C-band Servo Polarity Mod

[John]

@John How do you fix servo motor in the bracket? Is it just stuck inside? Is not that little bit overkill with strength of the bracket for the motor? If you have exact drawing of needed bracket, I could try to make one out of 2mm INOX.

The close proximity of the camera makes it look bigger than it really is ........ just knocked it up out of available bits and bobs out of the scrap bin.
The motor is a snug fit but has also got a very thin layer of silicone around it, when it is fitted to the lnb cradle spindle coupling and tested for functionality i will determine if it needs any further refinement then. Would look nice in INOX tho

 

[John]

This is the start of the coupling device between servo motor and lnb cradle spindle

Cheap and simple to make.

 

[John]

.... select the right size and modify to suit

Heat shrink and couple together for temp test later

 

[John]

... Bench testing done and seems to be ok. Final securing of servo motor bracket needed, fit weather shield over motor and bearing assembly and fit onto dish when it gets a bit more bearable working outside.

Test video's here ...

and here ....

 

[John]

EEkkkk first vid link duff, will check it out ...

try this ...

 

[nelson_b]

o.k. @John
as promised some pics of the recently purchased AV-Comm ... and some details
203 mm length
71 mm external diameter - both ends
63 mm internal diameter front
60 mm internal diameter rear
38 mm from front to start of 1st step
25 mm from end of last step to reduction in rear section
30 mm length of reduced rear section

 

[John]

o.k. @John
as promised some pics of the recently purchased AV-Comm ... and some details
203 mm length
71 mm external diameter - both ends
63 mm internal diameter front
60 mm internal diameter rear
38 mm from front to start of 1st step
25 mm from end of last step to reduction in rear section
30 mm length of reduced rear section

View attachment 90960 View attachment 90961 View attachment 90962

Thanks for that Nelson, it looks a well made item and more beefier wall thickness than my two types..... wether it's just the camera close proximity ??. Mine are in the freezing workshop at the moment but i will do some comparison measurements tomorrow for sure.

 

[nelson_b]

Thanks for that Nelson, it looks a well made item and more beefier wall thickness than my two types..... wether it's just the camera close proximity ??. Mine are in the freezing workshop at the moment but i will do some comparison measurements tomorrow for sure.

could be the camera - close up shot - its a bit uneven in its thickness but between 3.5 mm and 4 mm at the front and 5 mm to 5.5 mm at the back .. a chunky thing for sure ..

 

[John]

could be the camera - close up shot - its a bit uneven in its thickness but between 3.5 mm and 4 mm at the front and 5 mm to 5.5 mm at the back .. a chunky thing for sure ..

very chunky indeed, can't remember mine being 5mm or so at the back end. Nice and thick material though if you ever needed to machine any of the surfaces to suit personal modding requirements

 

[Captain Jack]

So would the offset feedhorn fit straight on? And how would the lnb attach on the other end?

 

[John]

So would the offset feedhorn fit straight on? And how would the lnb attach on the other end?

.... just about to go out into the workshop to measure my poloriser barrels for Nelson CJ so a quick answer first .... Look at post 33 pics, if you are going to use it as a static L/R circ only installation with a lnbf of your choice , then join all three together. Some machining of the outer / inner dimensions of the individual units might be required to establish this, as i had to do.
OR; .... as in same post, image 2629, insert the pol tube where the black mounting clip is shown so you have this final combination ..... Conical scalar > Poloriser tube > single C-band feed > C-band lnb.
The machining of parts will probably apply here as well. The scalar and poloriser tube remain in a fixed static position and only the single feed/lnb are either manually or motorised rotated in the end of the poloriser barrel to give you the L / R or H/V choice. Hope this helps .... off to the freezing workshop now

 

[nelson_b]

So would the offset feedhorn fit straight on? And how would the lnb attach on the other end?

No - C.J. - not a straight fit ... but managed to remove enough metal from the feed to get it on there (just).
for temporary testing i used a empty can to sleeve / join the l.n.b.f. to the AV-Comm. -- poor weather stopped me though ... to be continued at some point ....

 

[John]

o.k. @John
as promised some pics of the recently purchased AV-Comm ... and some details
203 mm length
71 mm external diameter - both ends
63 mm internal diameter front
60 mm internal diameter rear
38 mm from front to start of 1st step
25 mm from end of last step to reduction in rear section
30 mm length of reduced rear section

View attachment 90960 View attachment 90961 View attachment 90962

@ Nelson, the two types of barrel iv'e got are the 'AV-Comm' and the 'National ADL'.
The AV-Comm has exactly the same dimensions to yours apart from internal diameter rear which is 60mm on yours, mine is 63mm, as the front.

The 'National ADL' is 35mm from front to start of first step.
The overall length of the AV-Comm is the same, 203mm. The National ADL is 163mm.

 

[otokoc]

this my avcomm with testing esx241,bsc421,c1wpll and zinwell. i have best gain avcomm and zinwell lnb

 

[John]

this my avcomm with testing esx241,bsc421,c1wpll and zinwell. i have best gain avcomm and zinwell lnb

thanks for the information otokoc, very interesting. Glad to see that others have to have their units machined.

 

[nelson_b]

@ Nelson, the two types of barrel iv'e got are the 'AV-Comm' and the 'National ADL'.
The AV-Comm has exactly the same dimensions to yours apart from internal diameter rear which is 60mm on yours, mine is 63mm, as the front.

The 'National ADL' is 35mm from front to start of first step.
The overall length of the AV-Comm is the same, 203mm. The National ADL is 163mm.

Thanks- John- for the details ...
i wonder why the rear diameter should be reduced to 60 mm ? ... cant see any advantages

 

[John]

Thanks- John- for the details ...
i wonder why the rear diameter should be reduced to 60 mm ? ... cant see any advantages

I'm not a 100% sure but it might be to do with frequency range ??? don't really know. The barrels on different lnbf's are also slightly tapered , well mine are

 

[Captain Jack]

I find it annoying that you would spend £200 on the barrel and the having to machine it down to fit industry standard equipment sizes....

 

[John]

I find it annoying that you would spend £200 on the barrel and the having to machine it down to fit industry standard equipment sizes....

Too true, i recon it wouldn't be too much of a job to home brew one of those

 

[John]

Well .....
been doing a bit of evaluation between the old Cband Chaparral servo / new motorised project / single feed+scalar ring choice.
Briefly, the new motorised polarity servo unit + Primesat lnb for H/V ...LHC/RHC gives around 2dB better signal performance over the old unit. The use of just a single feed + Norsat pll lnb + conical scalar used on either H or V has a slightly better performance, 1/2 a dB or so, as you would expect. Here's a surprise ..... change the conical scalar on the single feed to a Cone scalar and got at least 1/2 db increase ... only small increases but every bit helps when trying to squeeze the last drop out of a 1.8 CM system.
Note: Everything in the pics are in prototype mode, a tidy up of all brackets, nuts & bolts, cables, earthing etc to be done in warmer weather. :-)