Best antennae for vHF Reception-Only

[solanderi]

I want to be able to monitor local vhf traffic from a home station and while I understand that a key factor will be height of the antennae, my question is about "Gain" and its relationship to the quality of reception.

Should I spend any extra dollars on a high gain antennae for a "listen-only" application. Also, is there any other antennae designs better than a conventional whip for this problem. Next, the tallest thing in my yard is a palm tree, is that a suitable vhf mount ? Lastly, I am sure that the resistance in the coax cable must limit the length of the cable run, any thoughts or equations for that. Thank you

 

[ThirdHatt]

Use a 9db gain antenna for maximum range. It will be perfect because mounted on land it will not pitch and roll as on a boat. Many boats use a 6db antenna for good range and reception allowing for moderate pitch and roll. Most sailboats and small boats use a 3db antenna for great coverage with somewhat less range but the antenna position is not nearly as important.

Mount it as high as possible with the shortest cable run possible.

 

[Passages]

I believe it is illegal to transmit VHF except from a waterborne vessel. Might want to check the rules.

If you are only going to receive, then gain is less important as it addresses an antennae's focus angle of radiated energy.

 

[ThirdHatt]

I believe it is illegal to transmit VHF except from a waterborne vessel. Might want to check the rules.

If you are only going to receive, then gain is less important as it addresses an antennae's focus angle of radiated energy.

That is true that it is illegal (FCC) to transmit from land, but marina's do it all the time. He doesn't plan to transmit, just listen but high gain works on receive and transmit as I understand it. For just local vhf traffic, a 3 or 6db will be fine but if you want max range, high gain is best. 6db is the best all-around antenna, and that is what most of our boats run.

 

[Boss Lady]

The whip is an omni-directional antenna, some vertical antenna designs can provide some gain over a standard 1/4 wave whip. Marine band VHF transmission and reception is a function of line of sight (LOS), versus ground wave. The normal radio horizon is 5-7 miles depending upon ground clutter and terrain. If you have your antenna at ground level and the other station is at ground level this is about the range you can expect. If you have your antenna at 35 feet and the other station is at ground level you can expect to double that range to 14-15 miles. You have to double your tower height to 70 feet to get the next 7 miles. This is due to the curvature of the earth. Of course larger boats will have their antennas higher than ground level. Height works to your advantage in a LOS application. There is some ground wave component to VHF especially over sea water, but this is a function of RF power to overcome the attentuation of the signal as it passes along the surface. You can also use antenna designs with more gain and signal amplifiers to improve performance of weak signals. However, the curvature of the earth can only be overcome by antenna heights above ground. If you have a 100 foot tower you can expect to receive signals from small craft out to 30-40 miles, and large vessels much farther.

Most common coax will have about 3db of loss per hundred feet of length at VHF frequencies, a good low loss coax is Belden 9913, this is an air core coax used by Ham radio operators and is easy to find.

 

[Jaxfishgyd]

While it is "illegal" to use a VHF from a house, I know of many folks who do.
I had one back when I lived on land so we could hear from the boats offshore and get an actual update on the water conditions.
It saved me many a day when I really wanted to go fishing and it was too nasty, despite what the "young thing" on TV was saying.
On the other hand, there were days I got to go as this same "young thing" said it was snotty offshore and it was actually flat seas.
And back in the 70'-80's before cell phones, I could call The Admiral and let her know when I was about to dock...

 

[Boss Lady]

In order to transmit legally from shore you need a marine utility license . This license is really restricted to those who provide a service to ships or control over a waterway or bridge, and marinas who have a bonifide need to communicate with ships. The FCC form is #605. You may be able to obtain a shore license if you have a water connected business that would pass scrutiny. There are license fees too.

 

[Trojan]

Boss Lady pretty much covered the restrictions of the band. His distance coverage was quite stingy though. A 2 meter 1/4 wave vertical antenna is just under 18 inches tall. This is a very small capture area. If you can afford the money by all means get the antenna which provides the most gain. Get it as high as you can in the air and use the best coax you can find. 9913 is a good grade, but hard to work with. It does not like sharp turns. RG-213 is a good coax. Radio scrap coax is junk. Most marine antennas come equipped with PL 259 connectors along with your radio. A better connection would be an ( N- connector ) at the antenna splice. This connector is water proof and military grade. A PL-259 is hard to water proof, creates an impedance bump and quite Lossy at this frequency. N connectors are the only connector I use out of doors. A high gain antenna mounted 50 ft up can easily receive 70 miles or more depending on the transmitting station and terrain. Keep the antenna away from all buildings and above the trees. The cable guy and cable x are 2 places that sell coax on the Internet. Buying the best at this frequency pays off. I have thousands of feet of coax strung out in my yard. I have 16 cables entering my home from 7 towers and 16+ antennas. When it comes to VHF reception purchase the best cable, the best connectors, the highest gain antenna you can find and get it as high in the air that you can. And keep your cable runs as short as possible. Don'T coil the left over coax under your bench. Cut it off. Keep the runs short.

