70cms Power amplifiers on ebay

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g8gtz
Posts: 1368
Joined: Wed Apr 07, 2010 6:26 pm

70cms Power amplifiers on ebay

Post by g8gtz » Tue Jan 12, 2021 11:02 am

These look a very useful amplifier for DATV use on 70cms.

The device is a wideband FET designed for wideband COFDM in the UHF TV broadcast band. Needs a couple of watts drive and 32v. The device S parameters indicate it should work on 70cms but the PCB may need tweaking on to 437MHz.

I'm just saying, not recommending - Caveat emptor!

https://www.ebay.co.uk/itm/150-Watt-UHF ... 1438.l2649

9 units left - I just bought one :D

Noel

radiogareth
Posts: 619
Joined: Wed Jan 06, 2016 9:46 am

Re: 70cms Power amplifiers on ebay

Post by radiogareth » Tue Jan 12, 2021 12:00 pm

Me too, be a LOT more manageable than my Nokia Dolphin for driving around with.......one of these will go nicely with it for a bit of nice linear drive too https://www.ebay.co.uk/itm/MOTOROLA-CA9 ... 2749.l2649

Gareth

G7JTT
Posts: 231
Joined: Fri Jun 10, 2016 5:05 pm

Re: 70cms Power amplifiers on ebay

Post by G7JTT » Wed Jan 13, 2021 6:30 am

g8gtz wrote:
Tue Jan 12, 2021 11:02 am
These look a very useful amplifier for DATV use on 70cms.

The device is a wideband FET designed for wideband COFDM in the UHF TV broadcast band. Needs a couple of watts drive and 32v. The device S parameters indicate it should work on 70cms but the PCB may need tweaking on to 437MHz.

I'm just saying, not recommending - Caveat emptor!

https://www.ebay.co.uk/itm/150-Watt-UHF ... 1438.l2649

9 units left - I just bought one :D

Noel
And gone 😪

g0uhy
Posts: 74
Joined: Fri Aug 05, 2011 3:09 pm

Re: 70cms Power amplifiers on ebay

Post by g0uhy » Sun Jan 17, 2021 9:27 am

Hi,

noticed that these are listed again if anyone is interested?

https://www.ebay.co.uk/itm/150-Watt-UHF ... Sws4te4gy6

73

Malcolm G0UHY

g8gtz
Posts: 1368
Joined: Wed Apr 07, 2010 6:26 pm

Re: 70cms Power amplifiers on ebay

Post by g8gtz » Sun Jan 17, 2021 3:50 pm

Ok, so he's sold at least 14 since I posted originally so time to own up if you bought one so we can share experiences!

I bought one and just about to connect it up.

Gareth XAT bought one and discovered an SMA socket has the same spacing as the input and output screw terminations.

Noel

g0mjw
Posts: 1458
Joined: Sat Sep 20, 2014 9:15 am

Re: 70cms Power amplifiers on ebay

Post by g0mjw » Sun Jan 17, 2021 3:58 pm

Good - saves me being the first to try it...

Mike

radiogareth
Posts: 619
Joined: Wed Jan 06, 2016 9:46 am

Re: 70cms Power amplifiers on ebay

Post by radiogareth » Sun Jan 17, 2021 4:39 pm

Amp came with data sheets and basic guidance. It works, but bias does not seem to be temp compensated and standing current rose as the pallet warmed up.
Input VSWR isn't very good ( I swept it from 400-550MHz by which time is was around 2.5:1. Maybe the tiny trimmer capacitors (are they trimmers?? need a tweak to improve that.
But it amplifies as described....my pre-drivers are not linear or powerful enough to explore what it can really do, so I resorted to a well attenuated and under-driven brick amp. This woke it up and I think I was getting about 10W of DBV-T before I saw any regrowth. It got hot quickly at this level so I'll wait for fans to arrive. But 'good on paper', maybe someone with more knowledge can suggest improvements to the match and such. Both in and out have these small trimmers.
In terms of output, I was monitoring the output into a dummy load via a -40dB (possibly more at 70cms) coupler, and the trace went up 40dBm. The only 'power meter I have isn't rated for 70 cms (200MHz nominally) and it showed 10 watts.....
Gareth
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