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Thread: Kenwood TK 3101 2-Way Radio Transmit Power Settings?

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    Kenwood TK 3101 2-Way Radio Transmit Power Settings?

    I have several Kenwood TK 3101 2-way radios that we use with our Autocoms for bike-to-bike communication. I just bought some Kenwood battery eliminators, a fake battery back that has a 12v cigarette lighter plug, and uses bike power to power the radios instead of the batteries. What I intend to do is wire the battery eliminators into the Autocom 2-way radio lead - it has 12v power along with the talk and listen wires - but I understand that the Kenwood TK 3101 has two transmit power settings, 0.5 watt and 2 watt. I downloaded the manual for the radios, but it doesn't say anything about how to change the transmit power setting. It does address setting sub-channels for privacy, but we don't use them.

    TK 3101s are no longer produced by Kenwood, but they're abundant, rugged and reasonably priced. It seems lots of car race teams use them, too. The internet says that you can program the radios with a PC, some software (KPG 48D) and a serial cable (KPG 22). I assume the programming not only addresses setting channel frequencies but the output power, too.

    Does anyone know anything about these radios? I don't know if the Autocoms ( Logic E11s) can handle the power requirements for 2 watts, and I don't know what ours are set for and I don't know how to find out, and I sure as *&$& don't want to burn out the Autocoms. Can't find anything on the internet, and Kenwood's tech department puts you on hold for eons.

    Does anyone have any experience with this issue? Can someone point me to someone else who knows, or some website? Thanx
    Roger Wiles
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    Hmmmm, while I didn't download the PDF manual, a Google search of kenwood tk 3101 manual took me right to it. With a background in RF electronics, if you get jammed up, I could take a peek. I have some 3130's and all the resets are easy. OM
    BTW, I'll move this to gear for you.
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    Tk 3101

    Thanx. I have the manual, downloaded it in PDF, and it addresses everything except the transmit power issue. At least, the edition I have does. I mostly want to know how much transmit power it is set for now, how to tell, and how to change it. Any help appreciated !!!
    Roger Wiles
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    Roger,

    More Googling yielded a TK-3101 service manual, with additional technical info: http://xa.yimg.com/kq/groups/17870964/932827890/name/TK-3101+Service+manual.pdf, but it also makes no mention of multiple power levels.

    Given that both Owners and Service manuals are silent on this, perhaps what you heard isn't true for this model.
    David Brick
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    Have you thought about actually calling Kenwood customer support. It's amazing the information you can get by using the old fashioned way, talking directly to the manufacturer.

    Unless I'm wrong, I believe the power setting refers to the strength of the radio signal that is broadcast to other radios, not what goes through the Autocom. It allows greater range, but "technichally" may require a license.



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    Kenwood Tevch

    Yeah, I've tried calling them, Will try again today. Yes, there is a difference between the transmit power output, and the current draw through the battery eliminator. However, one can assume that if a higher transmit power is selected - which now seems unlikely, based on the manual that I downloaded from the post above - the current draw through the battery eliminator would be greater. If a mistake, a costly one can be made, I'm usually up to the task.
    Roger Wiles
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    TX Power

    Quote Originally Posted by dbrick View Post
    Roger,

    More Googling yielded a TK-3101 service manual, with additional technical info: http://xa.yimg.com/kq/groups/17870964/932827890/name/TK-3101+Service+manual.pdf, but it also makes no mention of multiple power levels.

    Given that both Owners and Service manuals are silent on this, perhaps what you heard isn't true for this model.
    Thanx. I tried downloading that one from Google but it just cranked on forever. No luck. Your link did get the manual for me. In tech spec, back cover, it says the transmit RF power is 500 millwatts, 1/2 watt. So I guess that should settle it. I'm going to call Kenwood again today to verify.

    Thanx
    Roger Wiles
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    More on Kenwood TX Output

    Okay, Kenwood verifies that the TK 3101 IS a 2 watt RF output transceiver, and that it IS adjustable (the transmit output, as well as privacy freqs an other stuff) via the software, but the radio is no longer produced, and the software is unavailable from Kenwood. Further, the software runs in DOS and not Windows, and a serial cable is required.

