Pirate on 1180?

[therealjm12]

I was on I 87 today headn' to Rochester via I 90 today. I was trying to find the Yankee game and hit my 1180 button hoping to pick up WHAM. What I got was 60's music with old jingles loud & clear for about 5 miles. Hmmm, what do ya think? BTW, the Yankees were on WHAM.

 

[MHVRadiofan]

I was on I 87 today headn' to Rochester via I 90 today. I was trying to find the Yankee game and hit my 1180 button hoping to pick up WHAM. What I got was 60's music with old jingles loud & clear for about 5 miles. Hmmm, what do ya think? BTW, the Yankees were on WHAM.

It would help a lot if you said exactly where you were when you picked up the 'pirate station'. Obviuosly you were not near Rochester and WHAM's 50K transmitter. Was it at night. It could have been long distance skip too.

 

[therealjm12]

Sorry, guess I thought anyone from the Capital District would have gotten my location from my previous post.. As I said I was on I 87 heading north towards towards the Thruway I 90. I was coming from Boston. I did notice WROW's site on the East side just before I punched it up. I was a few miles south of Albany.

 

[fybush]

590 x 2 = 1180.

Dollars to donuts, what you heard was an image of WROW itself. The format fits, too.

 

[W2JUV_AL]

Scott, I don't believe images occur simply by multiplying the primary frequency x2. Seems though images are generated by adding and subtracting multiples of the receiver intermediate frequency from the tuned frequency. Many car radios are prone to front end overload and that is most likely what therealjm12 observed. In the presence of a strong RF field the preselector in the radio is not able to detect any other signals.

 

[therealjm12]

That's what it was. My passenger said they thought they heard 59 in the jingles. Mystery solved. I didn't know WROW was on 590.

 

[jlehmann]

Scott, I don't believe images occur simply by multiplying the primary frequency x2. Seems though images are generated by adding and subtracting multiples of the receiver intermediate frequency from the tuned frequency. Many car radios are prone to front end overload and that is most likely what therealjm12 observed. In the presence of a strong RF field the preselector in the radio is not able to detect any other signals.

I've certainly heard a station's frequency x2 many times. One example, when near 850 WEEI's TX in Needham, MA, they will also be there on 1700.

 

[cspence]

Driving along I81 in Harrisburgh WHP can be heard on 1160 for about 3-4 miles in either direction.

 

[JustPastBuffalo]

And in Hamburg, along the lake just west of the WKBW-WGR transmitter site, WGR 550 comes in clearly on 1100 during the day. At night, 1100 WTAM Cleveland can be heard.

 

[w9wi]

Scott, I don't believe images occur simply by multiplying the primary frequency x2. Seems though images are generated by adding and subtracting multiples of the receiver intermediate frequency from the tuned frequency. Many car radios are prone to front end overload and that is most likely what therealjm12 observed. In the presence of a strong RF field the preselector in the radio is not able to detect any other signals.

I've certainly heard a station's frequency x2 many times. One example, when near 850 WEEI's TX in Needham, MA, they will also be there on 1700.

It's a terminology thing. Scott & you are right, that it's common to hear stations on multiples of their actual frequency. The proper term is "harmonic": 850x2=1700 is the "second harmonic"; 850x3 would be the "third harmonic" (and would fall outside broadcast spectrum), etc... This "multiplication" can happen in the transmitter/transmission system, (but that's usually too weak to be heard off the transmission premises) in the receiver, (very common) or in some external poor connection. (like a loose gutter)

"Images" are receiver-generated signals, a natural result of the use of Armstrong's superheterodyne circuit. An "image" involves reception of a station at a dial setting 900, 910, or 920KHz higher than the station's actual frequency. (for example, reception of 590 on 1500)

Other combinations are possible. "Intermod", where two or more stations mix together to form a new signal on a frequency algebraicly (sp?!) related to the two stations' frequencies. (I think that's what W2JUV was thinking of) "Overload", which may result in a very strong station being heard on *every* frequency. (or at least, *many* frequencies) "Spurious emissions", when a transmitter fails and transmits on multiple frequencies at once. (in my experience a lot more common on FM)

All that is rather technical & confusing... it's probably safest.. when you hear a station on a frequency it's not actually broadcasting on.. to just call it a "spurious signal" & not worry about what type of spurious it is!

 

[rtetro]

Scott, I don't believe images occur simply by multiplying the primary frequency x2.

Actually they do. It is called the 2nd harmonic. I suppose that if you really want to be technical it is not so much an "image;" but an actual signal being transmitted by the station. The FCC rules are very specific about how far below the main carrier the second harmonic can be. At 5kw, WROW's 2nd harmonic should be heard within a mile or two of their transmitter on 1180. It is not at all uncommon to hear the 2nd harmonic of a station licensed on the low end of the dial further up the dial. For instance, you can easily hear WABC's second harmonic on 1540 within a few miles of their transmitter. Likewise, when I've been up in the capital district I've been able to easily hear WGY's 2nd harmonic on 1620 in the Rotterdam area.

 

[JustPastBuffalo]

Another interesting discussion here. As Scott knows, engineering folks and AM aficionados would have a field day around the WWKB-WGR Big Tree Road site, where RF from 1520 and 550 flow freely, then combine with the RF from the WNED AM 970 site on Cloverbank road a few miles south. What an RF circus: 1520 - 550 = 970, which leads to some severe complications and AM overloads in the southtowns RF corridor.

 

[rtetro]

Same thing here in the western suburbs of Philly on 1620 on the expanded band. 1060 KYW + 560 WFIL = severe intermod on 1620. The transmitter sites are about 2 miles apart. Surprisingly, we have never found such issues on 1550 (560 WFIL + 990 WNTP); I think that's because of the heavy filtering of the two stations on our diplexed transmitter site. The reason I say this is that the 1520 - 550 intermod surprises me. I would tend to doubt that, unless there are issues with their diplexing/filtering (which I doubt), the problem in Buffalo is much more likely due to receiver generator imaging.

I have seen some wierd things happen over the years, however. In New York, when I was the senior radio engineer at WBBR 1130, we got a frantic call from a ham in North Carolina that he was hearing us clearly on the 160 meter ham band. Our transmitter supervisor, Bob Janney (who is one of the best transmitter guys in the business) and I immediately went out and did analysis of our signal armed with field strength meters, a spectrum analyzer, and several portable radios for comparison. Sure enough, loud and clear on 1830, there we were, but only at night when we were on directional. It took a couple of days of monitoring and signal chasing but finally we found the problem -- but it was not with our transmitter or antenna system! The field strength meters showed that the signal was not coming from our site, but from WZRC 1480's transmitter, located about 3 miles north of WBBR's. When they would switch to their night pattern, they would begin transmiting a pretty good copy of WBBR's audio on 1830. 1480-1130=350 khz., Take that difference and add it to the 1480 carrrier and - voila - 1830! We worked together with WZRC's engineer and finally found a bad capacitor in WZRC's night phasor that was generating a 350 khZ signal with WBBR's audio and feeding it back into their transmitter to produce the 1830 signal.

So, hey you never know what can happen when you're around a lot of RF>