"The proof of the pudding is in the eating"
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Ernst Lobsiger
Dear All,
we all get older and cannot climb ladders and roofs at some point. The happy ones have their dishes on a flat roof accessible by a door or even better at GND level. Last night I looked again at some pictures of Robert's antenna and I just wondered, whether a 1.0 - 1.2m dish in his garden could do the job. If the current antenna is taken down and the apple (?) tree somewhat cut back it could work. Up to 25m of LNB cables should not pose a problem either. Actually that's what has worked here for more than 10 years. "Probieren geht über studieren". Any comments regarding antenna patterns (HPBW<2°) and dish pointing in a rather unusual situation like this? Cheers, Ernst P.S. Attached a picture taken with E10A right behind the dish center. At about 1.7m above GND, 2m left from here I would give it a try.  |
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Robert Moore
Yes, it’s an apple tree but the foreshortening in the photo misleads – the tree is behind the dish. Await responses with great interest!
Robert
From: MSG-1@groups.io <MSG-1@groups.io> On Behalf Of
Ernst Lobsiger via groups.io
Sent: 10 March 2023 17:14 To: MSG-1@groups.io Subject: [MSG-1] "The proof of the pudding is in the eating"
Dear All, |
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rnosborne@...
I can't comment directly on the question asked but if a ground based dish is a possibility then you could have up to 50m of LNB cable run to give more latitude in finding a suitable spot. I had a 20m cable run originally but extended this up to 50m with an F-Plug coupler when I moved my dish with no apparent ill effects. The LNB is the Inverto Black Ultra.
Richard |
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Ernst Lobsiger
On Sat, Mar 11, 2023 at 10:34 AM, <rnosborne@...> wrote:
I can't comment directly on the question asked but if a ground based dish is a possibility then you could have up to 50m of LNB cable run to give more latitude in finding a suitable spot.Richard, thanks for that but there are other trees limiting the possibilities in Robert's garden. Ernst  |
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On 11/03/2023 18:34, rnosborne@... wrote:
I can't comment directly on the question asked but if a ground based dish is a possibility then you could have up to 50m of LNB cable run to give more latitude in finding a suitable spot. I had a 20m cable run originally but extended this up to 50m with an F-Plug coupler when I moved my dish with no apparent ill effects. The LNB is the Inverto Black Ultra.Richard, Did you find that an in-line amplifier was necessary to get an adequate signal at the receiver? 50m is quite a long run! David -- SatSignal Software - Quality software for you Web: https://www.satsignal.eu Email: david-taylor@... Twitter: @gm8arv |
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rnosborne@...
David,
No. I'm feeding a TBS6983 and I don't use an amplifier. I believe that the Inverto LNB is classed as a high output model. My latest cable extension uses what I understand to be good quality cable which is Webro WF100. Regards, Richard |
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Charlie
The conversion gain of those Inverto Ultra series LNBs is very high - and if that's good cable like WF100 or similar should be more than capable of that length of a run so I'm not surprised. Vast majority of the noise is introduced before the cable so you can lose a lot of signal on the coax before even starting to worry. If worried you could always step up to WF125, but the main problem you're liable to get at those sort of lengths is voltage drop if it's CCA/CCS cable (stick with the full copper at that point). Re. pointing from the garden; outside of the 3dB beamwidth the next sidelobes are WAY down on a usual parabolic dish so if the concern is trees out of the "beam" I wouldn't entirely be worried. I've had no problems getting a dish on a tripod to perform; I suppose I can make a proof test by taking it down the garden (some tall trees here that very much block the view of 10° E from some parts of it) at some point shortly to compare performances.On Sat, 11 Mar 2023 at 18:57, David J Taylor GM8ARV 🏴 🇪🇺 via groups.io <david-taylor=blueyonder.co.uk@groups.io> wrote: On 11/03/2023 18:34, rnosborne@... wrote: |
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Charlie
Richard, Looks like you answered what I was thinking as I sent it - magic!On Sat, 11 Mar 2023 at 19:17, <rnosborne@...> wrote: David, |
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Ernst Lobsiger
Charlie, Richard and All,
treating 3cm wavelength quasi optic a 1m dish should just have a free cylinder of 1m diameter with its axis towards E10A. This is certainly possible from Robert's garden. A more physical view explains the dish with a diffraction pattern, main lobe and side lobes. What we observed with our solar outage measurements is that the effect of the sun shows up when the disk of the sun scratches the HPBW "radius". HPBW is the full "diameter" of the main lobe between -3dB points. For my huge Gibertini OP 125L it's specified 1.32° but of course there are strings attached like matched feed. First side lobes are said to be 24dB down again with matched feed. So I can assume that I'm safe as long as nothing looms into a "radius" of 1.35° degrees. But the problem I see is that this is in the so called "far field". We cannot assume a main lobe that starts at the center of the antenna with one HPBW. The transition from "near field" to "far field" for a 1m dish is at about 66m. So all the possibly disturbing obstacles we see here are in the "near field" where only the pudding might know what's going on. I would still assume that if we can offer a free cylinder with a diameter of 2-3m then it should work. That's just about what's possible. I attach an image that was taken last fall 2022/10/17 where the sun is already down at 26°. So this is a more flat view than the first image that was exactly at E10A elevation of 28°. You see the timber line at the horizon is now further up and to get the correct direction to E10A we have to move up app. 0.5m. From the gardening point of view the apple tree should get a cut anyway :-). There is no point in cutting it further down than the horizon behind. The HF antenna on the roof and the dish pole work both as "short circuits" for the vertical polarized HVS-2 signal. That's why we have to go 2m to the left for a first experiment. Cheers, Ernst  |
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Robert Moore
I will not attempt to enter a discussion of Half Power Beam Widths etc. Ernst says, ‘ …. we have to go 2m to the left for a first experiment.’ I am not sure exactly what this means, but about 1.5 metres to the east of the dish pole I have a concrete base with a metal socket for a pole. I used this when I started out with the hobby about 22 years ago and the shrubbery was shorter. This could be used to site a dish pole, or a pole for the airband stick aerial. If the reference to the HF antenna on the roof is to the long wire aerial, it would be more difficult because the long wire would then have to pass through the apple tree!
