I have had this issue now for a couple years now and I figured that it would go away eventually, but it never did. Only at night when KVCE and KVTT sign off after 8pm. I found out that KVTT 1110 AM's transmitter was located in Alvord, Texas, about 12 miles NW of my location. I hear that station on some shortwave stations over frequencies like WWV's frequency on 10 MHz. Even worse, KVCE 1160 is located 3 1/2 miles SSW of my location in Paradise, Texas. That can be heard up and down the shortwave frequency band on 4 radios I have. Is my position between these two transmitters the problem?
-
Get involved.
We want your input!
Apply for Membership and join the conversations about everything related to broadcasting.
After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
If you use a disposable or false email address, your registration will be rejected.
After your membership is approved, please take a minute to tell us a little bit about yourself.
https://www.radiodiscussions.com/forums/introduce-yourself.1088/
Thanks in advance and have fun!
RadioDiscussions Administrators
AM stations heard on Shortwave
- Thread starter eskipper411
- Start date
What frequencies are you hearing the AM stations on? Are you saying they disappear when the stations go off the air?
Its common for AM signals to show up on shortwave and vise versa especially if its a strong signal. I can't explain it exactly, but it has something to do with harmonics being created in the receiver. But this should disappear the second they sign off. If its happening only after they sign off then it sounds like it could be an issue with their broadcasting equipment. I have no strong AMs near me but some really shortwave signals, usually WEWN and WWCR will show up on one of my AM radios.
I usually hear 1160 and 1110 on WWV's frequencies. And when KVCE and KVTT sign off, the overlapping goes away then WWV's signal goes back to normal again. No overlapping after 8pm.
Sounds like overload/blanketing interference if it's all over the dial.
Years ago in the northern suburbs of Chicago I used to get WJJD on the 80 meter ham band. I was only about 6 miles from their towers.
The signal even came through an old webcor tape recorder I had in the 60s.
The signal even came through an old webcor tape recorder I had in the 60s.
Schroedingers Cat said:
Yes it does, and it looks like eskipper411 is right in one of the major lobes of KVTT and in one of the lesser ones of KVCE. I'm not an AM engineer, but by plugging his approximate location into V-Soft©, KVTT's field strength was shown to be over 120 mV/m while KVCE was about 15 mV/m (still quite strong).
In cheaper radios, there is no rf preselector amplifier stage which would keep such responses from appearing.
In many cases, the 455 khz IF frequency is the only real selectivity that matters, and at shortwave wavelengths,
images are only 910 khz away. Frequently WWV at 10 mhz can be tuned in on a cheap radio at 9.090 mhz.
(10 mhz- 910 khx = 9.09 mhz). In semiconductor radios as opposed to tube radios, intermodulation of strong signals
that have managed to "walk through" whatever selectivity is there is problem since AVC in a "transistor"-based radio does nothing to change the actual GAIN of the amplifier device itself. The amplifier stage, sorta, but AVC in a transistor circuit does not change the Beta of a transisitor as it changes the real gain (of the tube itself) in a tube rf amplifier circuit.
If you want to avoid image responses, make sure you use a radio with a real tuned rf stage, and
ideally use a tube radio, to take advantage of the the variable-mu aspect designed to cope with this particular situation.
Short of that, you can attenuate the input signal or provide some sort of outboard tuning circuits to do the job
that isn't being done inside the radio.
Loose-couplers are your friend with modern radios, and they can let you hear a weak desired signal that would have been previously covered by an image.
In the case above, an outboard (even passive) rf tuning circuit would help supress the
image response of WWV, allowing an easier time of hearing a desired signal actually on 9.090 mhz.
In many cases, the 455 khz IF frequency is the only real selectivity that matters, and at shortwave wavelengths,
images are only 910 khz away. Frequently WWV at 10 mhz can be tuned in on a cheap radio at 9.090 mhz.
(10 mhz- 910 khx = 9.09 mhz). In semiconductor radios as opposed to tube radios, intermodulation of strong signals
that have managed to "walk through" whatever selectivity is there is problem since AVC in a "transistor"-based radio does nothing to change the actual GAIN of the amplifier device itself. The amplifier stage, sorta, but AVC in a transistor circuit does not change the Beta of a transisitor as it changes the real gain (of the tube itself) in a tube rf amplifier circuit.
