[amsat-bb] Re: give the newbie the full story on ELK and ARROW please
jdanehy at cinci.rr.com
Sun Dec 28 10:46:52 PST 2008
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 . . . .
----- Original Message -----
From: "Andrew Glasbrenner" <glasbrenner at mindspring.com>
To: "Jim Danehy" <jdanehy at cinci.rr.com>; <amsat-bb at amsat.org>
Sent: Sunday, December 28, 2008 12:15 PM
Subject: Re: [amsat-bb] give the newbie the full story on ELK and ARROW
>> 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
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