Gor#f@mit-eddie.ARPA (03/26/85)
I find myself desiring an antenna that has a funny patern, and the usual HAM literature on antennas doesn't seem to cover what I want. I run a packet BBS, and many of my users get to me via a distant digipeater. They are in an area where there is no PBBS, and mine is closest to the mountain mounted digipeater. The trouble is that the digipeater can hear so well, that during busy times the path is not very usable, due to collisions between my packets and those of stations who can't hear me at the digipeater receiver. I don't want to increase power because the area north of Boston is congested enough. I don't want to simply use a beam pointed at the digipeater because I do have truely local users, and other PBBSs that I have a mail forwarding relationship with. What I would really like is a significant antenna gain in the direction of the digipeater, without any significant nulls in other directions. Any thoughts? 73's -Bill
Taylor.Wbst@XEROX.ARPA (03/27/85)
I WONDER WHAT THE POLARIZATION OF THE RECEIVING ANTENNA IS? ASSUMING THAT IT'S VERTICAL, I WOULD SUGGEST A VERTICAL ANTENNA FED IN PHASE WITH A VERTICAL YAGI. THIS WILL GIVE THE VECTOR SUM OF THE TWO (A CIRCLE PLUS A CARDIOID). THE ONLY FLY IN THE CARDIOINTMENT IS THAT THE YAGI HAS SOME MINOR LOBES WHICH ALSO ADD VECTORIALLY. I WOULD ASSUME THAT THEY'RE WEAK ENOUGH TO BE NEGLECTED. HAVE FUN! JIM (W2OZH)
McAfee.ES@XEROX.ARPA (03/27/85)
There are a couple of ways you can go. 1. Combine a directional antenna (yagi) with an omni antenna using a spliter has been used in commercial installations to control the pattern. 2. Use a collinear dipole array and skew the pattern by placing more dipoles on one side of the mast toward the distant mountain top. Pete KD6HR
uchuck@ecsvax.UUCP (Charles Bennett) (03/27/85)
A friend of mine once had a similar problem. He had several repeaters
(back when they were a new thing) on 6M linked and wanted local
general coverage and beamed coverage to the next link. He solved the
problem using a omnidirectional (ground plane, colinear, etc.) antenna
coupled to ( and spaced on the tower appropriately) a 15 element yagi.
This created a "Keyhole" pattern and worked quite well. I don't
remember the exact coupling or spacing but you can probably find out
from a good antenna reference manual.
-Chuck (WA4IFA)- (akgua,decvax)!mcnc!ecsvax!uchuck
--
-Chuck Bennett-
919-966-1134
... ...!(decvax,akgua)!mcnc!ecsvax!uchuckstekas@hou2g.UUCP (J.STEKAS) (03/29/85)
> What I would really like is a significant antenna gain in the direction of the > digipeater, without any significant nulls in other directions. > Any thoughts? > 73's -Bill How about a vertical for the locals AND a beam pointed at the digipeater? You would need to design a splitter/matching network but it sounds "do-able". Jim