roy@alanine.phri.nyu.edu (Roy Smith) (08/30/90)
I just bought an ICOM M-11 handheld VHF tranciever. It comes with
a removeable NiCd battery pack and a 110V recharger. The manual says you
can charge the battery pack while it is still attached to the radio, but
you should make sure the radio is off because you might damage it. Can
anybody think of any good reason why you shouldn't be able to run it while
plugged in?
While playing with the scan feature, I noticed it always stops on
24 and 70, even though there isn't anything there. Why should it do that?
It's almost as if somebody was broadcasting unmodulated carrier on those
channels. Is that possible and/or likely, or is there a better
explanation?
--
Roy Smith, Public Health Research Institute
455 First Avenue, New York, NY 10016
roy@alanine.phri.nyu.edu -OR- {att,cmcl2,rutgers,hombre}!phri!roy
"Arcane? Did you say arcane? It wouldn't be Unix if it wasn't arcane!"larry@kitty.UUCP (Larry Lippman) (08/30/90)
In article <1990Aug30.131140.20946@phri.nyu.edu>, roy@alanine.phri.nyu.edu (Roy Smith) writes: > I just bought an ICOM M-11 handheld VHF tranciever. It comes with > a removeable NiCd battery pack and a 110V recharger. The manual says you > can charge the battery pack while it is still attached to the radio, but > you should make sure the radio is off because you might damage it. Can > anybody think of any good reason why you shouldn't be able to run it while > plugged in? I have no knowledge of your specific radio, but based upon some familiarity with other rechargeable radio apparatus, I can give you some general reasons why such a caution notice might appear: 1. Many chargers have little voltage regulation beyond I^2R across a dropping resistor and/or inherent transformer loss current limiting. If the battery were disconnected, the open circuit voltage might be as high as twice the battery voltage. If the battery pack developed an open circuit fault (perhaps an internal fuse blew) && if the charger were connected to the radio && if the radio were turned on, the charger circuit could present a substantial overvoltage to the power input of the radio, thereby causing damage. 2. Same scenario as (1) above, but consider that some chargers have no filter capacitor, so there could be some pretty ugly DC powering the radio if the battery were open. While there might not be any damage (except for possible overvoltage), the radio would not likely operate with such huge ripple. 3. Same scenario as (2) above, but with the battery okay and charging. There might still be an excessive amount of ripple introduced into the radio, preventing its proper operation. No real damage here, but the manufacturer might simply want to avoid any possible customer complaint. 4. Many chargers do not have the current capacity to run the radio itself, especially in transmit mode. If the battery were deeply discharged && if the charger were connected to the radio && if the radio were turned on, the current capacity of the charger might be exceeded, thereby causing damage to the charger. 5. A remote possibility: there may be two much RFI radiated back through the AC powerline were a charger to be connected, but the radio itself meets type acceptance when operated as an isolated device. > While playing with the scan feature, I noticed it always stops on > 24 and 70, even though there isn't anything there. Why should it do that? > It's almost as if somebody was broadcasting unmodulated carrier on those > channels. Is that possible and/or likely, or is there a better > explanation? You live in New York City, right? Isn't New York City known as "The Intermodulation Capital of the World"? Need I say more? :-) Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 {utzoo, uunet}!/ \aerion!larry
wb8foz@mthvax.cs.miami.edu (David Lesher) (08/31/90)
In <1990Aug30.131140.20946@phri.nyu.edu> roy@alanine.phri.nyu.edu (Roy Smith) writes: > I just bought an ICOM M-11 handheld VHF tranciever. It comes with >a removeable NiCd battery pack and a 110V recharger. The manual says you >can charge the battery pack while it is still attached to the radio, but >you should make sure the radio is off because you might damage it. Can >anybody think of any good reason why you shouldn't be able to run it while >plugged in? Well, it's like this. Icom wanted a battery that made 14 volts in order to get the transmitter power up. But they ALSO wanted it to be rechargeable from a car's (roughly) 13.8 volt source. So when you plug in the charger, or 13.8 volts to the top of the radio, a little teeny-tiny relay inside the pack opens and splits the battery string into two 7 volt strings. THEN two transistors provide individual charging current regulation to the strings. There are also about 9 diodes inside there, too. So with the charger plugged in, you get ~~7 volts from the pack. The radio is unhappy with this. When this mess fails, you take apart the pack, and try to fix it. Then you give up, hardwire the pack to be 14 volts (no relay) and build a drop-in 14 volt charger. You can guess (;,} how I know all of this........ -- A host is a host from coast to coast.....wb8foz@mthvax.cs.miami.edu & no one will talk to a host that's close............(305) 255-RTFM Unless the host (that isn't close)......................pob 570-335 is busy, hung or dead....................................33257-0335
jeff@xanadu.com (Jeff Crilly N6ZFX) (09/01/90)
In article <1990Aug30.131140.20946@phri.nyu.edu> roy@alanine.phri.nyu.edu (Roy Smith) writes: > > I just bought an ICOM M-11 handheld VHF tranciever. It comes with >a removeable NiCd battery pack and a 110V recharger. The manual says you >can charge the battery pack while it is still attached to the radio, but >you should make sure the radio is off because you might damage it. Can >anybody think of any good reason why you shouldn't be able to run it while >plugged in? Typically the chargers are of the trickle charge type and don't provide nearly enough current for the radio to transmit. Also, because of the nature of nicads they should be discharged before charging. The radio may have some circuit to manage the charging (My IC-2SAT does) and only perfoms well if the radio is off and not drawing current from the charger and batteries. Of course, if you have a quick charger (which I belive provides pulsed DC to the nicads) then this would probably be bad for the radio. Using a scope you could see just what the charger puts out. > > While playing with the scan feature, I noticed it always stops on >24 and 70, even though there isn't anything there. Why should it do that? >It's almost as if somebody was broadcasting unmodulated carrier on those >channels. Is that possible and/or likely, or is there a better >explanation? Sorry, can't help here. ---------------------------------------------------- Jeff Crilly (N6ZFX) AMIX Corporation 2345 Yale Street Palo Alto, CA 94306 jeff@amix.com, {uunet,sun}!markets!jeff ----------------------------------------------------