10515Re: [loopantennas] Trask Amplifier for Wideband Active Loop Amp - mod suggestions?
- Feb 24, 2014
>Go for it! In case you're interested, there's a seller on eBay who is selling the MPS6521 at pretty reasonable prices. I bought two lots of 25 for $10 each from him, which will satisfy my needs. They're basically a 2N2222 with twice the current gain. It's a shame that they were never made in SMT so that they might still be available.
>> >Well, my bulk buy of BC549C's has arrived, so one more question before I get started on the amplifier...
>> >How closely do I need to match the transistor pairs? Can I just go by HFE reading on my cheap digital
>> >multimeter, or for best results do I need to break out something a bit more serious? If so, what exactly? :)
>> >Can I just use my 8405A and check that there's exactly 180 deg phase and equal amplitude on each side?
>> I never did go to the trouble of determining if hfe imbslance affected the performance, and it's less
>>important for common base amplifiers than it is for common emitter. But, my feeling is that a match of 5%
>>or less would be prudent.
>I've just started winding the transformers. I've only got AWG30 wire rather than AWG32 so I've had to use 2873000202 instead of 2873002402 as I an't fit 4 turns of it on the smaller core. Hopefully I can cram it all on the board I'm using.
>I still have to sort out some low ESR caps, but I've pretty much got everything I need to build one, finally.
N7ZWY / WDX3HLB
Senior Member IEEE
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