Cool!

I didn't know you were into this. I scratch build my own amateur regens and some other circuits to do SW DX'ing, but it is only for listening as I have no ham license. Had a brief TS chat about it with Arctic some time back, as he does (or did) it too.

It is quite a fun way to get through some time.

Show us your antenna, please!

EDIT:

Here's a video off an old Youtube channel of mine. It is the only video I ever made of my experiments. This one's a crystal radio prototype for AM, mainly to test my home-built variable air capacitor, which worked pretty good.

Don't have the time to watch the video right now, but I've always wondered how do you select the frequency? A simple combination of Low-pass and High-pass filters? Or fancier stuff?

That antenna will do the trick, for sure. It's often forgotten how important they are, it is a whole science with DX'ing, as you'll know, lol! It is an awesome setup, iCom is a great company. I have (and have had for years) an airband transceiver by them that I used to use to listen to students on their solos. Still works a treat, like new.

I haven't done any HF scanning since I moved house, so I haven't set up my antenna where I am now. My "standard" one was simple but effective, just a long wire type, three different lengths of solid sheathed 10 AWG copper wire parallel to each other with a selector. I'd experimented with an active antenna at one point, but after a while the only JFET I had found in Ecuador blew, lol! I also played around with a tuned loop, and was trying to make a circuit that could do some DF on AM stations using it. Fun time, but not too much success.

I'll have to set myself up again with my best HF receiver concoction and arrange to see if I can hear you, some time! Should be fun. Taken note of your call-sign!


Ktulu2;

Don't know if you were asking me, but here goes. (I'm a bit rusty with the terminology and formulae at the moment, and am writing this as a brief outline off the top of my head, so anyone who can correct any errors if they see them, please do so).

Where capacitors can be used as filters, then yes, you are on the right track. At the most basic level, like that AM crystal radio in the video, it is actually much simpler than you think. Put simply, the first key points of a receiver are;

Resonance. Rectification. Capacitance. (Among some others that would only complicate the simple description here).

When radio waves hit your antenna, they create a small alternating current in it. You create a coil that resonates more or less at the frequency of the radio wave range you want to tune, and feed the AC signal from your antenna into it. Once you get your coil resonating, you can use capacitors to "fine tune" to the exact frequency (resonance) you want by slightly altering the capacitance of the coil circuit. That is where the variable air capacitor comes in, as it is proportional and allows minuscule "tweaking" of the coil, allowing you to shift through a range of frequencies that the coil is capable of "receiving". Finally, the output AC signal must be rectified to DC with a diode (or transistor) or you'll only hear white noise, if that, when you plug in the listening device. Once you have cleared out the reverse current, you'll hear the transmitted signal. It is a cool moment when some TRF experiment or another works.

Transmission is not so much more complicated once you have got this far, in fact, but it is largely illegal to play with if you don't have a license. In any case, you'd need an oscillator IC. Easy enough to get.

Hope that's what you wanted to know. If not, I've just bored everyone again. LOL!

Dead on!
In my electronic class we didn't do RLC circuits, which turn out to be quite important lol.

Huh! Glad it helped! Some time I might even have a refresher question or two for you, as your taking of the course is certainly much more recent than mine, lol!

Incidentally, that home brew air variable capacitor is a bit miraculous, as it was made from a piece of galvanized sheet mild steel, a wholly inappropriate material for RF. All I had at that moment. I have a nice piece of duralumin now, which I will use to make another one before I take up this hobby again. Just need to locate some long, aluminum or brass nuts, bolts and washers to eliminate all ferrous influences and do a really good fidelity bit of kit.

LOL! Just looking at this thread again and laughing. There's Tracer's totally awesome iCom in post one and the still of my jumble of wires, a mysterious looking artifact and PVC plumbing pipe in the second. It strikes me that the comment is the same for each image, except for punctuation and emphasis...

"THAT'S a radio!!"

"That's a radio??"

Squid, part of your question; for long range HF DX I don't think the valley will be a major issue unless you live in a deep, narrow crevice. I'm in a valley, too, surrounded in all quarters by 15 to 20 thousand foot high mountains within 10 to 15 miles. I used to pick up WRMI, Cuba and Vietnam no problem on my regens. Just get or make a well thought out antenna (can't get tired of saying that, lol!). HF is not line of sight, and you would be listening to a source SW station, not repeaters. Unless you mean VHF/UHF only, but that's another story

PS: Tracer, have you ever looked into this DRM thing? I sometimes used to pick up data transmissions on two frequencies right next to each other and suspected these were DRM channels, but lack the know how to decode it, if it is.

LOL! N00b myself, hence the use of the word "amateur" in the first post. I've never heard of CTTY, whatever it is.

No, it is some data transmission, a bit like a slow fax sound. I've heard it spread out at points across the HF band, in pairs, always seems to be 5 Khz apart. I assume it is a channel, because of this. I was curious and read up some time ago, and DRM seemed to fit. From what I remember, it is a way of producing high quality audio off HF by processing the data through a computer, though whether it is as simple as plugging it into the audio jack (after correct impedance matching, of course!) and having the software to decode it, I don't know. In any case, I'd need to make two identical receivers to tune both frequencies together. Seems like too much hassle, but I'll read up on it again.

Radios are always awesome, and that one looks like a doozy.

I have a portable one that i can program frequency's into , i just use it for local fire / EMS / Police radio traffic in my area

That is a smart idea. and yes these little guys are pretty solid for a cheap price.