I would like to make a receiver for my RF signal generator - Page 1
Forum section: electronics / beginners

author: zdelarosa00
author_rank: Regular Contributor
timestamp: August 28, 2015, 09:24:51 pm
content: Hi, I have this really old RF generator O0 (image link below), and it can output in a range from 150KHz to 435MHz, i’m really not sure if its FM or AM (maybe you can help me tell?), and I have nothing to listen to it, I would like to make one of those DIY receiver boards, but they are for commercial radio and i have found that they tune other ranges above the ones I want, maybe you can help me out listing parts or giving me a schematic? im talking simple ic’s and a couple of tuners and switches thing. Thanks (: (stepping up my smiley game)

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 28, 2015, 11:34:27 pm
content: My Spanish isn't exactly stellar, but it looks like it's got an adjustable modulation level, and external input. I'd guess it's much like the classic kind, where the modulation is transformer coupled to the oscillator supply. Since the oscillator runs in saturation, this varies the output amplitude, giving AM.To listen to the modulation, it should be enough to connect a diode to the output. Crude, but effective.Is it vacuum tube or solid state? Take pics insideTim

author: w2aew
author_rank: Super Contributor
timestamp: August 29, 2015, 12:40:45 am
content: There are lots and lots of receiver plans available online, if you look among the ham radio homebrew community. Everything from tuned RF receivers, regerative receivers, super heterodyne recovers, direct conversion, etc. lots to experiment with.If you just want to check operation, a shortwave receiver can be used.

author: miguelvp
author_rank: Super Contributor
timestamp: August 29, 2015, 12:42:39 am
content: Would a Software Defined Radio dongle be of any use?They are usually cheap and the software is freely available.

author: zdelarosa00
author_rank: Regular Contributor
timestamp: September 06, 2015, 12:44:10 am
content: It is indeed tubes! GE tubes.... Okay so the simplest is wiring a diode and a speaker to the outpu t??? AM then it is... (: sorry for the long waithttp://imgur.com/a/o0M5z

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 06, 2015, 01:38:40 am
content: Ah yup, looks like a newer (maybe or not nicer) version of the Eico 322 I have. Audio modulation, changes the plate voltage a little thus modulating the RF output slightly. That's what the transformer is doing, strapped on there.The RF output level is high impedance (perhaps 1kohm at the maximum amplitude setting), not particularly powerful, and pretty high in distortion (which might be seen as an advantage or a hindrance). My 322 typically shows 10-20 nice strong harmonics on the spectrum, of varying amplitudes as the frequency and band are adjusted.As an instrument, it's pretty pitiful. A low impedance buffer, transformer, or other matching circuit, would be highly valuable for improving power output, and generally making it useful among 50 ohm systems. Not much can really be done about the distortion, either for reducing or eliminating it, or for trying to make it more consistent (the harmonics might be useful if they were a known and stable level for all ranges). The harmonics vary because of the class C oscillator (= distortion generator), the varying capacitance (shunts the harmonics differently over frequency), and resonant modes of the coils (which are especially important on the higher ranges, where peaks and dips occur).Tim

author: zdelarosa00
author_rank: Regular Contributor
timestamp: September 07, 2015, 11:58:24 am
content: Yeah, i didnt actually expect much of it, i think its fairly simple to modify the output to something more simple. Funny what you say about the Eico brand, i found this and also a tube oscilloscope laying around at ny grandpa's house, the oscilloscope was an Eico 427 i think, i will catch photos of it later for you (: