Re: [Cal_Boats] FM radio antenna

The real problem is that the actual antenna is not designed to work at the FM band. Particularly gain antennas have a matching network that may approximate a very poor connection, or even a short, at the frequency of the FM band. I have used, with reasonable success, the little short FM antenna which is no more than a wire on a pin that plugs into the back of the radio. Given that the boat is fiberglass (non-conductive) it works just as well as a similarly sized whip, out in the open. It is not, however, at the top of the mast. Al > > From: Chris Campbell <cl… [at] charterinternet.com> > Date: 2006/07/10 Mon PM 03:44:21 EDT > To: Seafarer <se… [at] list.sailnet.net>, Ca… [at] yahoogroups.com > Subject: [Cal_Boats] FM radio antenna > > Fellow sailors: > > Here's a peripheral question. Quite a few years ago I installed an FM > car radio/cassette player in the boat. I also bought a device made by > Shakespeare that splits the signal from the antenna (theoretically) > between the VHF-FM and the broadcast-band FM radio. It never worked > very well on the FM stereo. > > A few years later, I noticed that West Marine carried two versions: one > for the whip antenna with the base coil, and one for fiberglass > antennas. My model no. matched the fiberglass-antenna model, so I > bought the other one. It works just as poorly. > > The FM broadcast band is 88-104 mc, and the marine FM band is up at > 156-162 mc. It ought to be fairly easy to split these out. > > The device has coax running into a black plastic box, and then two coax > outputs, one with the standard VHF connector and one with the Motorola > plug for the car stereo. > > West used to carry (and maybe still does) an either/or switch. The > splitter device seemed easier for dummies like me who would forget to > switch over to VHF-FM to make a call or to listen on 9 and 16. > > Has anybody had better experience with these splitter devices? With the > switch versions? It would be nice to be able to use that nice whip way > up at the top of the mast for the FM broadcast radio. > > Chris Campbell > > > > > Yahoo! Groups Links > > > > > > >

Chris, my guess is that these splitters are passive, rather than active, devices. As such, they would most likely attenuate the signal, rather than boost gain. Also, the marine VHF antennas are intentionaly attenuating lower frequencies since these are considered interference sources. The splitter could not do a very good job with a signal that is down 20 db from 160MHz level. Just guessing. Cheers Charlie From: Ca… [at] yahoogroups.com [mailto:Ca… [at] yahoogroups.com] On Behalf Of Chris Campbell Sent: Monday, July 10, 2006 3:44 PM To: Seafarer; Ca… [at] yahoogroups.com Subject: [Cal_Boats] FM radio antenna Fellow sailors: Here's a peripheral question. Quite a few years ago I installed an FM car radio/cassette player in the boat. I also bought a device made by Shakespeare that splits the signal from the antenna (theoretically) between the VHF-FM and the broadcast-band FM radio. It never worked very well on the FM stereo. A few years later, I noticed that West Marine carried two versions: one for the whip antenna with the base coil, and one for fiberglass antennas. My model no. matched the fiberglass-antenna model, so I bought the other one. It works just as poorly. The FM broadcast band is 88-104 mc, and the marine FM band is up at 156-162 mc. It ought to be fairly easy to split these out. The device has coax running into a black plastic box, and then two coax outputs, one with the standard VHF connector and one with the Motorola plug for the car stereo. West used to carry (and maybe still does) an either/or switch. The splitter device seemed easier for dummies like me who would forget to switch over to VHF-FM to make a call or to listen on 9 and 16. Has anybody had better experience with these splitter devices? With the switch versions? It would be nice to be able to use that nice whip way up at the top of the mast for the FM broadcast radio. Chris Campbell ------------------------ Yahoo! Groups Sponsor --------------------~--> Something is new at Yahoo! Groups. Check out the enhanced email design. http://us.click.yahoo.com/SISQkA/gOaOAA/yQLSAA/A1TolB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links

Husar Charlie wrote: > > Chris, my guess is that these splitters are passive, rather than active, > devices. As such, they would most likely attenuate the signal, rather > than boost gain. Also, the marine VHF antennas are intentionaly > attenuating lower frequencies since these are considered interference > sources. The splitter could not do a very good job with a signal that > is down 20 db from 160MHz level. > > .__,_._,_ I think I've read that FM broadcast-band splitters (one antenna to two tuners) have a loss of about 3 dB. The problem with the Shakespeare splitter may be that it's dealing with a transceiver on one side and the car radio on the other--it has to not only split the signal from the antenna, but also keep the 25 watt VHF-FM transmitted signal out of the car radio. And it is doing it passively, so that's probably a high-loss process. The car radio's performance is notably increased when you unscrew the antenna from the VHF-FM. That means that any attenuation designed into the antenna isn't a huge factor. My guess is that 90 mHz is far enough from 156 that no additional attenuation was needed. Some old TV antennas had FM-band attenuation because the FM radio signals fall between channels 6 and 7 on TV, and the TV antenna had to be broad enough to work on channels 3 through 13. The easiest, and probably best, solution is to just go out and buy a separate car radio antenna, as various folks have suggested, and hide it somewhere in the boat, preferably in a vertical orientation to avoid directionality. What's a junkyard antenna going to cost, 3 bucks? And what are the Shakespeare devices, of which I've bought two--40 bucks each? These are things I should not admit in public. Wish we had the internet BEFORE I began buying these expensive non-fixes. Chris Campbell > ------------------------------------------------------------------------

"The easiest, and probably best, solution is to just go out and buy a separate car radio antenna...". Chris, I'll go out in the parking lot and rip one off. Just send me a mailing address. :~] Cheers Charlie From: Ca… [at] yahoogroups.com [mailto:Ca… [at] yahoogroups.com] On Behalf Of Chris Campbell Sent: Wednesday, July 12, 2006 9:40 AM To: Ca… [at] yahoogroups.com Subject: Re: [Cal_Boats] FM radio antenna Husar Charlie wrote: Chris, my guess is that these splitters are passive, rather than active, devices. As such, they would most likely attenuate the signal, rather than boost gain. Also, the marine VHF antennas are intentionaly attenuating lower frequencies since these are considered interference sources. The splitter could not do a very good job with a signal that is down 20 db from 160MHz level. .__,_._,_ I think I've read that FM broadcast-band splitters (one antenna to two tuners) have a loss of about 3 dB. The problem with the Shakespeare splitter may be that it's dealing with a transceiver on one side and the car radio on the other--it has to not only split the signal from the antenna, but also keep the 25 watt VHF-FM transmitted signal out of the car radio. And it is doing it passively, so that's probably a high-loss process. The car radio's performance is notably increased when you unscrew the antenna from the VHF-FM. That means that any attenuation designed into the antenna isn't a huge factor. My guess is that 90 mHz is far enough from 156 that no additional attenuation was needed. Some old TV antennas had FM-band attenuation because the FM radio signals fall between channels 6 and 7 on TV, and the TV antenna had to be broad enough to work on channels 3 through 13. The easiest, and probably best, solution is to just go out and buy a separate car radio antenna, as various folks have suggested, and hide it somewhere in the boat, preferably in a vertical orientation to avoid directionality. What's a junkyard antenna going to cost, 3 bucks? And what are the Shakespeare devices, of which I've bought two--40 bucks each? These are things I should not admit in public. Wish we had the internet BEFORE I began buying these expensive non-fixes. Chris Campbell