Feed pointing

[RimaNTSS]

Hi All! I just wish to collect ideas on the ways how to point the feed (LNB or LNBF) from it's position towards the dish. Some people (I am one of them) use laser-pointers installed in the LNB-holder to see where is LNB is really pointed. Some people use piece of plastic pipe or even piece of wood installed instead of the LNB to see the real pointing line. But my question here would be what would be the best way to do the feed-pointing check? Is that can be something very simple installed instead of the LNB? Should that be something with rotating mechanism to show some laser marks on the surface of the dish? On the picture attached I have collected some of the parts which I've used to point the LNB. But, in reality, is not that enough to have some universal piece of plastic which can be placed in 40mm or 63mm LNB holder with the laser pointer in the middle to see where exactly LNB is pointed? So, I would be interested in users thoughts on the ideal feed-pointer device.

 

[Channel Hopper]

I can help with that.

Your profile picture suggests offset dishes, but are you more centre fed ?

 

[RimaNTSS]

In case of my avatar there are no feed-pointing device can be used. But I think that universal feed-pointing device can be used in case of prime-focus or offset dish and for C-band and Ku-band. That could also be used for Ka-band, but I do not know the diameter of the LNB. Is that 23mm?

 

[Channel Hopper]

The Ka band LNBs I have used have all been bolted insde the housing for the SSPA, with an internal orthomode transducer, so are single polarity only.

From memory there has been no 'adjustment' at the feed end , since the dish design is perfected between the reflector and feedhorn.

 

[RimaNTSS]

Back to topic. Made this 40/65mm adapter which fit in C-band and Ku-band LNB holders. Inserted inside the adapter simple laser-pointer shows where LNB is pointed.

 

[blademedia]

laser-pointer shows where LNB is pointed

Its so much better making them to fit in the throat of the lnb,

By the time you've dismantled the laser from your design and installed a lnb it could be pointing anywhere .

 

[RimaNTSS]

Its so much better making them to fit in the throat of the lnb

Yes, agree with you. But, in case of LNBF (any universal Ku-band) it is impossible. Of course, I can measure inside diameter of the C-band LNB and make another adapter.

 

[blademedia]

Just take the plastic cap off and make one to fit inside the throat, warm the cap up before you put it back on it will slip back on easy, My C band one, it wont win any beauty contest but it does the job

 

[RimaNTSS]

For open throat of C-band LNB this way works pretty well. Rubber belt holds an adapter firmly.

 

[blademedia]

For open throat of C-band LNB this way works pretty well. Rubber belt holds an adapter firmly.

That's ok, personally I prefer the shorter laser down the throat, long laser stuck out like that could be susceptible to movement, but yes nice work

 

[RimaNTSS]

Longer laser body helps to additionally check whether it parallel to the adapter or not. Besides, 2 x AAA batteries have longer lifetime than tablet batteries. Speaking about switching laser on/off it is possible to adopt hole in the adapter that pushing the pen inside the hole will switch on it.
Also, piece of proper diameter plastic pipe can be used to slide over the switch.

 

[blademedia]

Longer laser body helps to additionally check whether it parallel to the adapter or not. Besides, 2 x AAA batteries have longer lifetime than tablet batteries. Speaking about switching laser on/off it is possible to adopt hole in the adapter that pushing the pen inside the hole will switch on it. View attachment 105132
Also, piece of proper diameter plastic pipe can be used to slide over the switch.

That long laser wont fit down the lnb that way using it stuck out the other way you had it is susceptible to movement, I'm speaking from experience,

Yes plenty of ways to make the switch work / make one, it depends how much time you want to spend making one, mine took around 2 minuets, if I spent two hours making one it would still do the same job, crack on.

 

[moonbase]

I measured the internal throat diameter of two C band LNBF's ready to cut a wooden plug and found that the Zinwell and the Titanium were a few millimetre different. The internal throat diameter of a Zinwell is 60.6mm and for a Titanium it is 63.7mm. a difference of 3.1mm.

@blademedia,
Question if you can please help?
Did you cut the wooden plug to a diameter that allowed it to go into the Titanium throat so that it passed over the grooves for the dielectric plate? Or did you not insert the plug into the LNBF throat as far as the grooves?


Thx

 

[Channel Hopper]

I measured the internal throat diameter of two C band LNBF's ready to cut a wooden plug and found that the Zinwell and the Titanium were a few millimetre different. The internal throat diameter of a Zinwell is 60.6mm and for a Titanium it is 63.7mm. a difference of 3.1mm.

Thx

This would suggest the Zinwell is mechanically tuned for the higher end of the band.

 

[blademedia]

I used 25mm chipboard, no just cut it to the same inner diameter of the throat, you could push it up to the groves to make sure you have it square in the throat/fasten some ply to the front larger than the plug to act as a stop

 

[moonbase]

This would suggest the Zinwell is mechanically tuned for the higher end of the band.

CH,

That's an interesting point.
If I get time I might try to compare the signal levels between a Tit and a Zinwell at the extreme ends of the band subject to signal availability re dish size. I wonder why they chose to make the Zinwell like it is, possibly aiming at a specific market in the USA or Asia/Europe?

Thx

 

[Channel Hopper]

CH,

That's an interesting point.
If I get time I might try to compare the signal levels between a Tit and a Zinwell at the extreme ends of the band subject to signal availability re dish size. I wonder why they chose to make the Zinwell like it is, possibly aiming at a specific market in the USA or Asia/Europe?

Thx

Since the Zinwells are a ten year old design it might also be that the extended band at the low end was not a consideration when the castings were created.

I will do some basic arithmetic later today to see where the centre frequency lies.

 

[RimaNTSS]

I've got several C-band LNBs laying around and all of them have different inside diameter of the throat.

 

[Channel Hopper]

I've got several C-band LNBs laying around and all of them have different inside diameter of the throat.

Showoff

 

[moonbase]

Showoff

The thing is, he has more dishes than LNB's

Rgds