    He didn't know how much current the battery eliminator draws.

    The software KPG 48D is available on the internet and on Ebay, and the cable is also available on Ebay (KPG 22) but I don't know how to run it in DOS.

    Two calls in to Autocom, still awaiting.
    Roger Wiles
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    IIRC, the TK3101 operates in two different bands: FRS and GMRS (or some such). FRS is limited to .5 watts but requires no license; the TK broadcasts with that output when operating on the FRC bands. GMRS radios (requiring a license) operate on a different band but at 2 watts. When operated on the GMRS band, it broadcasts at 2 watts. It is not possible, to the best of my knowledge, to operate the TK3101 at 2 watts on the FRS Bands.

    Larry Johnson
    El Paso Tx

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    Quote Originally Posted by ljjohns View Post
    IIRC, the TK3101 operates in two different bands: FRS and GMRS (or some such). FRS is limited to .5 watts but requires no license; the TK broadcasts with that output when operating on the FRC bands. GMRS radios (requiring a license) operate on a different band but at 2 watts. When operated on the GMRS band, it broadcasts at 2 watts. It is not possible, to the best of my knowledge, to operate the TK3101 at 2 watts on the FRS Bands.

    Larry Johnson
    El Paso Tx
    How can I tell which one, FRS or GMRS, mine are set for? Is that what the obsolete DOS software is for? Thanx, that was helpful
    Roger Wiles
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    GMRS and FRS in Kenwood TK 3101

    Well, this is interesting. Wiki says that the first seven channels on the 3101 are FRS (Family Radio Service), a license-free set of channels, and channels 8-15 appear to be GMRS channels, which require a license.

    Now, I wonder if the TK 3101 does in fact transmit at 2 watts if set to channels 8-15, and at 0.5 watts in channels 1-7. The two manuals I've found so far don't really address this.

    I hooked up a battery eliminator to a TK and to a 12v battery and put the multi-meter in series set to amps, but I didn't know what I was seeing. 47 somethings, depending on the range I had it set for, I guess. I COULD do the same thing, and see if the current draw is the same for channel 3 versus channel 14, for instance, and see if the battery eliminator draws more current on the GMRS channel. And then figure out if the Autocom can handle that current draw, or if it will turn in to smelly plastic with escaping smoke.

    It WOULD be nice to use the 2 watt settings (I can't see anyone busting us for not having a license - $85 for 5 years) - they'd have to find us and motorcycles are on the move, so I don't think using GMRS with a privacy code would be a big risk, and I would assume the range would be somewhat greater.

    Larry, are you pretty sure the 3101 transmits at different power levels depending on the channel selected? Thanx
    Roger Wiles
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    More Kenwood stuff

    Just heard from Bryan at Autocom. He says he thinks that the TK 3101 cuts broadcast power back to 1 watt when it senses that the battery is NOT in use, and something else is powering the radio, like a battery eliminator. Again, neither manual I have address this.

    Anyone know?
    Roger Wiles
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    Well, for some reason I'm not absorbing what the issue is.

    I have a Kenwood 2M mobile and I have messed with other Kenwood radios, and I find it completely plausible that it would reduce power to 1/2 watt for the FRS channels just for legal reasons. The mobile can receive AM aircraft band but refuses to transmit, for example.

    I don't buy in to the idea that it would reduce power consumption for the battery eliminator. That doesn't make sense. If anything you'd want to increase the power output if there's unlimited input power available.

    I also don't think it would have a 1W setting. It would have 2 power settings - maybe the software could lock in the .5 W output for the GMRS channels as a battery-saving scheme. But I don't buy it, with no way to change it back in the field.

    In fact I would bet that there isn't anything the DOS software can do that you can't do with your fingers on the radio, with the manual close at hand.
    The software probably makes it easier.

