After 2 years we tried to provide resources for HAM tools/component, which based on our experience will help and make HAM experiment more interesting and more easier we decide to say good bye to eBay. By 1st January 2018 we closed our store on eBay. We will continue to do experiment and do creative thing to make our hobby getting nice and better. We will launch and operate our web page at http://hambuilder.com that currently not fully operated yet (so sorry if you have visited this site but did not get the proper response). We hope by running this web by the end of this month, we could give better service and support.
Our road map for this year is:
*. increase the performace for our existing exciter (HBR10HF, HBR4HF and HBR1HF)
we will develop new PCB or additional daughter board consist of
*. accurate AGC (AD603? or similar)
*. accurate S-meter (AD8307)
*. accurate SWR reading (AD8307)
*. adding optional roofing filter
*. adding simple digital audio filter
*. get more RF amplifier power output (we reach 50 watt now)
*. Continue instrument development (Antenna Analyzer that always missed LCD stock we got new vendor now)
*. Antenna Tuner (semi automatic)
*. RF amplifier protector
*. Standalone SDR transceiver
There’s a lot homework we must do
RF mixer is a key building blocks in transceiver design. I tried several popular active mixer such like SA602, TA7358, MC3362. I never tried DBM until Om Farhan (V2ESE) introduce the BITX and its very success. Then I tried to build the BITX also by my self. I amazed its works on the first try. Based on my experience and comparing to other active mixer, for me BITX with its DBM is very stable. The design is straight forward, simple and easy to understand, the schematic actually describe basic function of each block on transceiver design. In my believing by choosing high quality component on BITX we can build high quality transceiver. In other case using low cost component we can build low cost transceiver without loosing the quality too much. This design is very compromise. Of course if your target is middle bass or high quality audio, crystal clear audio, do not choose BITX. There’s a lot transceiver with build in DSP. What do we expect on 3KHz bandwidth? I lost my hearing capability for frequency upper 3KHz when I work at utility department that assign me to handle 8 unit 1MW SKF and 2 unit 0.5 MW Niigata genset. So for my ear BITX is more than enough.
Why I see BITX is simple and straight forward? let we see heterodyne RX diagram below :
This diagram is really similar for each block what is inside RX chain BITX.
please visit Om Farhan web for circuit description http://www.hfsignals.com/index.php/2017/11/23/bitx40-circuit-description/
and a posting from https://hackaday.io/project/20067/logs, and also a lot BITX discussion on internet about it.
I capture what Om Farhan said about this half of bidirectional amplifier circuit (http://www.hfsignals.com/index.php/2017/11/23/bitx40-circuit-description/). This circuit is repeatable 6 times similar, may be little bit difference on some stage coupling.
For me BITX is a good entry point to learn and to get a little more exposure about RF design without too much doing math calculating. We just need to choose or put alternative component, give some additional of feature and try and try. You can easily modified or enhance but I cannot found any better explanation about building transceiver like what Om Farhan did, the simplicity and functionality.
Two thumb up for Om Farhan!