Home |
Search |
Today's Posts |
#61
![]()
posted to rec.boats
|
|||
|
|||
![]()
Eisboch wrote:
"HK" wrote in message . .. You're kidding about the difficulty in putting a connector on properly, aren't you? I've done it at least a dozen times over the years the old fashioned way (never used one of the quickie "crimp" connectors). Harry, the connector is not the issue (assuming it's done in a decent manner). The proper loading of any RF antenna is a complex relationship of the designed output impedance of the radio, the characteristic impedance of the transmission line (cable) and the impedance of the antenna. Higher powered RF transmitters have tuning boxes between the radio output and the transmission line/antenna arrangement that effectively changes the length with capacitors and inductors to optimize power transfer. I agree that at 25 watts and a on typical boat installation it isn't going to make much difference. To an RF engineer, it will all look and operate like trash anyway. Eisboch As I said, so long as I can reach the Coast Guard, I don't really care much about VHF communication. We have really good cell coverage most everywhere on the Bay. |
#62
![]()
posted to rec.boats
|
|||
|
|||
![]() "HK" wrote in message . .. Eisboch wrote: "HK" wrote in message . .. You're kidding about the difficulty in putting a connector on properly, aren't you? I've done it at least a dozen times over the years the old fashioned way (never used one of the quickie "crimp" connectors). Harry, the connector is not the issue (assuming it's done in a decent manner). The proper loading of any RF antenna is a complex relationship of the designed output impedance of the radio, the characteristic impedance of the transmission line (cable) and the impedance of the antenna. Higher powered RF transmitters have tuning boxes between the radio output and the transmission line/antenna arrangement that effectively changes the length with capacitors and inductors to optimize power transfer. I agree that at 25 watts and a on typical boat installation it isn't going to make much difference. To an RF engineer, it will all look and operate like trash anyway. Eisboch As I said, so long as I can reach the Coast Guard, I don't really care much about VHF communication. We have really good cell coverage most everywhere on the Bay. Until that Yamaha coughs, you drop your cell phone overboard, the wind is picking up, water splashing over that LT, and your radio's output stage sizzles because the SWR ratio is 4 to 1 or something. :-) I am a nerd about this stuff and set the boat's radio systems up with SWR meters because I can't help it. The result though is that I can communicate easily with boats 20 miles away. Eisboch |
#63
![]()
posted to rec.boats
|
|||
|
|||
![]()
Eisboch wrote:
"HK" wrote in message . .. John H. wrote: On Tue, 25 Sep 2007 14:51:44 +0000, Larry wrote: Another question: Most antennae seem to come with about 20 feet of wire. Mounted on a console with the radio right there, I could get by with about 3 feet of wire. Is all the extra wire necessary? No. You can cut the wire to the length you need. Not technically true, but probably doesn't matter in this application. Performance of the radio is going to be marginal anyway. He'd be better off coiling up the cable in a relatively large coil (not tight) for best performance. It's length *does* affect proper antenna loading. Eisboch wow, I guess Horizon and my installer knew what they were talking about. |
#64
![]()
posted to rec.boats
|
|||
|
|||
![]()
On Tue, 25 Sep 2007 16:40:58 -0400, "Eisboch" wrote:
"Larry" wrote in message .. . John H. wrote in : Another question: Most antennae seem to come with about 20 feet of wire. Mounted on a console with the radio right there, I could get by with about 3 feet of wire. Is all the extra wire necessary? No, it's not. If you're not a solderer, find someone who can put a new connector on the radio end of your cable or make up a new cable. The Metz does NOT have a cable attached to it....one of its great features. YOU put the cable on it so the cable can be replaced....not hard wired into the plastic, like the little whips from Shakespeare come. The farce of "tuning" the antenna with cable length is nonsense.... True, you don't "tune" the antenna with cable length, but you need a certain amount of it to properly tune the antenna. My memory is rusty and I'd have to go dig out the books, but I think you should have a 1/2 wavelength or so in cable length. Maybe it's a 1/4 .... can't remember. Too short will cause the antenna not to load properly (assuming it is the correct length) and result in an excessive SWR value that reduces effective transmitted power and, in the worst situation, cause damage to the output stage of the radio. If you have matching problems with the antenna and are fairly certain that the antenna, connectors are known good and the radio is presenting power properly, then the suspect is the length of the feedline. End result - you trim the feeline to bring the antenna to the correct match. Thus you are tuning the antenna using the feedline. That's why God invented antenna tuners. :) |
#65
![]()
posted to rec.boats
|
|||
|
|||
![]()
Eisboch wrote:
