A common base amplifier for the second stage of your buffer amplifier might be an idea as its low input impedance might be similar to that of the output of your emitter follower stage.
hola charlie. felicitaciones por ese trabajo de cristal filtro. te cuento que esa configuración la realice hace unos 30 años atrás aproximadamente. pero en frecuencia de 10 mhz. use en esos años un monitor de estación a válvulas heathkit que tenia incorporado un oscilador de doble tono para ser usado es ssb calibración. me construí un qrp en banda lateral única y lo quería en LSB con cristal filtro . para encontrar el corte ideal no seleccione los cristales de cuarzo, todos fueron al azar, solo que los capacitores fijos entre ellos los remplace por capacitores variables y usando el doble tono encontré los valores correctos para una respuesta decente. fue tan bueno el resultado que cuando salía en 40 metros todos pensaban que era un equipo de fabrica .jajaja. fueron muchas noches de ensayo y error pero el resultado fue espectacular. tu video me hace recordar aquéllos años cuando era un bebe en electrónica pero lo aprendido en general de construir tu propio equipo es impagable. nuevamente felicitaciones y me entretiene mucho tus videos. mil gracias por publicar. atte Enrique Vidal CE5LBM
Really hellpfull video. this helps me with my Diploma this year. Would like to see how i could imput this voltage for an esp32 in terms of amplification and such. 73 de OE8GKE
Hi Charlie, the wspr zl2ctm re78jr 20 encoded symbols shown on the screen demo of genwspr.exe don't match the low or high power symbols in your code on your web site. I generated a symbol table using jtencode in the arduino ide for zl2ctm re78 10 and that matched the LowPWR_WSPR_DATA array in your code.
I didn't see the main volume control on your schematic. From the photos I can see a cable with either 2 or 3 wires leading to a pot. What value pot did you use ? Did you use all 3 terminals on that pot ? Thanks.
This spiel covers a heat tabbed SMD mosfet that is a contender to replace the BS 170 in a lot of PP circuits and may indeed serve as cheap subs for the expensive LD mosfets ,VHF rated, which you used. They are likely hard to find on Ebay but are a part that can be found on Mouser and Digikey. The Tab on these is voltage hot so the copper pads have to be kept isolated when in service. -The PA mod accommodates two FDT86256 Mosfets and provides some heatsink PCB space with footprints matching the motherboard BS170 for easy installation. The FDT86256 offers several advantages over the BS170. The most notable advantage is its higher breakdown voltage (Vds), which stands at an impressive 150V, in contrast to the BS170's 60V. Another significant benefit of the FDT86256 is its ability to handle higher power levels, with a rating of 10 watts, compared to the BS170's 800 milliwatts. However, it's worth noting a drawback of the FDT86256 when compared to the BS170, and that's its higher input capacitance (Ciss), which measures 55 picofarads (pf). This higher capacitance can potentially impact its performance at higher frequencies. However, in a Class D configuration, it performs comparably to a pair of BS170s. Typically, the Ciss capacitance of a BS170 is around 24pf. When used in parallel pairs, the total capacitance reaches 48pf, which is not significantly different from that of a single FDT86256. This encouraged me to consider the FDT86256 as a replacement for a BS170 pair. End of snip . TEF (Relates to use of this Mos device in an RF PPull circuit. ). TheFDT is of the order of $1.50 US each from the normal supply houses like MOuser (and the high courier bill that goes with it).
I would love to build an AM Air band receiver around an Arduino and the Si5351, but i just don't understand the analogue part of the receiver. Something like the Signal Corp R-532 or 535.
A quick note about the resistor at TIP31C B-C. If you do a bootstrap by splitting that resistor into two in series and feeding the mid point from your amplifier's output, you can get a better positive swing. I like the design. I would have used TIP35 and TIP36 for my output but only because I have some.
Hi Charlie, have you, or ever thought of building an updated version of the Tucker Tin ssb transmitter with commonly available parts? Anyway, keep up the excellent work! Best regards, Lance ZL3LAD.
