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Through-glass antenna power limits
(I realize that a through-the-glass antenna is less than ideal.
Nevertheless, that's what I have to use in my situation.) The one I have is for 2 meters (NOT dual band), and the label says up to 50 watts. I have an Icom IC-2200H, which has a maximum of 65 watts output. What bad things may/could/will happen if I put 65 watts through the antenna? Thanks! Tom Mitchell -- KG7U Port Angeles, Washington. USA -------------------------------------------------------------------------- Tom Mitchell, Port Angeles, Washington, USA http://www.olympus.net/personal/kg7u -------------------------------------------------------------------------- |
Through-glass antenna power limits
"Thomas & Karen Mitchell" kg7uATolympus.net wrote in message ... (I realize that a through-the-glass antenna is less than ideal. Nevertheless, that's what I have to use in my situation.) The one I have is for 2 meters (NOT dual band), and the label says up to 50 watts. I have an Icom IC-2200H, which has a maximum of 65 watts output. What bad things may/could/will happen if I put 65 watts through the antenna? Thanks! Tom Mitchell -- KG7U Port Angeles, Washington. USA -------------------------------------------------------------------------- Tom Mitchell, Port Angeles, Washington, USA http://www.olympus.net/personal/kg7u -------------------------------------------------------------------------- Tom Through glass antennas work using capacitance. The two plates either side of the glass form the capacitance with the glass acting as the insulator. Attempting to put too much power through a capacitor usually results in overheating or a breakdown of the insulator. This could potentially result in a broken screen. Another thing to consider is the mismatch that the through glass capacitor makes with your transmitter. Some of the power will inevitably be reflected back to the output stages causing possible overheating at full power. I would guess that 65 watts would be safe enough for brief transmissions but for longer chats keep the power down below 50 watts. For mobile use, the difference in signal strength, a fraction of an S-point, is unlikely to be noticed by anyone receiving your signal. Mike G0ULI |
Through-glass antenna power limits
"Mike Kaliski" wrote in message ... "Thomas & Karen Mitchell" kg7uATolympus.net wrote in message ... (I realize that a through-the-glass antenna is less than ideal. Nevertheless, that's what I have to use in my situation.) The one I have is for 2 meters (NOT dual band), and the label says up to 50 watts. I have an Icom IC-2200H, which has a maximum of 65 watts output. What bad things may/could/will happen if I put 65 watts through the antenna? Thanks! Tom Mitchell -- KG7U Port Angeles, Washington. USA -------------------------------------------------------------------------- Tom Mitchell, Port Angeles, Washington, USA http://www.olympus.net/personal/kg7u -------------------------------------------------------------------------- Tom Through glass antennas work using capacitance. The two plates either side of the glass form the capacitance with the glass acting as the insulator. Attempting to put too much power through a capacitor usually results in overheating or a breakdown of the insulator. This could potentially result in a broken screen. Another thing to consider is the mismatch that the through glass capacitor makes with your transmitter. Some of the power will inevitably be reflected back to the output stages causing possible overheating at full power. I would guess that 65 watts would be safe enough for brief transmissions but for longer chats keep the power down below 50 watts. For mobile use, the difference in signal strength, a fraction of an S-point, is unlikely to be noticed by anyone receiving your signal. Mike G0ULI My friend has a 71 Dodge Charger, He used one because he didnt want to drill any holes in this classic muscle car. He made the mistake of running about 200 wats to the antenna and it caused the plastic sheet in the saftey glas to delaminate.. He has a big white spot on the edge of his rear window now. I have run one without any damage to the window but I got a lot of picket fencing with it. Didnt keep it for long. Unless you are talking about a classic car drilling a hole in the roof doesnt effect resell valure Jimmie |
Through-glass antenna power limits
Used a 110 watt MASTR 2 mobile through one in 1980s.