"HK" wrote in message . .. Eisboch wrote: "HK" wrote in message . .. You're kidding about the difficulty in putting a connector on properly, aren't you? I've done it at least a dozen times over the years the old fashioned way (never used one of the quickie "crimp" connectors). Harry, the connector is not the issue (assuming it's done in a decent manner). The proper loading of any RF antenna is a complex relationship of the designed output impedance of the radio, the characteristic impedance of the transmission line (cable) and the impedance of the antenna. Higher powered RF transmitters have tuning boxes between the radio output and the transmission line/antenna arrangement that effectively changes the length with capacitors and inductors to optimize power transfer. I agree that at 25 watts and a on typical boat installation it isn't going to make much difference. To an RF engineer, it will all look and operate like trash anyway. Eisboch As I said, so long as I can reach the Coast Guard, I don't really care much about VHF communication. We have really good cell coverage most everywhere on the Bay. Until that Yamaha coughs, you drop your cell phone overboard, the wind is picking up, water splashing over that LT, and your radio's output stage sizzles because the SWR ratio is 4 to 1 or something. :-) I am a nerd about this stuff and set the boat's radio systems up with SWR meters because I can't help it. The result though is that I can communicate easily with boats 20 miles away. Eisboch I've listened to the usual channels on VHF for hours at a time and hardly ever hear much conversation. I can call the CG on my VHF, and maybe with all the breaks some other boater within range will come by for a look see. But unless you are in one of the higher boater density areas, you're mostly all along out there. Where I fish for flounder, I can go half the day without seeing another boat. Frankly, I think we need something a lot better than VHF, some variant of marine cell (not satellite) for in shore and near shore. The bigger offshore boats that sink, well, we need more fishing reefs anyway, right? |
#66
![]()
posted to rec.boats
|
|||
|
|||
![]()
On Tue, 25 Sep 2007 16:44:13 -0400, HK wrote:
VHF is just a clunky way to communicate when you have cell phones and friends out in boats with cell phones. Tell me, just out of curiosity, what is your understanding of how cell phones work? |
#67
![]()
posted to rec.boats
|
|||
|
|||
![]()
Short Wave Sportfishing wrote:
On Tue, 25 Sep 2007 16:44:13 -0400, HK wrote: VHF is just a clunky way to communicate when you have cell phones and friends out in boats with cell phones. Tell me, just out of curiosity, what is your understanding of how cell phones work? Let's see. I dial a phone number on my cell, I hear ringing, and either the person I am calling answers, or I get his voice mail. The Bay shoreline is peppered with cell towers; the only dead spot I have encountered in years here is in the marina. Do I need to know more about how cell phones work? Do I need a SWR meter for my built in cell antenna? Directions in pushing the number keys? |
#68
![]()
posted to rec.boats
|
|||
|
|||
![]()
On Tue, 25 Sep 2007 16:58:32 -0400, "Eisboch" wrote:
I am a nerd about this stuff and set the boat's radio systems up with SWR meters because I can't help it. Amen brother - amen. I have an antenna tuner under the console so if I need to retune to get the best match, I can. Now that's obcessive. :) |
#69
![]()
posted to rec.boats
|
|||
|
|||
![]()
Short Wave Sportfishing wrote:
On Tue, 25 Sep 2007 16:58:32 -0400, "Eisboch" wrote: I am a nerd about this stuff and set the boat's radio systems up with SWR meters because I can't help it. Amen brother - amen. I have an antenna tuner under the console so if I need to retune to get the best match, I can. Now that's obcessive. :) So, what's the VHF reception like on that little lake you frequent? Better question: is anyone listening? :} |
#70
![]()
posted to rec.boats
|
|||
|
|||
![]()
Short Wave Sportfishing wrote:
On Tue, 25 Sep 2007 16:40:58 -0400, "Eisboch" wrote: "Larry" wrote in message ... John H. wrote in : Another question: Most antennae seem to come with about 20 feet of wire. Mounted on a console with the radio right there, I could get by with about 3 feet of wire. Is all the extra wire necessary? No, it's not. If you're not a solderer, find someone who can put a new connector on the radio end of your cable or make up a new cable. The Metz does NOT have a cable attached to it....one of its great features. YOU put the cable on it so the cable can be replaced....not hard wired into the plastic, like the little whips from Shakespeare come. The farce of "tuning" the antenna with cable length is nonsense.... True, you don't "tune" the antenna with cable length, but you need a certain amount of it to properly tune the antenna. My memory is rusty and I'd have to go dig out the books, but I think you should have a 1/2 wavelength or so in cable length. Maybe it's a 1/4 .... can't remember. Too short will cause the antenna not to load properly (assuming it is the correct length) and result in an excessive SWR value that reduces effective transmitted power and, in the worst situation, cause damage to the output stage of the radio. If you have matching problems with the antenna and are fairly certain that the antenna, connectors are known good and the radio is presenting power properly, then the suspect is the length of the feedline. End result - you trim the feeline to bring the antenna to the correct match. Thus you are tuning the antenna using the feedline. That's why God invented antenna tuners. :) That is the beauty of rec.boats, even when you think every possible boating discussion has been beat to death, a new informative topic will arise, that we can learn from. Of course, we will beat this one to death. |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
![]() |
||||
Thread | Forum | |||
Question for Harry | General | |||
SSB antenna question | Electronics | |||
GR100 - antenna question | Electronics | |||
Antenna question | Electronics | |||
SSB Antenna Question | Electronics |