437MHz Linear DATV Amplifier for TX into GB3NQ

GB3NQ Digital Conversion
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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!!!
The cutouts are marked in black

I removed the surplus power regulators

and cutout the gaps needed

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

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

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.
Here is a fuzzy photo of the mods
anyone interested can contact me for further info....

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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