Using 2 Astron 25 Amp Power Supplys to Power 6700

Ray - K6LJ

Would like to use 2 25 amp Astron Power Supplies in parallel to power the 6700. I have noticed when running FT8 at about 80 watts with the 1 supply that the output voltage drops from 13.6 to 12.5 V. I also feel the power cables to the radio get warm after a while running at 80 watts.

A second 25 amp supply running would help with the voltage drop but any negatives?

Thanks

Craig_KØCF

You absolutely CANNOT do this! The power supplies will fight each other unless they are specifically designed to lock to another supply. Get a new, better regulated power supply rated for 30 amps or more.

Ray - K6LJ

Thanks that's what I actually thought but was just hoping.

John - AI4FR

If the power supply is good. Consider making the cables as short as possible. Thicker cables would be a plus as well. It bothers me to hear that the cables are getting warm. That might very well be the cause of the issue you are seeing.

Ray - K6LJ

I understand. The standard plug in the back does not allow a larger power wire but making it shorter could help. Thanks for the comment

Keith Flint

Question. Why are you running 80 watts on ft8? Please read the documents. Maximum power recommended is 20 watts.. Keith W7zac

Dave - W6OVP

Ray - I have good luck with a 30A MFJ-42330 MVP with my 6300. Dave.

KY6LA_Howard

You actually can do this BUT you need a load balancing circuit so the power supply do not fight each other. Much easier solution unless you are an EE is to buy a 50A supply. A 30A supply is usually the peak supply rating with 24A continuous FT8 needs the continuous rating

KY6LA_Howard

Nonsense

FT8 is a Weak Signal Mode NOT A LOW POWER MODE

Sometimes you even need 1.5KW to work a -24 especially if you are using a Flex where you can have a 6dB gain advantage over a legacy radio with an external decode interface box.

Simple Math. He is -24dB but he is getting you at -24 -6 =-30dB. So he won’t hear you. For him To copy you at say -12dB you need to add 18dB Of gain So using 20W as a basis you need 1,262W for him to copy you

KY6LA_Howard

The Anderson plug will accept 45A fitting or at least #10 wire

Jay Nation

I shortened my power cable to 10", now I only drop to 14.4v with 14.7v supplied at the rear jack.

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Juan Rivera

I use a single Astron RS-20M charging an AGM battery.  If you go that route you need to adjust the output voltage to the correct level for AGM batteries.  It works great - no EMI and reliable power during a power outage.

Keith Flint

RTFM Guy!

Ray - K6LJ

Hi Keith - Thanks for the comment. I shortened the Power cord to about 18 inches and the voltage is now 13.73 to 13.05 @ 80 watts. Howard I have seen your post about FT8 many times thanks I agree.

KY6LA_Howard

@Keith

I did RTFM.. but I can also do communications math...

I now have 201 Countries on FT8 (162 confirmed) in about a year.  Many of them would have been impossible at 20W.  I do have an excellent antenna system and even that does no help enough at 20W when the other guy is weak

Why?

Because my Flex and most likely yours can hear FT8 about 6dB better (gain advantage) than most legacy radios with an external interface box.  On another thread, Tim went into some detail about the losses and distortion that Legacy Radios and Interfaces introduce to digital modes when they convert from Analog to Digital to Analog in order to be able to decode.  Flex with DAX stays totally in the digital domain so you do not have that extraneous distortion and decimation issues.

You need to add power to compensate for that 6dB gain advantage

You may need to add further transmit gain because many Legacy radios also do not hear as well as your Flex so you might need to add another 6-10dB to compensate for his **** radio/antenna...and that it just to get to a -24 at the other guy's receiver.  Realistically you want to be around -18 or better for him to copy you reliably and about -12 or better to bust a pileup.

BUT adding power can be very tricky as you do not want to increase the distortion and splatter on your signal as that will actually make you harder to decode.  So when you add power, you must absolutely keep the mike gain out of the red and when I run a KW or more I make sure the mike gain does not even hit the yellow...