Robert
Telephone: 44 (0) 1352 714456
From: MSG-1@groups.io <MSG-1@groups.io> On Behalf Of
Ernst Lobsiger via groups.io
Sent: 11 March 2023 21:48 To: MSG-1@groups.io Subject: Re: [MSG-1] "The proof of the pudding is in the eating"
Charlie, Richard and All, |
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Ernst Lobsiger
On Sat, Mar 11, 2023 at 03:59 PM, Robert Moore wrote:
Ernst says, ‘ …. we have to go 2m to the left for a first experiment.’Robert, just go again into the garden to the place you took these two shots from behind the antenna. That will also put your current dish in the middle of the main lobe a new antenna to be tested where you stand. That's why we have to move some two meters to the left from the line of sight. The circles I have drawn onto your image are not the antenna but show where your new antenna "beam" passes (where most of the energy from E10A will come from) . I try once more to add a better sketch of the situation below. The HPBW just shows you how sensitive the pointing of a dish really is. For HPBW=1.5° good pointing (azimuth and elevation) must be almost +/- 0.1°. Ernst  |
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Ernst Lobsiger
On Sat, Mar 11, 2023 at 10:34 AM, <rnosborne@...> wrote:
I can't comment directly on the question asked but if a ground based dish is a possibility then you could have up to 50m of LNB cable run to give more latitude in finding a suitable spot. I had a 20m cable run originally but extended this up to 50m with an F-Plug coupler when I moved my dish with no apparent ill effects. The LNB is the Inverto Black Ultra.Richard, the only unknown with long cables might be the power supply for the LNB that should receive at the antenna position 18V for H and 13V for V polarization. Routers like the SR1 or Novra S300 have a "long line compensation" (to overcome DC voltage drop along the line) that you can configure in the setup. I have no idea how TBS cards or boxes handle that. My four cables run only 25m. There is no voltage "booster" switch in GNU/Linux drivers and I have no clue on the Windows tools side. Regarding the TBS-5930 USB-box under Windows, Charlie had rather bad news for EUMETCast users with that OS. https://groups.io/g/MSG-1/message/34593 Nevertheless I still think someone should try the TBS-6904SE under Windows (it works quite well under GNU/Linux with the Telespazio signals). If you are still interested to try this card out send me your post address in a PM and I'll pack and give it to you. Maybe if it turns out that the TBS-6904SE has similar problems as the TBS-5930 (both use the M88rs6060 chip but different interfaces USB/PCIe) you could hand the card over to Charlie Johnson, Alan Curnow or someone else in the UK that uses GNU/Linux for EUMETCast reception. I might also give you a hand setting up your own GNU/Linux box on some old surplus PC if you are interested. Considering what you do with Python I think you could also master GNU/Linux. Best regards, Ernst |
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rnosborne@...
Ernst,
I can certainly try using the TBS-6904SE with EUMETCast under Windows if you are willing to send it to me. I have a "test" machine which I use for experimentation that is dual boot with Linux Mint and Windows 10 so I could try the card with both operating systems. My own experience to date suggests that the CPU/motherboard combination can affect the lost packet count, even with the same software configuration, so any results that I obtain may not be directly applicable to someone else. I will pass the card on if I don't need it but I would like to try setting it up with Linux first though to see what happens. I'll pass my details on a PM. Regards, Richard |
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rnosborne@...
Ernst,
Have you received my PM? I've just discovered that my email server is rejecting incoming emails sent from groups.io for some reason. Regards, Richard |
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Ernst Lobsiger
On Wed, Apr 5, 2023 at 10:05 AM, <rnosborne@...> wrote:
Have you received my PM?Richard, No. I only got your last two messages from this list (2023/03/31 and today 2023/04/05). Regards, Ernst |
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