Thanks Howard...Thin I've got it. Its going up this afternoon. Boom is drilled, elements made. Just mounting them now and then the harness..
Curt
Howard Long wrote:
Hi Curt
There are several ways to skin the same cat.
Although they are fed in phase, they are orthogonally mounted and with their spatial separation a 90 degree phase delay is created, thus creating CP.
If the elements are still orthogonal but are at the same location along the boom, then the delay would need to be inserted electrically, with an electrical 1/4 wave section of 50 ohm coax. Some CP antennas use a combination of both spatial and electrical phase difference.
To switch RHCP to LHCP can be achived by any of the following three means:
O Insert an additional 180 degree electrical delay between one arm of the power splitter and the antenna, with an electrical lambda/2 50 ohm coax section;
O Physically move one set of elements 180 degrees forward or behind;
O Turn one of the driven elements 180 degrees so the loop is on the other side of the antenna, but maintain the same electrical connections.
This may (of may not!) help... http://www.g6lvb.com/remotepolarization.htm
It takes a bit of lateral thinking, but once you've figured it out it's a bit like learning to ride a bike in that you don't forget, although in later years I find one may become a little wobbly.
73, Howard G6LVB
-----Original Message----- From: Curt Nixon [mailto:cptcurt@flash.net] Sent: 02 January 2009 16:50 To: Howard Long Cc: 'AMSAT-BB' Subject: Re: [amsat-bb] Question adding RHCP to Cheap Yagi
Hi Howard:
Thanks..I've looked at alot of your info on-line--especially the sub-500GBP AO-40 setup.
I guess I still don't get it..if I just feed them in-phase with both connections same polarity, what controls RH v. LH?
Or is it RH if the front half loop is to the right and LH if the front half-loop is to the left?
Thanks
Curt
Too cold to not get it right on the first try!!
Howard Long wrote:
Hi Curt.
Either way will work.
http://www.g6lvb.com/AO-40%2070cm%20uplink%20antenna.htm
I have had superb success with mine, in fact during the days of AO-40 I worked the world with it as an uplink antenna with 50W.
http://www.g6lvb.com/3A2%20ops.htm http://www.g6lvb.com/dayton_demo_2002.htm
73, Howard G6LVB
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Curt Nixon Sent: 02 January 2009 15:19 To: AMSAT-BB Subject: [amsat-bb] Question adding RHCP to Cheap Yagi
Good Morning All:
I've been using a 10el version of Kent Britain's Cheap yagi for my 70cm downlink antenna. It suffers from deep fades so I am going to add the second yagi with physical offset to get to RHCP in the x config.
Question is:
normally I would reverse the coax connections to a dipole driver but this is a hairpin (half of a folded dipole. )
Do I reverse the connections as normal? Kents instructions just say offset the elements and feed in phase.
Thanks
Curt KU8L
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