There is a lot of misinformation in Dan's post regarding antennas and batteries. 1. Alkalines produce MORE voltage then nicads although the curve is different. A radio that produces 5 watts with nicads may produce 7 or 8 with fresh alkalines. The nicads will maintain a more constant voltage, and therefore wattage output, but will die, virtually without warning. I've never heard the term "Energy Density"? 2. I don't know what type of telescoping antenna Dan is referring to, but the length of the antenna is not necessarily a key factor in determining the performance of the antenna. The small duckies tend to be inefficient but they are factory tuned for the frequency and radio they are designed for. A telescoping whip would have to be accurately tuned for the operational frequency by extending it to the exact length, assuming it was long enough to function as a 1/4 wave. Other factors including the connector can affect the tuning. This would ideally be done using a field strength meter. 3. Today's nicads are almost memory free and don't require much coddling. 4. Optimum performance from a fiberglass kayak would be obtained by mounting a 1/2 wave whip somewhere on the boat. The 1/2 wave performs well without a ground and should dramatically out perform an antenna mounted on the radio. A mag mount with a piece of ferrous metal under the deck or hatch cover may do the trick. 5. If you have any friends that are amateur radio operators, they can be a good source of information. The amateur VHF band is just below the marine band, and a lot of amateur equipment will operate (illegally) in the marine bands. Antennas and other gear can be easily modified to work in the marine bands and most amateur test equipment will operate in the marine band as well. Cya W2PN *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Bob Denton wrote: > > There is a lot of misinformation in Dan's post regarding antennas and > batteries. Well, one of us is confused (or possibly both). I will provide more specifics this time to help others determine who it is that is providing misinformation. First, you write: > > 1. Alkalines produce MORE voltage then nicads although the curve is > different. A radio that produces 5 watts with nicads may produce 7 or 8 with > fresh alkalines. This is true if you are comparing, say, AA's to AA's, but that is not relevant to my comparison of VHF alternatives. Let me use a specific example. I have a radio (Icom M7) that has both a manufacturer-supplied NiCad CM-89 battery pack (which does NOT use AA's) and a manufacturer-supplied AA pack for use with alkalines. The CM-89 pack is rated at 9.6 volts, whereas 6 AA alkalines that fit in the manufacturer-supplied AA holder produce 6 x 1.5volts for a total of 9.0 volts (when the alkalines are new) Of course it is less than 9.0 as the voltage drops through use. I asked Icom about the output of this radio when used with alkalines (since they don't publish a figure) and they said it would be LESS than 5 watts. I think that they are correct. >I've never heard the term "Energy Density"? I have seen this referred to in varous references on battteries. One place where have I seen this term is the Cadex Battery Book: http://www.cadex.com/cfm/index.cfm?Pg=52&Lp=144&Db=&Mo= Check out the section on "choice of batteries". It has a table with "energy density" (measured in Wh/kg). I did not make the term up. > > 2. I don't know what type of telescoping antenna Dan is referring to, > but the length of the antenna is not necessarily a key factor in determining > the performance of the antenna. The small duckies tend to be inefficient but > they are factory tuned for the frequency and radio they are designed for. A > telescoping whip would have to be accurately tuned for the operational > frequency by extending it to the exact length, assuming it was long enough > to function as a 1/4 wave. Other factors including the connector can affect > the tuning. This would ideally be done using a field strength meter. Suppliers of such antennas (including the marine electronics shop from which I purchased mine) claim that a properly matched telescoping antenna, mounted on the radio, can extend the range of a handheld significantly. You seem to claim otherwise. I do not have the expertise to tell who is correct as a matter of theory, so I must rely on my own experiences, which suggest that the suppliers are correct. Of course this relies on a properly matched antenna. > > 3. Today's nicads are almost memory free and don't require much > coddling. What you say disagrees with a major study by the Navy and GTE Government Systems. This study involved 3 ships and about 2100 batteries. They found that a proper maintenance routine *greatly* improves performance of NiCads. There is a link to this study at the above Cadex site. (Go to the link entitled "GTE report".) I agree with your point about using test equipment to test your set-up. Any good marine electronics shop will have such