A couple of technical vhf antenna questions.

[ChesBayBoatMan]

OK gang,

I get it. The taller the antenna the greater the range... and all the little quirks that go with that, but my question is about the antenna itself. I have narrowed my search down to two Shakespear antennas. One is the 8ft. 5101. The other is the 8ft. 5202. They are both 50 watts max input, both have RG-58 coax (and yes I know RG-8X is better), they both are 6dB (which by the way is there any other or is this generic for VHF), they both have 50 Ohms. The only differences between the two that I can see are; One has 20 feet of cable, and one has 15. Not a big deal for me. The only other thing I can see as being a difference is 5101 says "End -fed with matching stub", and the 5202 says "Collinear phased 5/8 wave.

So my questions are...
1. Are there other major differences I am missing that you know between these two antenna's.

1. What is the difference between "End-fed with matching stub", and "Collinear phased 5/8 wave"?

2. What is the difference in the directions when it says, "This antenna will read open circut when tested" and " This antenna will read short cirrcut when tested" and will the difference have an impact on performace when the VHF is in use?

3. What is the significance in "5/8 wave" and is there something different/better? Even the 5225 has a 5/8 wave and that is supposed to be the top of the line 8 ft shakespear antenna.

Thanks in advance!! Ya'll havn't let me down yet.

Ches

 

[LippCJ7]

Re: A couple of technical vhf antenna questions.

1. Not really sounds like you have done a pretty good job

1.(a?) without teaching you how/why the wheel came about, these terms are two different ways to tune the antenna to a specific frequency range, is one better then the other yes but for all intents and purposes that's a ford versus chevy debate

2. It would be nice if all antenna manufacturers did this reason being more for the "this antenna will read short circuit when tested" is that when you either have a problem or are simply checking your connector or line and you see a short on your DVM you shouldn't be surprised when you cut the connector off and still read a short.

3. anytime you use an antenna that is full wave it should get better range then one that is shorter, the problem is not everyone wants to have a 3 meter antenna (which would be more when you add in a mount and structure for the antenna), but both these antennas are 6db gain which is pretty good for a marine application

The difference between these two antennas is the Bandwidth, the 5101 is 5 MHz within 2.0:1 VSWR where as the 5202 is 3 MHz within 2.0:1, so what this means is the 5101 is broader banded, so with the center frquency being 156.8, it will cover 151.8-161.8 MHZ before the VSWR exceeds 2.0 to 1, Depending on your radio this may or may not be an issue, what is the frequency range of the radio you wish to use? if your radio has the capabilities of exceeding the 153.8-159.8 then the 5101 is your antenna if not then the 5202 is.

 

[dingbat]

Re: A couple of technical vhf antenna questions.

I'd seriously think about going with the XT5225 if for no other reason the durability of construction.

The 5101 and the 5202 are not the most durable antennas. They don't hold up very well to the pounding you get running the Bay on a regular basis. Snap, crackle and pop are just around the corner. Either way, a SS mount is money well spent.

 

[ChesBayBoatMan]

Re: A couple of technical vhf antenna questions.

Thanks for the info guys.
LippCJ7. Not sure about which vhf yet. I have always been told the antenna makes the radio so I was starting there with the needs I have in mind. More info may have been helpful. I am mounting on the cabin top of my Chesapeake Bay Deadrise. I know lots of guys go with the mega 14 - 16 footers and run them up the side of the cabin, or up the back of the cabin. Three reasons I am not doing this, 1) the over-hang on the sides of my cabin are more than a stand off bracket will accomidate, I have a three foot over hang off the back of my cabin so that won't work either. 2) Is the good ole fashion $$$$$ money. 3) I don't believe I need a huge super antenna that will call china as I do not go into the ocean far enough to be out of site of land or other boats. I am almost always in site of other boats and always within ear shot/ sight of land. I use the boat for pleasure and do not fish often so long distance comm. is just not a nessicary at this time. One reason I chose these two antennas is because if for some reason I want greater range, or I am not getting the range I expect, they can both be attached to an extension and get them higher off the waterline. Speaking of off the water line; without an extension, from the waterline to the tip of the antenna will already be about 16 feet. I know in the case of antennas you get what you pay for, but I cannot justify a $380 antenna for what I am going to use it for.
Any more thoughts? I am going to do the research on VHFs today. Thanks again for your info.

dingbat; Thanks for the heads up and I have not made my final decision yet. When I come into my financial windfall I am going to upgrade all of my equipment. I am running a 35' Deadrise. With the displacement hull and the "lack of speed" she runs at, I am not going to be beating myself or my boat to death. Nice clean smooth ride even in a light to medium sea, and if you catch me out there in rough conditions, it was a miscalculation on my part. As a former sailboat racer, and fairly hardcore fisherman I have been out in and seen my share of thunderstorms, high-wind days, snow, ice and less than ideal conditions. Don't get me wrong I love the thrill of hooking up a big tuna and few things beat a good rock-fish (striper) on the dinenr table, but my days of beating myself to death in the name of boating are behind me I hope. That's one of the main reasons I bought the boat I did.

ches

 

[LippCJ7]

Re: A couple of technical vhf antenna questions.

