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Author Topic: Icom 706MKIIG for emcomm use...  (Read 4229 times)
KT0DD
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Posts: 277




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« on: January 17, 2012, 06:43:45 PM »

Hi all, I am planning to keep my 706MKIIG for battery powered field day and emcomm use. I have heard that this model radio is sensitive to it's operating voltage, and if it drops below 12 volts, the audio distorts. I read the specs and the leeway given from 13.8 volts is +/- 15%. Has anyone experienced this problem? I woulld just like to the lowest acceptable voltage before I need to start re-charging the battery. Thanks for any info / help.  73, Todd - KT0DD
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KD4LLA
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« Reply #1 on: January 24, 2012, 08:09:53 PM »

Don't know about audio distortion, but generally a 706 will shut-off around 11.5 volts.  Best you use a battery and find out exactly what will happen, and when, for yourself.
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K9RFZ
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« Reply #2 on: January 26, 2012, 08:40:12 AM »

I have the low voltage shutdown problem with my IC-706MKIIG at just under 11V. I use a battery booster and short power leads from my 75 Ah battery to avoid the problem.

Joseph, K9RFZ
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KC2MMI
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« Reply #3 on: February 01, 2012, 09:22:30 PM »

Todd-
 They've been used for emcomm by hundreds if not thousands of users year in and out and five years ago it would have been "the" radio for that role. Many radios react poorly to being run at battery voltage when the real spec is 13.8, alternator voltage. You can look into a boost converter that provides 14.4 volts all the time, regardless of the battery voltage, or you can also buy a 16(?) volt battery from a number of race car parts suppliers. That will be an SLI not a deep cycle...but it is an option.

 Possibly of more concern is that Icom uses a 15-volt rated electrolytic cap across the power in that radio, and one prime maker told me bluntly their caps are produced with a 10% tolerance and a 15-volt cap should be expected to fail in that application. There have been discussions about the 706 being vulnerable in that area, so you might want to make sure it is also spike and overvolt protected. Or perhaps locate the cap & replace it with a 30V rated part. Other radios, including other Icoms, do use higher rated caps.

 Again, it was THE goto radio for that job, so it isn't a bad choice by any means.

Jared
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KT0DD
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« Reply #4 on: February 06, 2012, 08:04:50 AM »

Thanks all for the info. I will probably see if I can get a group 8D deep cycle diesel truck / heavy marine battery. A large battery like this hopefully will have a lot of capacity, and not drain for a couple days of use. They are heavy I know, but I can still lift and carry one a short distance, or i will get a small dolly and set up my gear on it. 73, Todd - KT0DD
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W8JX
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« Reply #5 on: February 06, 2012, 09:36:29 AM »

Possibly of more concern is that Icom uses a 15-volt rated electrolytic cap across the power in that radio, and one prime maker told me bluntly their caps are produced with a 10% tolerance and a 15-volt cap should be expected to fail in that application.

Somehow I doubt this. The tolerance is for its capacitance value and not voltage rating.... If it was there would be a LOT of 15 volt caps blowing in a lot of radios.
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KC2MMI
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« Reply #6 on: February 07, 2012, 08:56:43 PM »

"The tolerance is for its capacitance value and not voltage rating"
 I'm only quoting what a prime US component manufacturer told me about their own products.

Since automobile systems run at 13.8-14.4 volts under normal conditions, a 15v rated part should in theory be safe. The problem is, there's a very thin safety margin, and no allowance for aging parts losing some of their margin. And of course, there can be 600VDC spikes in a car, 2000VDC spikes in a truck, during normal startup or shutdown.

Try calling or emailing a couple of electrolytic cap manufacturers of your own choice, see what they have to say directly. Maybe the one I spoke with was confused, or simply has sloppy tolerances.

Either way if you search online, you'll find IC706 owners *have* had that cap fail, it is apparently an easily remedied weak spot in the design.
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W8JX
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« Reply #7 on: February 08, 2012, 11:52:46 AM »


Try calling or emailing a couple of electrolytic cap manufacturers of your own choice, see what they have to say directly. Maybe the one I spoke with was confused, or simply has sloppy tolerances.


Back in 60's and 70's my dad was a sales rep for Paktron capacitors. (I am sure they are gone today) I remember him telling me that the tolerance was for the value, not voltage. While it is fairly easy to maintain plate spacing for voltage rating with dielectric thickness between foil plates in a capacitor total plate area which effects capacitance value is tuffer to do consistently.

Update: I spoke to soon as I see Paktron is indeed still around today.
« Last Edit: February 09, 2012, 06:44:13 AM by W8JX » Logged

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