GB3GQ Update, 3.408Ghz Mixing & Filters

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Replacing the IO92GQ internet-only repeater
G8DKC
Posts: 197
Joined: Thu Jun 28, 2012 9:39 am

GB3GQ Update, 3.408Ghz Mixing & Filters

Post by G8DKC » Sat Mar 31, 2018 12:01 pm

Many have gone before, but...

DTX-1 at 1.3Ghz mixing with ADF4351 at 2.108GHz, filters and mixer...

Amazed how well 3.408Ghz working across workshop, very low signal from horn across to Titanium C1W-PLL Lnb, still playing with levels and filters...

RPi animated test card very useful, https://wiki.batc.org.uk/RPi_Test_Card :)

Peter

G4WIM
Posts: 128
Joined: Thu Jan 29, 2015 8:36 pm

Re: GB3GQ Update, 3.408Ghz Mixing & Filters

Post by G4WIM » Sun Apr 08, 2018 8:48 pm

Sounds like what I did for taking GB3FT at 1.315GHz up to 3.406GHz for GB3FB - check out the latest BATC mag for the post mixer filter.

I have some firmware I wrote for an Atmega328 to control the PLL, PA cooling fans and other stuff if it's any use to you.

G8DKC
Posts: 197
Joined: Thu Jun 28, 2012 9:39 am

Re: GB3GQ Update, 3.408Ghz Mixing & Filters

Post by G8DKC » Mon Apr 09, 2018 8:39 am

Hi Tim,

Yes I saw your line up and go back to your article, no good re-inventing the wheel :)

Was very lucky with a rare 3.4Ghz filter on EBay ~ 250Mhz band pass, but like your filter build.

Building in electrical equipment box, old Dell 12v 60A psu case and fan with speed control, pulling air from top of cabinet.

Pic attached...

Thanks for the firmware control offer, will see how my effort works out.

Pics to follow as I progress.

Peter
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G4WIM
Posts: 128
Joined: Thu Jan 29, 2015 8:36 pm

Re: GB3GQ Update, 3.408Ghz Mixing & Filters

Post by G4WIM » Mon Apr 09, 2018 9:37 am

Looks to be coming along nicely - suspect you have the same type of PSU which we use on FB / FT, sounds like a jet engine when its running so much so that Steve G3WGU built a sound box around it to keep it quiet as it resides in his attic !

Good find on the filter - be interested to hear more about that.

OK about the firmware, we also have DTMF control using another Atmega - one for encode and another for decode.
The control logic is yet another ATmega which controls which rx gets routed thru to the tx and finally there's a pi zero generating test card captions.

73 Tim

G8DKC
Posts: 197
Joined: Thu Jun 28, 2012 9:39 am

Re: GB3GQ Update, 3.408Ghz Mixing & Filters

Post by G8DKC » Tue Apr 10, 2018 8:05 am

Re 3.4Ghz filter

RLC ELECTRONICS F-10842 9619 Marked 3.4Ghz Fc ~ 250Mhz Bandpass.

http://www.rlcelectronics.com/products/ ... lters.html

I did some "very rough" external measurements totally sealed, 5 rods by the look of it, and used calculator on...

https://www.changpuak.ch/electronics/co ... signer.php

In practice cleans up and good signal out.

Peter
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G8DKC
Posts: 197
Joined: Thu Jun 28, 2012 9:39 am

Re: GB3GQ Update, 1.3Ghz IF

Post by G8DKC » Mon Apr 23, 2018 12:55 pm

DTX-1, 1.3Ghz driver and filter mounted on door.

Peter
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1.3Ghz on Door.jpg
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G8DKC
Posts: 197
Joined: Thu Jun 28, 2012 9:39 am

Re: GB3GQ Update, 3.408Ghz Mixing & Filters

Post by G8DKC » Wed May 02, 2018 3:32 pm

Attached the Mixer PA side of build, tested to maximum 20W out of Stealth SM3437 Power Amplifier.

Will be running at more like 5w or so out.

Next to put in box and add DTX-1 fitted on door, PSU wiring, over temp cut-out removing 5v from Stealth SM3437, turning off P.A.

Also a separate speed control for Cooling tube fan.

Other control systems to follow, mainly in Rx box.

Peter
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3.408 Tx 01.jpg
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G8DKC
Posts: 197
Joined: Thu Jun 28, 2012 9:39 am

3.4Ghz Antenna

Post by G8DKC » Wed May 09, 2018 9:07 am

3.4Ghz antenna has arrived :)

Supplied by Bert Modderman PE1RKI

Peter
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G8DKC
Posts: 197
Joined: Thu Jun 28, 2012 9:39 am

GB3GQ Ready for final tests...

Post by G8DKC » Tue May 15, 2018 3:37 pm

Tx has been run at full 20w over the last few days into load, testing the fixed speed heat sink fan, and the Cab venting variable speed.

The fan fitted in the old stripped out Dell 750W case to blow air through the Cab sucking in fresh from LH bottom of box.

Bottom grills yet to be fitted.

Fan has speed V temperature with sensor clamped to heat sink. Also over temperature set to cut 5v supply to P.A on second sensor.

The only control in the Tx Cab is a relay for remote control to switch off the P.A when requested as per NOV.

Also to provide a Tx sleep mode, yet to be decided.

When on the air it will be running at a modest 5W or so.

GQ should be on air by the weekend at it's temporary location while waiting for news of possible new site.

P.S have found a very old 3.4Ghz circulator, yet to test, also brought out to front Forward-Reflected connections, yet to play with...

Peter
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G8DKC
Posts: 197
Joined: Thu Jun 28, 2012 9:39 am

PVC Tube Tests

Post by G8DKC » Fri May 18, 2018 8:59 am

Testing PVC properties.

When GB3GQ Txing into slotted waveguide, SWR not effected by pipe with equipment available.

Checked old 3.4Ghz circulator, switches to dummy load port when antenna SWR persuaded to go high ;)

Transmitting from Adalm Pluto into antenna at low signal levels, Rxing on Sat Receiver, tested for pipe attenuation, no loss perceived.

And wouldn't a compact Pc, Pluto, filter and Pa make a great standby / Repeater Tx :)

Peter
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PVC Radome Tests.jpg
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