Attaching a WR42 flange to C120

[Vipersan]

No Idea if this will work ..but I had to try.
I have a C120 matched feed for my Gibby ..but of course Ka LNBs use WR42 connections/flanges.
So a total mismatch there ..but the C120 feed illuminates the Gibby correctly.
Out came the ally again ..and set to work making an adapter ..
How well it will perform ..I'll find out tomorrow ..
But looks a good mechanical fit now ..
rgds
VS

 

[Lazarus]

I have nominated you for the Nobel Prize in Jiggery-Pokery.

 

[Vipersan]

I do love a pit of Pokery ..not so sure about the Jiggery tho..

 

[Llew]

VS, surely the feedhorn scalar rings are designed to provide max signal to a KU band waveguide opening?

Won't there be some mismatch there?

 

[Vipersan]

VS, surely the feedhorn scalar rings are designed to provide max signal to a KU band waveguide opening?

Won't there be some mismatch there?

Hi Llew ..
How ya feelin buddy ?
Yep you're quite right ...there WILL be a mismatch which is why it most likely wont give excellent results ..but I gotta try.
All the signal collected by a the correctly illuminated dish will be funnelled to the LNB ..but no idea as to the effects of incorrectly sized and spaced concentric rings ...
So the Choke implemented will definately be a mismatch.

 

[Llew]

Still hobbling about. Just ordered a Promax HD Ranger+ out of the proceeds of the insurance valuation for my wrecked Polo - I don't envisage getting another motor until next year, so I may as well stick to the bus pass and spend it on something worthwhile.

Regarding feedhorns, I sliced open a KU SMW combined LNB/feedhorn I picked up on fleabay a while ago and oddly the inside diameter circular dimension is almost the same as for KA band ;)

I attached it Heath-Robinson style to the XMW LNB and Triax TD88 on 16E and had favourable results compared to the FD9000 feedhorn. Just need to make something similar to your flange to screw them together.

SMW Feedhorn before parting from the LNB -

 

[Vipersan]

..Nice Feed Llew ..
I could have some fun with that..
Just popped the Ka lnb c120 on the gibby ..
As expected ..not locking anything atm ..but getting 5.3db on Golfe TV @ 16 East ..
So ..sort of working I guess ..
A fair bit of cloud and light drizzle atm ..
Will play some more tomrrow ..and remove that gawdawful thick platic cap.
too dark and too cold to play out tonight.
Whats the feed SMW ident Llew..
I'll look out for one..
ya never know.

 

[Vipersan]

...There's hope I guess ..
Just locked TPA @ 7 East 4.2db with the hybrid combo..

 

[Llew]

..Nice Feed Llew ..
I could have some fun with that..
Just popped the Ka lnb c120 on the gibby ..
As expected ..not locking anything atm ..but getting 5.3db on Golfe TV @ 16 East ..
So ..sort of working I guess ..
A fair bit of cloud and light drizzle atm ..
Will play some more tomrrow ..and remove that gawdawful thick platic cap.
too dark and too cold to play out tonight.
Whats the feed SMW ident Llew..
I'll look out for one..
ya never know.

No identification on the feedhorn unfortunately.

I'll post a pic in a mo when I change the battery on my camera.

 

[Llew]

Feedhorn comparison with the C120 Gibby feed -

 

[Vipersan]

certainly looks a better match Llew ..
I'd like to get me one of those ..
Anyone got a spare one in their bitz box ?

 

[Vipersan]

Ok ..good news ..
This morning it was raining (not often I can say that) ..and TPA at 7E was unlockable with the combo at 3.3db..
So removed the assy ..and popped off the plastic cap which in itself only gained about 0.8db..as expected.
Then tried an idea that came to me whilst dropping off to sleep last night ..
Lined the inside of the choke cone with ally tape ..thus countering the effects of Tuning to a large degree ..
Popped the assy back on the gibby ..again with no cap ...and even in the rain TPA was instantly lockable at 5.5 db
So swung back to 16E ..and Golfe which was unlockable last night ..
Instant lock at 7.9 db..
Nice..

Yes I'll have to fit a cap ..as the feed is more inclined to funnel rain into the lnb ..but hey ...thats some improvement..
rgds
VS

 

[Vipersan]

A supermarket bag stretched over the feed atm ..
Rain has got heavier ..
Dish wet through ..
Sadly lost lock on Golfe around 5.5db
TPA still just about locks at 4.4db

 

[Vipersan]

The next stage is to try and construct a matched KA feed based on the C120 shape and design..for the gibby...in copper
Only cos this I can solder
So I now have my ideal outer feed diameter 289mm
and ideally the inner circle diameter would be 11.5 mm (1mm walls would be 13.5mm)
BUT ..such copper pipe doesnt exist in a rigid form (needed to support weight of lnb)
So I will get as close as possible..and use 15mm cold water pipe (15mm - internal diameter 13mm)
Close but not perfect..but hopefully would be an improvement.
Using these dimensions I should be able to make a cardboard template which could then be folded into a smooth sided cone ..copied to copper sheet..and soldered to a length of 15mm pipe.
Then construct a WR42 flange in copper for the other end...
Will it work ? ..who knows ..?
First I have to make my cone template ..and try and source some thin copper sheet to make it.
Another project for another day..
rgds
VS

outer
92mm diameter
289mm circumferance

Ideal inner
11.5mm
36.1 mm

Selected inner
15mm
47.1mm

 

[Vipersan]

Found a suitable copper sheeting on ebay :-

Had to go to Israel for a bargain ..
Too expensive here..
Grabbing sods..
10 inch x 10 inch sheet copper 24 gauge ..
£15 delivered

 

[Vipersan]

First template for the cone ..in paper..
Snug fit inside the Matched Gibby feed ..

 

[Vipersan]

Just tried to mount the Norsat LNB on the combo assembly ..and can't.
The screws supplied are the only ones that will fit the threads in the LNB.
They are too long and have an odd thread ..
coarser pitch than M3s ..but roughly the same diameter as illustrated in the photo..
..and of course I need shorter lengths and coutersunk anyway.
The top bolt is an M3 ..
the bottom ...I have no idea ...???
Can anyone help?

I'm guessing 1/8th or 2/16ths ..possibly bga thread..
HELP!!!

 

[RimaNTSS]

This year I've got some stuff made in USA and also old made in Japan LNBs. Here and there they used threads different from metric, which, I suppose is inch thread. Of course, nowadays is possible to buy any nuts&bolts including those inch-threaded. However not all shops have them and if they can find they would like to sell you whole box (50, 100 etc). When I needed fine threaded 12mm nuts, instead of 10 I was forced to buy 50!
So, those made in Japan LNBs have some nuts&bolts, perhaps you could also use some parts of LNBs for your project. I could offer you a couple.
Just took picture of some bolts I have: bottom line 6mm, 5mm, 4mm metric. At the top look like but not metric ~6mm, than ~5mm. 4mm is comparable to metric. And last ones little bit less than 3mm.
Small 3-4-5-6mm nuts and bolts is nothing in comparison to big ones (8 and bigger) my Prodelin and Andrew antennas have, I also need another set of wrenches.
Edit: http://www.bosunsupplies.com/ScrewSizesThreads/

 

[Vipersan]

Nice lnb collection Rima ..
Lots of fun and experimentation to be had there I suspect..
Chances are you'd have the bolts I need ...but first I need to accurately indentify the damned things..
Llew has the same LNB ..perhaps he can help.

 

[RimaNTSS]

Can not you exchange bolts to 4mm threaded studs or bolts made of INOX?