BILL

 

[Boss Lady]

i agree with Bill on the coax. I tend to be conservative about transmit/receive ranges with specifically talking about the antennas selected and the installed height. That way people don't think that they can just throw up some garbage antenna and talk great distances. Bill you have a lot of experience unlike most and without some technical assistance most people wind up disappointed when they buy the wrong equipment. I am sure that either you or I could make some sound recommendations if asked as to which model antennas would provide the desired results. I try to keep things simple in the beginning, and use general concepts to help keep people on the right path.

1. Get the antenna as high as feasible.
2. With a LOS system you reach a point where more power accomplishes nothing.
3. Proper installation including weather proofing is paramount (you can defeat the value of having good equipment and the right antennas.
4. Bill is right on the money about using N Type connectors, and RG213 is acceptable for runs under 100 feet.
5. Get the antenna as high as you can afford (repeat)

LOL

 

[solanderi]

Thank you for the thoughtful replies.

So the high gain antennaes have better reception as well as transmission capability ? Any takers on the palm tree antennae mount or is that just a lightening rod for that tree ? BTW, what about lightening strikes ?

 

[Boss Lady]

For lightning protection look at these. The go inline between the antenna and the radio, you need to put in a ground stake. The closer to the antenna the better since electricity takes the path of least resistance.

http://www.iceradioprodhttp://www.iceradioproducts.com/impulse1.htmlucts.com/impulse1.html

Bill, feel free to jump in here as well.

Chris

 

[Trojan]

Run your cable ALL the way to the ground. Make a short 90 degree bend without kinking the cable and run it into the house. You can bury the cable if you like. The reason for the 90 degree bend at the ground is that lightning does not like to take turns. The greater part of the strike will flash off the cable at the bend and go to the ground at the turn. During storms disconnect the cable from your radio and let it hang. I have a 3/4 X 3' X 3' wood panel mounted vertical on a wall inside the house that has 2 aluminum strips 1/2 X 2" X 2' mounted on edge and separate by 12". The lower strip has slots that retain the cables when hanging down on one side. The other is drilled and tapped for a 2" long feedthrough. This strip is grounded with a heavy ground wire and a ground rod out side. Input cables from the antennas are attach to the feedthrough on top. Feeds from the radios and transmitters are attached to the other side of the feedthrough for operation. During a storm or if I'm gone out. I unscrew the coax from the feedthrough on the bottom and slide them apart and let the coax hang from the slotted strip by the PL259 separated by about a foot. The feedthroughs and slots are in line to one another. Having so many coax cables entering the house I have to capture the loose cables and keep them in line so I don't connect the wrong antenna to a transmitter or receiver. So far in 32 years I have never had lightning enter the house through my cables. I have had antennas on the towers blown up and tossed 300 ft from the towers they were mounted on, but no lightning has ever entered the house. Except on the phone line. I lost 2 computers and 8 arresters in one week on the phone line. I hope this gives you some ideas.

BILL

 

[krush]

Holy nerd talk.

 

[garyd]

Once at the marina lightning hit the VHF antenna on the building. We didn't know what happened. We went outside under the over hang to look around. It appeared as if it was snowing. A bunch of small white flakes. We eventually saw the wire from the antenna on the roof as we ventured out and relized the small flakes of white was the only thing left of the fiberglass shapspeare antenna mast.

garyd

 

[Boss Lady]

When I was stationed in the Panama' Canal Zone we built a log periodic full wave loop array which we suspended between four telephone poles. It looked like a giant spider's web. It got hit by lightning and vaporized. The coax ran along the eves of the building and it actually blew chunks of concrete off the building everywhere the coax touched the building. There was a guy standing directly under the antenna when the bolt of lighting hit. He was one lucky guy, but he did have to clean out his pants. lol

 

[solanderi]

Hi HOF,

Thank you for the excellent technical advice and safety info. Which antennae and from whom would you purchase it. I definitely only want to buy the right one once. Of course it looks like a minimum of 20 ft height and at least 9db.

