Channel Master 1.2m Dish

Latest News and Discussion about the use of the DATV transponder on Es'hail-2
2W0ODS
Posts: 50
Joined: Sun Oct 21, 2018 5:15 pm

Re: comments on this dish from ebay

Post by 2W0ODS » Thu Apr 11, 2019 8:30 pm

G4WIM wrote:
Thu Apr 11, 2019 4:53 pm
Thanks for the link to the mount - not cheap but better than £99 elsewhere !

Just ordered one - cost 50% more than the dish but saves me the trouble of making one.

73 Tim
You had a bargain with that dish, it's a later "Andrew" version when they took over.
Mine is a Channel Master Branded one. Now looking for another to set up parked on 26e constantly for Rx.

RimaNTSS
Posts: 19
Joined: Fri Apr 12, 2019 9:29 am

Re: comments on this dish from ebay

Post by RimaNTSS » Fri Apr 12, 2019 3:10 pm

Hi dear forumers!
My first post. I am SAT-hobbyist from Latvia (Rx only). Channel Master is one of my favorite brands, man they are good! My major goal in this hobby is to do some hardware work (installing, tuning, wiring etc.) and not so much TV watching of feedhunting.
In last couple of days I got messages from 2 different users of this forum @2W0ODS and @G4GUO, both were pointing me to this thread. So, I am here and, TBH, delighted to see some of the CM LNB-holders I made in use by other users. When I designed the holder I was thinking of just holding Ku, Ka or C-band LNBs. In case of dual-feed LNB most of you guys using, this INOX holder will surely fit better than original CM plastic holder..... but it will still not provide perfect solution. I will try to explain this on the base of Charles' picture.
DualFeed.jpg
DualFeed.jpg (495.49 KiB) Viewed 452 times
The main issue here is the fact that LNB's Phase Center (red dot) is not co-located with antenna's Focal point (green dot). The new LNB-holder will probably do better but, again, not perfect. To get maximum performance of your antenna-system more radical approach is needed, namely “feedarms should be changed” . I have changed feedarms on CM dishes and if there is interest I could explain how to do that.
P.S. English is not my mother tongue, so please be patient if I write stupid or do wrong spelling.

G4WIM
Posts: 227
Joined: Thu Jan 29, 2015 8:36 pm

Re: comments on this dish from ebay

Post by G4WIM » Sat Apr 13, 2019 11:13 am

RimaNTSS,

welcome to the forum - it's a small world as I found this thread of yours https://www.satelliteguys.us/xen/thread ... ue.346696/ to be invaluable when setting up my 1.2M Channel Master.

I now await delivery of the C band mount for my dish such that I can install my dual band feed.

I'd be interested to hear about your feed arms modification for the CM 1.2 dish as every fraction of a dB helps !

Regards Tim

radiogareth
Posts: 294
Joined: Wed Jan 06, 2016 9:46 am

Re: comments on this dish from ebay

Post by radiogareth » Sat Apr 13, 2019 11:58 am

I found that I could recess the interior part of the Red Rocket into the copper tube with just the tiniest 'skim' inside the tube on my lathe. You could probably achieve the same by using a homemade flap-wheel in a drill. That allows the Outer red cap to sit ON the patch aerial.
I wonder if small cut-outs in the 105mm diameter reflector to clear the support poles would allow the feed/focus points to coincide better?
Busy making mine at the moment.
Gareth

