437MHz Linear DATV Amplifier for TX into GB3NQ

GB3NQ Digital Conversion
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admin
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Joined: Mon Jan 21, 2019 11:21 am

437MHz Linear DATV Amplifier for TX into GB3NQ

Post by admin » Mon Jan 13, 2020 4:52 pm

I have just finished the easy conversion of a Nokia Linear Amplifier ( on Ebay as 70cm UHF PA Nokia TTRX Dolphin Tetra 200W SSB ) for use as a DATV 437MHz Linear for my signal into GB3NQ. I have not got in yet as the repeater is not on at the moment, but here are some photos of the conversion.
The first one is a copied from the Internet ( www.m0dts.co.uk ) and shows the picture with the information on what to do.
70cm Driver.JPG
Now this is how I got the signal into the amplifier. I cut a SMA 30cm long lead into two and used a 437MHz filter as a combiner.
The path chosen is to allow the cables to run through the top cover after some cutouts have been made with my 8inch angle grinder!!!
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The cutouts are marked in black

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I removed the surplus power regulators

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and cutout the gaps needed

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and another one for the 5volt bias switch on voltage which I took from a nearby IC

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That is the red wire. You need to scratch off the varnish before soldering to the printed circuit board.

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And after the two mods to get the bias working the amplifier takes around 4 amps without a signal ( BUT CONNECTED TO A DUMMY LOAD )
When a signal was connected the amplifier gave out 50watts with a supply current going up to nearly 10Amps. This was driven by my DTX1 at 100% output.
No tuning has been done to improve the output and a clean signal is received on my Minitioune.
DSC04333.JPG
Here is a fuzzy photo of the mods
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anyone interested can contact me for further info....

g8lce
Posts: 21
Joined: Mon Jan 21, 2019 11:05 pm

Re: 437MHz Linear DATV Amplifier for TX into GB3NQ

Post by g8lce » Mon Feb 24, 2020 3:05 pm

Here are some more photos of my amplifier
The last one might be the clearest when zoomed in as I used flash

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