If you just wanted to listen to the station up the road you could have just done it with a few transistors and an AF amplifier 😅 Nup not good enough says Charlie... but I won't worry about an AGC hahaha, might as well set up an AGC now anyway 😂
@@CharlieMorrisZL2CTM I want to try playing around with a "crystal set"... okay I'll call it a detector 😆 But the idea is to use a stage of RF amplification ahead of it. Then of course bias the detector a little. Then play with an AF amp using AGC that has a LOT of open loop gain... might as well make a single conversion superheterodyne radio. I'm with you Charlie, you're doing great 😆
@@Dazzwidd For "extra credit" you can make a reflex amplifier that does the RF and the audio. There is a bit of a trick. You make the polarity of the audio such that more RF into your detector makes less current in the amplifier transistor. This gives it some AGC without even trying.
@@kensmith5694 yeah, you could do that. Being serious here, I would make an AGC arrangement that provides you with an S meter indication if I was doing what Charlie is. Might be better to gain control the intermediate frequency stages rather than the audio and maybe have a little AGC on the front end 🤔
@@Dazzwidd Normally, AGC is done in the IF stages. You want to take some gain before it just to be sure you are above the device noise. The AGC signal is usually a low pass filtered version of the detected output. The IF stages are run with emitter resistors bypassed so that the gain depends on "little re". This lets you have a fair range of gains. A meter on the AGC voltage works as a signal meter. With a bit of cleverness, you can make it work in dB.
Hi Charlie! The only suggestion I would have, is to try different semis. While the 510 is used in many RF applications, I’ve heard some people having better efficiencies with RF transistors. In fact, some great results were had (even over MOSFETS) by using RF bipolars such as recovered CB final transistors such as a 2N1969. This (to me) would seem more likely to be the area whereby the efficiency would most likely be compromised. The only argument against that is, if-so, one would think you’d see the inefficiency manifest as heating in the device. Anyway, even though you may have to ‘buck-up’ the input driver, I’d still give the RF bipolar a try. Thanks very much for your excellent explanations, analysis and demonstration. 73… 😊
I do love the engineers view on design, we will calculate what value we need then just pick a close preferred value. before PC's we would work out the affects of tolerances on the components, taking the min and max values to calculate what the tolerance spread would do in production and writing the test specification around it. PC's and lt-spice made that a much easer job. 🙂
@@CharlieMorrisZL2CTM it's not a short cut it's a design decision. In the same way we try to use a lot of the same values for components, reducing the amount of different parts in the BOM reduced costs. If you don't have any tolerances in your specification then you going to need exactly the right value which certainly puts the costs up.
BTW: You can use up to 3 .step commands in LTSpice. This way you can plug in all combinations of min and max for 3 components to see the spread of results. If you want more there is a trick where you step a "test number" and then make the resistor values with expressions.
@@kensmith5694 can you remember when you ran spice off a floppy on a 367. When I was doing it all by hand the only other option was on the mico-vax terminal. I don't think we had the spice program on the vax.
@@TheEmbeddedHobbyist My first PC was an 8088 based DOS box with two floppies. I am leaving out the ZX80 as a "PC" I still own my slide rule and can remember how to use it. The first simulation software I encountered range on an IBM360. Spice has made a lot of stuff easier. At one point I downloaded the source code for it and worked on fixing a few bugs. For a correct "deck" it was ok but some syntax errors would cause it to segfault without telling you what line caused it. My changes may even appear in versions today. I just made the uninitialized pointer lead to a syntax error. At least you would then know what line did it.
Missed watching Charlie....took a break from things for some life stuff.....kicking off my resurgence into radio this weekend at Hamvention! Hopefully i will add many things to my junk box for future trials into the homebrew world.
How did you decide on the inductance of the coil in the collector load? Why is a coil beter than a resonance tank or maybe a simple resistor? Also, I think your attempt to match the impedance of the filter is incorrect - if the input filter impedance is 910 ohm, this should be the output impedance of the common emitter amplifier stage. Since for CE config it's the collector load, your collector resistor should be ~910 ohm or equivalent. Shunting with a resistor makes it worse, since now you have 910 ohm in parallel with ~25uH of the coil which is roughly 1600 ohm at 10.7MHz.
Yes, I took a few shortcuts on this particular build. In the past I have made the effort to better impedance match crystal filters with the output/input impedance of the IF amps. While not ideal, it's working well for this particular radio.
