radio
- Thread starter wanna-be
- Start date
I'll tell you what I use and why. I put a SS ratchet handle on the top of the cabin house (putting an antenna base on the side deck, makes it even harder to get forward). I then put a 2' long 1" SS tubing, and then one of the Base lowed antennas with a 36" whip.which has the 1" x 14 threaded base:
The reason for this, is that you can easily lay this antenna down and it does not extend over the cockpit. If someone grabs it, it will not break, nor give way. These have a 3 dB gain. One might argue for the 8' 6 dB gain fiberglass antenna. It will have slightly more apparent radiated power. Probably rarely if every have any difference in signal strength. If going to the 8' antenna, I suggest that one use the "Digital" (brand)--better quality thru out. Also avoids soldering the PL 259 connector (to the radio), with the mini UHF male (allowing to go thru a ~1/4" hole in the deck or cabin top, about the same size as the cable. Although some use the "crimped on" connectors, it has been shown on many occasions that a soldered on connector gives better results, more corrosion resistance, and better reception.
Thru the deck/cabin house, there are several options--some use the mini clam shell, filled with some sealant over the ole drilled (If that hole is drilled thru a cored structure, then that should have the core routed out, and filled with epoxy, hole redialed, as is with any hole in a cored deck) Better options are either the "Cable Clam" or the "coax deck fittings", which have a rubber seal specific to the cable size (RG-58, RG-8x, or RG-213).
As for coax length--leave about 3 feet, but any more will cause a small loss of signal.
Old antennas--tend to get the "fuzzies" when the coating on the fiberglass outer layers detiorrate due to UV sun exposure. The best fix for this, is to sand the antenna lightly, and then spray it with saveral coats of white Krylon Fusion spray paint. Also broken antennas (if the wire element is not broken) can be "splinted" by heat shrink tubing. I have also made fiberglass repairs to the antennas--best to prevent with the SS whip.
The reason for this, is that you can easily lay this antenna down and it does not extend over the cockpit. If someone grabs it, it will not break, nor give way. These have a 3 dB gain. One might argue for the 8' 6 dB gain fiberglass antenna. It will have slightly more apparent radiated power. Probably rarely if every have any difference in signal strength. If going to the 8' antenna, I suggest that one use the "Digital" (brand)--better quality thru out. Also avoids soldering the PL 259 connector (to the radio), with the mini UHF male (allowing to go thru a ~1/4" hole in the deck or cabin top, about the same size as the cable. Although some use the "crimped on" connectors, it has been shown on many occasions that a soldered on connector gives better results, more corrosion resistance, and better reception.
Thru the deck/cabin house, there are several options--some use the mini clam shell, filled with some sealant over the ole drilled (If that hole is drilled thru a cored structure, then that should have the core routed out, and filled with epoxy, hole redialed, as is with any hole in a cored deck) Better options are either the "Cable Clam" or the "coax deck fittings", which have a rubber seal specific to the cable size (RG-58, RG-8x, or RG-213).
As for coax length--leave about 3 feet, but any more will cause a small loss of signal.
Old antennas--tend to get the "fuzzies" when the coating on the fiberglass outer layers detiorrate due to UV sun exposure. The best fix for this, is to sand the antenna lightly, and then spray it with saveral coats of white Krylon Fusion spray paint. Also broken antennas (if the wire element is not broken) can be "splinted" by heat shrink tubing. I have also made fiberglass repairs to the antennas--best to prevent with the SS whip.
journey on
New member
The 3 dB increase in gain between a 3' antenna and a 8' antenna represents a increase in radiated power of 2. So, an increase of twice the radiated power may be significant. Also the 8' antenna has a higher view to the horizon.
Go with the longest antenna you can use. The cost of the antenna doesn't affect performance, only sturdiness.
Boris
Go with the longest antenna you can use. The cost of the antenna doesn't affect performance, only sturdiness.
Boris
journey on
New member
Misteak
I don't disagree with Boris, and am not saying in any way he is wrong; but lets look at this in reality. Often a 6 dB gain antenna is not really 6 dB (and that is over 0 gain), nor is the 3 dB always 3dB over unity. There is a nice article here on VHF antennas.
