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WHy am I getting Now 92.3 on the 70.9 FM Frequency?

D

DesiArnez6

Guest
My radio ran out of battery power, so when i plugged it in, it was on 200 and something (point.) something FM ?!?!, but I tried to move the frequency up and It went down to 70.9 FM, with a clear station, so I waited through the commercials (Californian Psychics?) Thinking... weird, I must have some Cali station, ... Well It turned out to be NOW FM from here in NY


Now most radios wont tune to 70.9 FM, BUT can anyone explain why Now 92.3 is picked up perfectly on the 70.9 Frequency?
 
Perhaps the frequencies just repeat themselves? I just realized I pick up 91.5 WNYE on 70.1FM The differences are exactly proportional (0.8 Mhz down on the dial) but since lower frequencies travel further when lower, i think, right? (example AM Radio), by tuning into these lower "mirror" frquencies, will I get better reception farther away?
 
It seems like it's the second harmonic of WNYE... 10.7 MHz is the IF (intermediate frequency) for FM receivers. 92.3-10.7-10.7 = 70.9. Likewise, 91.5-10.7-10.7 = 70.1.
 
DesiArnez6,

I never heard of the 70.9 FM frequency.

What you've experienced MAY BE overloading. When I'm in the Garden City and Hempstead areas of Nassauu County on Long sland, on WCBS-FM' 101.1 I pick up WKJY (KJOY 98.3) because their transmitter is not far from Hempstead.

In the Maspeth and Middle Village areas of Queens around Fresh Pond Road and Metropolitan Avenue, on WABC and WFAN's frequencies I pick up AM 1560 whose transmitter is near 48th Street and Grand Avenue.



Thanks,
Kevin L. Sealy
 
If there's a reset button somewhere on the radio (sometimes it's a little hole on the side or back that you have to poke with a paper clip), try resetting it. If it's a battery-operated radio, try taking the batteries out for an hour or two and then putting them back in.

Either way, something's likely wrong with your radio. 70.3 MHz isn't part of the FM broadcast band anywhere but in the former Soviet Union. In the US, it's part of TV channel 4 (66-72 MHz).

There are strict FCC rules about out-of-band emissions, and it's highly unlikely that WXRK is actually putting out anything on 70.3. If your radio is actually tuned to 70.3 (and I somewhat doubt that it is, regardless of what the display is telling you), it might be getting overload if you're near the Empire State Building. More likely, your radio is really tuned to 92.3 and the display is broken.

Good luck!
 
Do you have an imported radio or zune0 There is an option on the zune player to listen to stations from 76.0 to 90.0, which the only audio I picked up was from WNYW on 81.7
 
what tv channel is supposed to be around the 70mhz?
I asked because currently a lot of the channels are not in use after the analog shutoff correct?
 
neo11 said:
It seems like it's the second harmonic of WNYE... 10.7 MHz is the IF (intermediate frequency) for FM receivers. 92.3-10.7-10.7 = 70.9. Likewise, 91.5-10.7-10.7 = 70.1.
Click to expand...

I still maintain that it's harmonics, and I'm surprised that no one else has mentioned this.

When I once had a walkman that also had an option to tune to the Japanese FM band frequencies (77-90 MHz), I was able to hear the first harmonics of the major NYC stations throughout that band, almost as clearly as the main frequency itself...and no, I wasn't always near the Empire State Building either.
 
It's not a harmonic, it's an image.
A radio tuned to a station generates a signal exactly 10.7 mHz above it. If it's tuned to 92.3, it generates a signal at 103.0. The 2 signals combine to 10.7 mHz, 103.0-92.3=10.7 mHz, which is the intermediate frequency. The receiver demodulates 10.7 mHz and you hear today's hits! It just so happens that 70.9 + 10.7 = 81.6, and 92.3 - 81.6 = 10.7. Your radio probably doesn't have good image rejection, so it can't tell the difference between 70.9 and 92.3. If it had good image rejection, it would filter out the part of the band not currently tuned to.

The first harmonic of WXRK is at 92.3 * 2 = 184.6, right in the middle of TV channel 8. If you hear Now FM on 184.6 (a scanner will be able to pick up that frequency) and aren't within a few blocks of Empire, something's wrong with the transmitter.
 