equipment, and will be willing to help you match an antenna to your radio to improve its performance. Dan Hagen Bellingham, Washington *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Standard supplies their radios with a tray that takes both nicads and alkalines. The nicads produce 5 watts at their nominal voltage. I am not familiar with Icom's marine radios but I own a number of Icom amateur handheld VHF/UHF transceivers and have been pleased with their quality and performance. > > 1. Alkalines produce MORE voltage then nicads although the curve is > different. A radio that produces 5 watts with nicads may produce 7 or 8 with * fresh alkalines. >I've never heard the term "Energy Density"? I have seen this referred to in varous references on battteries. One place where have I seen this term is the Cadex Battery Book: http://www.cadex.com/cfm/index.cfm?Pg=52&Lp=144&Db=&Mo= Check out the section on "choice of batteries". It has a table with "energy density" (measured in Wh/kg). I did not make the term up. > > 2. I don't know what type of telescoping antenna Dan is referring to, > but the length of the antenna is not necessarily a key factor in determining > the performance of the antenna. The small duckies tend to be inefficient but > they are factory tuned for the frequency and radio they are designed for. A > telescoping whip would have to be accurately tuned for the operational > frequency by extending it to the exact length, assuming it was long enough > to function as a 1/4 wave. Other factors including the connector can affect > the tuning. This would ideally be done using a field strength meter. Suppliers of such antennas (including the marine electronics shop from which I purchased mine) claim that a properly matched telescoping antenna, mounted on the radio, can extend the range of a handheld significantly. You seem to claim otherwise. I do not have the expertise to tell who is correct as a matter of theory, so I must rely on my own experiences, which suggest that the suppliers are correct. Of course this relies on a properly matched antenna. > > 3. Today's nicads are almost memory free and don't require much > coddling. What you say disagrees with a major study by the Navy and GTE Government Systems. What type nicads in the study? As for the antenna, is yours a telescoping antenna specifically designed for a marine hand held? If so then it will most certainly produce superior results to the standard ducky. There are also longer duckies made that are the length of a telescoping antenna, but are flexible and sealed. cya *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
As far as I can tell, energy density is not a formal term but used only to refer to weight vs power ratio. My local ham repeater belongs to the Motorola Radio club. I'll ask the engineers about both the nicad situation and the energy/density term. cya *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
There is a common misconception about the value of transmitting power and reception. "A dime on the antenna is worth a dollar on the radio" is one of the basic precepts. I used to talk from Virginia to Europe using 1/3 of a watt. I had a huge antenna set up for this purpose. When you increase the power 3 fold (or is it 4 fold) it will only make 1 unit difference on your signal meter...from S7 to S8. The only time that will be critical is when it takes you out of the noise floor and makes you audible. With typical environmental noise (audio) it's unlikely a weak signal would be audible even if just above the noise floor. The 1/2 wave antenna is excellent for marine use because it doesn't require an additional ground plane. The radio functions as the ground plane when using a duckie, which is less then ideal. The lack of a decent ground is what would make a co-linear perform poorly in a glass or plastic boat. The better antennas improve the effective power by flattening out the radiation pattern concentrating more of the 5 watts at the horizon and less at the sky. There are inexpensive portable 3 and 4 element VHF yagi antennas (TV antenna style) which are portable and could be useful for campsites if hitting the weather transmitter is a problem. Hope this is useful! cya W2PN *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Bob Denton wrote: >The better antennas improve the effective power by flattening out the >radiation pattern concentrating more of the 5 watts at the horizon and less >at the sky. There are inexpensive portable 3 and 4 element VHF yagi antennas >(TV antenna style) which are portable and could be useful for campsites if >hitting the weather transmitter is a problem. > >Hope this is useful! How about carrying a half wave dipole? That shouldn't take up much space... much less than a yagi. Any benefit of a full wave vs. half wave? *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
