Gigatec Amplifier for uplink

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g8vpg
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Joined: Fri Oct 11, 2013 9:35 am

Gigatec Amplifier for uplink

Post by g8vpg » Sun Mar 03, 2019 3:53 pm

I have been given a Gigatec GT-3079 amplifier which has a design frequency of 2593MHz, although I understand it is part of range of amplifiers with outputs in the 1.9-2.6GHz region. Unfortunately it has a fault and it has burnt out the terminating resistor on the output coupler, together with the pcb track, part of the pcb and whatever other components were on this track. I have been informed that this is a "forward power" amplifier, designed for very linear operation. An auxiliary amplifer is coupled into the main output to improve linearity and this is where the burn out has occurred. I have managed to solder some miniature semi-rigid co-ax onto the output wire of the coupler and bring this out to an external termination. I can get about 15W of RF out, but it is not very linear. Does anyone have any technical information about these amplifiers? If you have one, could you photograph the burnt out area, because there were some other components on the track too burnt to identify.
73 Shaun.
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G8GKQ
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Re: Gigatec Amplifier for uplink

Post by G8GKQ » Mon Mar 04, 2019 12:30 pm

The GT-3092 (ebay link above) is a nicely engineered amplifier, and will output 30 W of very clean DATV at 1910 MHz. However, it is over 10dB down at 2405 MHz. So a couple of watts out at the very most. The transistors are internally matched for 1900 MHz, so modification is almost impossible.

Dave

Denis Nicole
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Joined: Sun Mar 29, 2020 5:43 pm

Re: Gigatec Amplifier for uplink

Post by Denis Nicole » Sun Mar 29, 2020 6:24 pm

Hi Dave,

I have a Gigatec GT-3094. The output circulator is marked 2335MHz, so I assume that is the intended operating frequency. The output stage is a single NXP BLF6G27LS-135 whose data sheet says it is good for 20W from a 32V supply. The plug that came with it has obvious power cables, coax connectors for forward and reflected power sense, and two additional connectors:
  • * A four pole one with just the middle two pins connected to orange, and grey/blue wires.
    * A five pin one, carrying white/blue, brown, white/green, white/orange, and green wires.
Do you know if the intended power supply is indeed 32V? And should it "just work" if I power it up and apply appropriate RF, or do I need to do something with these two small plugs? And I guess moving operating frequency up 3% won't be too painful? I couldn't fine much more information on-line apart from Gigatec's history as a subsidiary of nagase.co.jp; they dropped off the annual report in 2011.

Thanks,
Denis

G8GKQ
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Re: Gigatec Amplifier for uplink

Post by G8GKQ » Mon Mar 30, 2020 4:09 pm

Hi Denis

Not sure about the details of the GT-3094, but I have sent you a PM with access to more information.

That series of amplifiers were designed to work from 28V and all the ones that I have seen had a switch line (it was pin 1 on a hybrid D-type connector) that needed to be connected to 5v through a 1K5 resistor to enable them.

Their bandwidth seemed to be around 10% so you shouldn't have any issues.

Dave, G8GKQ

Denis Nicole
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Joined: Sun Mar 29, 2020 5:43 pm

Re: Gigatec Amplifier for uplink

Post by Denis Nicole » Fri Apr 10, 2020 12:21 pm

Thanks,
I'll try it out.
73 Denis

G6GZH
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Re: Gigatec Amplifier for uplink

Post by G6GZH » Tue Jul 28, 2020 12:03 pm

Hello,

I've just been given a GT-3094 so I would be grateful for any more information.

Were you successful with it Denis?

Thanks, David

G6GZH
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Joined: Thu Jun 11, 2020 12:27 pm

Re: Gigatec Amplifier for uplink

Post by G6GZH » Sun Sep 27, 2020 4:56 pm

Thanks to a pointer to more info from Dave G8GKQ I've now bench tested the GT-3094 and it gives 20W of clean 333k QPSK at 2406 MHz drawing 6.8A at 28V when driven by a Portsdown using Lime DVB at lime gain 88

David

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