C-band Servo Polarity Mod

[John]

.... After having success with the Ka band version, it was decided to have a venture to apply the same idea to my ageing 'old school' C-band servo system.

** This is hoped to give same H/V - LHC/RHC use as before on the 'old school' servo + polorisor barrel system but with better performance. * This might work, it might not ----- "Nothing ventured / Nothing gained" as the old saying goes.

To be continued .....

 

[John]

Right then, off we go: This thread all relates to using a CM 1.8 off-set antenna.

I'm a big believer that when using small'ish dishes for C-band that you need all the help you can get to collect and make use of as much signal as you can lay your hands on, goes without saying really ...
I thought i would try and move out of the 'Iron Age' with my trusty old Chaparral servo / AVComm poloriser barrel that uses not the most efficient signal transfer arrangement.
The simplest signal collector for me being the Conical scaler + single feed + lnb . A quick side by side comparison of the one shown in the pic against the old Chaparral system resulted in nearly a 3dB difference on some HD channels, 3720 H on 58West. That set me off on how to put the 'old boy' into retirement and get a new kid on the block.
This is the 'old boy' ...

This is the new kid on the block in test mode but not fully had the works done on it ...

.... it will change considerably

watch this space

 

[scopus]

Does that Primesat come with the waveguide? or is that something you have made?

 

[RimaNTSS]

I like your "new kid", especially those shiny bolts, I think they are.... ow my gosh..... made of INOX!

 

[scopus]

I like your "new kid", especially those shiny bolts, I think they are.... ow my gosh..... made of INOX!

I think they are just plated bolts, look at the scalar below, looks like the bolts on that are rusting

 

[John]

Does that Primesat come with the waveguide? or is that something you have made?

no it's a separate item, SSS sells them but can be obtained off the net

 

[John]

I like your "new kid", especially those shiny bolts, I think they are.... ow my gosh..... made of INOX!

No not INOX, just the bog standard things that come in the lnb box. Will probably be A2 or A4's on the finished job though

 

[RimaNTSS]

No not INOX, just the bog standard things that come in the lnb box.

Very disappointed but will not remove my "like" ... at least till your bolts start to rust..

 

[John]

for a bit of fun (Llew set me off on this one) and what also helped me to chose the "Primesat" lnb , here are some grabs off the analyser of various Cband lnb's and lnbf's i have collected over the years. The "Old Boy"+ the JRC lnb failed to resolve the HD channel on 58 west but the Primesat arrangement did. It wasn't due to lack of signal strength on the Old Boy either. The Primesat also makes for a nice lightweight package.

I should also mention that the grabs were taken with no signal, lnb's looking into fresh air, with no external surrounding influences .... nothing scientific, just a bit of amusement.

 

[John]

.... this is the "Unknown" lnbf, it's absolutely years old, can't even remember buying it. It's built like a tank , big and weighty

 

[John]

... as with the Ka project, a very similar simple cradle needed to be fabricated around the "Primesat" C-band lnb and then grafted onto the single C-band feed. At this mock-up / fabrication stage any bolts used are just the common cheap rusting type lol.

 

[scopus]

About time you got in the modern world John!

 

[John]

About time you got in the modern world John!

... Ohh you are awful--- but i like you

 

[John]

... Ohh you are awful--- but i like you

..... Oh hello honky tonk .... Only the older generation will probably remember the British Tv comedian Dick Emery, Chris ?

 

[Lazarus]

Excuse me! Older Generation?

I remember him well and I shall be 60 this year - and I am still feeling myself.

 

[John]

One of the things that needed careful attention was to make sure everything was in a straight line once coupled together to enable smooth rotation of the two parts without friction. The servo motor driving this unit is only small so no additional friction is wanted.
Pic shows rough set-up to get alignment started, and one a bit further into build

 

[John]

.... To achieve the smooth rotary coupling between the stationary poloriser barrel and the rotating feed a ready 'off the shelf' bearing + and ali pipe joint off the famous web selling site

 

[John]

Excuse me! Older Generation?

- and I am still feeling myself.

Not sure how to answer that

 

[John]

...... and with a bit of paint..

 

[Trust]

Great job John , how do you cover it from rain ?