GB3GQ Update, 3.408Ghz Mixing & Filters

Locator: IO92GQ
Replacing the IO92GQ internet-only repeater
G4GUO
Posts: 626
Joined: Tue Feb 16, 2010 12:51 pm

Re: GB3GQ Update, 3.408Ghz Mixing & Filters

Post by G4GUO » Sat May 19, 2018 11:34 am

One trick I saw was to put a piece of test tubing into the microwave
turn it on and if the tubing gets hot you know you have a problem.

- Charles

G8DKC
Posts: 249
Joined: Thu Jun 28, 2012 9:39 am

Re: PVC tube tests

Post by G8DKC » Sat May 19, 2018 5:20 pm

Thanks Charles,

I put a spare end cap into the 800w microwave for a minute, big lump of a thing and it warmed up nicely :o

Don't know the effect of that on the 1.5 metre long tube with thinner wall.

The cap marked ERA PVC-U 110mm diameter, the tube PVC-U.

Will ask Tim G4WIM what they used on GB3FT, looked like box section down pipe?

Peter

g0mjw
Posts: 888
Joined: Sat Sep 20, 2014 9:15 am

Re: GB3GQ Update, 3.408Ghz Mixing & Filters

Post by g0mjw » Sat May 19, 2018 6:37 pm

You really need to put in a cup of water too, to give the microwave some load. You can then see if it still gets hot - but does it matter? The loss might not be significant. White PVC probably isn't carbon loaded, but isn't UV safe. You could paint it to deal with that.

Mike

G8DKC
Posts: 249
Joined: Thu Jun 28, 2012 9:39 am

RF UV Etc....

Post by G8DKC » Sat May 19, 2018 8:46 pm

Thanks Mike,

I'm thinking my present pipe is rather heavy anyway, so may go for a lighter white PVC pipe and then paint it as per link.

Found useful info here thanks to your input...

https://www.pvcfittingsonline.com/resou ... resistant/

Peter

g8gtz
Posts: 1156
Joined: Wed Apr 07, 2010 6:26 pm

Re: GB3GQ Update, 3.408Ghz Mixing & Filters

Post by g8gtz » Sun May 20, 2018 7:07 am

I use Wickes white square pipe on the 10GHz rxr at the Farnham WebSDR - passed the microwave oven test and seems to work well...

https://www.wickes.co.uk/FloPlast-RPS2- ... m/p/432025

73
Noel - G8GTZ

G4WIM
Posts: 257
Joined: Thu Jan 29, 2015 8:36 pm

Re: GB3GQ Update, 3.408Ghz Mixing & Filters

Post by G4WIM » Sun May 20, 2018 9:34 am

Just a quick mention,

Steve G3WGU has used 'helicopter tape' to cover the slots on the wave guide and seal any other openings.

We've not been able to detect any signal loss or de-tuning of either 1.3 or 3.4Ghz slotted wave guide antennas we use on GB3FT and FB.

It's very tough tape and sticks very well, plus it doesn't add any significant weight or windage to the antenna.

73 Tim

G8DKC
Posts: 249
Joined: Thu Jun 28, 2012 9:39 am

Re: GB3GQ Update, 3.408Ghz Mixing & Filters

Post by G8DKC » Sun May 20, 2018 4:12 pm

Thanks for all your suggestion's.

Unfortunately the slotted waveguide is 80mm x 30mm so won't fit inside 65mm pvc downpipe, have found another source,

of FloPlast pipe so looks like 80 to 100mm round.

Like Tim's Idea, perhaps we could clear vacuum pack our antennas to show off the engineering.

GB3GQ on the air today for the first time as a repeater, now to iron out the things I missed.

Slotted antenna up without cover, pop on old one if it looks like rain, hope to have new radome by the end of the week.

Did some tests with Pluto on 3.4 down inside the old tube with Hack-Rf as SDR looked ok.

The lid not so good, signal went up when distance adjusted, probably back scattering the signal.

Anyway far too heavy for manual hinge up mast.

Peter
Attachments
GB3GQ On Air.jpg
GB3GQ On Air.jpg (100.66 KiB) Viewed 1561 times

G8DKC
Posts: 249
Joined: Thu Jun 28, 2012 9:39 am

Latest Antenna Cover

Post by G8DKC » Fri May 25, 2018 8:33 am

Antenna safely covered before the rain started last night.

As it is 80mm x 30mm and allowing for Right Angle N plug, in the end went for 100 x 100 PVC trunking with end stop.

PVC spacers inside to keep central in tube.

Glued with solvent and sprayed with many coats of acrylic based paint.

100% pass on microwave test.

Peter
Attachments
New Radome.jpg
New Radome.jpg (71.48 KiB) Viewed 1528 times

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