>The problem is that VHF is vertically polarized so you would need to suspend >the 1/2 wave dipole vertically, then feed it from the middle without >compromising the radiation pattern. Then you end up with a 1/2 wave >vertical. The yagi will provide significantly more gain over a >dipole..usually 7 or 7 dB for 3 elements. Bob: Are there published documentation on the difference in gain between horizontal and vertical polarization in VHF frequencies? At most amatuer freq. range, I didn't notice significant problems communicating between the two. Do you happen to have the formulas handy for both the j and the dipole? I guess the best cut would be for Ch16. What are the dimensions for each? If you've got the fomulas handy, that is. > >The easiest antenna to use in the field is probably a J-Pole made from coax >and twin lead for pennies. It can be suspended from a tree and will produce >excellent results. Yes. I was thinking about carrying a spare antenna in the even I was stranded somewhere...rather than trying to errect a whip on the boat itself. Robrt *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Regarding accessory antennas... While it is impolite net style to add a "Me too." I'll risk it here as this is valuable information for perhaps many of us but I need help. Would one of you more knowledgeable posters give us some pragmatic instructions on making an extended antenna for in-camp emergency use. What materials should we use (coax, plain wire of what gauge?) How should the antenna be connected to the radio, how should it be deployed? Hung horizontally between tree limbs, vertically? A parts list and suggestions for places to obtain them would be a boon. Of course the formulas for length etc. would help too, along with any use advice regarding tuning (without additional equipment). Thanks for your guidance. Rich Mitchell Robert C. Cline wrote: > > >The problem is that VHF is vertically polarized so you would need to suspend > >the 1/2 wave dipole vertically, then feed it from the middle without > >compromising the radiation pattern. Then you end up with a 1/2 wave > >vertical. The yagi will provide significantly more gain over a > >dipole..usually 7 or 7 dB for 3 elements. > > Bob: Are there published documentation on the difference in gain between > horizontal and vertical polarization in VHF frequencies? At most amatuer > freq. range, I didn't notice significant problems communicating between the > two. > > Do you happen to have the formulas handy for both the j and the dipole? I > guess the best cut would be for Ch16. What are the dimensions for each? > If you've got the fomulas handy, that is. > > > > >The easiest antenna to use in the field is probably a J-Pole made from coax > >and twin lead for pennies. It can be suspended from a tree and will produce > >excellent results. > > Yes. I was thinking about carrying a spare antenna in the even I was > stranded somewhere...rather than trying to errect a whip on the boat itself. > > Robrt > > *************************************************************************** > PaddleWise Paddling Mailing List > Submissions: paddlewise_at_lists.intelenet.net > Subscriptions: paddlewise-request_at_lists.intelenet.net > Website: http://www.gasp-seakayak.net/paddlewise/ > *************************************************************************** Robert C. Cline wrote: > > >The problem is that VHF is vertically polarized so you would need to suspend > >the 1/2 wave dipole vertically, then feed it from the middle without > >compromising the radiation pattern. Then you end up with a 1/2 wave > >vertical. The yagi will provide significantly more gain over a > >dipole..usually 7 or 7 dB for 3 elements. > > Bob: Are there published documentation on the difference in gain between > horizontal and vertical polarization in VHF frequencies? At most amatuer > freq. range, I didn't notice significant problems communicating between the > two. > > Do you happen to have the formulas handy for both the j and the dipole? I > guess the best cut would be for Ch16. What are the dimensions for each? > If you've got the fomulas handy, that is. > > > > >The easiest antenna to use in the field is probably a J-Pole made from coax > >and twin lead for pennies. It can be suspended from a tree and will produce > >excellent results. > > Yes. I was thinking about carrying a spare antenna in the even I was > stranded somewhere...rather than trying to errect a whip on the boat itself. > > Robrt > > *************************************************************************** > PaddleWise Paddling Mailing List > Submissions: paddlewise_at_lists.intelenet.net > Subscriptions: paddlewise-request_at_lists.intelenet.net > Website: http://www.gasp-seakayak.net/paddlewise/ > *************************************************************************** -- Richard G. Mitchell, Jr. Department of Sociology Oregon State University Corvallis, OR 97331 U.S.A. (541) 752-1323 phone/fax mitchelr_at_ucs.orst.edu *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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