I'm hoping someone might be able to answer a question that I've had for years, with a definitive answer: Years ago when I was a kid, I had an old GE AM/FM clock radio (the same kind as in the picture below). As you know, AM (MW) radio in the US is around 530khz to 1600khz. So why... for as long as I owned this radio as a kid... was I able to pick up a shortwave station on it? Not just once or twice, but for the life that I had this radio? (Sadly, the clock radio got thrown away years ago, so this is all in past tense). Here's the info. Can anyone (seriously) explain it? ---------- - The station was WWV (WWV-B/WWV-H), the National Bureau of Standards Atomic Clock time-signal shortwave station, with a transmitter in Colorado (and another in Hawaii). Living in California, I assume the signal was from the Colorado transmitter, but both shared the same frequencies. -The frequencies for WWV were 5000, 10000, and 15000 (nothing in the AM or LW bands). So why could I easily pick it up on a GE Clock Radio's AM dial, when the AM dial only goes up to 1600? (by tuning to the 1600khz end of the dial). -Noticed no other abnormalities. Other than being able to pick up WWV at the (1600) end of the dial, all the other AM and FM stations came in normally, and I didn't notice any other "extra" stations or ghost stations either. In other words, it felt like if I bought 3 of these clock radios, they'd all act the same way, even though I only had one. -I can't recall now if reception quality varied in warm months vs cold weather months, but I remember being able to pick it up for years. If I was bored (or wanted to set a watch), I'd tune it to the high end of the dial and pick it up. -The clock radio had decent reception, but nothing (otherwise) extraordinary. -I was not living right by the transmitter (lived in California, transmitter in Colorado) -At the time, when I was a kid (pre-internet), I tried asking some people for an explanation, but never received a decent answer. -I also had a Sanyo radio with a shortwave band on it (AM/FM/SW), and I'd often listen to shortwave stations, so that's how I knew what WWV was -- and why I was so surprised that I could pick it up on my normal AM clock radio. I never became a ham, and have forgotten most of what I learned about the ionosphere in school, and how shortwave signals are bounced off of it -- but that still wouldn't account for being able to pick up a station (with frequencies of 5000, 10000, and 15000) at 1600khz on a GE clock radio, would it? Can anyone explain it? Thanks!
Though on the same frequency, Colorado and Hawaii broadcast with different voices -- male from Colorado, female from Hawaii. I've heard them alternate as they fade in and out. My first guess is that this radio had poor image rejection, allowing certain unwanted signals to pass through at undesirable levels: Image response - Wikipedia Radio receiver image response and image rejection :: Radio-Electronics.Com ====== PS. Both stations also broadcast on 2.5 MHz, so that is also a possible signal you may have been getting. In fact, I'll guess that you picked this up while tuned right at 1590 kHz. These radios have a 455 kHz IF stage, and the LO is normally on the high side, i.e. at (1590 + 455) = 2045 kHz when tuned to this point. But because of imaging issues, the radio doesn't adequately reject the signal coming down the antenna at (2045 + 455) = 2500 kHz. (I'm not a very good RF (radio frequency) engineer, but have spent considerable time around folks who were.)
I've got a portable radio out in the garage, has both an AC cord AND batteries. That thing is really handy in protracted power outages.
Image rejection is the accurate, uninspiring punch line here. Quite important is where @stevepea made those observations. WWV and WWVH are not strong emitters. But they've put much effort into transferring energy into that volume between ionic sea surface and ionized upper atmosphere. That being a spherical shell, but one can well imagine readers not caring Such constructions are imperfect and do leak. One cannot cook eggs with this type of EM field, but if within a 'leak', any decoding device (including some metallic tooth fillings) might be affected. Where was Steve? == Quite unrelated, just last night I was wondering about how to conceal transmitted information in HF spectrum as if they were sferics. With only small changes to frequency, amplitude, or phase contents.
In California. Interesting. That could perhaps be it. BTW, are you sure about 2.5Mhz? I thought WWV-B/H was only 5, 10 and 15, but I very well could be wrong, this was a while ago. I do believe it was the male voice though, which would mean Colorado. Hey, can you (or someone) translate that (below) into layman speak? (Remember, I'm not a radio engineer either) These radios have a 455 kHz IF stage, and the LO is normally on the high side, i.e. at (1590 + 455) = 2045 kHz when tuned to this point. But because of imaging issues, the radio doesn't adequately reject the signal coming down the antenna at (2045 + 455) = 2500 kHz. One more thing: this was the only radio where I could pick it up on AM. Couldn't pick it up on the car's radio, nor my Sanyo (on the AM band), nor my parent's clock radio (also a GE clock radio, but different model).
Yes: WWV (radio station) - Wikipedia WWVH - Wikipedia This article should fully muddy your waters: Superheterodyne receiver - Wikipedia For your decoder ring: LO = local oscillator (part of an early high frequency stage in the radio receiver) IF = intermediate frequency (a later stage, after the LO but before the regular audio detector stage) I.e. those radio models had better 'image rejection', suppressing that interference below your hearing threshold. They all pick it up to some degree, and we can measure it with high level electronic test instruments, such as were designed / built / sold by my old employer. But on the better radios, it is made too faint for us to notice.
