We probably disagree . . . . years ago we would hear "picket fence" as the guys would call it from an FM mobile stations on two meters into the repeater . . . or simplex . . . . the point I have been attempting to make : I had not seen any comment until Andy responded to my attempt to make folks aware of CP or elliptical ( I will not split hairs ) and despite using a vertical they still generate deep fades by being linear polarized . . . that is my point give the newbie the full story . . . which has been sadly missing from the advocacy of Arrow vs. Elk . . . .
Jim W9VNE ----- Original Message ----- From: "Andrew Glasbrenner" glasbrenner@mindspring.com To: "Jim Danehy" jdanehy@cinci.rr.com; amsat-bb@amsat.org Sent: Sunday, December 28, 2008 12:15 PM Subject: Re: [amsat-bb] give the newbie the full story on ELK and ARROW please
Arrow and Elk are LINEARLY polarized antennas . . . . the 17,000 mph moving satellite is throwing off CIRCULAR polarized RF energy . . . please SUBTRACT 3 db or more of gain from your Elk or Arrow when receiving the satellite's signal . . . some still do not understand this concept and never will . . . ignorance is bliss . . . .
This is not always correct. AO-27 and SO-50 both use linear antennas for their downlink transmitters. Even with AO-51, the downlink signal is likely to be elliptical most of the time depending on squint angles. The point to take away from this is when using a handheld yagi, always try to peak the signals on both uplink and downlink by rotating the antenna. The up to ~20db of potential mismatch is more important than the gain of the antenna. All the current FM satellites use linear whips for the uplink receivers; peaking the polarity from worst case to best case is like adding a 500 watt amplifier to your 5 watt HT. To do this on transmit requires full duplex.
Here's another way to look at it. After the launch of AO-51, we heard several people say AO-27 seemed to have a stronger signal. AO-27 typically ran a 500mw downlink, and AO-51 ran similar power. Users with handheld yagis or whips who matched polarity gained 3 db on AO-27 reception as compared with AO-51 (assuming a close to circular signal from AO-51). That's the same as effectively doubling the downlink power on AO-27.
Sorry to impede anyone's bliss.
73, Drew KO4MA