For some reason, I always find mic circuit amps a mystery (how much to bias MIC & transistors, etc), so many thanks for keeping things simple, yet very effective, 73
Great work again Charlie , i always enjoy ur video's as you take us through the circuit and show us what is happen on the test gear a top teacher and explained well ,so many thanks for that Charlie. I noticed ur HF Xiegu rig and just wonder how you find them on the operational side of thing ,certainly sounded ok ,We are in the steps at the moment of making up ur project for 80m ,then later i would like to try your designs construction and try a put one on for the 6m band. Many thanks again and for inspiring us.
Cheers Dave. These are just simple rigs, but a lot of fun for me. The Xiegu works well for me. I'm not a competition operator, so the small screen and buttons are fine. I do like it for it's small size, which works well for my small shack. As for 6m, I too am looking at the higher bands now that we are on the next sunspot cycle. Not sure when I'll tackle that though.
Thank you Charlie I needed some motivation this weekend! looks like things are working great. audio sounds good. what power output do you have like its setup? By the way, I made my LM386 sing very well last week. it was the preamp giving me problems. I figured it out while not knowing my LM380's were in my mailbox. lol I've been working on my VFO and BFO with the display. I put it in a box so I can reuse it on other radios or add on to it. something I am adding to it is an I/O expander board. you might want to check it out if you run out of I/O. this one is I2C. PCF8575 the module is open smart IO expander 1610. it adds 16 I/O and can make them a different voltage than your processor. I believe it was from 1.8v to 5v, and you can address them so you can have three modules if you needed. I think it was the Teensy project you were running out of I/O if I'm correct and had to use the larger Teensy. I needed it because I am using an esp8266 with built-in wifi and Bluetooth but it has a low pin count. it also runs faster so the display update is nice and fast. I also ran across an SMD IC that is an RF switch that looked interesting I want to play with one. works from 1Mhz to 500Mhz up to +30dbm. maybe in place of a relay? have a good weekend!
@@CharlieMorrisZL2CTM A PA sounds good I've been distracted thinking about that, so many different transistors. I was thinking for me 10 to 20 watts 100 at most. but I would like it to cover higher frequencies as well. I can drive something bigger for sure with that amount. I should probably just buy a few and see what I get. lol
Hi Antony. I must admit I am not sure how best to measure that. What elected to do with this build is sniff the output using a RTL-SDR and then adjust the TX BFO to get best TX spectrum, in this case minimal residual carrier and best received audio clarity. As it turned out, I cannot see any residual carrier (on the RTL-SDR or receiver waterfall) and get (in my view) really good received audio clarity. This is the first time I tried this approach and it seems to work well for me.
I just finished a Crystal Filter based off HC-49S Crystals (Mostly because I can't seem to find any cheap HC-49U Crystals.) I have a IF freq of 8.466-ish Mhz because that was the only freq I could find in bulk. (Was ordering off amazon because getting stuff from AliExpress takes well over a month sometimes.) I have some AD831 Mixers I am going to use. (Mostly because I have them). Annoyingly I only have about 1.7Khz of bandwidth in this filter, I may try to build another one with 3 crystals instead of 4.
@@CharlieMorrisZL2CTM I am going to make a second filter using some more of my Crystals and see what happens. I can use my current one as a Narrow SSB filter, sort of like how some professional rigs have that. (My IC-718 has the option but doesn't have a filter installed for it)
Thx for your vids Charlie. Qustion. Does it make a difference if you toggle BFO and VFO on Tx/Rx vs you "toggle" the input of the muxers. In my radio I am playing with I keep the BFO and VFO at the mixers and flip the mixer input. So I use the crystal filter in both ways.... hmmm. What approach is better? 73, Stefan, HB9GZE
Hi Stefan. Short answer is no. The reason I do it this way now is that I had several feedback issues with the small rigs. Essentially, I had RF from the output of the second IF amp finding its way back into the input of the first IF amp via the switching relay. This current format does away with the crossover problem and I have not had a feedback issue since. Each to their own I guess. 73 Charlie ZL2CTM
Could it be an idea to also make the Emitter resistor a trim potentiometer? the value ..... that 150oHm with at the runner that capacitor to the min . i am not an electronics engineer! I always made my FM pirate transmitters with an amplifier as indicated below: BC109 Emitter to min -- resistance 100K from base to colektor. 4K7 from colektor to plus. + input and output 4.7uF the rest is about the same! by the way, don't know if that's better or good enough! . Kind regards again from the Netherlands! Rob
Yes you could in theory. Just make sure the power dissipation at 10mA does not burn out the trim pot. That would provide varying negative feedback. It would also affect Rin, if that was an issue. Another way is to use a diode with a varying DC.