Radio Reloj - Wikipedia ??? If it really really was WWV, then it was probably a harmonics thing, or an IF thing...as mentioned above. Superhets were analog....and messy. My very very first watch as an periscope depth ESM operator was punctuated by a visit from the boss, interested to see how his brash young operator was doing on his first solo ESM watch on his first patrol. An equipment malfunction (specifics redacted) left me bedazzled by a strong and very out of band shortwave broadcast waaaaaay back deep in the cold war. Fun times.... May not matter, but if the latest 'Big Bird' story is true....and the OP ever finds the radio, then the spurious tones may just disappear.... Concern Rising within Amateur Radio Community over WWV-WWVH Shut Down Proposal. Long-Running U.S. Federal Radio Stations, Beloved by Hams, in Danger of Shutdown - IEEE Spectrum I'll be saddened if it happens, but that's the price of progress. After all..... People still get nostalgic about lighthouse keepers too......
Thermal inversion in the upper atmosphere trapping swamp gas and reflecting the waves? Weird thing like that happened to me a long time ago. The Chicago Sting was playing for the NASL cup and I was hoping to catch the score on the news. I was camping in Canada and the game was broadcast on an FM station, I had no hope of catching it. So I tuned to WGN am radio from Chicago to see if I could pick up a signal. WGN is drifting in and out and had a boat load of static. But guess what, they were broadcasting the game! As I struggled to listen through the static, they announced the station - as the normal FM station the game was supposed to be on. So I got the FM station signal on the AM station I tuned to for news. It still amazes me 40 years or so later. P.S. Der Sting won the cup in a shootout!
Regular harmonics don't fit, would have to be subharmonics somehow. But the IF numbers I noted fit quite well. That is insuffiencient to create the necessary frequency conversion. Long ago, when the Seattle Mariners went to the World Series, it was broadcast locally on AM radio. But we worked in a big metal building, and AM didn't propagate more than a few feet in past the windows. Fans wanting to listen in at their desks could get only FM, and no local FM stations had broadcast rights for it. But some way, somehow, the games magically appeared on FM radio within our building. No one knows how. In particular, I have no clue how my portable AM radio got parked atop that RF signal source mysteriously parked next to the windows. I had to go retrieve it. After the games, of course.
I remember driving clear around the Washington DC beltway listening to a NCAA final in 1965 because I was listening to what was called a clear-channel radio station somewhere out west and if I ducked into the city I lost the signal. And the headphone under my pillow letting me listen to a clear channel radio station out of Buffalo long after I was supposed to be asleep. Hallicrafter's radio. SW capable but some AM frequency. Clear-channel station - Wikipedia
Any signal can be reduced to a series of harmonics defined by a Fourier series. Normally these signals are greatly attenuated and a well defined front-end will suppress them. So if I relied on just the mixer for signal discrimination and the front end amplifier were a little too wide-band, then a harmonic outside of the target frequency could be picked up. There are very low frequency antenna farms used to communicate with submarines towing submerged antenna. But if you are within visual range, car radios would misbehave. Our local underwater expert, @ETC(SS) might have more details but he'd probably have to kill us all if he told us. I recommend reading: Communication with submarines - Wikipedia Bob Wilson
For some reason, this article doesn't mention another VLF station used to communicate with submarines, a station that was nearly in the back yard from where I once worked: Jim Creek Naval Radio Station - Wikipedia The day I toured this site, the sky was overcast as we arrived, so the vertical feed lines (or downleads) appeared to rise straight up and just disappear into the heavens. But before we left, the sky did clear enough to see the horizontal elements to which they were attached.
I actually thought about ELF but the OP is in Caly, and my limited knowledge on the subject made me lean away from that being a cause. RADIO comms with das boats isn't much sexier than one reads about in open source. For attack subs, it's pretty easy. They just have to phone home whenever they're not navigating by street lights and for this ELF is just a pager. For boomers (sub, not baby) it's a little more complicated and a LOT more important but the American boomer fleet is getting long in the tooth (21-34 years old) and one imagines that it's still wires and buoys. These are not very useful when maneuvering at speed in 3D but boomers are 'chickens of the sea' and low speed is....good 'nuff....which is one of the reasons why you can use these boats for 40-50 years before turning them into Gilette products. Refueling...a nucular powered wessel is almost as expensive as filling a dodge pickup with gas in LA. Fun fact: Our oldest "serving" sub at least recently is/was the USS Bremerton - now being recycled in.............Bremerton. Tiawan however has a boat on their active duty rolls that's 80! The Hai Shih (their SS-792)
Funny how the competing network's feed somehow becomes available on one of the test channels on the router during gametime... I thought everyone's facility had two inputs tied up with colorbars... hmm.
(Ohio) Boomers will be older still when Columbia class arrives in 2031. Hai Shih was built in New Hampshire (nee Cutlass) - credit where it's due.
I also used to work for a famous test equipment company, and we could demodulate FM on a spectrum analyzer (fancy name for a radio receiver) by tuning the analyzer so that the FM signal was in the rough middle of either side of the IF filter. The filters had slanted sides (see the display on my avatar at left) , so as the FM signal shifted it's frequency back and forth with the music or game, the vertical amplitude would change in sync, just like an AM radio, and one could listen to a broadcast on one of the most expensive radio receivers ever built. You could do the same thing on any cheap AM radio, just tune it a little off, say 5 MHz, from a subharmonic of the FM station, and you're there.