Interesting I did reset and everything. The radio still goes from about 70FM to 200FM

I couldn't receive anything above 107.5 FM

However Below 87.7 FM as I went further down, I heard every single station perfectly, in the same proportion from WBLS 107.5 down to Hot 97 , down to Now 92.3 etc all the way down to 91.5 (That was the lowest station I could hear) then my dial stopped. The exact amount of Mhz in separation remained the same throughout the entire 70-87 FM band, and I got every station from WNYE 91.5 to 107.5 crisp clear (nothing below 91.5) because there was no further space. I wish I had realized this during analog TV broadcasting (*slaps hand to forehead) THAT would have made for a good experiment

I do believe its an imported radio. And has shortwave (VERY good reception, and the whole band, they dont block out certain shortwave frequencies like most (I think around 11000 or so, and a few other spots) It gets the whole band.

From the descriptions you guys gave, at first I assumed it was "harmonics" (which I don't actually understand) but I didn't get anything above 107.5 . I am also not near the Empire State Building and then images? (Also don't understand)


So, harmonics vs image? Hmm
 
Harmonics are transmitted by the transmitter and the station's engineer does his best to reduce the power of the harmonics.
When TV was analog, you would have been able to get the audio of channel 4, 5, 7, and 9. Now, the only TV audio you can get is channel 6.
The highest New York station is 107.5, unless you can hear a pirate or WEBE on 107.9. 107.5's image would be 86.1.

This might be a reason why the FM band can't easily be expanded below 88.
 
Nick said:
Harmonics are transmitted by the transmitter and the station's engineer does his best to reduce the power of the harmonics.
When TV was analog, you would have been able to get the audio of channel 4, 5, 7, and 9. Now, the only TV audio you can get is channel 6.
The highest New York station is 107.5, unless you can hear a pirate or WEBE on 107.9. 107.5's image would be 86.1.

This might be a reason why the FM band can't easily be expanded below 88.
Click to expand...

Thanks, Dr. Nick!

The engineer does eliminate excessive harmonics or jeopardizes the license. The antenna is designed-also-to effectively minimize the harmonics as well. What is at work with stations apparently presenting signals at other parts of or in other bands altogether is front-end overload and/or poor receiver design.

Unless the radio is actually a TV-VHF Lo-FM model tuning into 70 mHz, it's just plain crappy. Something went wrong.
 
DesiArnez6 said:
My radio ran out of battery power, so when i plugged it in, it was on 200 and something (point.) something FM ?!?!, but I tried to move the frequency up and It went down to 70.9 FM, with a clear station, so I waited through the commercials (Californian Psychics?) Thinking... weird, I must have some Cali station, ... Well It turned out to be NOW FM from here in NY


Now most radios wont tune to 70.9 FM, BUT can anyone explain why Now 92.3 is picked up perfectly on the 70.9 Frequency?
Click to expand...

What is the make and model of the radio?
 
I have heard 107.5 WBLS on 86.1, but I always thought it was due to signal overload since New York is only 10 miles from my house. What I also notice is on my CD player I can hear local stations 6.0 mHz above or below that frequency. For example I can hear Fresh 102.7 on 96.7 or Z100 on 94.3 and 106.3.
 
Your CD player radio is crap if you are hearing spurs at +- 6 mHz when you're 10 miles away. At 10 miles from NYC, my radio doesn't overload at all.
 
DesiArnez6 said:
However Below 87.7 FM as I went further down, I heard every single station perfectly, in the same proportion from WBLS 107.5 down to Hot 97 , down to Now 92.3 etc all the way down to 91.5 (That was the lowest station I could hear) then my dial stopped. The exact amount of Mhz in separation remained the same throughout the entire 70-87 FM band, and I got every station from WNYE 91.5 to 107.5 crisp clear (nothing below 91.5) because there was no further space. I wish I had realized this during analog TV broadcasting (*slaps hand to forehead) THAT would have made for a good experiment

...

