Re: [amsat-bb] Antenna question
So as I understand the general consensus with this antenna a small up tilt is all I need even if my western horizon is almost 45 degrees.
Nobody mention anything about my ides of tilting the antenna at 45 degrees, halfway between horizontal and vertical? Any comments on that idea?
Or should I just install it horizontal with the UHF side up for better reception of the UHF downlink satellites.
Jacob Tennant WF8S
On Thursday, March 5, 2015, Rolf Krogstad rolf.krogstad@gmail.com wrote:
Jacob,
I have that same antenna which I use for satellite work. I have it mounted vertical polarization and I modified the mounting bracket so it is mounted at about a 15 degree elevation. It seems to work quite well except when the satellites are directly overhead. And that rarely happens in practice as I am not on that many passes every month.
The difference between us is that I have it above my HF yagi at the top of my 50 foot tower, so I am over the trees and houses and I find I can work down to the horizon. I think a 45 degree angle for your situation would be too much. Maybe something more like 25 to 30 degrees. Most of the time you will be aiming at satellites in lower elevations where they are farther away, so that should give you the best performance when they are the furthest. And when they are overhead they are much closer so it seems to work ok.
You will have to get a couple of diplexers to act as filters otherwise the desense of transmitting so close to your receiving antenna will make it hard to heard yourself on the downlink.
GL es 73
Rolf, NR0T Grid = EN34it Amsat #38889 Amsat-UK
On Wed, Mar 4, 2015 at 10:09 PM, John Geiger <af5cc@fidmail.com javascript:_e(%7B%7D,'cvml','af5cc@fidmail.com');> wrote:
Hi Jacob,
I have had a few of those antennas before. Are you only going to use it on the satellites, or are you thinking of using it for terresterial use as well? As you look at the antennas, one set of elements is on the top of the boom and the other set of elements are on the bottom of the boom. When it is mounted for horizontal polarization, the band that is on the top has a rather high angle of elevation. I always mounted it with the UHF elements on top, so the satellites would have to get up a bit in elevation before I could really pick them up well on Mode J. When VO52 was on, being Mode B, I would work it from horizon to horizon. The band on the bottom side of the boom seemed to function as one would expect a yagi to.
If you were only going to use it for the satellites, mounting it for vertical polarization might eliminate this problem and give similar performance on both bands. I have never tried that, but someone who has might answer that question for you (and for me if I ever get another one). I am now using separate antennas for 2m and 70cm and the Diamond 15 element yagi I have for UHF hears SO50 better than the A270-10S usually did.
73 John AF5CC
P.S. congrats on the 2 x 1 callsign as well!
On Wed, Mar 4, 2015 at 9:52 PM, Jacob Tennant <jakewf8s@gmail.com javascript:_e(%7B%7D,'cvml','jakewf8s@gmail.com');> wrote:
A buddy of mine has given me a Cushcraft A270-10S dual-band antenna. I
was
going to try to use it start my satellite antenna farm and was thinking
of
mounting it on a rotator, angled at 45 degrees up from the horizon and angled at 45 degrees polarization.
The main reason for the high up angle is that I live in a bit of a
valley
or as I call it a hole. North and South aren't to bad as I have heard passes at about 20 degrees, to the east my horizon is about 25 to30 degrees. To the west though I have a horizon of 40 degrees.
So I was thinking wit the antenna pointed at 45 degrees above the
horizon
would give me the best chance all around.
Am I on the right track or lost in the snow?
Or would I be better to just mount the antenna horizontal aimed at the horizon and take what I can get?
Jacob Tennant WF8S _______________________________________________ Sent via AMSAT-BB@amsat.org
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I also have several of these in use at field day. I suggest looking at the beam width of the pattern and doing a tilt up half that number above you local horizon. That way you get max gain as long as practical without elevation tracking. Once the bird is above the beam width you effectively are using a dipole. Bob Bruniga has made this suggestion for some time since birds spend much more time closer to the horizon than directly overhead.
Hi Jacob,
So as I understand the general consensus with this antenna a small up tilt is all I need ...
This page has a good explanation of things to keep in mind for fixed elevation antennas:
http://aprs.org/LEO-tracking.html
... even if my western horizon is almost 45 degrees.
Once the satellite gets below that horizon that is LOS for you.
-- 73 de JoAnne K9JKM k9jkm@amsat.org
participants (3)
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Floyd Rodgers -
Jacob Tennant -
JoAnne Maenpaa