Greg

 

[Bugsy]

"Boss Lady" and/or "Trojan"..

I've been following the exchange with interest though admittedly limited comprehension.

Some time ago, I asked about replacing the cable from my Shakespeare and I saved the responses, intending to make the recommended purchases before Spring launch.

I plan on putting a "mini-connector" at the antenna to "splice" the new cable to the cable within the antenna. Is there such a thing as a "N" mini-connector?

SuperX RG-8 cable was recommended on this forum. Is RG-213 better?

I will run directly from the mini-connector "splice" minimizing (as I am told) the power loss. I thought I required a PL259 to plug into the VHF radio. Does the "N' connector to which you guys refer replace the PL-259 for this purpose also?

Finally----how difficult is it to PROPERLY put the connectors onto the cable and is there a particular tool that I should borrow or buy similar to that used to put on home entertainment coax?

Thanks.

Bugsy.

 

[Trojan]

"Boss Lady" and/or "Trojan"..

I've been following the exchange with interest though admittedly limited comprehension.

Some time ago, I asked about replacing the cable from my Shakespeare and I saved the responses, intending to make the recommended purchases before Spring launch.

I plan on putting a "mini-connector" at the antenna to "splice" the new cable to the cable within the antenna. Is there such a thing as a "N" mini-connector?

SuperX RG-8 cable was recommended on this forum. Is RG-213 better?

I will run directly from the mini-connector "splice" minimizing (as I am told) the power loss. I thought I required a PL259 to plug into the VHF radio. Does the "N' connector to which you guys refer replace the PL-259 for this purpose also?

Finally----how difficult is it to PROPERLY put the connectors onto the cable and is there a particular tool that I should borrow or buy similar to that used to put on home entertainment coax?

Thanks.

Bugsy.

Trying to splice the antenna cable at the antenna is a real bear. If you have the room you could use an N connector. N's are hard to find and expensive. At the antenna is the worst place to splice it. Not the best, but a PL 259, a barrel connector and another PL259 is the next best. You will need a reducer for the smaller coax. BUT they must be soldered properly. The radio comes with an SO232. Without major changes you will have to use what comes with the radio. So the only way to improve your reception is by purchasing the better coax and the better antenna. The rule of thumb is the more wire or the denser the crosshatch shield wire is the better the coax is. Some of the cheaper vhf coax is a little wire with aluminum wrapped around the dielectric and center wire. Not good. If you can help it. Purchase coax with a stranded center wire and 80% or better shield wire. You will need to get a book to see how to solder the ends on. Don't buy any connectors from Rotten Shack they are a very poor quality for vhf. Remember they must be soldered properly. and properly waterproofed. Once water enters the cable its scrap. I don't think I could do justice trying to explain the correct way to put the ends on. I could show you. There is no special tool just a proper way to do it. It's not hard. I hope this helps you.

BILL

PS Don't use any mini-connectors there junk.

 

[solanderi]

Hi Bill,

There is someone offering this shakespear to me for about 160 dollars nib. The blurb below is from the Shakespear ad. What do you think regarding my "reception only" setup. Does the cable that comes with it need to be changed out. How about the fact that it is a 2 piece ? Thank you for any help.

Greg

Shakespear Galaxy Model 5309. This design invokes all the antenna engineers' tricks to produce the clearest possible transmission and reception over the longest range. 9 dB is substantial signal gain. This is the longest range Galaxy we sell. Phased 1/2 wave elements in a collinear array with a band-spread matching sleeve and a choking stub to suppress cable radiation. Sturdy urethane finish. Antenna mount not included.

Application: VHF - longest range
Gain: 9 dB
Length: 23' (two sections- base 172", tip 105")
Material: Fiberglass
Elements: Brass and copper
Base Type: Stainless steel ferrule with standard 1"-14 thread
Lead: 20' RG-8X coax with PL-259 connector (supplied but not installed)
Warranty: Five years

 

[Trojan]

A little over hyped on the advertising, but it should do a good job. 8X coax is the newest coax in miniature coax. About 10 years old. Works well on boats and short runs. Good stuff. 20 feet is not to long. If you are going to lengthen the run you need to add the bigger diameter coax for the rest of the run. I think that antenna uses all brass parts and silver solder on the construction inside. The cheaper antennas just use a modified coaxial 5/8 wave J-pole configuration. It works for short hauls, but is not top shelf.

BILL