tilt angle of TVRO dishes terrestrial 13cm use


G0FVI
 

Quick (and possibly daft!) question (still learning as far as uwaves go). Going to venture out /P for first time soon on 13cm terrestrial. I will be trying an 85cm offset TVRO dish which I have used to demo AO100 at local clubs.  I take it for terrestrial use the dish needs to tilted downwards from zero degrees? (it has the tilt bracket marked in degrees on rear and can be reverse mounted to allow downward tilt). 

TNX
Andy G0FVI


Pete G4HQX
 

If the feed arm is at the bottom the face of the dish will need to be tilted down around 25 degrees from the vertical. If you measure the height (h) and width (w) of the parabolic face the theoretical angle is given by arccos(w/h). You can mount the dish with the feed arm at the top which is sometime more convenient and the dish is then angled upwards. In  practice it’s useful to be able to alter the elevation a few degrees either way.

Pete


G0FVI
 

TNX Pete and others who replied (by Email), all sorted. As regards mounting I found an article where someone mounted their dish on it's side. Anyway next step is to get out at some stage (once I sort rotator mounting for /P), just wondering anyone near IO93RD I might sked with at some stage for test setup? (this is a hill above Lincoln, I can get unobstructed LOS to South, West, NW and especially East from various parking spots, will of course depend on terrain between us, drop me an email).


Pete - GM4BYF
 

Yes - I use a dish on its side - so that the vertical angle does not come into play. In my view much easier. The azimuth has to be established - for my dish it is conveniently along one of the supporting arms. See https://groups.io/g/UKMicrowaves/files/Channel%20Master%201.2m%20Dish 


73
Pete GM4BYF
On 15/04/21 11:28, G0FVI via groups.io wrote:

TNX Pete and others who replied (by Email), all sorted. As regards mounting I found an article where someone mounted their dish on it's side. Anyway next step is to get out at some stage (once I sort rotator mounting for /P), just wondering anyone near IO93RD I might sked with at some stage for test setup? (this is a hill above Lincoln, I can get unobstructed LOS to South, West, NW and especially East from various parking spots, will of course depend on terrain between us, drop me an email).

--
vry 73
Pete GM4BYF


David Law
 

I experimented with the angle to beacons last summer. On my 1m gibertini dish with home made pho/xdy horn the correct angle was 8 degrees. I still run this angle with good results.


on4cjq@...
 

Andy

I have 2 TRIAX dishes, a 85w*95h offset and with inclinometer on lnb-support arm i have -21° down, with the TRIAX 60w*65h i must have -23°. The tilt bracket on the back can't be used in both mounting positions with it's degrees when mounted on a vertical pole because it doesn' go low enough.
I mounted an alu plate on the bracket with 2 tubeclamps to use it on a horizontal round 42mm tube.

73's Jerry


Van: "G0FVI via groups.io" <Andrew.gilfillan@...>
Aan: "UKMicrowaves" <UKMicrowaves@groups.io>
Verzonden: Woensdag 14 april 2021 23:51:33
Onderwerp: [UKMicrowaves] tilt angle of TVRO dishes terrestrial 13cm use

Quick (and possibly daft!) question (still learning as far as uwaves go). Going to venture out /P for first time soon on 13cm terrestrial. I will be trying an 85cm offset TVRO dish which I have used to demo AO100 at local clubs.  I take it for terrestrial use the dish needs to tilted downwards from zero degrees? (it has the tilt bracket marked in degrees on rear and can be reverse mounted to allow downward tilt). 

TNX
Andy G0FVI


Nicholas Shaxted
 

Both of my Kathrein dishes (75cm and 95cm)  have a mounting bracket marked in 1 deg intervals. The minimum elevation angle is 5 (five) degrees. In both cases I milled out the slot to included 0 (zero) degrees actually a little less. This eased setting up on the mast as its stub mast could be vertical and the dish moved to point horizontal. From memory Central/Northern Europe dishes are built for a 22.6 deg offset, but that should not worry you too much 😉 as all you really need to do is look for the rise in noise and raise the dish until that noise has reduced by around 3dB. That should give you a good starting point. Beamwidth which will be of the order of about 10 degs for 3dB points at 13cm should mean you do not have to point the dish down as such.

 

Take an indelible ink marker pen with you and once you have confidence in your set up clearly mark some key reference points on the mount and tripod

If you only take a mobile phone image you will forget what it shows by the time you next get out.

