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Title: QRP Amp Circuit? Post by: WA2SQQ on March 10, 2015, 01:36:47 PM Working on a QRP project where the exciter gives me +15 dbm (31.6 mw). I'm looking for a simple circuit for an amp to get me to about 1.5-2W (31-33 dbm). Frequency range needs to be 1.8 to 30 mhz and capable of all modes, especially AM. A ready made amp would also be something I'd consider.
Any suggestions? Title: Re: QRP Amp Circuit? Post by: W3GMS on March 10, 2015, 04:50:51 PM This may get you there. I did notice some high frequency limits, but looking into the details I am sure would answer the question as to why that is. Anyway the circuit looks pretty basic and has considerable gain so its at least something to look at for starters.
http://www.kitsandparts.com/qrp_amp2.php 73, Joe GMS Title: Re: QRP Amp Circuit? Post by: w4bfs on March 10, 2015, 05:28:51 PM push-pull stage is unbiased .... with bipolar transistors it will be in class C .... adding a bias ckt to it would likely be necessary to reduce distortion
Title: Re: QRP Amp Circuit? Post by: W3GMS on March 10, 2015, 08:11:52 PM push-pull stage is unbiased .... with bipolar transistors it will be in class C .... adding a bias ckt to it would likely be necessary to reduce distortion On AM you could collector modulate it and leave the circuit as is without a problem. Obviously it can't be used as is on SSB. "Capable of all modes, especially AM" so maybe SSB is not a must. Joe GMS Title: Re: QRP Amp Circuit? Post by: kb3ouk on March 10, 2015, 08:29:11 PM push-pull stage is unbiased .... with bipolar transistors it will be in class C .... adding a bias ckt to it would likely be necessary to reduce distortion A class C amp can be used as a linear amplifier for AM, there's several discussions about that on here. Title: Re: QRP Amp Circuit? Post by: WA2SQQ on March 11, 2015, 11:14:05 AM Here's what I'm going to go with
http://www.qrpproject.de/UK/qrppa2008.html 57 Euro, delivered Title: Re: QRP Amp Circuit? Post by: W3GMS on March 11, 2015, 05:09:07 PM I saw that one as well. Would work well on SSB and AM since its linear. A quick view of the Circuit seems like it will do what your looking to do. Not sure if your going to modulated your very low power driver or not or do it high level in the external amplifier. Not great efficiency, but maybe that's not your objective. I can't imagine 2W of AM, but to each his own!
Title: Re: QRP Amp Circuit? Post by: WBear2GCR on March 12, 2015, 10:25:23 AM One might take this sort of little amp and use it as a pre-driver for something like and EB-104??
Title: Re: QRP Amp Circuit? Post by: WA2SQQ on March 12, 2015, 11:48:05 AM So, here's my intention ... AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
I have a fairly stable Panasonic signal generator that covers up to 220 mhz. I want the QRP amp so I can use the generator as a QRP transmitter. I've tried externally modulating it and it sounds great. Whether I use it at 2W, or driving a second amp to a higher power, it will make for an interesting project, re-purposing a piece of test equipment not being used. |