Danny:
The guys have hinted....
The problem is that any transmitter (and the synthesized ones are probably the worst offenders) can put out all kinds of RF at frequencies somewhat different from the "center" - usually what you've tuned it to when "in-band".
Usually, this stuff has very low levels, but some odd things can happen. For example, a transmitter tuned to 150.000mhz (round numbers
) but not designed to work there, can provide a substantial signal at 300mhz. Might not bother anything, but who knows. Add to that the ability to put signals out at 150mhz + and/or - the 10.7mhz (likely) IF frequency, as well as all kinds of other combinations, and you've got a potential mess. Low-power gear may never bother anything, but a 75Watt transmitter may have some significant output at just the wrong place. (A spectrum analyzer really is the only way to fly.) The low-power stuff may wipe out a local PS frequency, too, if you're close to the receiver.
(Presuming that you're very close to the same frequency, an FM decoder will generally "hear" only the strongest signal on the tuned frequency. If the PD's on 158.73, and you're across the street from their receiver site, your spurious output may just wipe that receiver out - at least for HT's some distance away. Needless to say, this will make nobody happy. Type-accepted radios are certified to keep these signals down to a certain level. The Amateur Radio version may have some of that missing.)
Some decades ago, I was a student at Case Institute in Cleveland. I took a 6M AM (Ham) transceiver along, and set it up in my dorm room. (It was fairly easy to pop an antenna out a window as needed.) I'd learned that there was a net on 51.000Mhz and brought crystals (remember those?
) along for it. I used the radio elsewhere (51.000Mhz, while well in-band, was kind of off-the-edge for most people in 1963) with good results. Tune the thing to 51.000Mhz and I found extreme noise between about 50.7 and 51.5Mhz.
It took a while to find it, but it turned out that TV Channel 3 was active in Cleveland, and the video carrier was more or less exactly at the local oscillator injection frequency, and riding through the receiver, causing the noise.
(Before anybody yells - I don't recall if the TV carrier was 10.7 mhz above or below the 51.0mhz target. The idea was to mix the a local oscillator signal with the 51.000mhz signal, and then further process one of the mixing results as if it was an "original" at 10.7mhz. In many cases, another mix is done to put the incoming signal on 455Khz, and in some cases only one such mix to 455Khz is done.)
In this case, a simple trap on the antenna cleared the problem up, but what if I'd been an ambulance service?
The trap? You can combine a capacitor and an inductor so it's a dead short at a particular frequency (which sort of kills any signals coming into the receiver there) but effectively not there at all at other frequencies.
Slightly more recently - say "before 1970" - a friend of mine and I got volunteered to install a new sound system in his Church. My friend lived down the block from the Church, and was a sort of unofficial sexton.
We spent a few bucks, and set up a slick system that'd let 'em remote the Sanctuary audio into the basement social hall/overflow area, with separate level controls, monitoring speakers, and all kinds of magic stuff. Worked exactly like it should. (Sometimes even a blind pig finds a truffle
.)
Then, come Sunday AM, as they rang the bell to start the Mass about 0700, the thing started playing music. Youngstown State University's FM station, at 88.5mhz, was only a couple miles away, and strong enough to turn up at the microphone inputs (even though the cable was shielded). In those days, WYSU was on a restricted schedule, and it just happened that we'd not been working on the thing while they were on the air....
The fix? Simple, but I couldn't do it for a couple days. You grab a handful of small capacitors, and while playing with the length of the capacitor's leads, you try to find a combination of capacitor value and lead length that shorts out the 88mhz signal without any effect on the use of the amplifier. Turned out to be pretty simple - it almost took longer to pop the covers off the amplifier.
That, btw, is part of the "no cellphones on airliners" view. From a practical standpoint, the aircraft probably is immune, but it's not necessarily been tested for the frequency that your phone may select. Not to mention the possibility of using multiple sites on the ground at the same time. Gotta be hilarious to bill.
The short answer is that "yes, it can"....
If a radio hasn't been "opened up", especially if it's type accepted, it should not cause problems. One that's not type accepted, and opened, it's hard to say what will happen.
Regards,