 

 

Nick – g4ogi

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of G0FVI via groups.io
Sent: 14 April 2021 21:52
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] tilt angle of TVRO dishes terrestrial 13cm use

 

Quick (and possibly daft!) question (still learning as far as uwaves go). Going to venture out /P for first time soon on 13cm terrestrial. I will be trying an 85cm offset TVRO dish which I have used to demo AO100 at local clubs.  I take it for terrestrial use the dish needs to tilted downwards from zero degrees? (it has the tilt bracket marked in degrees on rear and can be reverse mounted to allow downward tilt). 

TNX
Andy G0FVI


Dave (G1OGY)
 

On Wed, 14 Apr 2021 at 22:51, G0FVI via groups.io
<Andrew.gilfillan=ntlworld.com@groups.io> wrote:

Quick (and possibly daft!) question (still learning as far as uwaves go). Going to venture out /P for first time soon on 13cm terrestrial. I will be trying an 85cm offset TVRO dish which I have used to demo AO100 at local clubs. I take it for terrestrial use the dish needs to tilted downwards from zero degrees? (it has the tilt bracket marked in degrees on rear and can be reverse mounted to allow downward tilt).

Hello Andy

FWIW I recommend mounting the dish "horizontally".
With a round off-set dish you should find that your `bore-sight` is
parallel to the feed arm of the dish.

When we can get out (!!), M1CRO/P use a PF dish on 13 (and 9) but on 6
and 3cm a 90cm (old, round) `Sky` offset dish is used; mounted
horizontally.
We don't need to mess about with dish tilt angles. You will need to
ensure your feed is correctly orientated for horizontal polarization.
but it won't matter how the dish `tilt` mechanism is set up.

We assemble with the arm vertically straight down at the rotator
setting (whatever the luffed tower direction is) using a level or
plumb-line and merely peak the dish on the beacon when upright. If you
are using a standard rotator (as we do) you will not get better than
+/- 3 degrees accuracy anyhow.
Simple matter then, if necessary, of altering the pointer on the
controller a little to align it up.
OK. We have a couple of local beacons; which helps.

I think that our results show that on those higher bands - with
narrower beamwidths - `it works`.
I expect you'll find the same on 13cm.

Dave, G1OGY


Pete - GM4BYF
 

Yes good advice from Dave. It works. Also means the centre of mass is closer to the supporting pole.  Best dx from home (Io85) is IO91 on 13cm.  I also do the same on 3cm. If using a waveguide feed, remember that horizontal polarisation is with the narrow part of the waveguide is horizontal - i.e.. like this  █

73
Pete GM4BYF

On 16/04/21 20:58, Dave (G1OGY) wrote:
On Wed, 14 Apr 2021 at 22:51, G0FVI via groups.io
<Andrew.gilfillan=ntlworld.com@groups.io> wrote:
Quick (and possibly daft!) question (still learning as far as uwaves go). Going to venture out /P for first time soon on 13cm terrestrial. I will be trying an 85cm offset TVRO dish which I have used to demo AO100 at local clubs. I take it for terrestrial use the dish needs to tilted downwards from zero degrees? (it has the tilt bracket marked in degrees on rear and can be reverse mounted to allow downward tilt).
Hello Andy

FWIW I recommend mounting the dish "horizontally".
With a round off-set dish you should find that your `bore-sight` is
parallel to the feed arm of the dish.

When we can get out (!!), M1CRO/P use a PF dish on 13 (and 9) but on 6
and 3cm a 90cm (old, round) `Sky` offset dish is used; mounted
horizontally.
We don't need to mess about with dish tilt angles. You will need to
ensure your feed is correctly orientated for horizontal polarization.
but it won't matter how the dish `tilt` mechanism is set up.

We assemble with the arm vertically straight down at the rotator
setting (whatever the luffed tower direction is) using a level or
plumb-line and merely peak the dish on the beacon when upright. If you
are using a standard rotator (as we do) you will not get better than
+/- 3 degrees accuracy anyhow.
Simple matter then, if necessary, of altering the pointer on the
controller a little to align it up.
OK. We have a couple of local beacons; which helps.

I think that our results show that on those higher bands - with
narrower beamwidths - `it works`.
I expect you'll find the same on 13cm.

Dave, G1OGY



--
vry 73
Pete GM4BYF