What happens after about 2 minutes of talk time -- box heats up and SWR rises substantially. When I removed the tuning box a couple years later -- components toasted. SO, when it says 50 watts maximum -- they mean it. gb "Thomas & Karen Mitchell" kg7uATolympus.net wrote in message ... (I realize that a through-the-glass antenna is less than ideal. Nevertheless, that's what I have to use in my situation.) The one I have is for 2 meters (NOT dual band), and the label says up to 50 watts. I have an Icom IC-2200H, which has a maximum of 65 watts output. What bad things may/could/will happen if I put 65 watts through the antenna? Thanks! Tom Mitchell -- KG7U Port Angeles, Washington. USA -------------------------------------------------------------------------- Tom Mitchell, Port Angeles, Washington, USA http://www.olympus.net/personal/kg7u -------------------------------------------------------------------------- |
Through-glass antenna power limits
Thomas & Karen Mitchell wrote:
(I realize that a through-the-glass antenna is less than ideal. Nevertheless, that's what I have to use in my situation.) The one I have is for 2 meters (NOT dual band), and the label says up to 50 watts. I have an Icom IC-2200H, which has a maximum of 65 watts output. What bad things may/could/will happen if I put 65 watts through the antenna? Thanks! Tom Mitchell -- KG7U Port Angeles, Washington. USA -------------------------------------------------------------------------- Tom Mitchell, Port Angeles, Washington, USA http://www.olympus.net/personal/kg7u -------------------------------------------------------------------------- Tom; The only thing you want to watch out for is to not place the antenna pads on one of the defrost wires. I have used one in the past with good success. Dave WD9BDZ |
Through-glass antenna power limits
These are not the most effecient, and depending on
the glass, you may find that there is some metalic content in the glass, makeing a perfect match impossible. Think was a pic, in QST couple months ago of one (struck by lightning), showed the fractured glass. But, the difference between 50 and 65 watts is very little in the scheme of things, Maybe 1 Db. Most likely would make little difference- the METAL CONTENT of the glass, would make more difference , as the loss would be heat! Jim NN7K Thomas & Karen Mitchell wrote: (I realize that a through-the-glass antenna is less than ideal. Nevertheless, that's what I have to use in my situation.) The one I have is for 2 meters (NOT dual band), and the label says up to 50 watts. I have an Icom IC-2200H, which has a maximum of 65 watts output. What bad things may/could/will happen if I put 65 watts through the antenna? Thanks! Tom Mitchell -- KG7U Port Angeles, Washington. USA -------------------------------------------------------------------------- Tom Mitchell, Port Angeles, Washington, USA http://www.olympus.net/personal/kg7u -------------------------------------------------------------------------- |
Through-glass antenna power limits
"Thomas & Karen Mitchell" kg7uATolympus.net wrote in message ... (I realize that a through-the-glass antenna is less than ideal. Nevertheless, that's what I have to use in my situation.) The one I have is for 2 meters (NOT dual band), and the label says up to 50 watts. I have an Icom IC-2200H, which has a maximum of 65 watts output. What bad things may/could/will happen if I put 65 watts through the antenna? Thanks! Tom Mitchell -- KG7U Port Angeles, Washington. USA -------------------------------------------------------------------------- Tom Mitchell, Port Angeles, Washington, USA http://www.olympus.net/personal/kg7u -------------------------------------------------------------------------- Further to my earlier posting and slightly off topic but I have been browsing through my car manual and note that the manufacturers specifically forbid the installation of transmitters operating at more than 10 watts power. Checking up on this reveals that in the event of some of the electrical earth bonding connections in the car becoming faulty or breaking two possible disaster scenarios exist. The first is that the computerised engine management unit might misfunction causing the engine to suddenly stop or the antilock braking and stability systems to malfunction. The second is that the pyrotechnic charges in the airbags might be triggered. Admittedly these two situations are dependent on a chain of faults/failures occuring and the manufacturers are just trying to cover themselves against law suits. Vehicles are tested for electromagnetic immunity at far higher levels than this, but you might want to double check your manual or with the manufacturer about the maximum permissible transmitter power if the vehicle is fairly new, fitted with electronic engine management, safety equipment and airbags. Take a deep breath before transmitting with all the controls set to 11... Mike G0ULI |
