When I walk my toddlers in the morning, I tune to KPCC for Larry Mantle or Take Two on my Sangean DT400. Half the time I'm getting Palm Springs KCRW 89.3 bleeding into the Pasedena KPCC 89.3 so that voices from different stations are chattering at the same time, enough to make me go nuts.
I tried my Sangean DT180 and the problem is less pronounced. I really need a new portable that will get me KPCC without this station bleed. But I suspect there's nothing out there.
This is related to FM capture effect. With FM, you're only supposed to hear the stronger of two signals on the same frequency. This is in contrast to AM, where many signals can be heard at the same time on the same frequency.
There is a limit to the FM capture effect, and it's measured by the capture ratio, which is the number of dB that one signal must be stronger than the other for only the stronger signal to be heard. If the signals are closer in strength than the capture ratio of the receiver in use, then both will be heard. It sounds like this is what's happening in your case, and it may not be easy to resolve with a different inexpensive portable radio.
If you move location slightly, this will probably change the strength of the two signals enough for one or the other to become dominant.
Posted by: Gary | March 16, 2013 at 11:00 AM
Jeff,
Maybe the new CC POCKET radio would do the job? I heard it has better selectivity than SANGEAN DT 400?
Posted by: Ante | March 16, 2013 at 10:53 PM
Yeah, I'm thinking of getting one.
Posted by: herculodge | March 17, 2013 at 06:30 AM
The CC Pocket may have better selectivity on FM than the DT-400W, but this is not relevant for separating signals on the same frequency. Selectivity relates to separating signals on adjacent frequencies. For this particular situation, what is needed is a lower capture ratio, not better selectivity.
Posted by: Gary | March 17, 2013 at 11:54 AM
Gary, can you recommend a portable lower capture radio?
Posted by: herculodge | March 17, 2013 at 11:56 AM
Jeff - Unfortunately, capture ratio doesn't seem to be mentioned in the specifications or reviews of portable radios today. If the two FM signals you're hearing are very close in strength, then it will be very hard to separate them. With a stationary radio, the solution is a directional FM antenna, but this is of no help with a walk-around portable.
In the past, capture ratio was specified by manufacturers for their component FM tuners and receivers. For example, this Pioneer ad in the September 1975 "Popular Science" indicates a capture ratio of 1 dB, which is quite good.
http://books.google.com/books?id=RwEAAAAAMBAJ&pg=PA17&lpg=PA17&dq=Pioneer+%22capture+ratio%22&source=bl&ots=aIN094HpaY&sig=tE6UMEYq8Qts4nF4ZYcDJ6x_s0g&hl=en&sa=X&ei=NxlGUeTRNonnqgHspIHoDQ&ved=0CDEQ6AEwAA#v=onepage&q=Pioneer%20%22capture%20ratio%22&f=false
Posted by: Gary | March 17, 2013 at 12:34 PM
Jeff - I had sent a more detailed post, but I guess it got lost somewhere. I don't know which portables have a lower capture ratio, as this isn't something that seems to be indicated in the specifications or mentioned in reviews these days. Perhaps one of the DSP radios would do better in this regard, but I'm not sure. I get the impression that the CC Pocket is DSP-based, so it might work better than what you have. I guess the only way to know for sure is to try one.
Posted by: Gary | March 17, 2013 at 01:04 PM