g0mjw
Posts: 816
Joined: Sat Sep 20, 2014 9:15 am

Re: comments on this dish from ebay

Post by g0mjw » Sat Apr 13, 2019 12:11 pm

RimaNTSS wrote:
Fri Apr 12, 2019 3:10 pm
Hi dear forumers!
My first post. I am SAT-hobbyist from Latvia (Rx only). Channel Master is one of my favorite brands, man they are good! My major goal in this hobby is to do some hardware work (installing, tuning, wiring etc.) and not so much TV watching of feedhunting.
In last couple of days I got messages from 2 different users of this forum @2W0ODS and @G4GUO, both were pointing me to this thread. So, I am here and, TBH, delighted to see some of the CM LNB-holders I made in use by other users. When I designed the holder I was thinking of just holding Ku, Ka or C-band LNBs. In case of dual-feed LNB most of you guys using, this INOX holder will surely fit better than original CM plastic holder..... but it will still not provide perfect solution. I will try to explain this on the base of Charles' picture. DualFeed.jpg
The main issue here is the fact that LNB's Phase Center (red dot) is not co-located with antenna's Focal point (green dot). The new LNB-holder will probably do better but, again, not perfect. To get maximum performance of your antenna-system more radical approach is needed, namely “feedarms should be changed” . I have changed feedarms on CM dishes and if there is interest I could explain how to do that.
P.S. English is not my mother tongue, so please be patient if I write stupid or do wrong spelling.
I have a 2.4m CM dish but it came with a different feed arm arrangement. There is work to be done to replace this. A key point is adjustability of the feed so its phase centre aligns with the focus without things getting in the way. My idea is to bring the three feed arms to a point a little behind the focus. say 12" behind. The feed can then be mounted between the three arms on an adjustable saddle, rather like the holder in the photo, but designed for the feed.

RimaNTSS
Posts: 19
Joined: Fri Apr 12, 2019 9:29 am

Re: comments on this dish from ebay

Post by RimaNTSS » Sat Apr 13, 2019 9:37 pm

g0mjw wrote:
Sat Apr 13, 2019 12:11 pm
I have a 2.4m CM dish but it came with a different feed arm arrangement.
I think I know what kind of feedarms you have on your antenna. Sidearms are made of pipes and bottomarm is made of parallelepiped tube. Am I right? If yes, than best option for LNB-holder is something like on the attached picture. Smaller clamp could be used to hold 22mm neck of dual feed LNB.
IMG_20190303_084415 (Large).jpg
IMG_20190303_084415 (Large).jpg (227.84 KiB) Viewed 578 times
g0mjw wrote:
Sat Apr 13, 2019 12:11 pm
My idea is to bring the three feed arms to a point a little behind the focus. say 12" behind.
I have tried something like this (just for experiments)
IMG_20160822_193900 (Large).jpg
IMG_20160822_193900 (Large).jpg (325.2 KiB) Viewed 578 times
but then you get issue how to install LNB.
G4WIM wrote:
Sat Apr 13, 2019 11:13 am
I'd be interested to hear about your feed arms modification for the CM 1.2 dish as every fraction of a dB helps !
Tim! As I've mentioned before, my approach is radical- trow away original feedarms and replace them by new ones, adjustable in length, that gives possibility to place feed in any position. I will look for proper photos and post them later.

RimaNTSS
Posts: 19
Joined: Fri Apr 12, 2019 9:29 am

Re: comments on this dish from ebay

Post by RimaNTSS » Sun Apr 14, 2019 5:30 am

There are some self-explaining pictures of extendable feedarms. Image Image Image Image Image Image Image
For antennas up to 1.2m 10x1mm pipe is more than enough. Of course, instead of 40mm clamp (Ku-band LNB) it is better to use clamp which can hold 22mm LNB neck.

g8gtz
Posts: 1125
Joined: Wed Apr 07, 2010 6:26 pm

Re: comments on this dish from ebay

Post by g8gtz » Mon Apr 15, 2019 12:46 pm

Hi

The mount is currently out of stock on ebay - do you have any more?

Looking to see if I can make up the modified arms from boat supplies.

Noel - G8GTZ

g8vpg
Posts: 307
Joined: Fri Oct 11, 2013 9:35 am

Re: comments on this dish from ebay

Post by g8vpg » Mon Apr 15, 2019 1:32 pm

You can buy 1m lengths of threaded steel bar in 6, 8, 10 & 12mm sizes very cheaply at Screwfix or Toolstation.
73 Shaun.

g8gtz
Posts: 1125
Joined: Wed Apr 07, 2010 6:26 pm

Re: comments on this dish from ebay

Post by g8gtz » Mon Apr 15, 2019 2:09 pm

And these look good for the turnbuckle through the dish to mount the arms on https://www.boatfittings.co.uk/p/turnbu ... d_ring_pin

Need some eyes on the end of the threaded rod.

Noel

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