) along with the number of days (d) Or hours (h) before (-) or after (+) these events. At NM sun noise can be a problem while at FM the stable night time conditions can be advantageous.
• Conditions : Summary of EME conditions as controlled by DGRD at 144 MHz and NM. Conditions may be worse due to ionospheric disturbances but not better than Indicated. In general 144 MHz DGRD under 1.0 dB is considered excellent, 1.0 to 1.5 is very good, 1.5 to 2.5 is good, 2.5 to 4.0 is moderate, 4.0 to 5.5 is poor, and over 5.5 is very poor. High sun noise at new moon (NM) can make conditions very poor, irrespective of the DGRD.

 

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