Through-glass antenna power limits
On Mon, 4 Jun 2007 02:43:18 +0100, "Mike Kaliski"
wrote: Take a deep breath before transmitting with all the controls set to 11... Hi Mike, Is the warrantee void within 100 yards of a 50KW AM antenna? Or howabout those half megawatt LF stations that litter the continent? 73's Richard Clark, KB7QHC |
Through-glass antenna power limits
Thanks to one and all. The Icom IC-2200H doesn't have a choice of 50
watts output; it goes from 25 to 65. So: I'll stay at 25 when in the car. -- KG7U -------------------------------------------------------------------------- Tom Mitchell, Port Angeles, Washington, USA http://www.olympus.net/personal/kg7u -------------------------------------------------------------------------- |
Through-glass antenna power limits
In my search for knowledge I recently went through a big thrash with
antenna tuners... Because of cost I built my own variable caps... To keep the size down I experimented with various insulators between the plates, from air up to glass... Being that the tuners on 40 and 20 were end matching a half wave antenna element the circulating tank current was considerable... On 20 meters where the capacitor plates are 1.5" square for resonance the glass would simply shatter at about 800W for 5 seconds... Plexiglass would boil internally in roughly 20 seconds leaving this interesting rippled piece with 'steam' bubbles in the center of the plexi... Ceramic tiles seemed to work OK, but I didn't find any thin ones locally and the thick pieces resulted in plates being awkwardly large... On 80 meters the glass plates are 4" X 6" and the glass runs barely above ambient at 2KW... denny / k8do |
Through-glass antenna power limits
"Denny" wrote in message ps.com... In my search for knowledge I recently went through a big thrash with antenna tuners... Because of cost I built my own variable caps... To keep the size down I experimented with various insulators between the plates, from air up to glass... Being that the tuners on 40 and 20 were end matching a half wave antenna element the circulating tank current was considerable... On 20 meters where the capacitor plates are 1.5" square for resonance the glass would simply shatter at about 800W for 5 seconds... Plexiglass would boil internally in roughly 20 seconds leaving this interesting rippled piece with 'steam' bubbles in the center of the plexi... Ceramic tiles seemed to work OK, but I didn't find any thin ones locally and the thick pieces resulted in plates being awkwardly large... On 80 meters the glass plates are 4" X 6" and the glass runs barely above ambient at 2KW... denny / k8do An very odd result considering that glass dielectric capacitors are sold specifically for high rf current use by people such as AVX and the like. I guess it depends on what type of glass you used. You shouldn't have used your old lead crystal glasses (;-)) 73 Jeff |
Through-glass antenna power limits
Thomas & Karen Mitchell wrote:
... So: I'll stay at 25 when in the car. -- KG7U -------------------------------------------------------------------------- Tom Mitchell, Port Angeles, Washington, USA http://www.olympus.net/personal/kg7u -------------------------------------------------------------------------- Every engineer, worth his pay, which I know, allow at least a 20% excess on ratings. 50 X 20% = 10 watts 50 + 10 = 60 watts I'd run the 65 and examine the glass mount now and then. You'll see if damage begins and switch lower power. Warm regards, JS |
Through-glass antenna power limits
"Richard Clark" wrote in message ... On Mon, 4 Jun 2007 02:43:18 +0100, "Mike Kaliski" wrote: Take a deep breath before transmitting with all the controls set to 11... Hi Mike, Is the warrantee void within 100 yards of a 50KW AM antenna? Or howabout those half megawatt LF stations that litter the continent? 73's Richard Clark, KB7QHC Richard It's all about RF actually within the vehicle. The bodywork acts like a Faraday cage against external influences. But I suspect you know that already :-) A couple of years back a lightning bolt hit a field I was driving past during a storm. The dash completely blanked for 2 seconds and then came back to life - no other ill effects noted - just as well because the road was nearly completely under water at that point. The radio key remote locking can fail if you park too close to a mobile phone mast, or someone is transmitting on 70 cms nearby, but that's about it. As I only operate QRP I hadn't given the matter much thought until I checked in the vehicle manual and saw a footnote. Mike G0ULI |
