Antenna Help...Pinging 1Mainiaic...

[usmcpaul]

Mainiac, I am going to buy an antenna for my radio in the next few days or and I need some advice on what to get and you sound like the man to ask. I thought about PM'ing you, but figured it would make a nice informative thread to help clear up some things I have been reading about radios and antennas.

Firstly I am not a radio'holic and have very little/no hands on experience with VHF radios. I am not name brand biased, as long as it works and I can afford it, I am good, so please lets not turn this into a manufacturer bashing thread. I am not trying to contact Martians, but would like the best performance I could reasonably get.

With that being said, I already have a gently used, Uniden Oceanus that I want to install and my boat has a cracked Shakespeare 8 foot antenna that needs replacing with a stainless steel adjustable base that still looks good.

I know there are a ton of variable when it comes to antennas, but I would like to narrow it down a bit.

What are the most important things to consider when buying and mounting it? Currently the antenna base is located only about 3-4 feet from the radio and I have heard this is a no-no? Secondly, do I need to have my radio 'tuned' to the antenna. If so, who or how, would be able to do it well? As far as grounding, what should I do to make sure the radio and antenna are ground properly(i.e. ground directly to battery?) should I coil the antenna wire or cut and splice it to make a straight run to the radio?

With a limited budget, I would like to make a correct, educated guess the first time.

Thanks, Paul

[1mainiac]

Well most would know from reading my posts in the past I am not much of a Shakespere fan however from the Galaxy line up they are actually decent antennas I have one I don't personally care for it because I know several things I would have done to improve it before production that is just me. You cannot tune a Marine VHF antenna this is one of the things that bugs me there are some tricks you can use to fool the radio into thinking the antenna is better than it is but no need for that stuff. Some of these things are built into cheaper antennas. Distance between radio and antenna does not matter having as much of the antenna completely above your boat will make a difference the higher you can get it the better. If you have a rocket launcher put the antenna up there as well. Makes sure all large peices of metal are grounded as the antenna can couple with them yep rocket launcher included. The better everthing on the boat is grounded the less issues you will have. The shortest possible length of coax is best not less than 19in no kinks or tight bends. Use a quality coax connector solder it on have someoone else do it if you are not comfortable doing it. Part of my issue with my current setup is I have a antenna analyzer and know a lot about antennas so when I mapped out my SWR curve I went yuk then I started doing some other tests and was further disappointed. Still I have many friends who would be proud to have a radio that works as well as mine does. One last thing once everything is pretty much installed there is a ground lug on the chassis of your radio run a ground wire from there to your lower unit or motor so that it is grounded to the water. The best setup would be like they used to do for LORAN which was mount a couple of grounding blocks on the transom below the water line but pretty much anything you do to improve the radio to water ground will make a difference. On the power side of the radio make sure you run the shortest possible 12v power wires to the radio to reduce any interference. A clean well layed out and thought out installition will keep you safe and happy for many years. Get the best you can afford and install it correctly you will be happy with it I tend to overthink some of this stuff which can be confusing to others.

[usmcpaul]

Thanks man. Next week I plan on getting the boat set up/rigged, and your help is greatly appreciated.

So is there anything to the gain differences that are advertised? ( 3,6,9 db. gain) Or is that all marketing B.S.? For example I just Googled a site that advertised an antenna that said:

* Powerful brass radiators

* Soldered connections

* Power directing ferrite choke bead

* High gloss urethane finish

* 316 stainless steel ferrule

* 6dB gain

The only thing I really understand is the welding/machining properties of 316 stainless steel, other than that, they may as well have told me that my "Flux capacitor is rated at 13,000 Jiga-watts" ( from "Back to the Future" circa 1986)

Is there a "standard" or some type of placard/data card on my radio that states what I should look for when buying an antenna?

P.S. I am not trying to put you on the spot, nor am I asking for a specific model number, but am I asking for some unbiased advice on the "general qualitys" to look for, just because I think your advice is better than the advice from some 19 year old, zit faced, high school kid, posing as an expert. LOL (no offense to 19 year old, zit faced, high school kids posing as experts)

[Paulywood]

Paul,

I don't pretend to know anything about radio's or antenna's but this is the antenna that I use and I have installed on a few friends' boats. I have had days where I have been able to talk to people up to 20 miles away. All of the people I know who have them have been very happy with the performance. And they are actually economical. Check 'em out:

http://www.westmarine.com/webapp/wcs/stores/servlet/producte/10001/-1/10001/223411/377%20710%201407/0/Antennas,%20Mounts,%20Cable/Primary%20Search/mode%20matchallpartial/0/0?N=377%20710%201407&Ne=0&Ntt=Antennas,%20Mounts,%20Cable&Ntx=mode%20matchallpartial&page=CategoryDisplayLevel1&isLTokenURL=true&storeNum=5003&subdeptNum=3&classNum=309

