Easy to build AM receiving antenna for your radio

Nice idea!

Could the cross-arms be made of corrugated plastic, like the kind used for inexpensive signs?

Make a great give-away with the station frequency printed on the plastic cross-arms.

Help your listeners become DXers

Experimental broadcasting for a better tomorrow!

You could make the cross arms out of any thing you have around. I went with oak because I have some left over from my kitchen remodel. It helps keep cost down.

These are cool antennas,they look retro! I built a couple which only need to be near the internal antenna and they work well too. Might be easier than a user needing to hook up to their radio. I am also on freewebs. See my site at www.freewebs.com/wilcomlabs
I finally got around to putting a website together with my parts for sale list and more..... Regards,Lee

Once upon a time I built one of these for receiving and it worked well.

Though I have no other experience with a loop they also work for transmitting. Just thought I would mention this in case anyone wants to pursue it.

Neil

Any more ideas on loop tx antennas sounds like another cool project to try. You wouldn't loop from the rf out to the ground would you? Would the antenna itself act as the coil?

You can place an inner loop that connects to a wire with a clip and connect the clip to the antenna of the radio itself too. Passive inductance.

Definitely a cool looking little antenna there, Brian!

I'd been looking at some old style loops as part of a project I'd been considering of seeing if I can get some of the kids in the neighborhood into the idea of building crystal radios when I get an AM transmitter up. Yeah, I know, a crystal radio isn't going to have the range of something like a car radio, but for kids (or maybe some adults) in the near neighborhood it may be workable.

I always found a certain fascination in recievers that take no battery or power supply. And there's that "built it yourself" thing to it that makes it more interesting.

I did an antenna experiment that I gave to a neighbor/listener back a bit before xmas. I was over at his place briefly and he mentioned it was a pity he couldn't get my station on his home entertainment system, only his boombox. And then with it next to the window with the antenna up. Checking his home entertainment unit, no antenna at all. Place to hook a 300 ohm for FM, but not even a random piece of wire in it. We were talking about antennas and he was thinking of getting one of the ones basically made of twinlead that you tack up on the wall like he'd had years ago.

I remembered I had some twinlead over at my place and that I'd recently seen a webpage about making a "slim jim" antenna for FM 2 meter out of twinlead. FM BCB is 3 meter, only a bit physically bigger. So I looked at the diagram with what fraction of a wavelength, hit an online wavelength calculator and then roughly cut a piece of twinlead to length and cut out the notch and bared and tinned the wire for the sliding connection to the feedline to tune it, did the rest of the little bit of soldering and took it over with the rest of the twinlead I had. We put it right in the corner of the room, where it wasn't very noticeable and ran the feedline back behind a bookcase and a small table, under the windowsill and into the back of his reciever. Almost invisible unless you know right where to look.

Then I set his receiver to my xmitter frequency and played with sliding wires up and down till it was coming in fairly good. That antenna is *very* picky about where the wires connect I found, and a lot of moving it a tiny bit and moving back away and then moving it a little more moving away was necessary before we actually got pretty decent reception happening. Like moving the wires even a 16th of an inch can be the difference between "nothing" and "hey, it's coming in pretty good now!". I soldered the ground (shortest) side first, then played with the "hot" side a little more and found that moving the wire up the teeniest bit brought my signal in nice and solid. Soldered it there, move back, still very nice. A little black electrician's tape to cover the bare bits and it was done.

Then he checked other stations as well and found that while he'd only gotten a couple of the strongest locals before, now he had *lots* of stations. All over the band, in fact. It seems to make a really nice little reciever antenna, though tuning it is a bit of a pain.

My logic was that it's a variation on a 300 ohm twinlead folded dipole, which at least used to be a very common FM reciever antenna. I didn't use a balun, because I really don't know much about them, and the 300 ohm feedline (is it still a feedline on a reciever?) is a balanced line, so a "BAlanced/UNbalanced" transformer seemed unnecessary. Besides, never used them for twinlead dipoles on an FM reciever before. Also, sites I'd read say the "slim-jim" has some gain to it. Which was good on the reciever end in this situation, since my transmitter across the street wasn't even audible at all on his home entertainment center. I wasn't sure how well it'd work as a recieve antenna, but I had a few yards of twinlead and he was up for trying it, so it seemed a good experiment.

Antennas with gain for the *transmitter* are pretty useless if you're trying to stay legal part15 FM. Even the crudest simple dipole with no matching beyond cutting the elements roughly to length is probably more than you need and could put you over field strength limits. But gain antennas on the receiver end can be *very* useful if somebody *should* be near enough to pick you up and would like to but just can't or can pick you up but not very well. I've thought about building some of the various high gain directional antennas I've seen on ham sites, cut to the FM frequency of my xmitter and doing some experiments with a portable radio this summer to see just how far receiver antennas can extend the practical range for part15 FM.

