The recent record contact between OM3BD and AC0RA peaked my interest in the subject. Congratulations and thanks to both of them. Stuff like this gets even old geezers like me excited.

This is slightly technical and there is a question. I was testing my pass prediction program and found that my program indicated that a contact between my location and JO41KW was not possible. I use JO41KW since it is sort of on the edge and DK1TB lives there. I checked and found that SatPC32 indicated that a contact was possible using FO-29. I knew that nothing could be wrong with SatPC32 so I dug a little deeper. You may know this but FO-29 is a little different than most of the other LEO satellites. It has a very high eccentricity compared to the rest of the fleet. To try and speed up my calculations I was calculating the diameter of the coverage circle and comparing it to the distance between the two locations. If the distance between the stations was longer than the coverage circle diameter I dumped it. This worked fine for everything but FO-29. With the current LEO sats it is easy to forget about eccentricity. There is a difference between the minimum and maximum coverage circle diameter of 910 miles for FO-29. By comparison AO-27 has only a 67 mile variation.

QUESTION: This eccentricity might result in a longer delay between good passes for max range contacts. You need the satellite to be in the right spot and at the max altitude to get a max range contact. The unknown at this point is the effect of inclination. It seems as if a satellite with a very low inclination and stations are located at high latitudes could result in a condition where a contact would not be possible even though the distance between them is within the coverage circle diameter. With the speed of our present computers and the simplicity of the calculations it is easy to just brute force it and check to see if contacts are possible but I wonder if anyone has looked at the effect of inclination and station latitude on max range.

-------------------------------------------------------------------------------------------------------- AO-27 Min Elev: 0 Coverage Circle Diameter (Miles): 3756.9 To 3823.1 Location1 Lat: 43.104167 Long: -89.458333 Grid: EN53GC Location2 Lat: 51.937500 Long: 8.875000 Grid: JO41KW Distance between locations (Miles): 4270.3

Contact theoretically not possible using AO-27

Theoretically possible using: AO-07 Coverage Circle Diameter (Miles): 4896.0 To 4932.4 FO-29 Coverage Circle Diameter (Miles): 3814.7 To 4724.8 ---------------------------------------------------------------------------------------------------------

73 W9KE Tom Doyle