    So is the issue that we don't want to set fire to the wiring?
    How bout some rough estimates...
    If we figure the radio puts out 2W RF and is 50% efficient, then it burns up 4W DC. If we assume the battery eliminator is 50% efficient, that brings us to 8W at 12 (14 actually) Volts - Watts is Amps times Volts, so I get 2/3 (0.666) Amps.

    Not very much. And I would be shocked if they are really only 50% efficient. Put a 1A fuse on it, done.

    The license requirement for GMRS is because you can transmit with a useful amount of power, therefore there is the possibility of interfering with some other equipment - the license information might help the FCC track down the offending transmitter and get it fixed or off the air. That's not going to be enforceable if the transmitter is riding around on a motorcycle, and unless you modify the radio (I don't mean with the DOS software either) it won't be transmitting out of band or anything like that, so it isn't likely they'll be looking for you in the first place.

    Range is going to vary a lot depending on where you are and what materials are close by.
    FRS at .5 W with the rubber ducky antennas will work pretty well for about 1/2 mile and might go as far as 2 miles, maybe.
    GMRS at 2 W will work much better, although it will still be easily blocked by hills, trees, people, etc.
    If transmitter and receiver are both on high ground you might get 10 miles in the extreme, with 1 to 2 miles across the flat being more likely.
    Take cell phones too in case you get separated more than a mile.

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    Scott's Reply

    All good stuff, Scott. Thanx. I'm an electronics newfie, and it's all greek to me. I got the battery eliminators, but one is defective, and I will have to send it back. I guess I can tap the 12v in the Autocom radio lead and use it to power the radios without fear.
    Roger Wiles
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    Quote Originally Posted by scott.lambert View Post
    Well, for some reason I'm not absorbing what the issue is.

    I have a Kenwood 2M mobile and I have messed with other Kenwood radios, and I find it completely plausible that it would reduce power to 1/2 watt for the FRS channels just for legal reasons. The mobile can receive AM aircraft band but refuses to transmit, for example.

    I don't buy in to the idea that it would reduce power consumption for the battery eliminator. That doesn't make sense. If anything you'd want to increase the power output if there's unlimited input power available.

    I also don't think it would have a 1W setting. It would have 2 power settings - maybe the software could lock in the .5 W output for the GMRS channels as a battery-saving scheme. But I don't buy it, with no way to change it back in the field.

    In fact I would bet that there isn't anything the DOS software can do that you can't do with your fingers on the radio, with the manual close at hand.
    The software probably makes it easier.

    So is the issue that we don't want to set fire to the wiring?
    How bout some rough estimates...
    If we figure the radio puts out 2W RF and is 50% efficient, then it burns up 4W DC. If we assume the battery eliminator is 50% efficient, that brings us to 8W at 12 (14 actually) Volts - Watts is Amps times Volts, so I get 2/3 (0.666) Amps.

    Not very much. And I would be shocked if they are really only 50% efficient. Put a 1A fuse on it, done.

    The license requirement for GMRS is because you can transmit with a useful amount of power, therefore there is the possibility of interfering with some other equipment - the license information might help the FCC track down the offending transmitter and get it fixed or off the air. That's not going to be enforceable if the transmitter is riding around on a motorcycle, and unless you modify the radio (I don't mean with the DOS software either) it won't be transmitting out of band or anything like that, so it isn't likely they'll be looking for you in the first place.

    Range is going to vary a lot depending on where you are and what materials are close by.
    FRS at .5 W with the rubber ducky antennas will work pretty well for about 1/2 mile and might go as far as 2 miles, maybe.
    GMRS at 2 W will work much better, although it will still be easily blocked by hills, trees, people, etc.
    If transmitter and receiver are both on high ground you might get 10 miles in the extreme, with 1 to 2 miles across the flat being more likely.
    Take cell phones too in case you get separated more than a mile.
    While I can't confirm for that particular model.......^^^^^Me likey. It's a great explanation of how this kind of radio works.
    And.....now that I realize you were looking for possible 12 volt power consumption- I wouldn't give it a second thought. OM
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