8 foot antennas are not all equal-some have 5/8 wave, some have stacked 18" antennas, some have single wires, some use other tricks to increase the theoretical gain. Thru the years I have done a lot of testing on marine VHF antennas, since I have the antenna test gear left over from when I was helping cruising sailors install effective HF antennas for their sailboats. I find that many of the 8' antennas, only have 4 to 5 dB gain--Most of the SS tip (while they are called "36"--they are closer to 37", which is half wave for many of the VHF marine channel are close to 3 dB.
I have also measured the SWR of the antennas in the store--and found a wide variation--good to pick an antenna with the best characteristics! The SS whip can be easily tuned--not so with the 8' fiberglass enclosed wire antenna. Generally the higher the price, the better quality the antenna, and the better it will work.
OK, lets assume that we do have a 3 dB gain and 50% increase in power. Can you really tell the difference. Again, I did a lot of experimenting with HF antennas, where we measure the perceived "power" by "S" units. (I would change the ground system, or turn on a 600 watt amplifier over the 100 to 150 watts "barefoot". These are measured on a distant receiving radio, and are subjective, because there are many factors which vary from second to second--having to do with radio propagation of any signal. But it takes 6 dB gain for most people to see any difference in a signal. That means, that 3 dB gain, will not be noticed by most people. However, it certainly could mean a faint signal being heard and not being heard. There are many other factors, (loss in the coax, proximity of other antennas, the condition of the connectors, corrosion in the antenna soldering etc which can also effect the signal strength, etc). Also the higher dB, the narrower the beam put out in the horizontal plane. (Mostly figures in sailboats where there is more angle of heel, but in a rolling C Dory, there can be times when the wider "cone" of signal concentration, is going to be heard better than a narrow "cone". (See article referenced)
Without getting into too lengthy a discussion of theory, there is the other issue of range vs height. There are simple formulae, and calculators here. Lets say that the antenna base is 5 feet off the water, and both boats have the 36" whip on 2 feet of SS tubing--total height off the water is 10 feet. The range between two boats will be only 8 miles. Increase the height to 13 feet (that of the 8' fiberglass antenna), and your range only increases by one mile, to 9 miles. Lets say you are corresponding with a CG shore station, where the antenna is 1000 feet, and your antenna is 10 or 13 feet off the water. With the 36" SS whip the range will be 49 miles, and the range with the 8' fiberglass antenna, will be 50 miles. Again only one mile (using theoretical radio horizon).
So the range and power increase are not that much more--and you have an antenna which is far less likely to be broken, plus will not develop the "fuzzies".
I have used both types--and feel comfortable with either. Again, one boater's opinion.
8 foot antennas are not all equal-some have 5/8 wave, some have stacked 18" antennas, some have single wires, some use other tricks to increase the theoretical gain. Thru the years I have done a lot of testing on marine VHF antennas, since I have the antenna test gear left over from when I was helping cruising sailors install effective HF antennas for their sailboats. I find that many of the 8' antennas, only have 4 to 5 dB gain--Most of the SS tip (while they are called "36"--they are closer to 37", which is half wave for many of the VHF marine channel are close to 3 dB.
I have also measured the SWR of the antennas in the store--and found a wide variation--good to pick an antenna with the best characteristics! The SS whip can be easily tuned--not so with the 8' fiberglass enclosed wire antenna. Generally the higher the price, the better quality the antenna, and the better it will work.
