The C-band Tin-Dish challenge

A

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Actually, the active antenna surface of the LNB would ideally just be a section of a sphere (ball), as this i assume is what the idealised form of the wavefront coming from the reflector is.
I'm just wondering if there would be a negative effect from the out-of-focus signal coming in, working in counter-phase with the real signal, as we are talking wavelenghts in the 1-2 cm range?
 

Channel Hopper

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I seem to have problems finding documentation on how flat, square dishes work.
Can some-one here enlighten me on how those square dishes really work as antennas?

There are at least two types, slot array and active element (though the latter will be out of your budget)
 

s-band

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Long before I bought the decent large dishes, I bought a 2.4m Fortec. I finally got around to assembling it and now it's time to come out and admit to what I have done. The one I got had been damaged in transit and had kinks on one edge of most petals and a slight dents in the middle of a couple. I straightened the kinks by compressing the edges between blocks of wood but left the dents. Thanks to aceb for your notes.

Putting the dish together took a few hours:
All fixings were replaced by stainless ones and I used copper grease when assembling.
The ribs that hold the petals to the ring were not at 90 degrees to the ring fixing so they had to be corrected. I sprayed Waxoil inside the ring and all the tubes.
I built the frame and mount first
With the ring set so that the dish would be pointing at the horizon, I attached the first 2 petals. I then moved it to the "bird bath" position to do the rest. When adding petals, I found it easier to use a couple of extra long bolts and the drift to locate the petal (see drift_53.jpg). I then added the fixing bolts. Using a drift,it was reasonably easy to align the panels. Once together, I tweaked the alignment a bit but it was not too bad to start with. I haven't tried it yet as the weather hasn't been great.

OK, so the metal will probably decay faster than the pallet but for less than the price of an AV-Comm polariser etc you could get a C Band starter kit which will not need planning permission.
Dish £Free-£180 (mine was £100, new but mangled)
Cheap LNBF e.g. Titanium Lite £18
Castors £15
Pallet £Free
The stainless fixings were about £25 extra

I'll make sure I tie it down if I leave it outside as it probably will not make a very controllable land yacht. Once it have it running I will report again.

In_box_17.jpg part_built_52.jpgdrift_53.jpg almost_finished_57.jpg side_63.jpg 1265.jpg back_67.jpg
 
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A

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Long before I bought the decent large dishes, I bought a 2.4m Fortec. I finally got around to assembling it and now it's time to come out and admit to what I have done. The one I got had been damaged in transit and had kinks on one edge of most petals and a slight dents in the middle of a couple. I straightened the kinks by compressing the edges between blocks of wood but left the dents. Thanks to aceb for your notes.

Putting the dish together took a few hours:
All fixings were replaced by stainless ones and I used copper grease when assembling.
The ribs that hold the petals to the ring were not at 90 degrees to the ring fixing so they had to be corrected. I sprayed Waxoil inside the ring and all the tubes.
I built the frame and mount first
With the ring set so that the dish would be pointing at the horizon, I attached the first 2 petals. I then moved it to the "bird bath" position to do the rest. When adding petals, I found it easier to use a couple of extra long bolts and the drift to locate the petal (see drift_53.jpg). I then added the fixing bolts. Using a drift,it was reasonably easy to align the panels. Once together, I tweaked the alignment a bit but it was not too bad to start with. I haven't tried it yet as the weather hasn't been great.

OK, so the metal will probably decay faster than the pallet but for less than the price of an AV-Comm polariser etc you could get a C Band starter kit which will not need planning permission.
Dish £Free-£180 (mine was £100, new but mangled)
Cheap LNBF e.g. Titanium Lite £18
Castors £15
Pallet £Free
The stainless fixings were about £25 extra

I'll make sure I tie it down if I leave it outside as it probably will not make a very controllable land yacht. Once it have it running I will report again.

View attachment 100580 View attachment 100582View attachment 100587 View attachment 100583 View attachment 100584 View attachment 100585 View attachment 100586
Applaud on a very nice build. Probably the most meticulous I've seen so far.
But you should ditch the stand ASAP. It's really cr*p.
I know others get some mileage from it, but really, the time spent fiddling with the dish deserves a proper polar mount.
Just can't think of an easy source of good, cheap polar mounts... :(
 

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The shot with the skylights in it makes me imagine a switch getting flicked and the sloped roof moving up and out the way like a bond film lair or Thunderbird's lol.
 

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Looks like lubricant for slidey parts

1265-jpg.100585
 

moonbase

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s-band,

Are you going to put some ballast on the pallet? I have a similar temporary setup with a 1.5m dish on it and placed two concrete kerb stones on it for anchorage (pic. attached)

There seem to be a few forum members going for the castors option as a get around for planning permission. Does anyone know if the castors are mandatory on a pallet as a get around? In practice, the pallet without castors could be easily raised and moved using a trolley jack. It might inspire some of the ultra modders to construct a steel pallet from heavy duty box section, over to you "blade..."

