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Post by finatic on Sept 12, 2023 18:49:13 GMT -5
I hooked up my 2nd 8ft Shakespeare antenna for my fusion radio today. The newest one is attached to the VHF. So today when I key the microphone it cancels out the fusion radio sound, unkey radio is back on. I thought I read somewhere that because the 2 antennas can't be spread apart enough this happens. The reception is unbelievable i was getting stations 60 miles away. Anyone experience this ?
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jerryk
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Post by jerryk on Sept 12, 2023 19:00:09 GMT -5
I'm not too surprised. The close proximity to the 25 watt output of the marine VHF in frequencies not too far separated from the FM broadcast band is what is going on. Antenna placement, front end filtering of the Fusion radio, and the power output of the VHF all come into play. It may also be some sort of built in mute to prevent the radio's speaker output from getting into the microphone of the VHF when you are transmitting, making your (priority) communications clearer.
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Post by finatic on Sept 12, 2023 19:26:36 GMT -5
I'm not too surprised. The close proximity to the 25 watt output of the marine VHF in frequencies not too far separated from the FM broadcast band is what is going on. Antenna placement, front end filtering of the Fusion radio, and the power output of the VHF all come into play. It may also be some sort of built in mute to prevent the radio's speaker output from getting into the microphone of the VHF when you are transmitting, making your (priority) communications clearer. Thanks that makes sense.
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jerryk
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Post by jerryk on Sept 12, 2023 20:20:09 GMT -5
Finally...4 years of electrical engineering college degree schooling, 22 years working at one of the worlds premiere wireless communications companes (Motorola), and 49 years of being a licensed amateur radio operator and I can add an answer here that makes sense. My life is complete ;-)
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Post by finatic on Sept 13, 2023 6:17:25 GMT -5
Finally...4 years of electrical engineering college degree schooling, 22 years working at one of the worlds premiere wireless communications companes (Motorola), and 49 years of being a licensed amateur radio operator and I can add an answer here that makes sense. My life is complete ;-) Wow,, LMAO
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Post by nickbhw on Sept 13, 2023 6:45:44 GMT -5
That's interesting. Makes sense. I wonder if you find the right channels on the VHF and the Fusion, you could hear yourself through the boat speakers??
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Post by outtadblue on Sept 13, 2023 8:23:26 GMT -5
I have never had this problem.
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Post by finatic on Sept 13, 2023 9:11:26 GMT -5
I have never had this problem. Maybe because they are both v h f antennas. A month ago I forgot to lower the antenna hit tree while on trailer it was ugly. I purchased a new one and repaired the old one because it still was transmitting fine. I purchased a digital antenna Motorola AM FM solder connector for the RG-8X cable DA-140 Awesome reception, and I like the look of the two antennas.
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jerryk
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Post by jerryk on Sept 13, 2023 9:53:29 GMT -5
You SHOULDN'T have the problem of losing FM broadcast stereo reception when you key up your VHF marine radio, but there may be a couple of things going on. Most likely if the antennas are close, or the FM receiver doesn't have a great front end filter to allow only energies received near the tuned frequency, your VHF marine radio can overload the Fusion stereo. Most likely your 25 watt tranmit energy is coming in strong enough to "cover up" the weaker broadcast FM signal coming in from miles away. You transmit on marine frequencies around 156 Mhz and your FM broadcast is at 88-108 Mhz, but the energy created when you transmit is not all at your transmit freqency, it kind of looks like a Christmas tree in the frequency spectrum with the majority of the energy at the trunk of the tree (your transmit freq) but some of the energy spills out on either side of the tree trunk to frequencies above and below the intended transmit frequency. If that spillover energy is strong enough to overpower the relatively weaker FM broadcast signal, your Fusion radio can't decode the music information and the radio mutes. I've had a similar situation when trying to use my cell phone in the vicinity of a large tower full of antennas (including broadcast TV/radio, cellular wireless networks, and public safety radios (police and fire). My cell phone just "looses" the cell signal amidst all of the other noise that exists right under the tower, but moving away a little bit drops the noise level enough to re-aquire the cell network and make a phone call.
I've also seen some marine/FM antennas that use one antenna for both radios. I don't know how those are wired up but have to assume there is some kind of relay or switch to prevent keying up your marine radio directly into the FM stereo and instead direct the energy out to the antenna alone...and in that case the FM stereo would go "deaf" while you are transmitting on the marine radio.
To address nickbhw's comment, it is unlikely that the marine radio will be heard in the speakers of the stereo because the modulation is different between the two signals. The stereo is decoding a much broader modulation which can carry music information with high fidelity, whereas the marine radio transmits a very narrow modulation type designed to be good enough to carry voice intelligence but it isn't optimized for music so if you try to broadcast music on your marine radio it ends up sounding tinny and cheap...there is the trade-off between channel size (spectral efficiency) and fidelity that can be carried on the transmitted signal. The Fusion radio likely won't even decode the type of modulation coming in from the marine radio.
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Post by finatic on Sept 13, 2023 11:39:40 GMT -5
Wow awesome explanation. My simple solution is just turn off the fusion before using the vhf.
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Post by reelkul on Sept 14, 2023 8:05:19 GMT -5
jerryk when you say " Most likely if the antennas are close,......." What is close? 1-inch, 1-foot, 1-yard, etc? I have two antennas, one on each side of the t-top. One dedicated to the radio, and one dedicated to the vhf. I have never noticed any interference in the radio when using the vhf.
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jerryk
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Post by jerryk on Sept 14, 2023 10:16:19 GMT -5
Close as in close enough to overload the front end of the stereo...which depends on the stereo as well as the antennas and their placement relative to each other. I don't have this issue myself either, but understand how it can happen. Each boat, each radio, and each antenna is different so to really know what is happening better you'd need a spectrum analyzer and some analysis time.
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