OK, lets assume that we do have a 3 dB gain and 50% increase in power. Can you really tell the difference. Again, I did a lot of experimenting with HF antennas, where we measure the perceived "power" by "S" units. (I would change the ground system, or turn on a 600 watt amplifier over the 100 to 150 watts "barefoot". These are measured on a distant receiving radio, and are subjective, because there are many factors which vary from second to second--having to do with radio propagation of any signal. But it takes 6 dB gain for most people to see any difference in a signal. That means, that 3 dB gain, will not be noticed by most people. However, it certainly could mean a faint signal being heard and not being heard. There are many other factors, (loss in the coax, proximity of other antennas, the condition of the connectors, corrosion in the antenna soldering etc which can also effect the signal strength, etc). Also the higher dB, the narrower the beam put out in the horizontal plane. (Mostly figures in sailboats where there is more angle of heel, but in a rolling C Dory, there can be times when the wider "cone" of signal concentration, is going to be heard better than a narrow "cone". (See article referenced)
Without getting into too lengthy a discussion of theory, there is the other issue of range vs height. There are simple formulae, and calculators here. Lets say that the antenna base is 5 feet off the water, and both boats have the 36" whip on 2 feet of SS tubing--total height off the water is 10 feet. The range between two boats will be only 8 miles. Increase the height to 13 feet (that of the 8' fiberglass antenna), and your range only increases by one mile, to 9 miles. Lets say you are corresponding with a CG shore station, where the antenna is 1000 feet, and your antenna is 10 or 13 feet off the water. With the 36" SS whip the range will be 49 miles, and the range with the 8' fiberglass antenna, will be 50 miles. Again only one mile (using theoretical radio horizon).
So the range and power increase are not that much more--and you have an antenna which is far less likely to be broken, plus will not develop the "fuzzies".
I have used both types--and feel comfortable with either. Again, one boater's opinion.
My antenna is mounted to the roof forward of the front cabin wall. The penetrations of the roof are outside of the cabin in the brow area. Mine has a SS ratchet mount. It is backed on the bottom surface with a larger piece of starboard to distribute the loads.
My antenna has a 8' mast with a 3' whip on top (although we don't usually use the whip).
My antenna has a 8' mast with a 3' whip on top (although we don't usually use the whip).
journey on
New member
Part of my job (at one time, long ago,) was to define and maintain RF link budgets for spacecraft. That included everything from the transmitter to the receiver, everything including the fittings, lines, space loss and antennas and the tolerances. We designed for a SWR of 1,which says the line is matched to the antenna: it doesn't affect the antenna gain.
All the antennas were defined mathematically and then tested to make sure the gain and its directivity was correct. The antennas were operated at high frequency and aimed at the receiver or transmitter.
While I worked with RF systems operating at a single frequency (if I remember correctly) marine VHF operates between 156.0 and 162.025 MHz. No antenna is going to have a constant gain over that frequency, but I assume that reputable manufactures specify 6 dB minimum. Bob says he's tested them so he's better versed that I on that subject. And testing an antenna is not trivial. The 2 reputable manufactures I know of are Shakespeare and Digital Antenna.
So I'm saying that link design is complicated and antennas are only one part. Also, I'll admit that dipoles (rod) antennas weren't what we used, especially marine consumer units.
So, based on experience, here's what I'm saying: VHF radios are there primarily for emergency communication. One may talk to a buddy or get the weather report but when you're in trouble, you want to call help. And radiating +3dB more power is one way of assuring that the message is heard. Or, if receiving an emergency message, you're receiving twice the power and the signal is clearer. Your choice 3 dB or 6 dB antenna. Lower or higher power. You may not make an emergency call, but when you do, you want help.
Now for SWR, a ratio of power out the antenna versus power supplied, sort of. Digital Antenna specifies a SWR of <1.5 over the transmitted range. And they supply the co-ax cable and fitting which with the SWR was measured. So when you hook up the antenna to your radio, follow the instructions and if you're using extender cable, don't change type/size/etc.
A last thought, or two. All 6 dB antennas have the same specs, what you're buying is strength and looks. The cheapest breaks easily but has the same gain as the more expensive. And all antennas are analog, no matter what the company name is.
You're right, Bob, I'm killing time until the sun is low enough to hook up the new solar panels I've mounted.
Boris
All the antennas were defined mathematically and then tested to make sure the gain and its directivity was correct. The antennas were operated at high frequency and aimed at the receiver or transmitter.
While I worked with RF systems operating at a single frequency (if I remember correctly) marine VHF operates between 156.0 and 162.025 MHz. No antenna is going to have a constant gain over that frequency, but I assume that reputable manufactures specify 6 dB minimum. Bob says he's tested them so he's better versed that I on that subject. And testing an antenna is not trivial. The 2 reputable manufactures I know of are Shakespeare and Digital Antenna.
So I'm saying that link design is complicated and antennas are only one part. Also, I'll admit that dipoles (rod) antennas weren't what we used, especially marine consumer units.
So, based on experience, here's what I'm saying: VHF radios are there primarily for emergency communication. One may talk to a buddy or get the weather report but when you're in trouble, you want to call help. And radiating +3dB more power is one way of assuring that the message is heard. Or, if receiving an emergency message, you're receiving twice the power and the signal is clearer. Your choice 3 dB or 6 dB antenna. Lower or higher power. You may not make an emergency call, but when you do, you want help.
Now for SWR, a ratio of power out the antenna versus power supplied, sort of. Digital Antenna specifies a SWR of <1.5 over the transmitted range. And they supply the co-ax cable and fitting which with the SWR was measured. So when you hook up the antenna to your radio, follow the instructions and if you're using extender cable, don't change type/size/etc.
A last thought, or two. All 6 dB antennas have the same specs, what you're buying is strength and looks. The cheapest breaks easily but has the same gain as the more expensive. And all antennas are analog, no matter what the company name is.
You're right, Bob, I'm killing time until the sun is low enough to hook up the new solar panels I've mounted.
Boris
gulfcoast john
New member
Wanna-be,
you probably got more good advice than you can digest.
But that's what's so great about this site!
I agree with Bob that a SS whip can offer much of the performance of a thick manly 8 footer as a practical matter for most of our boating (it would look out of place on a 22). I've had one for 35 years on 11 boats (including as a backup on Cat O' Mine) and the practical difference in performance at avg hailing distances just doesn't seem as big as you'd suppose.
Marginal conditions are marginal, so stay away from them.
Happy Shopping!
John
you probably got more good advice than you can digest.
But that's what's so great about this site!
I agree with Bob that a SS whip can offer much of the performance of a thick manly 8 footer as a practical matter for most of our boating (it would look out of place on a 22). I've had one for 35 years on 11 boats (including as a backup on Cat O' Mine) and the practical difference in performance at avg hailing distances just doesn't seem as big as you'd suppose.
Marginal conditions are marginal, so stay away from them.
Happy Shopping!
John
colbysmith
Active member
You can check out various photos of my boat in it's album, and a few should show somewhat clearly where my antenna's are mounted. I have two radios, so run two antennas. Both 8' fiberglass. I also have a splitter for an AIS transmitter on one of the antenna's. That particular antenna use to be a 4' SS whip, prior to my decision to split it for a AIS transmitter. It's hard for me to tell if one is better than the other, as I run an older radio on that 8' that use to be a 4'. And rather it was the older radio or the antenna, that particular combination was weaker than my new radio with the original 8' antenna. (Just ask anyone that has cruised with me about the difference between my radios when I transmit. lol.) I like the 8' as it is higher on the boat, thus is going to have better range for that reason alone. Both antennas can be laid down either for or aft with their individual ratchet mounts. They are both mounted toward the forward part of my roof, on the side of the high top. When folded aft, they hang past the rear of the roof above the cockpit. I trailer them in this position. However, when I install the boat's cover, I have to fold the antennas down forward, and they stay inside the bow rails, basically laying on top the rail. When folded back, if I don't keep them raised just a bit, I do have a problem running into them when climbing into my boat. In any case, the installation has worked out fine for me. Colby
Unfortunately I have done "post mortums" on several marine VHF antennas--ones I have broken by accident along the way--some long before I had a C Dory. I first started working with Marine VHF in 1965. This is the year that the USA spectrum was finalized and Standard Horizon brought out their first 3 channel crystal controlled marine VHF. Before that the ship's radios were AM, and on most sailboats used the backstay, and some dubious ground system (where often the biggest problems were). The VHF was a huge improvement! I bought one for my father's boat.
Although probably the best known Marine VHF radio company for small boats is Shakespeare, Digital has been known for somewhat better quality. (As Boris points out Digital is the name, nothing to do with the "type" of antenna, which are indeed analogue.) I have used several Metz antennas in my boats, and they are a higher quality than Shakespeare. Comrad, Glomex and Morad are used more on commercial vessels, larger ships and large yachts. These are high quality antennas. There are at least 2 dozen other manufacturers of Marine antennas, including what appears to be a number of new comers--probably made in China
There is an interesting treatise on Marine VHF spectrum my NMEA in 2010:
http://www.nmea.org/Assets/nmea_vhf_history2009.pdf
The spectrum is located between 156.0500 to.162.0125 (AIS 2) (plus weather channels 162.400 to 162.550. (There are also several land mobile users in this same band spread.)
I am not aware of any VHF marine radio antenna which can be used with or with out a "stinger". (The whip referred to by ssobol,) When a piece of wire--(the stinger) is removed or added, it will change the resonance frequency. Even moving the "stinger" up or down a few mm will change the resonant frequency, and where the lowest (best) SWR is loacated. This is why the base loaded antennas are supplied with a small wrench, and need to be "tuned" for each installation... It is possible that a signal is being sent out by the radio, and thus transmitted buy the antenna, but with a higher SWR--still audible for a short distance. But when the antenna is properly tuned, then the optimal signal is sent. The modern VHF radio has a protective circuit to protect the final output diodes, and will decrease the power if the SWR is high. For example, where the radio might be radiating most of its 25 watts, with a properly tuned antenna, if the SWR is high, it may only be putting out a few watts. (Which is fine for many distances). Remember that we send signals many thousands of miles in space with very low power radios.
No argument that one wants to have the best output possible. But as Boris, notes, there are many factors, and they all have to be working well.
One other comment: occasionally you will see a boat with a VHF antenna at an angle--"Looks good sloped back". The problem is that with the higher gain the antenna, the more that the "lobes" of transmission, will be either going right into the water, or off into the troposphere. --and a marked decreased range!
In November 1983, we were at Norfolk, VA. on board our boat. I was stuck in the bunk, because of back surgery, and had obtained a 2 meter hand held radio to help pass the time. I was in touch with other hams in Norfolk, and someone decided it was going to be a great idea to contact the space shuttle from a sailboat. They brought a very specially made 2 meter (145.550 mhz) antenna tracking from the aft deck, to see if we could make a contact with Space Lab I. I did make contact with W5LFL Owen Garriott, aboard aboard STS-9 (Space Lab 1) with 5 watts of power. Even got a write up in the local newspaper.
Although probably the best known Marine VHF radio company for small boats is Shakespeare, Digital has been known for somewhat better quality. (As Boris points out Digital is the name, nothing to do with the "type" of antenna, which are indeed analogue.) I have used several Metz antennas in my boats, and they are a higher quality than Shakespeare. Comrad, Glomex and Morad are used more on commercial vessels, larger ships and large yachts. These are high quality antennas. There are at least 2 dozen other manufacturers of Marine antennas, including what appears to be a number of new comers--probably made in China
There is an interesting treatise on Marine VHF spectrum my NMEA in 2010:
http://www.nmea.org/Assets/nmea_vhf_history2009.pdf
The spectrum is located between 156.0500 to.162.0125 (AIS 2) (plus weather channels 162.400 to 162.550. (There are also several land mobile users in this same band spread.)
I am not aware of any VHF marine radio antenna which can be used with or with out a "stinger". (The whip referred to by ssobol,) When a piece of wire--(the stinger) is removed or added, it will change the resonance frequency. Even moving the "stinger" up or down a few mm will change the resonant frequency, and where the lowest (best) SWR is loacated. This is why the base loaded antennas are supplied with a small wrench, and need to be "tuned" for each installation... It is possible that a signal is being sent out by the radio, and thus transmitted buy the antenna, but with a higher SWR--still audible for a short distance. But when the antenna is properly tuned, then the optimal signal is sent. The modern VHF radio has a protective circuit to protect the final output diodes, and will decrease the power if the SWR is high. For example, where the radio might be radiating most of its 25 watts, with a properly tuned antenna, if the SWR is high, it may only be putting out a few watts. (Which is fine for many distances). Remember that we send signals many thousands of miles in space with very low power radios.
