ES13Raven
Member
Does it matter if you have the power to the scanner on when you change antennas? Will that damage anything?
Changing Antennas - Power off or on?
- Thread starter ES13Raven
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With a scanner there shouldn't be a problem although 30 years ago I had a Regency that was flowing about 50 volts thru the antenna somehow. Kinda thought that aluminum didn't feel right when I was up in a tree making an adjustment.
Now, if you are using a transmitter do NOT key up the to transmit with no antenna or
antenna load. Serious and expensive repercussions are likely to ensue.
Now, if you are using a transmitter do NOT key up the to transmit with no antenna or
antenna load. Serious and expensive repercussions are likely to ensue.
mjthomas59
Member
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- Nov 29, 2006
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- 510
I always thought that removing the antenna on a scanner while the unit was on could potentially desensitize it. I've never had it happen to me, but i religiously power off the reciever before i mess around with the antenna. Hopefully someone else will chime in with a better answer for you because i'm also interested in hearing others' experiences!
Can't imagine how a permanent desensitization would occur, but, when in doubt play it safe.
(It would desensitize it as-far-as receiving signals while no antenna is installed but that's kinda understood).
(It would desensitize it as-far-as receiving signals while no antenna is installed but that's kinda understood).
N
N_Jay
Guest
mjthomas59 said:
To use a line from "Young Frankenstein", "Well, they were wrong then, weren't they?"
Igor: Dr. Frankenstein...
Dr. Frederick Frankenstein: "Fronkensteen."
Igor: You're putting me on.
Dr. Frederick Frankenstein: No, it's pronounced "Fronkensteen."
Igor: Do you also say "Froaderick"?
Dr. Frederick Frankenstein: No..."Frederick."
Igor: Well, why isn't it "Froaderick Fronkensteen"?
Dr. Frederick Frankenstein: It isn't; it's "Frederick Fronensteen."
Igor: I see.
Dr. Frederick Frankenstein: You must be Igor.
[He pronounces it ee-gor]
Igor: No, it's pronounced "eye-gor."
Dr. Frederick Frankenstein: But they told me it was "ee-gor."
Igor: Well, they were wrong then, weren't they?
gcgrotz
Member
I remove antennas all day long on all kinds of junk and never hurt any of it. Sometimes even on a transmitter but you'd better be trained on the equipment before you do!
Just make sure if you're in a dry environment with a lot of static electricity, grab the metal case of the scanner, or some nearby metal, and discharge the static from yourself before grabbing the antenna element.
fineshot1
Member
ES13Raven said:
No - scanners and conventional type radios it should not effect, however concerning trunking and cellular radio gear you should always power off the equipment before disconnecting the antenna due to the radios sometimes transmitting a burst of data trying to locate the system they are on.
jonny290
Member
The only way you should worry about connecting antennas to live units is:
1: you do not have shunted antennas (dipoles, certain verticals, discones) and they build up static. Usually only an issue in windy and/or dry areas, though it can happen anywhere on occasion. If there's DC connection to ground on the *center* conductor of your feed coax, you are static protected, for the most part.
2: You live *extremely* close to a very high power transmitter (10kW or more and less than 1/2 mile) and as such, there may be significant induced currents in large antennas that may discharge through your scanner's input.
However, I'd wager that very few people have to worry about #1, and probably 0.5% of the scanner population has to worry about #2.
For what it's worth, I hot swap antennas ALL THE TIME (think 3-6 times in a 15 minute period) when satellites pass overhead.
If you're concerned about large spikes hitting your front end, run two 1N914 diodes from hot to ground, one reverse polarity from the other. This will, for all casual purposes, leave the normal signal alone, but if you ever get a voltage above 0.7 volts on your line (extremely high for RF signals, but very low for induced currents), the diodes will clip and shunt the charge to ground with little problem (the diodes will have far less resistance to these large signals than the input to the scanner.
You should be able to fit them into a small RF box or connector - 914's are tiny. If you want permanent protection you can do this inside your scanner, on the antenna input.
1: you do not have shunted antennas (dipoles, certain verticals, discones) and they build up static. Usually only an issue in windy and/or dry areas, though it can happen anywhere on occasion. If there's DC connection to ground on the *center* conductor of your feed coax, you are static protected, for the most part.
2: You live *extremely* close to a very high power transmitter (10kW or more and less than 1/2 mile) and as such, there may be significant induced currents in large antennas that may discharge through your scanner's input.
However, I'd wager that very few people have to worry about #1, and probably 0.5% of the scanner population has to worry about #2.
For what it's worth, I hot swap antennas ALL THE TIME (think 3-6 times in a 15 minute period) when satellites pass overhead.
If you're concerned about large spikes hitting your front end, run two 1N914 diodes from hot to ground, one reverse polarity from the other. This will, for all casual purposes, leave the normal signal alone, but if you ever get a voltage above 0.7 volts on your line (extremely high for RF signals, but very low for induced currents), the diodes will clip and shunt the charge to ground with little problem (the diodes will have far less resistance to these large signals than the input to the scanner.
You should be able to fit them into a small RF box or connector - 914's are tiny. If you want permanent protection you can do this inside your scanner, on the antenna input.
