[Moon] [Moon-Net] 1.8M DISH/ 2.4M DISH

Sun Jun 7 19:44:22 CEST 2020

Thank you Bob, Charlie, John & many others that is why this reflector is so
useful to all of us. It also shows how little I know about the use of dishes
on EME. I have had a 77CM offset dish & LNB for the last few years just to
receive the beacon I am still struggling to get it going. So tracking should
be easy or at least easier as I read all of your emails.

Thank you to all again

Serge VE1KG

From: Bob Atkins <ka1gt at hotmail.com> 
Sent: June 6, 2020 21:39
To: ve1kg at eastlink.ca; Philip Aquilina <philip9h1pa at gmail.com>
Cc: moon at moonbounce.info; moon-net at mailman.pe1itr.com
Subject: Re: [Moon-Net] [Moon] 1.8M DISH/ 2.4M DISH

The only reasons why a smaller dish would be "better" might be

(1) It may be easier to make a smaller dish with good surface accuracy than
a larger dish (depends on the individual dish of course, and may be
reflected in the price)

(2) The larger dish has a smaller beam width and so required greater
pointing accuracy if you expect to get the full gain and maximum possible
signal

(3) A smaller dish is often lighter, a bit easier to mount, has less wind
load and may not need as powerful (heavy and expensive) a rotor system.

A 1.8m offset dish might also be preferable to a prime focus 2.4m dish
because there is less (ideally no) feed blockage and the higher f/d of most
offset dishes might make it easier to feed efficiently (though that's not
necessarily the case).  There may also be less spillover noise pickup at low
elevation angles.

So it's not always a simple choice, especially when the cost of the system
is part of the equation. I've looked at (new) disha and prices here in the
US for about a year now. For a good 2.4m offset dish (Ku band) you're
looking at maybe $2000-$2500. For at 1.8m offset dish(Ku band) you're
probably looking at $500-700. Shipping extra (quite a lot extra sometimes!).
How good they would be at 24Ghz is unknows since they are only rated for
12Ghz. Probably OK, but not guaranteed.

There are cheaper dishes. I've seen a 2.4m (.05" aluminum) offset for around
$1200, but I don't know how good the profile would be. Claimed surface
accuracy was 0.5mm RMS. Wavelength at 24GHz is about 12.5mm. That should be
good enough, if you believe the specs and the dish isn't distorted in
shipping or the weight of the feed! The more expensive (and heavier)
reinforced fiberglass dishes may be more dimensionally stable.

 Not many sources either. Dishes seem to be much easier to find in Europe
than in NA.

73

Bob, KA1GT

  _____  

From: Moon-net <moon-net-bounces at mailman.pe1itr.com
<mailto:moon-net-bounces at mailman.pe1itr.com> > on behalf of Philip Aquilina
via Moon-net <moon-net at mailman.pe1itr.com
<mailto:moon-net at mailman.pe1itr.com> >
Sent: Saturday, June 6, 2020 2:41 PM
To: ve1kg at eastlink.ca <mailto:ve1kg at eastlink.ca>  <ve1kg at eastlink.ca
<mailto:ve1kg at eastlink.ca> >
Cc: moon at moonbounce.info <mailto:moon at moonbounce.info>
<moon at moonbounce.info <mailto:moon at moonbounce.info> >;
moon-net at mailman.pe1itr.com <mailto:moon-net at mailman.pe1itr.com>
<moon-net at mailman.pe1itr.com <mailto:moon-net at mailman.pe1itr.com> >
Subject: Re: [Moon-Net] [Moon] 1.8M DISH/ 2.4M DISH 

Hi Serge, 

What I can tell you is that the Prodelin offset dishes are very good. Have
about 14 of them at my qrl and they are superior to other dishes. The 2.4 m
offset that we have are better than 3 m prime focus. This is at Ku band.

73's

Philip 9H1PA 

On Sat, 6 Jun 2020, 19:06 Serge, VE1KG via Moon, <moon at moonbounce.info
<mailto:moon at moonbounce.info> > wrote:

Some what recently said that a 1.8M dish was the best for 10GHz & 24Ghz. I
wonder if a 2.4 M dish would not be better??

Can someone explain to me the reason why  the smaller dish is better for
10ghz?

Serge VE1KG

DXCC: 144MHZ

_______________________________________________
Moon mailing list
Moon at moonbounce.info <mailto:Moon at moonbounce.info> 
/mailman/listinfo/moon

Join eQSL.cc  https://eqsl.cc/qslcard/Index.cfm