Roger_W6VZV

It is really amazing how many people think that you are only supposed to run QRP on the digital modes such as FT8, PSK, etc.  The laws of physics are the same.  Sometimes QRO is *necessary* for a solid contact or any contact.

k3Tim

Curious if a Shotky diode could be used at each power supply to run them in parallel? I would think it's possible.

Greg N8GD

If you want to use Astron linear supplies, I would never use anything less than an RS-35 model - the "35" is peak, intermittent amperage.  The RS-35 is rated at 25 Amps continuous, so if you want extra "head room", get an RS-50 model.

Keith Flint

Digi modes do not use any mike, they use DAX audio.

KY6LA_Howard

I was referring to the Mike LEVEL METER which needs to stay out of the red when running low power and out of the yellow when running High Power on FT8

KY6LA_Howard

I totally agree with your recommendation... I use 50A linear Astron's for my 6700 as the RS-35 does not have any significant headroom.

Stan VA7NF

Juan's suggestion is the best.  My supply charges a battery which has an 8 gauge wire with marine breaker and 75A Anderson PP connector going to a 4x45A cube with one 10 gauge to the rig. 
Alternate connection when not using the battery is a power supply to 75A cube cable.
See https://powerwerx.com/ for marine breaker and connectors

Pat N6PAT

And if legal limit was 2K then folks would say you need to run 2K to make contacts and that 1.5 isn't enough....and if legal limit was 5k......

Keith Flint

Yes. I have never messed with it though, since I keep my power at or below 20 Watts, and adjust it with the DAX level control. I routinely work weak stations (dx) at low power levels here. My noise levels are very good here in NV. w7zac

Ian1

A while back Howard published s powerpoint on setting up a quiet station it was well written and thought out. I run my station via a AGM battery and have a powergate isolating it and a powersupply charging the battery. No noise works great all load conditions my powersupply can putout 30 amps continuous. FT8 is not mean for low power I had that misconception as well until i read Joe Taylors papers again. Ian Km4cqg

Jim Ricker

Juan
what AGM battery are you using? I tried an Optma Yellow Top interfaced with a West Mountain Radio 
PowerGate PG 40S. The battery did not last a year. Spoke with the guy at Auto Zone he said they get more than a few of these back every year.Looking to replace it now.
 Don't want to hijack the tread
Jim K6CEF

Greg N8GD

I use an Exide AGM battery in my car (a 2015 Honda CR-V).  I upgraded it from the anemic lawn tractor-sized battery that it originally came with to provide extra capacity for my 3 radios in that vehicle.  I also have another Exide AGM battery that I use for a medical refrigerator (being a diabetic on insulin), and it also serves as a portable power source for EMCOMM work.  I've never had any trouble with either one of them in the 3 years I've had both of them.  The refrigerator battery saw some pretty heavy charge-discharge use on a 5 week road trip from Ohio to California and back in the Fall of 2015.  I was careful to follow the rule that says to discharge no more than 50% of capacity.  It kept my solid state fridge working quite well in 100+ degree temperatures (with the engine off - it's separate from the car battery and fed by a Power Gate unit) while we visited many national parks out west,  The Exide units are flat plate style AGM batteries, while the Optima units are circular/cylinder would.  That may have something to do with reliability?  They're not cheap, though.  I paid $185 each from Amazon (but that did include free shipping!).

Varistor

Why is the 6700 drawing so much current that it overloads the PS? None of my radios draw more than 16 amps at full power.

KY6LA_Howard

@Rudy. Which Flex radios do you own?

Juan Rivera

Jim,
I'm using two Odyssey PC-680 batteries: https://shop.odysseybattery.com/p/pc680
I normally use these for DC power in a home-built helicopter.  One would be plenty for the Flex, but I had two that I wasn't using, so I used them both.
Juan WA6HTP --> www.helicycles.org

John - AI4FR

Not to mention that all the power supply's and batteries in the world will not solve the issue of the power cables getting warm.