Lake Champlain United - Forums

just purchased a new cobra F75B class D Dsc for my boat, never had a fixed mount radio before had a hand held that was garbage, you could just about yell farther then the thing would transmit. anyway after a little research i bought it and a Shakespeare 5206 8' antenna in black, with a shakespeare 4187 stainless steel ratchet mount. the antenna is a 6db gain, anyway should this setup work well? its on a 19' fisher hawk. Also looking for a little info on where the best place to mount the antenna would be, they say to keep it 3 ft. from the radio any input on that, i have seen alot of guys boat with them only a foot or so away.

chris

Fraid
Marine radios can be a major cause of interference with other electronics on the boat. I have seen them cause issues with graphs and control kings. Test your locations before you drill any holes! Often times the issues are when the mike is keyed on high power and does not cause problems when on low. Only one way to find out.
Good luck
Thorny

Fraid-Knot wrote:Also looking for a little info on where the best place to mount the antenna would be, they say to keep it 3 ft. from the radio any input on that, i have seen alot of guys boat with them only a foot or so away.

I think they say at least 3ft to protect your head from the 6dB radiation of the antenna with a 25Watts radio. (cell phone are only 1 Watt).

edit: I thought is was to protect your head from the 6dB, but after having read the first link from Andre, it's false

Some questions & answers:
http://www.shakespeare-antennas.com/media/faq.asp

Very important:
http://www.shakespeare-antennas.com/med ... lt.asp?p=7
http://www.shakespeare-antennas.com/med ... lt.asp?p=8

Ludo wrote:

Fraid-Knot wrote:Also looking for a little info on where the best place to mount the antenna would be, they say to keep it 3 ft. from the radio any input on that, i have seen alot of guys boat with them only a foot or so away.

I think they say at least 3ft to protect your head from the 6dB radiation of the antenna with a 25Watts radio. (cell phone are only 1 Watt).

edit: I thought is was to protect your head from the 6dB, but after having read the first link from Andre, it's false

It is not entirely false...

Low level and intermediate level RF and EMF *can* effect the body and brain. Modern cell phones are most often in the 600 miliwatt range, but the frequency and wavelength is close to other RF radiated energy that is known to effect tissues and organs. It's not just your head (brain) but your whole body tissue.

While Marine radios (which are in the VHF range and considered relatively "safe") are not likely to cause any effect we can see, consistent exposure is theoretically harmful. It is wise to make antenna placement in consideration of limiting close proximity exposure. Tissue "heating" from even 1 watt transmissions can occur from this radiation. Microwave ovens typically operate at 600 to 1200 watts; this power makes the

Marine radios operate in the electromagnetic spectrum below the frequency of microwave ovens and above over-the-horizon radar. They are not "safe" but can be operated safely with proper installation and appropriate distances from humans. On a small boat, this requires a little forethought but can still be done.

In response to OP's question- the 8-foot antenna should give good broadcast and reception characteristics for a moderately priced setup.

great, thanks for the info guys. any input on polarity when installing the radio?

chris

Fraid-Knot wrote:great, thanks for the info guys. any input on polarity when installing the radio?

Maybe I don't understand the question...

VHF radios are DC; polarity is vital! Black will be negative (-) and "+" (positive) will likely be red and it should or will likely have a power supply pigtail with a fuse holder included. Backwards will likely let the factory smoke out...and factory installed smoke never goes back in well.

fishhuntadventure, you're right, I've edited my message because of the "3 ft. from the radio" that I was wrong

I am installing the same model Cobra with a Shakespeare Galaxy antenna (birthday present), replacing my older unit on a 17' Starcraft
dual console. My antenna is mounted just foward of the windshield on the starboard side. The radio is on the starboard dash, as far left as I could mount it, next to the walk-thru, about 40" from the antenna. I have a Lowrance sonar/GPS on the dash about 18" from
the antenna. I never had any interference problems with my old unit. Both radio and GPS are powered from separate connections
on a fuse block under the dash. I assume you will using your radio mostly for short-range communications, so can transmit at 1 wattt.
Good luck with your new gear. Maybe we will connect some day on the lake.

A: Yes. It is best to locate the antenna at least three feet from any metal objects or other antennas.

From Shakspear website. I position mine on the opposite side of the boat: port side

Will metal or other objects that are close to the antenna affect it?
Can I mount the antenna beside the radio?
A: No, it must be at least three feet away from the radio, so transmission will not interfere with the radio's reception (usually resulting in a squeal coming out of the speaker).

fishhuntadventure wrote:

Ludo wrote:

Fraid-Knot wrote:Also looking for a little info on where the best place to mount the antenna would be, they say to keep it 3 ft. from the radio any input on that, i have seen alot of guys boat with them only a foot or so away.

I think they say at least 3ft to protect your head from the 6dB radiation of the antenna with a 25Watts radio. (cell phone are only 1 Watt).

edit: I thought is was to protect your head from the 6dB, but after having read the first link from Andre, it's false

It is not entirely false...

Low level and intermediate level RF and EMF *can* effect the body and brain. Modern cell phones are most often in the 600 miliwatt range, but the frequency and wavelength is close to other RF radiated energy that is known to effect tissues and organs. It's not just your head (brain) but your whole body tissue.

While Marine radios (which are in the VHF range and considered relatively "safe") are not likely to cause any effect we can see, consistent exposure is theoretically harmful. It is wise to make antenna placement in consideration of limiting close proximity exposure. Tissue "heating" from even 1 watt transmissions can occur from this radiation. Microwave ovens typically operate at 600 to 1200 watts; this power makes the

Marine radios operate in the electromagnetic spectrum below the frequency of microwave ovens and above over-the-horizon radar. They are not "safe" but can be operated safely with proper installation and appropriate distances from humans. On a small boat, this requires a little forethought but can still be done.

In response to OP's question- the 8-foot antenna should give good broadcast and reception characteristics for a moderately priced setup.

For serious???? Mine is like a foot away from my head!!? Maybe thats whats wrong with me Good info. My radio causes all sorts of issues for me on high power. Think I want to take it out now.

wouldn't mind mounting the antenna on the port side of the boat but what a pain in the butt it would be running the cable.

chris

Fraid-Knot wrote:wouldn't mind mounting the antenna on the port side of the boat but what a pain in the butt it would be running the cable.

chris

I know very well!!