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Radome for your dual band patch

Posted: Wed May 15, 2019 7:43 pm
by radiogareth
I've been inspired to see the various re-purposing going on to keep the WX out of the dual band feed. Inevitably I have been thinking about a simple design for a radome that traps a sheet of polythene (or cereal packet polypropylene) as the low loss 'window. I quite liked the idea of having the outer disc of the dual band feed 'snap in' but its proving tricky to get the dimensions right. It's also putting force into the weakest plane of the 3-D print. Vile colour as this is the only PETG (fizzy drinks bottle plastic) I have ATM. PLA isn't long term WX proof but PETG is both UV and WX stable.

The radome cover retention works well but I think I'll re-design the back side to just slot in and then secure with some suitable glue (UHU etc) or maybe a couple of lugs/tabs/screws.

Technical observations and comments welcome....

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Re: Radome for your dual band patch

Posted: Thu May 16, 2019 8:16 pm
by radiogareth
Well I swapped over my 1.1x1.05 TRIAX dish for my 1.2x1.15. Same LNB but a lower MER on the beacon? This new dish is easier to adjust but heavier so I still have to raise it up to the original height (+2')before I can try 'direct comparison'. I may just be squinting over the roof of the house opposite but had 8.5 early this morning but 7.7 now on the bigger dish.
Worked on a /P dish support instead to make use of a mesh dish I was given last year. It has suffered bottom arm corrosion so I braced across the weakened part. Sundry bits from my 'handy-pile', angle-grinder and MIG and its good to go. Also mounts a 65cm dish for yet to be decided use.
Surveyors tripod has been waiting for this day since 1986! A really nice bit of kit, extends to 6' plus and levelable in all axis. Both dishes can rotate 360 degrees should the need arise.
You can just see the edge of the 1.2 dish to the right of 'Maspro'. I can raise it above that but need local assistance (wife Jayne :-))
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Re: Radome for your dual band patch

Posted: Wed May 22, 2019 6:17 pm
by G7JTT
Thanks for the idea this is my take on it using a clip a seal pot I had. All I done was cut the front of the lid out and then clamp a sheet of plastic between the lid the pot.

Cheers John G7JTT
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Re: Radome for your dual band patch

Posted: Wed May 22, 2019 7:42 pm
by radiogareth
Happy to share :-)
What brand of plastic box? Did the MER improve with just the thin polythene?

Re: Radome for your dual band patch

Posted: Wed May 22, 2019 7:58 pm
by G7JTT
Just a generic one from "The Range" about £3, with the original lid I lost 2db on 3cm but was ok on 13cm. Once the lid was cut out I tried the LNB and was back to the normal around 8db, with the plastic stretch out and clamped in place I saw no difference in the received MER level. It looks a lot better than it did with the hi-tech bag waterproofing technique LOL.
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Re: Radome for your dual band patch

Posted: Tue Jun 04, 2019 8:53 am
by g8lce
How about a small hole at the bottom for pressure relief ( hot and cold weather ) and drainage should any water get in? I have had a 5.665GHz rx on the roof in a plastic icecream container for years but it has an opening at the bottom just incase rain got in. I am still using the second method with a plastic bag on my dish but now will save the cereal wrappers and get a plastic container!
A few days later....
Having bought a plastic container and fitted it I have found a problem! The plastic lid with the centre cut out - so it is just the rim - reduces the received signal!!! Even though it is well away from the centre and does not alter the position of the LNB so I am surprised. I have just rested it in position for the measurement and photo.
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And now with the lid surround resting in place
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You can see the drop in signal and these conditions were not the best. The maximum signal difference was 1dB !!
So I will keep this for now but buying a container with a clip on lid may be a waste of time and just a plastic base with a piece of polythene over the opening my be best.

Re: Radome for your dual band patch

Posted: Wed Jun 05, 2019 10:21 am
by G7JTT
Odd I thought I'd already replied to this post but seems it's no longer here ? Anyway I did find that before I cut the front out of the lid I lost a couple of dB on the beacon, but after cutting it out and replacing with thin film I saw no difference in signal from the beacon with the lid on, off or no box at all. Wonder if the use of a square box as apposed to round make any difference ? Maybe different plastic used or maybe thicker plastic ? Plus it looks like you have a different lense to me. At the end of the day it's always trial and error to see what works for each individual scenario, and more importantly your method works for you. Oh and as for the small hole good shout will add one at the weekend 👍

All best John