Rgds
 

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s-band

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Applaud on a very nice build. Probably the most meticulous I've seen so far.
But you should ditch the stand ASAP. It's really cr*p.
Thanks. I followed aceb's lead but I think his may be more precise as I have not strung it.
Please tell me that's something you've applied and not rust... :)
Looks like lubricant for slidey parts
Yes, it's a mixture of Waxoyl and grease
s-band,
Are you going to put some ballast on the pallet? I have a similar temporary setup with a 1.5m dish on it and placed two concrete kerb stones on it for anchorage (pic. attached)
I liked the idea of a water tank as ballast (Terryl's?) so may try that if I leave it outside for any length of time.
I saw this airport cargo/pallet trailer with rotating table | eBay and thought it would be a possibility especially as it has a turntable for azimuth.
I'm not sure what I'll do with it once I have enough time to do the big dish. I thought of making it az-el. The el is easy but for az I was thinking a pole could be used as a bearing vertically through the centre of the pallet and the other end of the pole would go into a socket in the ground. Another pole in the ground could hold the fixed end of a jack with the moving end attached to the pallet. If that were done it would be better to have fixed wheels as opposed to castors. Crazy idea? Probably would not last long and I doubt that I'll do it.

The castors are fine on concrete but are not ideal here as they tend to sink in the ground so I need to keep away from the swampy areas of garden.
 
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blademedia

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It might inspire some of the ultra modders to construct a steel pallet from heavy duty box section, over to you "blade..."

I could easily fabricate some if peeps was interested, I could make them bolt together for easier shipping, A couple of quotes received from planning while making enquires for my project.
ooooppp.PNG pppp1.PNG
 

moonbase

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I could easily fabricate some if peeps was interested, I could make them bolt together for easier shipping, A couple of quotes received from planning while making enquires for my project.
View attachment 100613 View attachment 100614


blademedia,

It is an interesting point re "...easily moveable..." and could be open to interpretation. I think wheels is guaranteed to exclude it from planning, however, a steel pallet with a trolley jack might get a thumbs down. A steel pallet with castors is possibly the way to go. The steel pallet could easily be secured against movement even on castors.


Rgds
 

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blademedia,

It is an interesting point re "...easily moveable..." and could be open to interpretation. I think wheels is guaranteed to exclude it from planning, however, a steel pallet with a trolley jack might get a thumbs down. A steel pallet with castors is possibly the way to go. The steel pallet could easily be secured against movement even on castors.


Rgds

The way forward imho, is to ask and explain your intensions before you do anything, planners can bend the rules to suite themselves, once permission is granted I would imagine its hard to go back on there word,

There was a case regarding a ham radio beam on a trailer, the person put it up without asking (perfectly in his right) he was made to take it down after a long court case :(
 

s-band

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There was a case regarding a ham radio beam on a trailer, the person put it up without asking (perfectly in his right) he was made to take it down after a long court case :(

Do you have a link to the ruling(s)? I'm sure the results would be different between siting it in a suburban front garden compared to a field in the middle of nowhere. Actually moving the thing must also help the cause.
 

blademedia

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Do you have a link to the ruling(s)? I'm sure the results would be different between siting it in a suburban front garden compared to a field in the middle of nowhere. Actually moving the thing must also help the cause.

This is the case in question, I had to dig deep to find the final decision, he was made to take it down, it was in his bungalow back garden
Inspector to decide on radio mast appeal
 

s-band

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I had some time to try it out. 1st problem, I couldn't get it out of the garage so I had to remove the feed tripod! Dragging it across the grass, it goes where it wants to but I won in the end. With the dish pointing at the horizon, it feels a bit front heavy so needs a bit more weight on the back. Aligning it on 40.5W didn't take long. I used an inclinometer to set the elevation and roughly set the az using a compass. Tweaking elevation slightly is awkward as it is not well balanced below 30 deg. Tweaking az can be hard as it tends to sink into the ground. It really needs to be used on solid ground. Observations:
  • It works - it was about 3dB better than a 1.5m (vs 4dB theoretical). However when I removed the feed I noticed that the dielectric plate in the Tit LNBF was out of place so another dB may have been possible.
  • On 40.5W 50 TPs locked vs 24 on the 1.5m
  • The beacon on 3947.5H was 30dB s/n in 1kHz both the Titanium Lite & normal (I don't have 1.5m figures for comparison)
  • It would be much easier to use with a jack for elevation even if it were not fully motorised.
  • The AV-Comm polariser in Zinwell scalar ring combination does not allow the feed to extend far enough through the ring to optimise focal point or scalar position for the dish's f/d
  • The Tit scalar is fine for both Tit LNBF and the AV-Comm polariser
  • As per earlier comments, it is a cheap entry to C-band without planning issues.
I might play some more but I need to get the garage back so will probably list the dish for sale soon.