Through-glass antenna power limits
"Mike Kaliski" wrote in message ... "Richard Clark" wrote in message ... On Mon, 4 Jun 2007 02:43:18 +0100, "Mike Kaliski" wrote: Take a deep breath before transmitting with all the controls set to 11... Hi Mike, Is the warrantee void within 100 yards of a 50KW AM antenna? Or howabout those half megawatt LF stations that litter the continent? 73's Richard Clark, KB7QHC Richard It's all about RF actually within the vehicle. The bodywork acts like a Faraday cage against external influences. But I suspect you know that already :-) A couple of years back a lightning bolt hit a field I was driving past during a storm. The dash completely blanked for 2 seconds and then came back to life - no other ill effects noted - just as well because the road was nearly completely under water at that point. The radio key remote locking can fail if you park too close to a mobile phone mast, or someone is transmitting on 70 cms nearby, but that's about it. As I only operate QRP I hadn't given the matter much thought until I checked in the vehicle manual and saw a footnote. Mike G0ULI I had a similar experience with lightning. The lightning hit a tall comm tower on the side of the road, jumped out the side of the tower, hit the roof of the truck I was in, and then struck a pine tree on the other side of the road. The engine diesd and I coasted to the side of the road. After a few minutes of getting my composurer back together and surveying the damage I was able to start the truck like nothing had happened. I was expecting all the electronics to be fried. Jimmie |
Through-glass antenna power limits
Richard Clark wrote:
On Mon, 4 Jun 2007 02:43:18 +0100, "Mike Kaliski" wrote: Take a deep breath before transmitting with all the controls set to 11... Hi Mike, Is the warrantee void within 100 yards of a 50KW AM antenna? Or howabout those half megawatt LF stations that litter the continent? I'd venture that the concern is not so much radiated field (although, in the nearfield it drops off pretty quick, so a 100W transmitter on a car might well create larger field strengths than that 50kW AM station. It's probably more the potential for conducted RF via the radio's power leads, etc. Imagine that if the chassis of the radio is RF hot, relative to the car body (oh no, that never happens, no waygrin), so now you have significant RF current flowing in the vehicle wiring harness. From a straight field standpoint, it's easy to exceed the ANSI RF field Maximum Permissible Exposure(MPE) with a 2m transmitter and 50W on a car. Combination of the limit being lowest, close proximity to the radiator, etc. (I seem to recall the limit is reached at about 1 meter away from a groundplane/whip antenna at 50W, albeit at 100% duty cycle) But then, you have done your RF safety analysis, right? (Even though there's a categorical exemption from the requirement for routine evaluations for amateur mobile and portable operations, that doesn't relieve you from the requirement for safety). In comparison, you're not going to be driving somewhere the field exceeds the limits, because they'll have a big fence keeping you beyond the distance for uncontrolled exposure limits. As far as the original question about through glass... Glass isn't the lowest loss dielectric to make a capacitor of (heck, even at the 100kHz used in tesla coils, it's lossy enough to crack from the thermal stresses). The glass is the dominant source of loss in using FR-4/G-10 PC boards at microwave frequencies, for instance. However, even a spectacularly bad loss tangent of 0.01 is only going to result in a 1% loss. (wood has a loss tangent of 0.03 or thereabouts at 100MHz, depending on moisture level) A bigger issue would be wires/conductive films for defogging. Jim |
Through-glass antenna power limits
Jeff wrote:
"Denny" wrote in message ps.com... In my search for knowledge I recently went through a big thrash with antenna tuners... Because of cost I built my own variable caps... To keep the size down I experimented with various insulators between the plates, from air up to glass... Being that the tuners on 40 and 20 were end matching a half wave antenna element the circulating tank current was considerable... On 20 meters where the capacitor plates are 1.5" square for resonance the glass would simply shatter at about 800W for 5 seconds... Plexiglass would boil internally in roughly 20 seconds leaving this interesting rippled piece with 'steam' bubbles in the center of the plexi... Ceramic tiles seemed to work OK, but I didn't find any thin ones locally and the thick pieces resulted in plates being awkwardly large... On 80 meters the glass plates are 4" X 6" and the glass runs barely above ambient at 2KW... denny / k8do An very odd result considering that glass dielectric capacitors are sold specifically for high rf current use by people such as AVX and the like. I guess it depends on what type of glass you used. You shouldn't have used your old lead crystal glasses (;-)) Lots of kinds of "glass" out there. fused silica is pretty low loss borosilicate glass (e.g. Pyrex, Kimax, etc.) is medium windowglass (soda lime) is all over the place. |