Brian's loop project got me thinking again, and next time I run across some twinlead that's being thrown away or I see some going cheap, I may make up a couple slim-jims to keep onhand for any new neighbors or people in my "fringe" range.. (meaning everybody 2 or more houses away..LOL) Even if they still can't pick up my station, a twinlead antenna is cheap enough to make to just let them keep as a "friendly neighbor" gesture.

Kudos to Brian, great project.

Daniel

"Yeah, I know, a crystal radio isn't going to have the range of something like a car radio"

I dunno, you might be surprised there. The Crystal Radio I owned as a kid seemed like it was more sensitive than other radios. I distinctly remember wanting to tune in some of the previously unheard stations I picked up with my crystal set on a radio that didn't need an earphone and I never could.

My Crystal set was my first DXing experience 🙂

Experimental broadcasting for a better tomorrow!

You may be showing your age here..LOL Some old receivers werent very sensitive after the tubes went soft.... but I did get amazing reception with my crystal set too. I also learned to put my loopstick pocket radio near the lightning arrestor ground leads on our farmhouse for some amazing dx! And then there was the 2000 foot longwire we ran a long city block between my house and a friends on the other end. We could hear amazing stuff on that puppy until neighbors tore it down. Something about bothering their t.v. reception. Ahhh,the 60's were so much fun!!! Regards,Lee

IIRC, early solid state receivers were awesome, but in the last ten years or so most of the receivers I've used have so much ALC, adjacent channel rejection and crap sensitivity & selectivity that you can barely tune a dozen stations on the AM BCB. A delightful exception are those Sangean receivers Sony sells - those are some of the best tuning radios around.

I have two of these and they are unbelivable, especially for the price - under $12.00!

Oh yeah, I had to take my longwire down when it started catching birds - I used recovered transformer wire (not 2000 feet, more like 50 feet) and the birds couldn't see it. A bird would hit the wire, break it, get all tangled up in it, and, well, mom didn't like that too much!

Age? Yep, I'm an Eisenhower baby!

Experimental broadcasting for a better tomorrow!

Can you say "Roosevelt baby"? My first set was a kit where I had to wind the coil on a cardboard tube, sand a strip along the top, and tune it with a metal slider. I was about 7 yrs. old and this was before I discovered, by experiment, that it is not a good idea to put metal things into wall outlets.

The detector (coherer) was a galena crystal embedded in a lead slug. Those who had these remember spending a lot of time with the "cat whisker" to find the "sweet spot", but once found the rewards were great.

It came with a rather low grade earphone, but my cousin was an Air Force pilot and he gave me a set of phones which were so sensitive that if you touched one of the leads, you could hear the 60 cycle hum (remember Roosevelt babies talk cycles).

It worked really well, but I don't remember what I used for an aerial.

Thanks for bringing this topic to the thread and allowing me to remember some good times.

Neil

Yeah,cats whiskers,condensers,rheostats,2 prong outlets,15 cent McD's hambugers,balloon tire bicycles...making me feel pretty old right now! I also had one of those kits and many more including the 100 in one lab (which I still have!). The bright eyed wonder of my youth and enthusiasm to discover what radio had to offer was intense. By age 15 I had built my own little studio and am transmitter and was live on the air! I had discovered how to make a transmitter from a table radio and modulate it too. I am just sad that todays youth couldnt experience it the way we did,but I bet they will have fun with it too and maybe take it to the next level. Well,enough reminiscing(sp?),lets get on with it Regards,Lee

I grew up in the time of satellite and computers, but my interest in radio sparked when I was 7 years old I bought an old AM radio at a thrift sale for ten cents which had the power cord cut off. I bought it with the intention of ripping that baby apart like I did with every broken electronic we had around the house. Instead I wired a new power cord and at night when I was supposed to be sleeping I would tune around the band to see what I could hear and how far away it was comming from. Later in life an old black and white TV and lots of atempted antenna designs became my DXer. Now that I have kids of my own I want to try to spark the interest with them. They already think its cool to talk on the radio. So I found a easy to build crystal radio with a meter which I think we will build together any one who wants to check out the link go to: http://sci-toys.com/scitoys/scitoys/radio/homemade_radio.html

I was born in 1990, in the small town of Cullman, Alabama. My love for radio started when I was 10 in the 4th grade. I had decided to see what the AM band on my grandpa's '88 Silverado had to offer. There were three AM stations I took interest in. The only one that's still the same format is 650 WSM out of Nashville. By the time I was in the 6th grade I tried my luck at my crude radio station: Two Dollar store walkie talkies, and a walkman with plenty of cassete tapes and earphones. I got the amazing range of 50 feet. But I discovered the world of part 15 AM when I was in the 9th grade, and had my AM station, "Classic Country 1610", on the air by the end of summer. Maybe one of these days I can figure out how to convert solid state stereos to transmittters.... And, by the way, I was a George Bush baby....Travis