fortec_84.jpg incl_83.jpg
 

s-band

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38E My go to satellite for testing, locked a total of 14 transponders from this yesterday.
Capital 4184V 8.8dB
Waseb 4114V4.7dB

I tried 38E and got 12 transponders but not the 2 above (EBSPro vertical scan attached). I just managed to lock 4184V at about 4dB but got nothing from 4114V. I was using a Norsat 3220 but tried a Tit to double check, it was about 1dB down. Looking at the posts on Satellites Community my figures are all over the place compared to others. Some better, some worse (taking dish sizes out of the equation). I could see the horizontal transponders (4005 & 4060)on the analyser but there was no chance of locking.

I am suspicious that I may not have the correct focus. The instructions say 912mm, I was getting best signal at around 885mm. I can't get the LNB further away than 895mm and at that point it picks up lots of ground noise from the feed side lobes. If I get a chance, I'll move the feed arms to the wrong side (inside face) of the scalar to see if the focus is really closer to 912mm. My gut feel is that there are a couple more dB to be had by optimising focus and stringing the dish.

38E.JPG
 

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I usually attack my set-up procedure for PF and Off-sets this way Graham ...
..... String it and adjust and adjust for best if necessary for peace of mind ,

Use a spare scalar ring Graham located further back than the 912mm for the sole purpose of anchoring the lnb arms .... you might have to extend the arms ?? ., check alignment of the lnbf barrel on both axis to ensure it's looking straight at the centre bolt fixing accurately of the circular plate. , tune the lnbf barrel only for max sig strength, .... on Cband you may find it a bit "wooley" to obtain a precise point which is the obvious right spot, i did on my 1.8 off-sets ...... if so start off at what they say-- 912mm, then fit the 2nd floating scalar and adjust for best C/N, finally carefully tweek both lnbf and floating scalar to obtain maximum C/N. Do it tomorrow while the sun is shining :)

Edit: I'll have a quick look and scan of 38E
 

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I usually attack my set-up procedure for PF and Off-sets this way Graham ...
..... String it and adjust and adjust for best if necessary for peace of mind ,

Use a spare scalar ring Graham located further back than the 912mm for the sole purpose of anchoring the lnb arms .... you might have to extend the arms ?? ., check alignment of the lnbf barrel on both axis to ensure it's looking straight at the centre bolt fixing accurately of the circular plate. , tune the lnbf barrel only for max sig strength, .... on Cband you may find it a bit "wooley" to obtain a precise point which is the obvious right spot, i did on my 1.8 off-sets ...... if so start off at what they say-- 912mm, then fit the 2nd floating scalar and adjust for best C/N, finally carefully tweek both lnbf and floating scalar to obtain maximum C/N. Do it tomorrow while the sun is shining :)

Edit: I'll have a quick look and scan of 38E
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>> I'll have a quick look and scan of 38E[/QUOTE]<<

Well your doing a lot better than me G, i can't see nowt up here in North Notts from 38E but the footprint suggests there should be no drop off.
Tried the Zinwell+Barrel and also a dedicated H/V only motorised single feed with lnb and practically zilch apart from the odd low level spike here and there, yet the next bird along at 40E is booming in.
 

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..... String it and adjust and adjust for best if necessary for peace of mind ,

Use a spare scalar ring

Cband you may find it a bit "wooley"

Do it tomorrow while the sun is shining :)

Strung it last night and it was pretty close. Aligning the holes and the petal levels must have helped. Spare scalar - good idea, thanks.
2.4m at C band is about the same as 90cm at Ku on the woolyness scale.
I'll try but work gets in the way

i can't see nowt up here in North Notts from 38E but the footprint suggests there should be no drop off.
That confuses me even more. I find it hard to believe that the footprint varies as much as it appears. The strongest TP for me was 3984V at 9.3dB SNR.

7 transponders on 40E locked whilst pointing at 38E.

I can't find the beacons on 38E 3702.9H & 4196.5H according to http://frequencyplansatellites.altervista.org/Beacon-Telemetry_Europe-Africa-MiddleEast.html . 40E beacons are strong.
 

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Hi - john .
Recalling past results posted on here, i think folks near the south coast have done better with this sat than us further north :(.
Using 1.8 C.M. offset with a Zinwell + stepped conical feed (no Avcom barrel) i,m locking Dunya Ent ..
4091V 3330 this morning ... a number of others are showing some signal but are not lockable .. using DR HD F15 receiver.
The AJK transponder usually locks on 1.8 here but is only on air for a few hours in the afternoon.

@s-band .. will look with the 2.4 C.M later if i get time to put the C band l.n.b on ...
the only time i,v had 10 or more transponders though - up here in the north west - from this sat was using the 3 M Prodelin :)
regards ...
 
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