Through-glass antenna power limits
John Smith I wrote: Thomas & Karen Mitchell wrote: ... So: I'll stay at 25 when in the car. -- KG7U -------------------------------------------------------------------------- Tom Mitchell, Port Angeles, Washington, USA http://www.olympus.net/personal/kg7u -------------------------------------------------------------------------- Every engineer, worth his pay, which I know, allow at least a 20% excess on ratings. 50 X 20% = 10 watts 50 + 10 = 60 watts I'd run the 65 and examine the glass mount now and then. You'll see if damage begins and switch lower power. Warm regards, JS Obviously the engineers who established the maximum power specification would not advocate using greater than 50 watts. ac6xg |
Through-glass antenna power limits
Jim Kelley wrote:
... Obviously the engineers who established the maximum power specification would not advocate using greater than 50 watts. ac6xg 1) No engineer would advocate over-clocking computers the way I do. 2) No engineer would advocate pushing rigs and liners (power amps) to the limits I do. 3) No engineer would advocate doing the mods to equipment I do. 4) No engineer would advocate the antenna experiments I carry out. 6) No engineer would advocate the engine mods to my vette which I have done. 7) No engineer would advocate the levels of exposure to RF I expose myself too. 8) ... That's what makes it fun, now doesn't it? JS |
Through-glass antenna power limits
John Smith I wrote: 1) No engineer would advocate over-clocking computers the way I do. 2) No engineer would advocate pushing rigs and liners (power amps) to the limits I do. 3) No engineer would advocate doing the mods to equipment I do. 4) No engineer would advocate the antenna experiments I carry out. 6) No engineer would advocate the engine mods to my vette which I have done. 7) No engineer would advocate the levels of exposure to RF I expose myself too. 8) ... That's what makes it fun, now doesn't it? It's unquestionably something which separates fools and their money. ac6xg |
Through-glass antenna power limits
Jim Kelley wrote:
... It's unquestionably something which separates fools and their money. ac6xg Yes, well, I am still working on a way to take to the grave with me ... so far, NO PROGRESS! I wish you better luck ... however, I guess others who will benefit from the money will be more than grateful ... granting that I will be unsuccessful in finding a way. JS |
Through-glass antenna power limits
"John Smith I" wrote in message ... Thomas & Karen Mitchell wrote: ... So: I'll stay at 25 when in the car. -- KG7U -------------------------------------------------------------------------- Tom Mitchell, Port Angeles, Washington, USA http://www.olympus.net/personal/kg7u -------------------------------------------------------------------------- Every engineer, worth his pay, which I know, allow at least a 20% excess on ratings. 50 X 20% = 10 watts 50 + 10 = 60 watts I'd run the 65 and examine the glass mount now and then. You'll see if damage begins and switch lower power. Warm regards, JS That sounds like a girl waiting until she is just a litte bit pregnant to stat us birth control. Either the glass cracks, it starts to delaminate, or you fry your finals, all could be too far by the time you see it. |
Through-glass antenna power limits
Jimmie D wrote:
"John Smith I" wrote in message ... Thomas & Karen Mitchell wrote: ... So: I'll stay at 25 when in the car. -- KG7U -------------------------------------------------------------------------- Tom Mitchell, Port Angeles, Washington, USA http://www.olympus.net/personal/kg7u -------------------------------------------------------------------------- Every engineer, worth his pay, which I know, allow at least a 20% excess on ratings. 50 X 20% = 10 watts 50 + 10 = 60 watts I'd run the 65 and examine the glass mount now and then. You'll see if damage begins and switch lower power. Warm regards, JS That sounds like a girl waiting until she is just a litte bit pregnant to stat us birth control. Either the glass cracks, it starts to delaminate, or you fry your finals, all could be too far by the time you see it. If the glass breaks, replace glass (highly unlikely! Bordering on impossible!) Glass cracking? Very unlikely! Delamination? Perhaps, over much time ... Fry the finals? What idiot would ever start using a rig and antenna with no SWR indication? JS |