If you want to avoid image responses, make sure you use a radio with a real tuned rf stage, and
ideally use a tube radio, to take advantage of the the variable-mu aspect designed to cope with this particular situation.
Short of that, you can attenuate the input signal or provide some sort of outboard tuning circuits to do the job
that isn't being done inside the radio.
Loose-couplers are your friend with modern radios, and they can let you hear a weak desired signal that would have been previously covered by an image.
In the case above, an outboard (even passive) rf tuning circuit would help supress the
image response of WWV, allowing an easier time of hearing a desired signal actually on 9.090 mhz.
I have a C. Crane radio with an RF Gain dial. Problem is that no matter how low I turn it, I still hear KVCE and KVTT.
Before we moved here, 80 or so miles north, where we lived in NE Philadelphia was across the Delaware River from the stick of omini WCAU 1210.
They came in on 1210, 2420, 4840, whatever, on up the various short wave dials, on a Lafayette HA 600, a pretty sensitive and decent receiver.
I don't recall hearing any of the other Philly stations doing that. Just WCAU 1210. Others here might know if it was because WCAU's tower was so close and/or they were omni.
I did all my DXing from that spot in NE Philadelphia at night, but I doubt that during the daytime WCAU repeating itself would have been any different. If I'm not mistaken, WCAU was the only Philly AM station to be omni at night except for the wee WHAT 1340.
They came in on 1210, 2420, 4840, whatever, on up the various short wave dials, on a Lafayette HA 600, a pretty sensitive and decent receiver.
I don't recall hearing any of the other Philly stations doing that. Just WCAU 1210. Others here might know if it was because WCAU's tower was so close and/or they were omni.
I did all my DXing from that spot in NE Philadelphia at night, but I doubt that during the daytime WCAU repeating itself would have been any different. If I'm not mistaken, WCAU was the only Philly AM station to be omni at night except for the wee WHAT 1340.
Steve Green NEPA said:
Those frequencies are the fundamental and harmonics, (2 x 1210 is 2420...etc). All transmitters produce harmonics. Harmonic radiation from a 50kW station should be 80dB down from the carrier power, but if you are close, it isn't unusual to pick up the harmonics. This isn't normally a receiver function, but usually related to transmitter.
Another possibiltyis the generation of harmonics by non-linear devices, which could be something as crude as bad connection in fence material, gutters, or any two pieces of metal which aren't making good electrical contact.
Many years ago, I recall a scheduled tune-up frequency on a short wave transmitter caused interference into a two-meter ham repeater about 20 miles from the transmitter site. The harmonic output level of the transmitter was very low, meeting specs, and very little signal seen on a spectrum analyzer. We never found any real cause for the harmonic radiation, but cured the issue by using another tune-up frequency.
80 db down from 50000 watts is .0005 W or .5 mW or 500 uW. If this were fed into a half wave radiator, it would have an inverse field of 166 uV/m @ 1 mile. My feeling is that the harmonic is more likely to be receiver induced.
Schroedingers Cat said:
Agree with your analysis, but suppose a station's second harmonic is not attenuated to the full 80dB. Some years ago I witnessed that measurement being made for our local 1Kw station on 1600Khz. At a mile or so away the 2nd harmonic was so far down in the mud that it did not show up on the measuring equipment. But today, at a distance of say 3 mi. from the Tx site, I hear the station with slight distortion on 3200Khz on a sensitive ham transciever connected to a 260ft dipole antenna. Don't know if its' my receiver or an actual transmitted 2nd harmonic.
Although my analysis of the horizontal efficiency would be accurate if the antenna was 1/4 wave at the fundamental and the 2X harmonic would be 1/2 wave, if the antenna is 1/2 wave at the fundamental it is full wave at the 2X harmonic. This would make the lobe radiate well above the horizontal and the horizontal would have a theoretical null as I recall.
I have indeed heard harmonics, but it seemed to be related to the receiver. I have heard WSGW 790 on 1580 on I-75 in the minor lobe toward Saginaw in full view of the six tower array. I never remember hearing the harmonic on an analog tuned Delco radio from the 1970s though and I drove through there quite a few times.
