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Go Back   SailNet Community > On Board > Gear & Maintenance > Electronics
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  #11  
Old 10-24-2012
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Re: VHF Output

"Buck converters (step-down), boost converters (step-up) and buck/boost converters (anything to anything) aren't special. They're in almost every electronic device over a few watts.... on the oder of $15 in lowish quantities."
Actually, not. First of all, dcd-dc converters of any type are not used in anything like a mass or majority of consumer electronics. Bulk regulators, when needed. But anything more? No, not without a real need. You go add $15 worth of components, or even $5 worth of components, to a VHF that is designed to sell for $100-150. You'll bump the retail price by $20-30 and lose market share, that's the reality of the mass market. If you can knock one buck, one dime, off each board? That's sometimes the difference between success and bankruptcy. That's just the way it is. And there are engineers who are hired specifically to say "OK, we've got this, what can we knock out of it?" including electronic components.
What you would like, has been proven impossible in the mass market. In a $500 VHF, sure, you could expect that. And we could all buy bespoke suits instead of khakis. Ain't gonna happen.

"A cheap incandescent flashlight won't have regulation but a good LED one will." Not really. Many LED flashlights have no regulation, they rely on the battery voltage being the limit and don't regulate anything. SOME use upconverters, in order to get a 4.5V white LED running off a single AA cell, but that's because it has to be done that way--not because someone wanted to spend the money doing it. Others use *power* regulators, simply because using a power regulator on a $10 prime LED can double the operating life, and some folks will pay for that. Again, it is not mass market. Like a Bose stereo, they ay sell a lot of them, but it is not mass market.

"but being able to put out 25W on your VHF at 11.5V in a boat is a pretty damn good reason for regulation. " Not really. If all you can supply is 11.5 volts, the "operator" has already failed to maintain their nominal power supply. That's user error, failure, and not common operating mode. In order to make that happen with an ordinary regulator, you'd have to design the whole radio to work at 10.5v,not 11.5, then add a regulator which only had a one-volt power drop in it. Oh yes, all regulators consume power and further reduce source voltage, until you get into dc-dc converters and then again you drive the costs up AND you create RFI in the radio itself, which makes a bad thing even worse.

You think you can do a DC-DC regulator to make your VHF happy with 11.5 volts for under $15? Great, wire it up, hook it on! But the industry has good reasons for not doing it, starting with that HUGE $15 extra cost, from their point of view.

Sure, there are all sorts of new poewr supply chips on the market now. They still cost money. They still need engineering expenses. They still need HEAT SINKS which means more space and more money again. You're not going to do the job with a 2mm x 2mm chip.

And coming back to the most important point of all: 99% of the buyers have no need for it, no understanding or appreciation for it, and no budget for it. Did I mention, "Ain't gonna happen." ?

For those buyers who want better emergency operation, buying a $20 dedicated VHF battery and mounting it behind the radio will do very nicely. It will buy you more protection that any regulation of the vulnerable ship's power system.

But coming back full circle, if you've tested two radios and both put out the (curiously same) 15W of power...I'd look to what you are feeding them. Especially since both are being degraded to the same power level, indicating that's all the power they can find on the DC line. tell me how easy it is to improve the electronics--when the way simpler problem of wiring is still apparently in the way?

First fix it. Then worry about whether it needs to be improved.
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Old 10-25-2012
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Re: VHF Output

Hello,

You're making a number of generalizations which aren't accurate.

Whether or not the VHF has regulation is not in question. The microcontroller driving the menu, the screen, backlights, audio amplifier for speaker, beeper for registering button presses the serial interface to external GPS's, the flash memory for storing settings etc. etc....these internal devices all require various regulators to create whatever voltage(s) they each require - probably linear because they're low power but perhaps one or more bucks to knock down the bulk of the voltage more efficiently. The only question, because I don't have the analog/amplifier or VHF radio experience say with certainty is how would the amplifier react.

As for mass market devices well those cheap compact Apple imitation square AC USB chargers use high frequency switching supplies for a few bucks. This dual usb car charger is $5.54 putting out 2A@5V and certainly isn't using a linear regulator which would mean 2A@12V in for a loss of 14+ watts - not in that small package (I have this in my boat). So you're completely underestimating the prevalence and low cost of various regulators, as well as their outright necessity for modern low voltage electronics.

For example something like the victron battery monitor won't have anything that internally runs on 12V. It's all regulated down. This generally applies to other marine instruments. For what it's worth I've designed 50A shunt sensing 12V current measurement circuits.

Again, we're largely wasting everyone's time with this debate except for the small area where this stuff intersects debugging marine equipment. The point to what I'm saying is that with modern digital based equipment, input voltage issues are farther down on the priority list of debug than they might have been in the past. Not to mention the fact you keep glossing over which is that all these radios are specified to operate between 10V and 15V - if 10+V is getting to the VHF when transmitting at full power that's in spec (if and only if it's 10+ volts WHILE transmitting and drawing full power). The next logical debug step is to look elsewhere. Of course starting the engine to raise the input voltage is low hanging fruit and I don't discourage it.

The fact that two entirely different radios measure the same (how close was it actually?) output power calls the tester in question more than anything else. It's kind of like measuring two cars maxing out at 35Mph with the same speed gun and concluding the gas is bad. Two different radios would have significantly different reactions to low voltage/high resistance input power which makes seeing the same output power pretty unlikely.

Edit: This picture actually shows the IC and inductor for the internal 10W buck conveter (DC-DC) of this $5 usb car charger.


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Last edited by asdf38; 10-25-2012 at 01:34 PM.
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Old 10-25-2012
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Re: VHF Output

There may be a problem with the cable that you are using between the radio and your antenna meter. I suggest that you try another jumper cable. If the reading is still low, you should consider the possibility that your meter is not working properly. Borrow another meter from someone and compare readings.
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