Robert, Nice piece of work! Thanks for sharing all of it in such great (and easy to replicate) detail. I just wanted to add some comments on (the debate about) antenna pointing angle for LEOs... based on many (too many?) years of chasing states, countries, grids, etc.: it may all depend on your own particular situation AND goals (i.e., there is no one magic formula/solution/design for everyone).
The single biggest factor (after getting past HOAs, partner objections, and fear of heights) is: can you see the horizon unobstructed by building and foliage? If trees are a problem, are they deciduous... so possibly not an issue in winter? If you do have blockage, Bob's (WB4APR) recommendation of pointing the antennas at 15 degrees above the blockage is pragmatic and well proven. Read no further.
If, however, you are lucky enough to see the horizon, you might consider pointing your antennas directly at it. This gives you maximum gain from the antenna AND maximum ground gain (you will know it when you hear it, typically under 5 degrees) when the satellite is the farthest from you, giving you brief access to the farthest/hardest/most rare states, countries, and grids. I can't count the number of rare grids I have snagged at -1 and -2 degrees (yes, negative, over-the-horizon) just as the downlink faded! The null you may/will experience directly overhead is very brief and only on passes typically above 75 degrees. Those contacts are the easy ones anyway.
One final word: if you have worked everyone within near-LEO range and you ONLY want those at your horizon, orient (regardless of pointing angle) your antennas at horizontal (flat) to maximize your ground gain potential. There is practically no ground gain on vertical polarization, and you lose half if you orient your antenna at 45 degrees. You will only hear below-the-horizon signals with horizontal polarization.
73, Jerry, K5OE Satellite WAS/DXCC/VUCC 1,000
-----Original Message----- From: AMSAT-BB [email protected] On Behalf Of Robert Sent: Wednesday, December 19, 2018 11:56 PM To: [email protected] Subject: Re: [amsat-bb] Cheap rotator setup
Hi Eli,
I am the author of that webpage you're using for a guide for your own set up. I humbly appreciate that you have chosen the page for some guidance - that page is one of the Top 5 pages at my site so lots of folks have successfully used it. Several of them have been pushing me to submit this to QST as an article which I may do (my last one was exactly 30 years ago - so it may be time for the next one.)
:::::::::::::::::::::::: Note that I extensively edited the web page today so I genuinely am seeking additional help from all to help make this page even better and to give it more clarity or correct any technical errors - especially before I submit the page info to QST.... ::::::::::::::::::::::::
Eli, as a result of your question, I just added the below info to the web page - along with a slider that shows 31 new photos that give more details and a detailed diagram of the antenna's beamwidth....check out the page for more info since those cannot be shown here...but for those who don't want to look, here is a highlight quote from the page to hopefully answer Eli's question.
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“Why Are You Using a 45° Angle for Fixed Elevation Instead of the Recommended 15°?”
I thought I had better add a comment as to why I am obviously using a 45° angle instead of the recommended 15°.
I am personally surrounded by RF eating 65 foot trees and a RF eating two-story house. As a consequence, I chose to move the A430S10 50° antenna beamwidth (see below) and center them on a fixed 45° instead of 15°.
Ostensibly, I would lose coverage from 0° to 20° (45° center angle minus half of the 50° beamwidth of the antennas, or 25° = 20° ) by doing this – but I’m going to lose those angles (and then some) anyway because of the tree and house QRM.
Trust me when I tell you that trees and houses do a damnably good job of blocking RF at satellite frequencies – in my case below 30° in summer and 22° in winter! (This is going to be one of my next videos on my YouTube channel at http://Youtube.com/K3RRR.)
Beamwidth is loosely defined as the width of the main lobe of radiation for both transmit and receive. This is a whole discussion by itself but for my cheapie antenna system, you’re better off with a wide beamwidth versus a more narrow beamwidth for your antennas. The following diagram from Diamond Antennas shows the comparison of what that width of the main lobe looks like with my orange arrows showing where they cross the 3 db points.
If you kinda sorta extrapolate, you can see that an imaginary line from the 3 db intersection point to the outer circle would translate to about 25° either side of the zero mark – for a total spread from both sides equal to about 50° of beamwidth. (The other chart shows the same info for Diamond’s bigger brother the A430S15 – 15 elements instead of 10. you can see how much narrower the beamwidth is albeit with not that much difference in gain.)
In more technical terms, the A430S10 has an E-Plane 3 dB Beamwidth = 50 degrees. In layman’s language, this means that you will have a good receive AND transmit signal 25° above and 25° below your center angle – which in my case is 45° due to the constraints of Home Depot.
Home Depot?
I picked 45° because Home Depot sells PVC connectors for that angle – and only that angle since 90° angles really are not that useful for the hamsats!
Again, with these antennas having a 50° beamwidth, my setup handled passes between 20° and 70°. This same wide beamwidth also makes pointing the antenna more forgiving – which is important for cheap rotators which are not all that accurate between calibrations.
(The E-Plane 3 dB Beamwidth = a whopping 95 degrees for the A144S5 two meter five element Yagi – so it was not the limiting consideration.)
But enough about me and why I chose 45°. Let’s talk about you and your need for 15°.
Permanently Bending Schedule 40 PVC With My Wife’s Help
I need to plagiarize myself and steal a couple of paragraphs I have on this other webpage on my site:
Attic AMSAT Antenna – Working the Ham Radio Satellites With A Rotatable, Computer Controlled, Yagi Attic Antenna
“If you have played with PVC for antennas for a while you will already know they don’t make 15° connectors. So, I was faced with trying to bend a straight piece PVC – which I thought was going to be difficult.
“As it turns out, it is surprisingly trivial to heat even Schedule 40 PVC so that it becomes bendable with a standard 1500 watt hair dryer in less than 10 minutes of your time! (Thanks to YouTube for this education!)”
Wife Jan’s hair dryer actually had some attachments and gizmos which focused the heat better than mine so I swiped hers for this task. She was surprisingly unamused and recommended I get a heat gun for future applications. I obediently followed her recommendation and got this particular heat gun.
Something about briar patches came to mind for some reason – even though there was no mention in the Amazon description.
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Eli, I have just now added the above information to the cheap antenna page – I appreciate the heads up on helping make this clearer for other folks too.
Hope this helps...and hope to work you on the birds soon!
73,
Robert K3RRR
-.- ...-- .-. .-. .-. 73 de Robert K3RRR http://K3RRR.com @K3TripleR http://YouTube.com/K3RRR -.- ...-- .-. .-. .-.
On 12/17/2018 6:37 PM, Eli Caul wrote:
Hi folks -
In my ongoing effort to figure out how to use the SSB satellites, I duplicated this setup over the weekend:
http://k3rrr.com/cheap-computer-controlled-tv-rotor-for-amsat-satellit es-and-includes-free-satellite-tracking-with-pstrotator-and-the-usb-ui rt/
I bought a list of materials based on the photograph, and it didn't occur to me that the PVC parts pictured put the antennas at approximately 45 degrees and not the recommended 15 degrees.
Has anyone done this setup? If so, how did you assemble it so that the antennas ended up at the recommended angle?
There were a couple of higher angle passes yesterday (one was at 50 degrees) but so far I haven't been able to 'loop' the satellite. I'm using a Yaesu FT-991A for uplink and an Airspy SDR on the downlink.
Advice appreciated. So far I've gotten some excellent advice from AMSAT members and I really appreciate the groups level of expertise and patience with my fundamental questions.
73 de KK6ZHZ,
- Eli Caul
Director of Customer Care Sonic 707-237-6201 Direct 707-521-0131 Faxline
_______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb