Question for the Ham Radio guys..?

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Feb 6, 1998
11,711
Canadian Sailcraft 36T Casco Bay, ME
I am thinking about adding a cell phone amplifier to our boat as many areas have a weak signal that often drops. This was very frustrating Sat night when we were trying to communicate with our dog/house sitter. With a booster I could likely be able to get a call out?

My questions is one I can't seem to find a solid answer to. Can I use my VHF antenna with a cell phone or a cell phone booster? I know they operate on different frequencies but is it possible to get "some" gain from utilizing my VHF antenna 60 feet off the water?

It seems all these systems require a dedicated cell antenna, which makes sense, but would they work at all with a VHF antenna? I have a Metz antenna now... Considering a Wilson amplifier..

Not being a Ham or radio type guy I know enough to be dangerous but don't know if a VHF won't work at all or will work slightly better and no antenna at all..?..
 
Sep 25, 2008
7,463
Alden 50 Sarasota, Florida
Probably not a good option as the mismatch will cause loss (commonly measured as SWR) which could equate to or exceed the normal loss along the coax length resulting in an effective radiated power (ERP) less than the phone itself and could be bad enough to negate any apparent height advantage. There is no way to predict short of modeling the system. To make it more convoluted, all VHF antennas are not loaded similarly which means they are fed and impedance matched differently. These variables can effect the performance of an antenna on a non-resonant frequency in an unpredictable way.

Short answer - you could try it - the only thing you could lose by trying is the cell phone amp by feeding it into a mismatch. If it passes the smoke test, it might work.
 
Feb 6, 1998
11,711
Canadian Sailcraft 36T Casco Bay, ME
Don,

What are your thoughts on the amplifiers? Are they all they are cracked up to be? I don't mind spending the money but also want to get what I pay for. I just don't want to run a second RG-213 / LMR400 type cable to the top of my mast if I don't have to..

P.S. Did you happen to get my PM about the Alden?
 

RAD

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Jun 3, 2004
2,330
Catalina 30 Bay Shore, N.Y.
Many years ago when Nextel was very popular there was an area that had terrible service and one of my customers who needed to talk from his office bought an amp and antenna and it worked some what better so I said lets run a coax up the side of the building temporary and hook the antenna to that and it worked real well.....that coax got tie wrapped to a down spout and stayed there for three years till he moved.
buy an amp and try sending it up a halyard as a test
 
Sep 25, 2008
7,463
Alden 50 Sarasota, Florida
I would agree with Rad. Everyone I know who has tried one has noticed an improvement albeit not as great as they might have thought so as long as you don't expect miracles, I'd suggest you go for it, the more powerful, the better for obvious reasons. Just make sure of one thing - that it is "SWR protected" so you don't blow it.

Did get your message. Great boat but sails like a barn door.
 
Feb 6, 1998
11,711
Canadian Sailcraft 36T Casco Bay, ME
I would agree with Rad. Everyone I know who has tried one has noticed an improvement albeit not as great as they might have thought so as long as you don't expect miracles, I'd suggest you go for it, the more powerful, the better for obvious reasons. Just make sure of one thing - that it is "SWR protected" so you don't blow it.
What does SWR protected mean? From the research I've done it seems Wilson is a fairly reputable company. Would something like SWR protected be in the specs?

Did get your message. Great boat but sails like a barn door.
Yeah those Alden's like wind. I used to sail on one out of Little Harbor NH. Gorgeous boat with a teak & ash interior. Sailed like a dream in 18+ and well trimmed/reefed in 35-40 felt like 15-18 on lesser boats....:) So are you a two boat family now? Did you sell the Hunter?
 
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
A couple of options

First, the VHF antenna is tuned for 160ish MHz, your phone antenna is tuned for 800ish Mhz. MIGHT work on receive but certainly not on transmit. Since your cell is constantly "pinging" the cell towers it needs to transmit before it can receive. Conclusion, you can't use your VHF antenna to extend your cell phone range. The losses in the coax would be horendus too.

You can use a dedicated full wave antenna and/or pre-amp. The problem with that is figuring out how to get the signal to the phone. I have not looked into this but the principal is sound. Given you are transmitting over water you should be able to get at least LOS ranges with a 60ish foot tower on the other end.

You can use a directional antenna (yagi) but again the problem is getting the signal to the phone. This is also limited to LOS but your signal will get there with a yagi antenna. If you can find an external antenna "jack" then making a yagi is pretty simple. you do have to mount it on a stick and point is toward the cell tower which may take some practice.

You can use your VHF to do a phone patch. This is just calling the phone operator on the appropriate VHF freq (usually in the 70s). This capability used to be very common but has become spotty in recent years.

You can do the phone patch over a ham radio pretty easily but there are some prerequisets the primary being you have to be a Ham and you have to have a phone tone generator. The range is measured in hundered or thousands of miles though.

You can do a phone patch on a marine SSB radio also. This is much more common than on VHF and the ranges are longer. Course you need a marine SSB radio and associated antenna.

You can use a satcom phone

A not so cool option is to get ahold of someone ashore on the VHF and have them relay the info.

There are several other "email over RF" solutions but these requre a marine SSB/HAM radio, computer, TCN and antenna.
 
Sep 25, 2008
1,096
CS 30 Toronto
No cell over water

The cell phone carriers don't want to invest capital money to provide service over open water. Not just the high cost of equipment. They have to pay for the spectrum. From a business point of view, there isn't enough revenue to offset the cost. They are not charity.

