VHF antenna connector - bad reception

[sdoomaha]

Searched forum, but couldn't locate an answer to my specific question.

Recently installed a new marine radio in my boat. Saved a few $$$ by purchasing a 4 ft Shakespeare VHF antenna that had no connector on the end of the coax. Purchased the Shakespeare gold connector and followed installation instructions.

Used it once, great transmission....the fisherman I was out with could hear me over long distances, but my reception was pathetic. Unless I was within a coupld hundred yards of the other boats, I could not hear them. Adjusted the squelch over and over...never any better. Changed stations....no effect.

With the coax, there is a center wire, and then the wire on the outside just inside the initial insualtion. Any chance one part of the wiring is responsible for transmitting and the other for reception? If so, which is which? I have checked the connector and it appears I am getting excellent contact with each...but with a new radio, and a new antenna exclusive of the connector....I am leaning towards a problem with the connector.

Thanks for any insight.

 

[dingbat]

Re: VHF antenna connector - bad reception

Searched forum, but couldn't locate an answer to my specific question.

Recently installed a new marine radio in my boat. Saved a few $$$ by purchasing a 4 ft Shakespeare VHF antenna that had no connector on the end of the coax. Purchased the Shakespeare gold connector and followed installation instructions.

Used it once, great transmission....the fisherman I was out with could hear me over long distances, but my reception was pathetic. Unless I was within a coupld hundred yards of the other boats, I could not hear them. Adjusted the squelch over and over...never any better. Changed stations....no effect.

With the coax, there is a center wire, and then the wire on the outside just inside the initial insualtion. Any chance one part of the wiring is responsible for transmitting and the other for reception? If so, which is which? I have checked the connector and it appears I am getting excellent contact with each...but with a new radio, and a new antenna exclusive of the connector....I am leaning towards a problem with the connector.

Thanks for any insight.

The center conductor is your transmit and receive signal. The wires on the outside are just the shielding.

 

[sdoomaha]

Re: VHF antenna connector - bad reception

Thanks. So obviously if I am transmitting well....the connection is fine. Hmmm.....will try a buddies radio wth my antenna to see if I can isolate to one of the other.

Will also disconnect my GPS antenna...it is mounted near the maribe radio antenna and try it again. Someone mentioned the GPS antenna can interfere with the radio. Seems odd....but my electronics knowledge it limited.

Thanks for the help.

 

[dingbat]

Re: VHF antenna connector - bad reception

A GPS antenna is a passive device. It is not interfering with your VHF reception.

 

[sdoomaha]

Re: VHF antenna connector - bad reception

Thanks again, and take care.

 

[Gary H NC]

Re: VHF antenna connector - bad reception

The 4ft antenna is most likely the receive problem.With VHF the 8ft antenna is the way to go.VHF is more of a line of sight signal and the antenna height makes a big difference.
The squelch has nothing to do with it.It is just to adjust out the back ground static and noise.If it has a RF gain knob that is the one you want all the way up to help pull in weak signals.

 

[RickJ6956]

Re: VHF antenna connector - bad reception

It's due to the short antenna. Also, if you've purchased a splitter so the same antenna can be use for both the VHF and the stereo, you're cutting the power in half to both radios.

 

[jhebert]

Re: VHF antenna connector - bad reception

Radio reception is very different than transmission. Many of the remarks made in this discussion offering you advice are based on misunderstandings of the fundamentals of radio communication.

In radio reception, particularly FM radio reception, there is an enormous difference than in transmission. In transmission there is a limit to the power, determined by the transmitter. A low level signal in the transmitter is increased by amplification, then sent to the antenna. The amount of amplification is limited by the power permitted. In the VHF Marine Band for recreational boat transmitters, the limit it 25 watts.

In reception, a low level signal from the antenna is sent to the receiver to be amplified. The receiver amplifies this signal until it is strong enough to drive a loudspeaker. The most significant different is there is no limit on the gain that can be used. An FM receiver will an enormous amount of reserve gain so that even the weakest signals can be amplified to loudspeaker level. Therefore, if an antenna has a few decibels less gain than another, the receiver can generally compensate. In fact, in an FM receiver, the gain stages are all set to run at maximum gain all the time, so as to drive the amplified signal into saturation.

The only time a change in antenna gain can affect reception is when the received signal is at the absolute threshold of the receiver sensitivity, that is, when the receiver, even operating at its maximum gain, still lacks gain to boost the level sufficiently. This seldom occurs in marine radio communication except on very long paths. In most cases, a receiver will be able to receive well using an antenna that would be extremely poor on transmission. Most receivers work reasonably well with just a hunk of wire for an antenna. In fact, in most installation, when the antenna has a serious malfunction and is useless for transmitting, the reception is not affected at all.

In light of this, recommendations that your problems with reception are due to a poor antenna, and that you should change to an 8-foot antenna, are very likely not accurate.

If you can transmit well with the antenna, but you cannot receive well with it, there are two possible problems:

--the receiver has a serious malfunction and its sensitivity is greatly reduced; or,

--there is a very strong local interference on your boat that is suppressing the receiver sensitivity.

Sources of local interference could be the ignition system of your engine, other electronic devices on your boat, or a local transmitter that is causing a large reduction in sensitivity.

A good way to check the sensitivity of your receiver is to use the NOAA Weather Radio station broadcasts as test signals. I have described how to do this in an article published at

Assessing VHF Marine Band Antenna Performance Using Remote NOAA Weather Radio Broadcasts
http://continuouswave.com/whaler/reference/antennaRange.html

 

[Shore Guy]

Re: VHF antenna connector - bad reception

Did your VHF come with a NMEA and external speakers wiring bundle and if yes how did you deal with these loose wires if problem has not been rectified yet?

 

[BLU LUNCH]

Re: VHF antenna connector - bad reception

Did you check the SWR? You might have water logged coax.......