4ft vs 8ft - The Hull Truth

chrisrack · 10-13-2009, 07:13 AM

Need to purchase 2 VHF antannaes mounted atop a "radar tree" which of course is mounted to the top of the cabin. The top of the radar tree (where the antannae would mount) is 10-11ft above the WL. Will be offshore fishing but generally not more than 40 nm. Would like have 4ft antannaes due to bridge clearance issues but also want range.

Question is: Will the 4ft-er's give me as near equal range as an 8ft-er when mounted atop the radar tree?

Riptide828 · 10-13-2009, 10:32 AM

I just replaced my old 8 ft with a Shakesphere 5400 4 ft antenna that I received from BOE last week. I am very pleased with it and I think it is doing better then the 8 ft even when it was brand new. The 10 - 11 ft would really help with the 4 ft antenna.

For 40 miles I do not know, Jim will know better, but I was talking to somebody 23 miles away on Saturday and it was loud and clear..

yachtjim · 10-13-2009, 08:24 PM

VHF is line of site. so the 8' antenna will work better, assuming we are talking the same grade of antenna. I don't know an exact figure, but Ii would guess the 8'er should go an additonal 5 miles over a 4'er.

surfcaster51 · 10-14-2009, 02:36 AM

All other things being equal the 8 foot will reach out approximatley 1.8 miles further. then the 4 footer

chrisrack · 10-14-2009, 01:08 PM

Surfcaster - Did I read that correctly .... JUST an additional 1.8 miles?

kchace · 10-15-2009, 01:45 PM

Quote:

Originally Posted by chrisrack

Surfcaster - Did I read that correctly .... JUST an additional 1.8 miles?

Yup. Here's a calculator:

http://www.qsl.net/kd4sai/distance.html

And here's maybe more info than you ever wanted to know about Marine VHF:

http://members.toast.net/boatguy/vhfant.htm

Ken

chrisrack · 10-15-2009, 03:29 PM

Thanks Ken - Yeah, the 1st site was very helpful; 2nd was TMI.

Love your Tolman. My long range plans are to build one similiar to your's w/o the forward cabin. Already have the book and read it 3 times.

yachtjim · 10-15-2009, 06:40 PM

That's a nice calculator. Much shorter than I thought.

chrisrack · 10-17-2009, 05:18 AM

Jim -

Tried to order 2 VHF antenna's, 2 radios and maybe a 585 on Friday but Beth tell me you were busy swimming with the ducks in a pair of Noreasters at the Annapolis boat show. Give me a call on Monday.

Miss Trial · 10-20-2009, 07:54 PM

Man, I've talked further than 5 miles before with my 8 foot antenna. Something can't be right with that.

LI32 · 11-20-2009, 06:13 PM

Quote:

Originally Posted by Miss Trial

Man, I've talked further than 5 miles before with my 8 foot antenna. Something can't be right with that.

It depends on the height of the antenna on the other end too. I can pick up the USCG more than 50 miles out with my 8' Antenna mounted 11' above the water - I think the CG antenna is 450' above sea level.