Cell tower antennas are very directional. You can see them on cell towers. They are essentially phase array emitters that can even be "steered" electronically. A cell tower eithe has 3 sides (rural) or 6 sides (urban). They certainly won't put an antenna facing the water side. Cell frequency are either 800ish mHz or 3ish GHz. The handset antennas are very tiny.

There are repeaters on the market. For example
zBoost YX 510 Dual Band Cell Phone Signal Booster


Essentially it receive signal and retransmit to your device. The head antenna must be at least 16 feet above to avoid interferrence. But you have to have signal to start with.

Don't waste your money. I can't even get good cell coverage at my slip. Maximum 1 bar.

The alternative but somewhat limited solution is WiFi internet. A lot of marina and YC provide paid or free WiFi service. With a high gain antenna, you can get good coverage. Skype is a phone service over Internet. Skype has a handset so you don't need a PC to make phone calls. Just a wireless router (external antenna) and a Skype base station.
 
Sep 25, 2008
615
Morgan 415 Out Island Rogersville, AL
At 800 Mhz an antenna can be small but still be "electrically" big.

Have you considered putting an antenna on top of a shakespear fiberglass rod mounted to your stern rail. If you mount your amp just under the deck where the coax comes in then you will be minimizing coax losses.

If you get an amp with an automatic antenna tuner (don't know it there is such a thing or if it is common) then you could use an insulated stay as an antenna (but beware of lightning ;-).
 
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
800 MHz and 1.3 GHz antennas

For the record
Freq * wavelength = speed of light = C
or more usefully
wavelength = C/freq

For an 800 MHz frequency the resonate length is:
3X10^8/800X10^6 = 0.375 meters or about a foot. Your antenna is about half of that for a 1/2 wave and, more commonly, about a 1/4 of a foot for a 1/4 wave antenna. That would mean a 1/4 of a foot or 3 inches which fits nicely into a cell phone.

Using a MUCH longer antenna, like a backstay, will not imporve reception as you also have to transmit on the same antenna to establish the link in the first place. While reception would most likely work transmitting with a very low (< 1 watt) transmitter into that kind of mismatch would be folly.
 
Feb 17, 2006
5,274
Lancer 27PS MCB Camp Pendleton KF6BL
And for the record, that is c, not C. "C" is for Celsius, "c" is for the speed of light. :)

Maine, you know it might be easier for you to just study for the Technician license and get a 2 meter transceiver. I am sure you have phone patch repeaters in your area. You can check with the ARRL and see what repeaters are accessible and which have phone patching. Just a thought.
 
Dec 4, 2006
279
Hunter 34 Havre de Grace
A quarter wave at 160 Mc is 5 wavelengths at 800 Mc.
Impedances repeat every odd multiple of a quarter wavelength.
You might get lucky.

What I'd try as an easy test is to put a clip lead on the center conductor, wrap it around the phone and see if you get more signal indicated on the phone. If you do, it might play.
 
Sep 25, 2008
615
Morgan 415 Out Island Rogersville, AL
Theoretically, a back stay should work provided a tuning circuit is used to match it to the amp. The law of reciprocity states that an antenna will transmit with the exact quality as when receiving (and vs. versa.)

Correct me if I am wrong, but, an antenna that is a multiple of a wavelength in length will be just as well matched (not using an antenna tuner) as a 1/2 wavelength dipole (or 1/4 wave wip with a good ground plane). I believe it will even have a gain over a 1/4 wave whip. (Though I've had an antenna theory class in grad school, this is not my area of expertise. Constructive criticism welcomed.)

Maine, one of the posters alluded to not being able to transmit and receive on the same antenna. You need to find out if the amp is concurrently transmitting on one frequency while listening on another. That would imply 2 antennas; however, I don't see two antennas on my cell phone. Anyone know why this ain't so?
 
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
Don't think so Snotter

A matching circuit only matches the transmitter to the transmission line. It does not provide a resonate antenna. The transmitter can transmit full power into the coax without there being a mismatch and power being reflected back to the transmitter so your transmitter is protected The antenna is not in any way matched to the frequency however. The amount of power that makes it to the antenna is what is important. Most of it gets reflected back to the matching unit and does not end up as transmitted RF.
A common misconception BTW.

You need a resonate antenna to get the power out.
 
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
multiple wavelengths

Bob P
I don't disagree that 1.8 MHz is a multiple of 800 MHz but what is your point? 1.8 MHz is 160 meters. This is one of the hardest antennas to get to work on a boat due to its length.
And I think you got your units mixed up.

As a general rule trying to make an HF antenna operate on the UHF is difficult and requires LOTS of power. Also there are other factors like the capacitance of the long wire sucking up most of the electrons from such a low power transmitter. It is like trying to make a wave in the ocean that will reach England by splashing in the water on the beach in Maryland. Sure the wave will get there but it will be so attenuated no one can pull it out of the background noise.
 
Dec 4, 2006
279
Hunter 34 Havre de Grace
Bill, where are you getting 1.8 MHz?

"A quarter wave at 160 Mc is 5 wavelengths at 800 Mc."

Perhaps lost in the translation between Mc and MHz.
Sorry, spent too many years working in Megacycles and Kilocycles.
 
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
My bad

Thinking Ham 160 meter (1.8 MHz). I get it now 160 MHz is marine VHF
Still that is a pretty big (~1.5 meter) for an 800 MHz antenna.

I don't get the hangup in not just building your own antenna. The thing is only a few inches long. Why even bother with all the losses using a VHF antenna on UHF?
 
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