[1mainiac]

Paul in simple terms 3db is twice as loud my issue is they all us computer modeling references such as dbi rather than real world references such as dbd. dbd gain is gain acheived versus a real antenna which is a half wave dipole this is something you can actually build and use to compare signal strength. Antennas can be designed to amplify the signal output so to speak this happens because as the antenna becomes physically larger it has more surface area to radiate signal this creates multiple lobes of signal coming from the antenna at the point where the most of these lobes concentrate you get the maximum signal which can be much higher than the actual signal input to the antenna this is considered gain. Since most antenna manufactures use dbi figures which is comparing against something that does not exist they can actually give gain figures to antenna designs that produce negative gains in real world tests. The final real number is ERP effective radiated power so lets say a antenna has 0 db gain and the radio puts out 25 watts then the ERP should be 25 watts if it had 3db gain the ERP would be 50 watts at 6db gain it would have a ERP of 100 watts and at 9 db gain the ERP would be 200 watts. This is where I me and my Shakespear antenna went seperate ways as it claims 9db gain however doing actual field strength tests with a friend of mines meters at 25 watts it could not out preform our 1/4 wave test antenna at 5 watts. But no matter what it still works and had I not done this testing I probably would be darn proud of it. I guess since I know you have raced it is kinda like buying a new race pipe that advertised big gains and you put it on and it seems to work great than you get a chance to actually dyno the bike and find it is actually putting out less than stock power. As far as your radio is concerned all it will care about is SWR which in this case is Standing Wave Ratio ideally it would be 1 to 1 meaning every electron goes out and is transmited this seldom happens and would only be possible on 1 channel because as you change freq the wavelength changes which will effect SWR. As SWR increases it restricts output and bounces it back to the amplifier making it work harder and creating heat when SWR reachs 2 to 1 it begins to seriously effect performance at 3 to 1 it will damage the final output transistors which can blow up the radio. Many radios have a ant warning light that will come on above a 2 to1 swr nearly all modern radios begin gain reduction at a 2 to 1 swr this means it reduces output power to prevent overheating the final output transistors. WHile I have spent a lot of time pointing out all the new cool things on our radios the antenna is the most important componet.

[usmcpaul]

Jim, I don't pretend to understand all of the above, however it makes me feel better to know a little something more. Thanks for taking the time to explain it.

Nick thanks for the link, I will order one today when I get home.

[1mainiac]

I can personally vouch for Nick's radio I have talked to him from at least 15 to 20 miles away on a couple ocassions. I don't remember off the top of my head which Shakespear I have but it was on sale for 99 bucks when I bought it. One thing I wil do this year is add a 2 ft extension to get my antenna above my boat having as much antenna in clear space helps eliminate dead spots. I had a 8 ft ant on my 18ft boat taller is better bumper stickers should be issued.

[GLF]

Very informative posts Jim. Nice job!

[1mainiac]

Thanks Mike I have to keep trying to simplfy what I say As even I don't want to get out my Scientific calculator and work on this stuff I just want to fish. I am pretty sure no one wants to hear me discuss velocity factor of differant coax or any of the other stuff that goes along with this. But hey we can all get out our calculators and turn to page 235 of the ARRL antenna handbook LOL ( I have the book but off hand have no idea what is on that page LOL ). But some days it is amazing what I can still pull out of the non pickled portions of my brain.

[Priority1]

I think Jim must have been an old HAM bone. He talks the talk, and walks the walk.

[1mainiac]

pretty much Frank still am a Ham love my radios all winter but they collect dust in the summer when the weather and work let me fish.

[Yoda]

Jim

What marine antenna do you feel is worth the money spent , or bang for your buck..

[1mainiac]

Shakespear Galaxy 5225 XT for a Shakespear is a good antenna. and worth the money spent however bang for your buck you would likely go to a Mariner 8700XT West Marine sells. Try and keep in mind the average guy does not care much about his radio performance till it don't work and many only want a radio to meet Coast Guard requirements this is fine and remember there is no competition to own the best. I have no dog in the hunt for your money I just want people to understand a bit what happens when you push the mic button and how to get more use out of a radio you invested money into. And God forbid the day comes you need the radio to save your life I want it to work and work well.