Advice Needed How to convert circular feed to linear

[Dishy274]

I have an old Seaview c band feed horn that is manufactured for circular polarisation.
Can any one suggest how it can be used on linear. It has a 4 ring scaler which I presume will provide extra gain to the standard feed horns of today

 

[moonbase]

I have an old Seaview c band feed horn that is manufactured for circular polarisation.
Can any one suggest how it can be used on linear. It has a 4 ring scaler which I presume will provide extra gain to the standard feed horns of today

I am not familiar with the Seaview feed. However, if it has a dielectric plate in the throat of the feed that can be removed then by removing the dielectric plate you should be OK for linear polarity signals?

If your Seaview feed is similar to an AV-COMM polariser barrel with internal steps then it should work OK for linear polarity as it is, provided you adjust the feed to the correct skew for the satellite you are looking at.

 

[Topper]

I thought it was the other way round, don't you need to insert a dielectric plate to convert circular to linear?

 

[Channel Hopper]

I thought it was the other way round, don't you need to insert a dielectric plate to convert circular to linear?

You could insert a second plate for an alternative solution, some of the earlier C band feeds had the dielectric glued into place that makes removal almost impossible without damage.

 

[Topper]

I suppose it may be time to get rid of my 30 year collection of chopping boards then

 

[moonbase]

I thought it was the other way round, don't you need to insert a dielectric plate to convert circular to linear?

That was what I indicated.

...by removing the dielectric plate you should be OK for linear polarity signals...

I was working on the assumption that the feed was currently configured for circular polarity as per the topic title and that removal of the plate would enable improved reception of linear polarity

 

[Channel Hopper]

One of the quirks of a common language.

The device needs the removal of the plate to receive linear polarised signals, however circular polarised signals need to be passed through a depolariser to be - efficiently - received by a linear type detector.

 

[moonbase]

One of the quirks of a common language.

The device needs the removal of the plate to receive linear polarised signals, however circular polarised signals need to be passed through a depolariser to be - efficiently - received by a linear type detector.

The simple fact is that if the OP has a C-Band feed currently configured for circular polarity via a dielectic plate, removal of the plate if possible should enable reception of linear polarity signals. I think that is all the OP wishes to achieve?

If the OP has a polariser barrel type of feed with intenal steps or a feed like a Prodelin rib tickler they should be able to receive linear signals without any modification apart from rotational adjustment of the feed for polarity skew.

If the OP provides some feedback then a clearer picture may emerge, possibly of a linear satellite TV channel?

 

[Satfaca]

Are you sure it is Seaview, not Seavey?
Can you attach an image?

 

[Dishy274]

Are you sure it is Seaview, not Seavey?
Can you attach an image?

My apologies
It is a Seavey ESR-40C-1 which I have since learnt is used for both circular and linear.
Need to know how to switch to linear.

 

[John]

... get your camera out or your smart phone and take a really close up picture of the front of the Seavey so that we can see clearly the internal structure of the feed. Then transfer the pics onto your computer and take note of the 'size' of the picture file - if it's a recent model of phone camera then the taken picture size could well be anywhere between 2 to 3 Mb in size which is too large to post on this site. You will have to reduce the image size to 1Mb or just under by using a PC program such as 'Paint' where you will see the option to 'Re-size'. Re-size it to just under 1meg and save it to your desktop. When you reply to a message to show us your pictures you will see in the bottom left of the forum screen the "Attach files" - click on that and then drag & drop your Reduced desktop pic ..... it's pretty straight forward after that. You need to do this Dishy otherwise we are all just guessing at an appropriate answer for you

 

[Satfaca]

Simply by adjusting the skew. It's usually 45° opposite from linear.
Seavey has unique solution for circular polarized signals, not with dielectric plates like others.
You might want to check this and this.