minikits PGA-103 LNA 0.05-3GHz

[VK2FAK]

Hi all..

Has anyone had any experience with these amplifiers.....are the worth buying..

[VK2JDS]

Yes, the pga103 is a good little device. I bought half a dozen from Minikits a while ago and put them in as the front end of a couple of 2m rigs and a tait vhf repeater and they really worked well.

But ... they need protection on the input. Back to back diodes and a tuned circuit (or cavity) will make sure they dont die. I killed a couple of mine.

73 Dave

[ZL1RS]

Killed a couple of the devices here too ... but not using Minikits circuit, on a prototyping board from the manufacturer/distributor. One device had a slow decline in gain until there was no more left and by that time the S/N improvement was non-existant. While they were working they performed VERY well over a wide range of frequencies (which can come with it's own set of problems). If the back to back diodes on the input will save them, then definitely worth a go.

73,

[VK1DJA]

I built a MiniKits PGA-103 amp that met the gain specs for the device at 2 M. Didn't measure IP3. It needed a front-end filter to kill IMD noise but I'm only 10 km from Canberra's TV/FM transmission site. I haven't managed to destroy it yet.

I killed several devices in DIY circuits. They seem more robust if there is that stabilising circuit on the input.

Also see some discussion in this Forum under Switched LNAs, the Applications Note on PGA-103 stability on the MiniCircuits website, and the PGA-103 amp on the G4DDK website.

Dave

[VK2HRX]

Hi John,

There is one of these on the 23CM repeater at Chatswood in Syndey, been there for 2 or so years so far. It has proven to be reliable and the in built filtering means it is effectively imune from RF noise, especially in the 3G bands and all the stuff on the Ch 9, ABC and every one elses gear on the BA towers at Gore Hill, just a stones throw away that services Sydney for TV and FM broadcast etc bands. At Chatswood we have if I recall around 12dB of attenuators in line with it to give a gain around the 18dB mark so it matches the Tx footprint of the 40W amp. These figures are from my memroy so are only approximate.

If you want to test one out fire up on 1273.200/1293.200

Cheers,

Compton

[VK2FAK]

Hi all...

Thanks for the comments guys..

Yeah, I did read that a PS regulator added could also increase the NF in not properly filtered....

Seems to be questions about other strong signals....the claim they need to be very close to cause problems....

Guessing, as mentioned ,, some sort of protection to the input would be required...

[VK4REX]

Hi John

I have used the PGA103 in 2 and 432Mhz preamps. I have measured the following performance on a HP8970B test set:

144Mhz Gain 24dB noise figure .35dB
432Mhz Gain 18dB Noise figure .42dB
1296Mhz Gain 14dB Noise figure .62dB

I use the board and machined enclosure from RF Basic store :

http://www.ebay.com/itm/Designer-Kit-RF ... 5d52dfa4d2

plus I use their filter board to make a suitable BPF for the output of the amplifier

http://www.ebay.com/itm/Develop-PCB-LC- ... 22f8d5d6c7

For optimum performance the bias should be 4.75v at 95mA. This gives the best noise figure and a good IP point. I use an 8v 78M05 regulator and 2 parallel 68 ohm resistors between the regulator and the PGA103. If you use the RF Basic board you can fit 2 x 0805 smd resistors on top of each other on the provided pads.

Hope this helps

Rex