From the descriptions you guys gave, at first I assumed it was "harmonics" (which I don't actually understand) but I didn't get anything above 107.5 . I am also not near the Empire State Building and then images? (Also don't understand)
Click to expand...

Harmonic: A signal on a multiple of the station's desired frequency. For WBLS-107.5, the 2nd harmonic is on 107.5*2=215MHz. The 3rd harmonic is on 107.5*3=322.5MHz, etc... (theoretically WBLS's "first harmonic" would be on 107.5*1=107.5MHz, but in practice the term "first harmonic" is almost never used)

Harmonics can be transmitter faults. They can also be externally generated, either in your receiver or in other electronic gear near the transmitter. With FM stations, the modulation also increases with the order of the harmonic -- WBLS's 2nd harmonic would be 200% modulated, their 3rd harmonic 300%, etc...

Image: The spurious response of your receiver to a signal whose frequency has a specific relation, through the receiver's "intermediate frequency", to the frequency the receiver is tuned to. An image response is usually separated from the frequency the receiver is tuned to by twice the "intermediate frequency". The intermediate frequency of most FM radios is 10.7MHz, so the image response of most FM radios is to a frequency 21.4MHz higher than the frequency to which the receiver is tuned.

Note that 70.9+21.4=92.3. The signals you're hearing are images.

Images are always a receiver characteristic - they are not a transmitter fault.

There are other possible ways of receiving signals that aren't really there, or of generating signals that a station doesn't intend to generate.

_________________________________________________

Presuming you live well within the NYC area (the desired signals are strong) I don't think there's anything wrong or necessarily "cheap" about your radio. Most FM radios don't have a very good "preselector" circuit for rejecting images: they don't need it. Normally the only signals in the "image band" 21.4MHz above the FM band are aircraft stations. These aren't very powerful and can't cause much interference to FM reception.

I think the only reason you're hearing this is because your radio is (unusually) capable of tuning these lower frequencies below 88MHz. I think if most other FM radios could tune this band, they'd receive the same spurious signals.
 
w9wi explained it perfectly.
It is for this reason that no two FM stations separated by fifty three or fifty four channels (10.6 or 10.8 MHz) will everbe located with overlapping city grade signal contours. Were two stations thusly located, many receivers would hear both stations mixed together throughout their entire tuning ranges.
 
There's also intermodulation, which is the most common interference near a transmitter site with multiple signals. It's formula is 2*freq1-freq2=interfered frequency and 2*freq2-freq1=interfered frequency. The frequency that is multiplied by 2 will sound louder on the interfered frequency. This is completely generated by the receiver.
Let's use 92.3 and 93.1. 2*92.3-93.1=91.5 and 2*93.1-92.3=93.9. On 91.5, NOW FM will sound louder than WPAT, vice versa on 93.9.
Since all the Empire stations are spaced .8 mHz apart, you hear a lot of intermodulation near the ESB.

There is another way to hear interference, but it usually only works near a transmitter site with one station. When I'm near the WEBE 108 (107.9) transmitter, I can hear WEBE 108 on 102.55. Let's see why
102.55+10.7=113.25 (radio generates a signal 10.7 mHz above tuned frequency)
113.25-107.9=5.35 (generated signal combines with WEBE to 5.35 mHz)
5.35*2=10.7 (2nd harmonic of combined signal)

The radio demodulates 10.7 and you hear WEBE 108 where you're not supposed to! It sounds twice as loud (or 3 dB louder) because second harmonics are always 200% modulation.
 
Wow, I have learned so much. I am extremely appreciative of the knowledge on this board.

As for radio model, it is a fairly new Kaito KA1102, not a bad radio. I don't remember low FM being a feature, or high FM, but whether fluke or not, the dial certainly reaches on the FM from 70.00 FM to 108.0 Consistently

As for reaching up to 200 and something FM, apparently maybe I accidently discovered some programming glitch, I can't repeat it today, but before all I had to do was go to the AM band and then hit the 3 key and immediately i was in the 200's on the FM

Th radio does seem generally very good quality, (And for Pulse, I can tune into exactly 87.75FM, so I get a crisp signal. I can't get WEBE 108 though, like I do on the tabletop
 
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