@CharlieMorrisZL2CTM Of course, working radio >> perfect theoretical design. On the other hand, this could be a starting point to pretty interesting experiments on fine tuning and squeezing the max performance out of it. If you have a signal generator and basic measurement tools like a decent audio interface and software, you could do a couple of follow-up videos on those. Would be interesting to see the effect of impedance matching on the distortion introduced by the filter stage. Cheers!
I love the world according to Charlie! Brilliant job as always. I'm certainly going to play around with an infinite impedance detector and maybe even a Franklin oscillator (if I can prize the Si5351 from my hands!). So good to have you back on RU-vid. 73, Nick M0NTV
@@CharlieMorrisZL2CTM Maybe not a masterpiece. However, it's designed beautify, and beautify built! And good enough to be (picture) framed. Perhaps you should change your channel name to Electronic Arts (EA™) 😆
Really nice Charlie. It sounds great. I like your constuction technique. I too make a lot of use of solder wick. And I like copper clad on wood. More room is better than not enough room. And there is a benefit in keeping all the circuitry visible. 73 and thanks, Bill N2CQR
Another fantastic, scratch built, radio. I must have missed it, but I'm intrigued about the variable, vernier-drive tuning capacitor. Where did you get that from. Such things are now almost imposable to find! 73 de VK6AWK
@@CharlieMorrisZL2CTM Those air_gap variable capacitors, especially the vernier drive models, are impressive. More so, when considering the technology (manufacturing) of the time, compared to today's CNC laser cut, and robotic mass production, can't make equal quality for the price today. And I can't argue with having the circuit naked. But perhaps a clear Polycarbonate cover to deter dust?
I really like the way you make your circuits. They are very beautifuls and make me want to do the same thing. Also it works well and the sound is amazing, sorry for my basic english !
Thanks David. I'll see what the next build will be. I'm conscious that my approach to things is not textbook, which opens myself up to criticism. To me these are just a video diary of what I have been playing with. All good fun.
@@CharlieMorrisZL2CTM I am an EE, and frankly, I think your approach, and designs, and methods follow a very good process, and you use most of the rules for transistor biasing and design that I learned. in school, and used through the years. Your results speak for themselves. You do great work, and follow a consistent, well thought out design process that yields good results. Kudos! The only thing that might be something else to add to your design toolbox for transistor biasing is a little stability analysis. I can't think of anything else you are really missing in the process.
I would welcome extra rf-gain. For years we, in the Netherlands, have been deprived of the big broadcast transmitters. What's left is an ever changing offer of LPAM stations. (between 1 and 100 Watt).This requiers close proximity and/or a very good radio. Absolutely love your radio. Scrambling for parts now. PE1LLA.
Beautiful work Charlie. I'm guessing that that variable cap has the rotating vanes (and thus the panel contol) grounded, with the stator vanes going to the circuit. That may be why you can touch it with no frequency shift. FB on NOT having shielding around the VFO. Too often dogma and lore has us putting unnecessary metal boxes around this stage. 73 Bill N2CQR
Thanks Bill. Yes, the rotating vanes are grounded, which adds to the stability. As you know, I prefer not to have enclosures arounds the circuits as I enjoy looking at them and thinking about what each component is doing. 73.
Anither great radio..the very neat and artistic work...the oscillator capacitor is a piece of art with that gear arrangements..radiofun242 also made experiment once by varrying gains in different sections ..in rf and if...most am radio have tuned fromt end and 1970 80 radios advertised turned rf stage..you completely skipped tuning the rf ...the second capacitor of gang capacitor could be used for rf front end tank circuit...i saw 3 trf stages in a russian ishim radio...the radio you built sound amazing without any of those...i wander if you may need turned front end for weak am stations and dxing....you vedios helps us a lot and its always fun to watch and listen tou doing these stuff...
Hi Charlie! Great to see you back in the saddle, and your soldering-iron out of its holster! Always enjoy the projects and all the explanations and conversation about circuits and their options. I finally retired and managed to get some pretty good used HP gear, so will be getting back into the lab myself. Anyway, thanks for putting out more great videos! 73...
