[Moon-Net] RFhamDesigns mesh dish on 10Ghz

Paul Andrews w2hro.fn20 at gmail.com
Thu Sep 19 14:23:35 CEST 2019


Regarding 10 GHz band and self assembly mesh dishes.

The size of the holes in the mesh reflector is just one factor.   We must
consider the accuracy of the manufactured dish ribs and ultimately the
assembly of the dish into a true parabola.  This is all before being sure
the feed will effectively illumination of the dish.

I plan to activate a Channel Master Type 243 - 2.4m 2 piece fiberglass dish
during the next few months.   This dish was designed for Ku-band (12/14
GHz) and be transmit legal for 2 deg commercial satellite spacing.   This
dish is a 2 piece design because it's not easy to maintain good performance
when bolting together 8 panels due to panel alignment error.

Amateur radio doesn't have requirement for clean transmit patterns so a
mesh dish is ok but it may never be as efficient as a commercial 1 or 2
piece solid dish.

I'll provide performance data on the 2.4m dish when I'm QRV.








On Thu, Sep 19, 2019 at 6:47 AM G4LDR via Moon-net <
moon-net at mailman.pe1itr.com> wrote:

> 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
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