Through-glass antenna power limits
Thomas & Karen Mitchell kg7uATolympus.net wrote in
: (I realize that a through-the-glass antenna is less than ideal. Nevertheless, that's what I have to use in my situation.) The one I have is for 2 meters (NOT dual band), and the label says up to 50 watts. I have an Icom IC-2200H, which has a maximum of 65 watts output. What bad things may/could/will happen if I put 65 watts through the antenna? If your transceiver really does make 65W into a 50 ohm load, and you connected say 4m of RG58C/U to a 50 ohm load, line losses are such that only 54W reaches the load. So you might not be quite feeding the antenna with 65W, the likely amount depends on your feedline type and length. Your antenna is probably not exactly 50 ohms, and there could be higher current or higher voltage at the coupler than for a true 50 ohm load... but the designers should have included a safety margin to cover this factor. (The on-glass coupler is the achilles heel of these things, you will feel them warm up with a bit of use.) If the antenna is rated for 50W, and can't reliably stand 60W, it is a bit marginally rated, but on-glass mounts are a bit that way. Owen |
Through-glass antenna power limits
That sounds like a girl waiting until she is just a litte bit pregnant to stat us birth control. Either the glass cracks, it starts to delaminate, or you fry your finals, all could be too far by the time you see it. It is the ratings of the components in the matching unit that limit the power rating not the glass, you will get smoke well before any damage to the glass. Jeff |
Through-glass antenna power limits
On Jun 3, 9:57 am, Thomas & Karen Mitchell kg7uATolympus.net wrote:
(I realize that a through-the-glass antenna is less than ideal. Nevertheless, that's what I have to use in my situation.) The one I have is for 2 meters (NOT dual band), and the label says up to 50 watts. I have an Icom IC-2200H, which has a maximum of 65 watts output. What bad things may/could/will happen if I put 65 watts through the antenna? Thanks! Tom Mitchell -- KG7U Port Angeles, Washington. USA -------------------------------------------------------------------------- Tom Mitchell, Port Angeles, Washington, USAhttp://www.olympus.net/personal/kg7u -------------------------------------------------------------------------- On a personal note, I have a dual bander through the glass mount. I use a 857 yeasu and managed to fry the matching unit on the inside of the car. From what I saw when I repaired the unit was the main resonating cap is a brass screw in a brass tube with a 'plastic' insulator in between. With the wattage I get from the 857 the plastic dia-lectic melted. I replaced the cap with a professional glass 0.5 to 5 pF trimmer cap and it has worked fine ever since. Regards bob zs6bxi |
Through-glass antenna power limits
Lots of kinds of "glass" out there. fused silica is pretty low loss borosilicate glass (e.g. Pyrex, Kimax, etc.) is medium windowglass (soda lime) is all over the place.- Hide quoted text - Exactly... If I were serious about using my capacitor design for the higher bands I would either redesign the circuit to increase the plate area or go to borosilicate glass... My 80 - 160 remote tuners are working like gangbusters, take all the power I can make, and cost roughly a hundred bucks a pop to build... I don't operate the other bands much and can make do with simple dipoles.... Being that I have ADD (antenna deficit disorder) I am busily working on other ideas now... denny / k8do |
Through-glass antenna power limits
"Jeff" wrote in message . com... That sounds like a girl waiting until she is just a litte bit pregnant to stat us birth control. Either the glass cracks, it starts to delaminate, or you fry your finals, all could be too far by the time you see it. It is the ratings of the components in the matching unit that limit the power rating not the glass, you will get smoke well before any damage to the glass. Jeff So far the only damageI have seen from this is to the lamination inside the glass. I wouldnt want to wait until this occurs before I decided to quit. |
Through-glass antenna power limits
Jimmie D wrote:
... So far the only damageI have seen from this is to the lamination inside the glass. I wouldnt want to wait until this occurs before I decided to quit. De-lamination on the vettes' rear window? Absolutely WON'T take the chance! The Park Avenue Buick? Who cares? Doubt it would even affect resale/trade-in value ... JS |
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