[Moon-Net] RFhamDesigns mesh dish on 10Ghz

G4LDR g4ldr at btinternet.com
Thu Sep 19 12:42:33 CEST 2019


Hello Bob,

I think you may be correct about surface accuracy. I purchased a 3m dish
with the 2.8mm mesh size (good to 11GHz as you say), a couple of years ago.
I have been struggling to get the performance predicted by the VK3UM
programme in terms of sun and moon noise on 3.4 and 5.7GHz. I'm about 4dB
below prediction on 3.4GHz and about 5dB at 5.7GHz and that is using feeds
loaned to me by G3LTF and G4NNS as well as a feed for I bought with the dish
from RFhamdesign. I was only just able to hear the VK6 station (400W to 28m
dish) on 5.7GHz that was operational for the Apollo 11 50th anniversary 

I'm currently making some measurements and tests suggested by Peter G3LFT
and he is going to look at the results; but it is looking like dish surface
accuracy is not good enough at the higher frequencies; (I think G4BAO has
come to the same conclusion regarding his 1.9m RFHamdesign dish at 10GHz).

I admit that I built the dish in a bit of a hurry last year to work GB6GHY
from Goonhilly (one week from starting to build the dish to being
operational, including getting all the other equipment and cables in place).
I probably didn't take enough care in ensuring it was dimensionally as
accurate as it should have been.

I'm planning to remove the mesh from the dish and replace it taking more
time and doing as good a job as possible to see if I can improve
performance.

I suspect that performance on 23 and 13cm will probably be nearer
predictions but I have not tried those bands yet.

(I have used the RFHamdesign 1.5m dish with 6mm mesh for my terrestrial 2.3,
3.4 and 5.7GHz set up mounted on my tower with very good performance for the
last 12 years).

73 Neil G4LDR.

Message: 3
Date: Wed, 18 Sep 2019 17:26:04 +0000
From: Bob Atkins <ka1gt at hotmail.com>
To: "moon-net at mailman.pe1itr.com" <moon-net at mailman.pe1itr.com>
Subject: [Moon-Net] RFhamDesigns mesh dish on 10Ghz??
Message-ID:
	
<DM6PR07MB471623FC2E9E7D57CDF88812E78E0 at DM6PR07MB4716.namprd07.prod.outlook.
com>
	
Content-Type: text/plain; charset="iso-8859-1"

Has anyone tried to use one of the RFHamDesigns mesh dishes on 10Ghz? They
offer 2.3mm mesh, good to 11Ghz, but I have a hard time thinking that the
surface accuracy would be good enough for 10Ghz.  I have the 2.4m dish with
6mm mesh which is great at 1296. I'm wondering if there would be any point
trying it on 10Ghz with smaller mesh.Changing or overlaying the mesh would
not be a trivial task.  My gut feeling is that it probably wouldn't work
well and a smaller solid dish would outperform it. Has anyone tried using
one of their larger dishes (1.5, 1.8 or 2.4m) on 10Ghz?

Bob, KA1GT
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://mailman.pe1itr.com/pipermail/moon-net/attachments/20190918/ab40a172/
attachment-0001.html>

------------------------------




More information about the Moon-net mailing list