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Lokalizacja:: Kłodzko JO80IK06AO
Posty: 42296 #2269881 Od: 2013-10-18
| A systematic approach to operate 70 MHz from 3A/Monaco - 3A/OH5ZA
3A/Monaco is considered to be a difficult VHF-location, first of all due to geography, with fairly high surrounding mountains in a wide sector “screening” much of Europe from direct low-angle skip.
I arrived here (actually at Beausoleil, France) a few days ago at about a 50 meters crawling distance from 3A-soil. This is a social visit, with very few private time slots, so the outcome of VHF-activity may be very low, but a pile of tools and antenna hardware has been purchased, adding to 19 pcs of 100 cm 3.2 mm AlMgSi bent at a 90 degrees angle at 35/65 cm to fit in the suitcase. The best product (nr. 817791-1164) for making AlMgSi element extensions is the Carrefour brass 6 square mm 2 x 6 "Connection strip" (Barrettes de connexion / Verbindungsstellen / Aansluitstrip), we call them sugarcubes in Finland, when cut off in pairs. Only one barrel with 2 screws is needed, e.g. to make a 70 MHz director with two 3.2 mm welding rods, with one shortened for the right total length.
Before the trip I studied the skyline with Streetview from the most Southern 3A-areas. That seems to place 1800 m mountaintops at about 8 km distance, which would mean a cut-off of the lowest 10 degrees to the Northerly horizons.
For VHF meteor-scatter a good take-off angle would probably be about 11 degrees for the lobe maximum, which on 70 MHz for a horizontally polarized antenna would mean about 6 meters height over flat ground or Mediterranean waters. The search is on for such a spot. The height of the antenna is very critical. If one puts it at 12 m height, there will be a deep null in the radiation pattern at 11 degrees take-off angle and a maximum at about 25 degrees, which will shorten the meteor-scatter range enormously. Then there is also a take-off maximum at 6 degrees, but it will hit the mountains. For 50 MHz these heights must be multiplied by 1.4 x to get the same angles.
We have a brandnew IC-7300, and hopefully it can be driven with a USB cable for digimodes. Only got one hour to play with the new rig before packing for this trip.
Will be continued …. (steno, to save time for hardware) ...
Cheers/73, “Zaba” OH1ZAA (3A/OH5ZA)
_________________ 73! Stanisław SP6MLK Kłodzko JO80IK06AO http://ra-ukf.iq24.pl/default.asp http://www.ukf-te.iq24.pl/default.asp http://spukfcontest.atthost24.pl/
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