voltage drops chart

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I just purchased a PWRGate PG40S and decided to do some voltage measurements at different points along the setup. The rig is a Flex-6500 and the meter is a Fluke 87 V. I have a graphical representation (Google drawing) here: Voltage Drops

The drops along the cable, especially between the Flex and the PG40S seem a little high to me. On receive it's 40 mV and on 50 watts transmit it is 230 mV. Does this seem unreasonable? The cable is the stock cable that came with the rig with power poles on each end.

The power supply is capable of 32 Amps peak at 15 VDC (variable) and 30 Amps continuous.

Should I adjust the power supply for 13.8 VDC at the Flex at 50 watts (full power for me)? If everything is linear that would be an increase of 1.02 VDC bringing the receive voltage to 14.32 VDC. Too high?

Thanks,
Kevin K4VD
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Kevin K4VD, Elroy

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Posted 2 years ago

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George Molnar, KF2T, Elmer

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Not too high, but likely unnecessary. Battery is charging, rig is running, you're getting enough power for your requirements. If it bugs you, sure, tweak the PS, make the leads shorter, etc. Otherwise, seems pretty well put together as it is.

I have a similar setup. Flex runs max 30 watts out for JT65 without amp. That level runs the amp to full output when I operate CW or (gasp!) phone. Everything's happy.
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Kevin K4VD, Elroy

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Thanks George. That's what I was hoping to hear. I never paid much attention to the power supply as, until recently, it was just a power supply and rig with nothing but cable in between. Now with the PWRGate and battery on it I got a little interested.

Kev
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Steve - N5AC, VP Engineering

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George, my recollection is that I get 100W out with JT65 ... I don't see any reason why you would not as well.
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George Molnar, KF2T, Elmer

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Hi Steve, I absolutely can run it full tilt. Should have clarified that it is set to run lower usually. Have set the RF output level so that I won't accidentally overdrive the amp, and find that running it there keeps the fan quiet. Works great.
(Edited)
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Gerd Henjes

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Kevin...

My 15 year old Astron RM-35 was adjusted to 14.5 volts the day it was delivered. I also was inside and soldered all the crimp on connections and snugged up the screws on the capacitors.

In running many ham rigs over the years, which include a Flex 5000 and now a 6300 I use the shortest possible power lead length to prevent a voltage drop. 

My thoughts have always been it's easy lowering the power output than raising it. For example, my 6300 is set at about 45 watts to drive my Alpha easily past the legal limit.

If your voltage is wagging around the first thing I'd suspect is you power lead... after that I'd look inside your power supply and make sure everything is wired with the lowest losses in mind... solder and tighten down those connections should do it.

Gerd, W2ISB
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Jay / NO5J

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Kevin

The published spec for supply voltage is 13.8 v +/- 15%.

IOW 11.73 v to 15.87 v. 14.32 v is within spec.

I'm currently running my 6500 at 14.71 v in RX/idle an 13.9 v TX/max output. which is a little shy of a 7% increase at idle.

My power supply is adjustable via a front panel knob. I'm less concerned about the increase being applied to my 6500, than I am about the increase being applied to the panel lamps, on other pieces of equipment.

I can run the supply voltage higher, but I don't need to.

73, Jay - NO5J
(Edited)
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Rick Hadley - W0FG

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I run my supply at 13.94 volts in front of the fuse, 13.78 following as measured by FlexMeter.  It will drop to just below 13 volts in continuous transmit, but I get 95+ watts output on all bands.  Only disadvantage I can see is that I blew the 12v dial lamp on my G-8000DXA rotor and it's nearly impossible to replace.  Oh well....I can live with that, but Yaesu just lost a few brownie points with me.
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Jay / NO5J

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That's what I like about FlexMeter. It shows you all the values based on what the radio thinks they are. My digital VOM agrees with the analog front panel volt meter on the power supply, if close one eye and move around enough. But FlexMeter gives me an accurate readout of what the radio actually see's on the other side of the 12 inch power cable.
In fact that's how I set the output of the power supply. I read the FlexMeter 13.8A value and increase the voltage until it just changes from 13.8? v under load to 13.9 v. which depending on the VFO frequency will also show 93+ watts out on the FlexMeter FWD Power scale.

Do I wish that 93w was actually displaying 100w?
You bet!,

But I also know the output tends to spike a little when I key the radio. I've seen it spike at a peak of 106w a few times. It spikes to @106 drops to 95-96w, then after the finals warm up it drops to a little less than 94w.

I get different values from my PowerMasterII meter, A meter I trust almost as much, based on nothing more than the fact that I paid the most for it. Unless you count the total cost of the 6500,s internal metering being displayed by FlexMeter, which I didn't pay anything for.

The only output spec I've seen from Flexradio for the output is 100w (nominal), with no mention of a tolerance range. So it's probably close enough and not worth the hassle of, failing to get it to read 100w. 

My amp only wants 74w of input to reliably output @Legal Limit. Which means I never set the radio for MAX power anyway. If anyone claims to see any decrease in my signal running it at 74w barefoot, I hit the Oper button on DDUtil and show them Legal Limit. Most of my barefoot usage is 20w or less digital so I don't have any real reason to worry about where the 95,96,97,98,99,and 100w readings are hiding.
   

73, Jay - NO5J
(Edited)
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Kevin K4VD, Elroy

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Lots of good info. Thanks all.

I downloaded Flex Meter (1.1). At the moment I'm running 14.30/14.18 before/after the fuse. At 10W that's 13.86/13.74. At 50, 13.74/13.62.

Based on George's comments above I'll probably end up dropping it back down to 13.8V from the power supply, shorten up the cable to the rig and let it go at that.

I have an Astron RS-50 I've been through mechanically and found no issues (suspected hum) but I haven't put it on the scope under a load yet. I'll do that soon and if it all looks good, swap the Alinco back out for other purposes.
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Rick WN2C

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OK, I have to ask...what is flex meter and is or does it work on a 6300?
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KY6LA - Howard, Elmer

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Flexmeter is a 3rd party app that uses the Flex API to display a lot of the internal parameters of the 6000 series including 6300

It can be found at

https://db.tt/A9TEtwQK
(Edited)
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Chris DL5NAM

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... how many QSO you will made more if you run 14,1V or 14,14567834234567V?

Sorry, but if you have problems with voltage lost: don't trust your power supply labels and use much thicker power cables. This discussion remember me like old CB'er time before 40 years!
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Kevin K4VD, Elroy

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Hi Chris:

Thanks for the advice.

Kevin
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Chris DL5NAM

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Your welcome !

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