3162	2009-06-08 11:56:41	Eduardo Alonso	minimum parts transceivers presentation available
Message	Date	From	Subject
hello all, last weekend was the annual meeting of EA QRP CLUB, near of the city of Valencia, in the mediterranean see. Joan EA3FXF and me, EA3GHS talked about minimum parts transceivers: micro80/pixie, curumin and pulga/mosquito. you can download the presentation. It is in spanish, but the short comments are easy to understand. http://www.ea4rct.org/trx_pocos_componentes.pdf 73/DX eduardo ea3ghs/4
3165	2009-06-08 23:30:39	Ashhar Farhan	Re: minimum parts transceivers presentation available
minimum part rigs often help us get homebrewing quick and dirty. the 'dirty' part is reliable, the 'quick' part is not ... more often, i have struggled with trying to coax a design that is working at the limit of the components in order to save a few pennies worth of second stage. more often than not, a two stage transmitter will work at the first power and a single stage crystal oscillator will take a longer time to 'tune up'. quick, cheap and easy. choose any two. quick and cheap (won't be easy): if you want to do it quickly and cheaply, you have to be a pro. consider a single stage power oscillator based on IRF 510 as a simple CW transmitter. you should know now much power you can force into an FT-234 crystal as opposed to an HC-49/U. you should know that the IRF510 has enough internal capacitance to make it sing on it's own without regard to the crystal strapped around it, you should know when the current is creeping up into a thermal runaway and what effect your random wire antenna is having on your IRF510's output. quick and easy (won't be cheap): this is my preferred approach. I'd rather add a low power crystal oscillator, follow it up with a stable, negative feedback enabled driver, that drives the IRF510 through an 6-db pad. Our component count is up. Almost tripled. But realistically, it has added less than a dollar's to the cost of the rig. However, the rig is not much more stable, almost guaranteed to work on powering it up, and it will require far less equipment to check if the IRF510 is not oscillating (just kill the oscillator). Another example would be the superreg receivers. Though many a beginners have tried it successfully, I would wager that had they tried building even the simplest direct conversion receivers, they would have been more satisfied and less stressed. I for one, don't understand the entire theory behind them at all. Here is some for those who want to take a stab at it: http://www.eix.co.uk/Articles/Radio/Welcome.htm Beginners like me have often been trapped into accepting that the minimum part coun translates to minimum fuzz. this is not entirely true. I am not advocating that beginners try building the triad as their first project. but build something that has enough complexity to make it a stable design. As Einstein had famously said "Everything should be simplified as much as possible, but not more". - farhan
3168	2009-06-09 16:26:26	Eduardo Alonso	Re: minimum parts transceivers presentation available
Hello Ashhar, Thanks for your long answer. I love your BITX circuit. It is a very clever design, congratulations. Please forget my English language mistakes :-) I think that we talked about this some time ago. I just talked about my last year works to my local colleagues. Really, I do not intent to convince anybody, only I am writing about a kind of circuits not well covered by amateur literature. I am very happy and surprised about their performance, but I understand their limitations. It's more a engineering challenge than a circuit for novices. > more often, i have struggled with trying to coax a design that is > working at the limit of the components in order to save a few pennies > worth of second stage. more often than not, a two stage transmitter > will work at the first power and a single stage crystal oscillator > will take a longer time to 'tune up'. we are not trying to save some euros, we can not use buffer stages without breaking the bidirecionality of the amplifier. in this circuit, the idea is applicated to a superhetereodyne receiver: http://ea3fxf.googlepages.com/SUPERPULGODYNO.jpg/SUPERPULGODYNO-full;init:.jpg (be aware, circuit not tested) now, let's talk about philosophy... > quick, cheap and easy. choose any two. in Spanish, "bueno bonito barato" good,beauty,cheap > quick and cheap (won't be easy): > if you want to do it quickly and cheaply, you have to be a pro. > consider a single stage power oscillator based on IRF 510 as a simple > CW transmitter. you should know now much power you can force into an > FT-234 crystal as opposed to an HC-49/U. you should know that the > IRF510 has enough internal capacitance to make it sing on it's own > without regard to the crystal strapped around it, you should know when > the current is creeping up into a thermal runaway and what effect your > random wire antenna is having on your IRF510's output. yes yes, it's true i can see that problems The way I am thinking is more like this: I read in the IEEE a high power (>50W) class E oscillator with a simple MOS transistor... Well, 1) can the frequency be controlled with a external PLL? 2) can the oscillator be used in reception? (sure!!) 3) Will be the frequency stable? 4) can I make a QSO with it? The circuit will be hard to reproduce, the performance,levels,.. will change changing the antenna... If you try to solve all this things... you will arrive to the same solution of yaesu's engineers. > quick and easy (won't be cheap): > this is my preferred approach. I'd rather add a low power crystal > oscillator, follow it up with a stable, negative feedback enabled > driver, that drives the IRF510 through an 6-db pad. Our component > count is up. Almost tripled. But realistically, it has added less than > a dollar's to the cost of the rig. However, the rig is not much more > stable, almost guaranteed to work on powering it up, and it will > require far less equipment to check if the IRF510 is not oscillating > (just kill the oscillator). yes, i will try to remember this ideas in the future. maybe it's more natural to understand first the basic mechanics under every basic subcircuit and their limitations first, and then try to improve it in a second loop I am living in the first loop. > I for one, don't > understand the entire theory behind them at all. Here is some for > those who want to take a stab at it: > http://www.eix.co.uk/Articles/Radio/Welcome.htm yes, it is a complex theory. i am not completely sure if pulga/mosquito working in oscillation but without quenching, the regeneration occurs in baseband, or/and in rf, or if regeneration occurs at all. > Beginners like me have often been trapped into accepting that the > minimum part coun translates to minimum fuzz. this is not entirely > true. I am not advocating that beginners try building the triad as I am agree. You need to be a experienced operator to understand what happens and what to do all the time. > their first project. but build something that has enough complexity to > make it a stable design. As Einstein had famously said "Everything > should be simplified as much as possible, but not more". yes, and you must to be able to explain how it works to your grandmother. here, it is more like... "look mom, i can run with biclycle without hands" please, if you visit spain and/or catalonia, i will happy to meet you here you have a home 73 eduardo
3171	2009-06-10 08:44:13	Ashhar Farhan	Re: minimum parts transceivers presentation available
eduardo, thanks for the response. i guess, it's my bad to have not set the tone for my long rant ... while, i think that very simple rigs are an excellent way to investigate, i'd recommend something slightly more complex to a beginner, where the complexity goes into making the rig work the first time (instead of making it perform better). on the other hand, look at the fun Wes' has had with the crystal radio he has been investigating for some time ... but it would be challenge for someone to achieve those performance levels. i usually end up buidling most of the simple stuff, just to 'check it out', hehe ... there is something magical about simple radios. i remember, once, when i visited my elmer VU2OZ, there was a moving mobile of radio parts hung out on his window, it buffeted in the wind, but if you grab the earpiece hanging out from it, you could hear radio deutsche welle coming in from europe. off topic, i took my build of the FLEA to my recent hike to harki doon . unfortunately, the vegetation around the glacier was 'himalayan meadows', much above the treeline and i didn't find any tree support for the antenna. i regret not being able to claim 'the mile high FLEA operator' award. the oxygen levels were really down as a result i skipped carrying any antenna support. (I had the FLEA, four Lithium Ion batteries from Nokia (3.6 V, 1200 mAH, each), a small antenna tuner and some wire, total of less than 500 grams). - farhan