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Hi Raven and all,
It is imperative you turn off the scanner before disconnecting the antenna or the smoke will escape. Smoke is essential for operation of electronic equipment. If the smoke escapes you can't get it back in and the unit stops working. Only electronic smoke will do, you can't use ordinary smoke because it not only won't work but damages working equipment. Until replacement smoke becomes available it's wise not to let the original smoke they put in at the factory escape.
"If you're concerned about large spikes hitting your front end, run two 1N914 diodes from hot to ground, one reverse polarity from the other."
That should work, in theory. Should a spike enter through the antenna connector the diodes will burst releasing smoke into the scanner. Since it's electronic smoke put in there at the factory it just might work but being tiny they may not contain enough smoke. There is a down side, those inexperienced in soldering techniques may release the smoke or worse, release smoke from the scanner by overheating components. Solder smoke easily masks electronic smoke so you may not realize you released the smoke until you turn the scanner on. Then another thing can happen, if you haven't released the smoke up to this point there is a chance you'll release it when power is applied. That's why it's best to have a qualified technician install the diodes if you doubt your own ability. An experienced tech knows the difference between solder smoke and radio smoke.
Quoth the Raven, nevermore.
It is imperative you turn off the scanner before disconnecting the antenna or the smoke will escape. Smoke is essential for operation of electronic equipment. If the smoke escapes you can't get it back in and the unit stops working. Only electronic smoke will do, you can't use ordinary smoke because it not only won't work but damages working equipment. Until replacement smoke becomes available it's wise not to let the original smoke they put in at the factory escape.
"If you're concerned about large spikes hitting your front end, run two 1N914 diodes from hot to ground, one reverse polarity from the other."
That should work, in theory. Should a spike enter through the antenna connector the diodes will burst releasing smoke into the scanner. Since it's electronic smoke put in there at the factory it just might work but being tiny they may not contain enough smoke. There is a down side, those inexperienced in soldering techniques may release the smoke or worse, release smoke from the scanner by overheating components. Solder smoke easily masks electronic smoke so you may not realize you released the smoke until you turn the scanner on. Then another thing can happen, if you haven't released the smoke up to this point there is a chance you'll release it when power is applied. That's why it's best to have a qualified technician install the diodes if you doubt your own ability. An experienced tech knows the difference between solder smoke and radio smoke.
Quoth the Raven, nevermore.
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Don_Burke
Member
In all the years I have been working in electronics, that smoke has been a factory only item.kb2vxa said:
That sounds like a conspiracy to me...
Yes Don, having worked in the manufacture of electronic components I can tell you there are new hazards to contend with. Since transistors and ICs are potted in epoxy, under certain conditions they can explode. I have been peppered with "buckshot" on more than one occasion and believe me it's painful, never mind the smoke! It gets worse the larger the component, I have seen potted transformers and filter networks blown to bits by excessive smoke pressure. Thankfully I only had to analyze the forensic evidence and wasn't around when Jamie and Adam worked for Bendix.
Yup, it's a conspiracy alright and the military is at the bottom of it. The components I tested were made primarily for guidance and avionics but the exploding filters were for the M1-A1 Abrams tank. Maybe they should have used them for munitions.
Oh, I'm working on a contract deal with a radio control software company to have an .mp3 of my hit song bundled on the CDs. So, what could be such a hit with hams and scanner enthusiasts you ask? Why "Who Let The Smoke Out?" of course!
Yup, it's a conspiracy alright and the military is at the bottom of it. The components I tested were made primarily for guidance and avionics but the exploding filters were for the M1-A1 Abrams tank. Maybe they should have used them for munitions.
Oh, I'm working on a contract deal with a radio control software company to have an .mp3 of my hit song bundled on the CDs. So, what could be such a hit with hams and scanner enthusiasts you ask? Why "Who Let The Smoke Out?" of course!
N
N_Jay
Guest
I have found that, for their size, old electrolytic capacitors contain more smoke than most other components.
Another favorite is the little 555 timer. They seem to have the ability to focus their smoke in a stream from the bottom side burring a hole right through a breadboard.
Another favorite is the little 555 timer. They seem to have the ability to focus their smoke in a stream from the bottom side burring a hole right through a breadboard.
I never power down a scanner simply to change antennas. The fact is you can damage a scanner even if the power is off -- thing about plugging an antenna cable into a 110v outlet. I've seen damage happen because of the power cycle moreso than the antenna change. There is some good advice in this thread though. For example, it is a great idea to discharge static that might have built up before connecting the cable/antenna to the scanner. This holds true for external power cables or speaker/headphone cables as well.
jonny290
Member
Pfft. Everybody knows that the most smoke is contained in the transistor which is configured to blow just before the fuse protecting it does. 
When I was 12 and hooked up a radio reverse polarity, I had the doubly good misfortune of a:doing it with a battery, and b: not using a fuse in line. You wouldn't believe the volume of that diode popping. (I desoldered the diode and the radio works perfectly to this day, 15 years later).
When I was 12 and hooked up a radio reverse polarity, I had the doubly good misfortune of a:doing it with a battery, and b: not using a fuse in line. You wouldn't believe the volume of that diode popping. (I desoldered the diode and the radio works perfectly to this day, 15 years later).
gcgrotz
Member
I've heard that story about the smoke before, years ago it seems. Where did it come from Warren?
RPSINFOMAN
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- Jan 20, 2007
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- 48
Changing the antenna with the unit on has no effect and presents no danger. However, if your using an amplified device (e.g. pre-amp, distribution system) then YES, I would turn it off.
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