All I told you was pretty simple RF advice, I am in the RF industry but do not do much marine. As far as the Mounting and general application of marine communications I have to defer to dingbat, he uses it in your situation and would be a much better resource for you.

I would say to be careful when you say you don't need long distance communication, your on the ocean not a lake(like me) and when you start hailing England after floating for a month you may regret your words! I know its an extreme example but you know what I mean, the reason why we have marine radio is for emergency's first everything else is secondary.

Yes the higher you can get your antenna the better but lets be honest your not likely to see any mountains in the middle of the ocean are you! do the best you can, try not to have any other structures higher then the mounting section of the antenna within the length of the antenna, if you mount your antenna on the side of your radar(just as an example) arch then the radar arch that is next to the radiating part of the antenna will block a lot of the signal that's why marine radio antennas are normally at the highest point of the boat/ship. AM/FM radio antennas are receive only and therefore do not have the same problem.

All fiberglass antennas have three basic parts that make the antenna, the base/mounting surface, the shell and then the actual antenna inside the shell. Depending on the manufacturer the bottom 6"-10" is nothing but base/mounting structure, the actual radiating antenna would extend from there with the fiberglass shell for protection and structure. If you were to cut the antenna 12" from the base the actual antenna would simply slide out of the shell...just FYI

 

[dingbat]

Re: A couple of technical vhf antenna questions.

dingbat; Thanks for the heads up and I have not made my final decision yet. When I come into my financial windfall I am going to upgrade all of my equipment. I am running a 35' Deadrise. With the displacement hull and the "lack of speed" she runs at, I am not going to be beating myself or my boat to death.
ches

It?s not the speed; it's the torque on the base from the pitch and roll that snaps antennas. Mounting them on the roof just magnifies the effect.

I have two 8' antennas mounted on my hardtop. They are roughly 10' to the base, 18' to the top of the antenna. On a nice flat day I have roughly a 10-15 mile range. On heavy overcast days with the stars aligned, I can go close to 20 miles. If it's rough, the pitch and roll will knock you down to @ 5-7 miles

BTW: Never seen anyone hyphenate Rockfish before. Not a native I take it?

 

[jhebert]

Re: A couple of technical vhf antenna questions.

What is the difference between "End-fed with matching stub", and "Collinear phased 5/8 wave"?

The term "End-fed with matching stub" refers to some detail about how the transmission line is connected to the antenna, and says nothing about the arrangement of the antenna elements.

The term "Collinear phased 5/8 wave" refers to the arrangement of elements in the antenna array, and says nothing about how the transmission line is connected.

These two phrases are talking about two completely different things. I would ignore them. As for being useful as a basis to choose between the antennas, I find them insignificant.

If you are interested in some technical details of VHF Marine Band radio communication and antennas, I suggest:

VHF Marine Band Antennas
http://continuouswave.com/whaler/reference/antennaVertical.html

Marine VHF Radio Communications
http://continuouswave.com/whaler/reference/VHF.html

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

Estimating Path Loss on Marine Non-Line-of-Sight Paths
http://continuouswave.com/whaler/reference/pathLoss.html

I am the author of the articles linked above.

 

[Boatist]

Re: A couple of technical vhf antenna questions.

All the antenna talked about are good right out of the box.
For me the 5225-XT or better still the 5225-XP are worth the extra cost.
I would not pay $380 either but here at IBoats the 5225-XT is $103 and the 5225-XP is $122.

The main difference to me is the construction.
The 5225 is bigger around and stiffer so it does not flex as mutch in the seas or wind.

The mount is stainless and holds up better than cromb plated brass.

They have a 5 year warranty instead of 2 years becuse they hold up better with less flex. You do need a Stainless mount.

When I replaced my first antenna with a 5225-XT I was shocked at the difference in the number of boats I could here and they could here me also. Both my old and new antenna were 8 foot and 6 DB gain but the 5225-XT was far better.

I am adding a second radio this year and antenna will be 5225-XP.

It has RG-8X Coax for less loss and more durabilty.

Antenna are 8 feet so shipping may be extra but shop around and a top quality antenna will be less than $380.


http://www.iboats.com/Marine-VHF-Ra...068--submit.x.21--submit.y.11--view_id.248076

http://www.iboats.com/Shakespeare-5...88742214--**********.619487068--view_id.90432

 

[ChesBayBoatMan]

Re: A couple of technical vhf antenna questions.

Thanks guys for all the information. Great stuff, and I take it all in. I am just one of those crazy people who likes to learn as much as I can before I come to a conclusion.

Dingbat

BTW: Never seen anyone hyphenate Rockfish before. Not a native I take it?

Oh no I was born and raised in Hampton. I have been on the water so long my toes are webbing together. I don't know if I hyphenated it, or the word processor wrapped it. A lot of times I will type a message in Word and cut and paste it. If you communicate with me long enough you will find out I am the worlds best creative spellar. Ha!