One method of telling whether it is from the transmitter or receiver is if you could rig up a band reject LC coupled to the receiver and tune it to the fundamental. If the harmonic disappears, it's from the receiver. If it's just as strong, it's being radiated from somewhere, the transmitter facility or some nonlinear junction. I just talked to an engineer who suggested sending an engineer named "Rusty Gutters" out to investigate those nonlinear sources. It would be good to have a decent signal strength meter on the radio you are using to do this if you can't find a field strength meter.
I have indeed heard harmonics, but it seemed to be related to the receiver. I have heard WSGW 790 on 1580 on I-75 in the minor lobe toward Saginaw in full view of the six tower array. I never remember hearing the harmonic on an analog tuned Delco radio from the 1970s though and I drove through there quite a few times.
One method of telling whether it is from the transmitter or receiver is if you could rig up a band reject LC coupled to the receiver and tune it to the fundamental. If the harmonic disappears, it's from the receiver. If it's just as strong, it's being radiated from somewhere, the transmitter facility or some nonlinear junction. I just talked to an engineer who suggested sending an engineer named "Rusty Gutters" out to investigate those nonlinear sources. It would be good to have a decent signal strength meter on the radio you are using to do this if you can't find a field strength meter.
Schroedingers Cat said:
I know of a fellow ham who lives close to a 5Kw station on 1260Khz who installed a broadcast band notch filter between his antenna and transceiver. Indeed, the "harmonics" dissappeared. Interesting comment in regard to the re-radiation of a harmonic from something other than the main transmitter.
My local KIXI can sometimes be heard on the SW bands, if I am pointing south. The biggest harmonic is 1760 khz (2 x 880 is 1760), as well as many on the AM band. 610, 760, 1420 and 1270 are the main ones.
I was near the I-90 trail yesterday, not far from the 50kw stick of KIXI (maybe 1 block?) and the radio picked up KIXI on a few open FM frequencies, due to it being so close. Also, while changing channels, it could pick up KIXI without even turning to a channel! Wonder if tooth fillings could hear KIXI there...
-crainbebo
I was near the I-90 trail yesterday, not far from the 50kw stick of KIXI (maybe 1 block?) and the radio picked up KIXI on a few open FM frequencies, due to it being so close. Also, while changing channels, it could pick up KIXI without even turning to a channel! Wonder if tooth fillings could hear KIXI there...
-crainbebo
D
Darth_vader
Guest
The local MW stations on 1550 (currently KKOV) have continually hammered away at 3100 kHz (1550 * 2) on nearly every shortwave rig I've ever owned. When I was a kid mucking about with my old Realistic DX-375, first time I stumbled across it I thought they (KVAN, at the time) were actually running a shortwave simulcast on that frequency.
Rusty Gutters?
I thought he was an on-the-air personality on the late '60s third harmonic commercial shortwave station that was located on the M.V. Hildegarde, 20 miles offshore from NYC. Some of you may remember Rusty. He played a lot of underground music, and the only advertiser on his show sold mail order "smoking materials".
I could be wrong, though. I was in a purple haze during most of the late '60s and early '70s. My, those were good times.
Now what was that station's name? Radio Swan? WRUL? Radio New York Worldwide? Radio Sofia? Lourenco Marques Radio? HCJB? The Happy Station? Radio Andorra?
We now take you back to the thread, already in progress.
I thought he was an on-the-air personality on the late '60s third harmonic commercial shortwave station that was located on the M.V. Hildegarde, 20 miles offshore from NYC. Some of you may remember Rusty. He played a lot of underground music, and the only advertiser on his show sold mail order "smoking materials".
I could be wrong, though. I was in a purple haze during most of the late '60s and early '70s. My, those were good times.
Now what was that station's name? Radio Swan? WRUL? Radio New York Worldwide? Radio Sofia? Lourenco Marques Radio? HCJB? The Happy Station? Radio Andorra?
We now take you back to the thread, already in progress.
Schroedingers Cat said:
Considering the sensitivities of fair to decent short wave receivers, and a decent antenna, a signal of that field strength isn't doing to be difficult to receive.
Could harmonic reception be a function introduced by the receiver? Sure, and some experimentation with tuned circuits could help. Using a high end tube type receiver, as an R-390, might also help to determine if it is from the transmitter or more accurately, external to the receiver.
If someone has access to a FIM-41 or equal, that would really be an interesting use of test equipment for this experiment.
- Status