No argument that one wants to have the best output possible. But as Boris, notes, there are many factors, and they all have to be working well.
One other comment: occasionally you will see a boat with a VHF antenna at an angle--"Looks good sloped back". The problem is that with the higher gain the antenna, the more that the "lobes" of transmission, will be either going right into the water, or off into the troposphere. --and a marked decreased range!
In November 1983, we were at Norfolk, VA. on board our boat. I was stuck in the bunk, because of back surgery, and had obtained a 2 meter hand held radio to help pass the time. I was in touch with other hams in Norfolk, and someone decided it was going to be a great idea to contact the space shuttle from a sailboat. They brought a very specially made 2 meter (145.550 mhz) antenna tracking from the aft deck, to see if we could make a contact with Space Lab I. I did make contact with W5LFL Owen Garriott, aboard aboard STS-9 (Space Lab 1) with 5 watts of power. Even got a write up in the local newspaper.
Barry Rietz
New member
When installing any transceiver, especially mobile, I find that if you really want an optimal signal out, you need to begin with an antenna analyzer.
Then try to obtain as close to "unity" as possible by adjusting length of feedline coax, length of antenna, size of counterpoise, and location of the radiator (antenna). And perform all of the foregoing well away from large obstacles, especially metal ones.
Then try to obtain as close to "unity" as possible by adjusting length of feedline coax, length of antenna, size of counterpoise, and location of the radiator (antenna). And perform all of the foregoing well away from large obstacles, especially metal ones.
Barry, Do you mean an antenna analyzed such as the MFJ 259/269 ($250 to $350) or just a plain SWR meter for VHF? A simple MFJ-812B is 120 mhz to 220 mhz is available for less than $40. Shakespeare makes one for a little over $100. .
Do not use a CB or HF SWR meter!
The only marine VHF antennas which are adjustable are the 36" to 38" base loaded whips, as I described in my first post. The length of the lead will not change the SWR in any of these. Counter poise is not a factor in the marine VHF we have any control over with the antennas made for fiberglass boats.
A lot of these factors are definitely important for HF antennas, but we just don't have that much control over the simple marine VHF (especially the enclosed fiberglass with wire inside)
True one should install any of the VHF antennas at least 3 feet from another VHF antenna, or other large metal structure (in the same plane).
Do not use a CB or HF SWR meter!
The only marine VHF antennas which are adjustable are the 36" to 38" base loaded whips, as I described in my first post. The length of the lead will not change the SWR in any of these. Counter poise is not a factor in the marine VHF we have any control over with the antennas made for fiberglass boats.
A lot of these factors are definitely important for HF antennas, but we just don't have that much control over the simple marine VHF (especially the enclosed fiberglass with wire inside)
True one should install any of the VHF antennas at least 3 feet from another VHF antenna, or other large metal structure (in the same plane).
NancyandBud
New member
wanna-be
Not mentioned is most modern VHV marine radios have a hi and low power switch. When you are chatting in the harbor with your friends, you don't need hi power.
Not mentioned is most modern VHV marine radios have a hi and low power switch. When you are chatting in the harbor with your friends, you don't need hi power.
Barry Rietz
New member
Sorry for the delay, I was not watching for followup on this subject. The MFJ model #266-C is an anylizer that will do what was mentioned in my previous posting. One feature that it has is the ability to generate its own signal on any given frequency thereby eliminating the need to transmit on the radio itself. This provides the ability to make adjustments of the various components between the transmitter and antenna until the optimal radiation pattern, SWR, unity, and current is established. The "266-C" can be used on high frequency, very high frequency, and super high frequencies all in one model. Its costly at $350.00 but is an essential tool for anyone who desires to achieve ultimate performance from their transmitter. Any C-Brat that is uncertain about what they are doing would do well to confer with one of their local amateur radio operators for assistance.