Using 2 Astron 25 Amp Power Supplys to Power 6700

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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

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Ray DeVreugd

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Posted 3 months ago

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Craig - KØCF

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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.
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Ray DeVreugd

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Thanks that's what I actually thought but was just hoping.
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KY6LA - Howard, Elmer

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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
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Juan Rivera

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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.
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k3Tim

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Curious if a Shotky diode could be used at each power supply to run them in parallel? I would think it's possible.
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Stan - VA7NF

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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
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John - AI4FR

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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.
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Ray DeVreugd

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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
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Keith Flint

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Question. Why are you running 80 watts on ft8? Please read the documents. Maximum power recommended is 20 watts.. Keith W7zac
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KY6LA - Howard, Elmer

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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
(Edited)
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KY6LA - Howard, Elmer

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The Anderson plug will accept 45A fitting or at least #10 wire
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Jay / NO5J

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

    #FlexRadio IRC chat

For real-time discussions

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User created documentation.
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         73, Jay - NO5J

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Roger J. Buffington

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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.
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Pat N6PAT

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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......
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Mark - WS7M

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Since I started in radio as a 50W limited novice in 1972 the stations on the bands seem to have continuously used more and more power.

I am not saying this is bad but it does seem to indicate that the general trend follows Jeremy's motto on the old UK motor sport show TopGear:   Power... POWER...  MORE POWER!!!

I do run power but I start low, work high depending upon who I am working.  I use a solid state amp.

90% of the time my Flex is putting out 8W to 12w into my amp which is putting out like 200w to 400w.

5% of the time I switch my amp to mid power level and put out:  500w.

3% of the time I switch my amp to full power and output 1500w.

2% of the time the amp is off and I run 10-50w direct out of the flex.

I use the amp most of the time simply because I can keep it underrated rather than trying to push the flex finals to higher power.

During my 90% operation both my flex and amp are loafing along at WELL BELOW their rated power.  Fans hardly ever come on.

Now on your point:

I personally know 3 hams that have 5kW amps.  I know they run them at 5kW as well.  It seems that this is becoming more and more the norm as these guys get WANIAC awards:

(Worked All Neighbors In All Counties)

One local ham I know has a fake QSL card from a neighbor that basically reads:

<my friends call>
<neighbors address>
RST <599> received
RST 0 sent
Mode: RFI
Comment: You sound great coming through my stereo while the game is on!  Nice work!

The neighbor actually went online figured out how QSL cards look, made one up on his printer and hand delivered it.  Together they went and solved the RFI problem but I thought that was pretty funny. 
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Dave - W6OVP

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

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RTFM Guy!
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Ray DeVreugd

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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.
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KY6LA - Howard, Elmer

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@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 crappy 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...


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Greg - N8GD

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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.
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KY6LA - Howard, Elmer

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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.
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Keith Flint

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Ok, you guys run your kilowatts, I will just keep my 20 W and my finals intact. W7zac
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Keith Flint

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Digi modes do not use any mike, they use DAX audio.
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KY6LA - Howard, Elmer

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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
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Keith Flint

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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
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KM4CQG

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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
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Paul

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I take the view that one day conditions WILL be right for an elusive country even with low power. But patience is needed to resist the temptation to crank up the power. Surely 'mañana' will do?

Ps. I do have a vey nice solid state linear which I use when too many mañana's have passed :)
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KY6LA - Howard, Elmer

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(Edited)
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Jim Ricker

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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
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Greg - N8GD

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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!).
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Juan Rivera

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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
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Varistor

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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.
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KY6LA - Howard, Elmer

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@Rudy. Which Flex radios do you own?
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John - AI4FR

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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.
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Varistor

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I do not own one, but keep on experimenting with a 6500. Have not measured it’s consumption, but have for the others and every 13.6V rig outlet is fused at 20 amps.

I run a single 100 amp PS that feeds into 3 RigRunner distribution boxes, one for each radio position, each fused at 45 amp total with the rigs fused at 20 and the other 4 ports fused at 5 amps. It’s much easier to keep RFI from the 13.6V power bus this way. There is an identical spade PS should the first dies for some reason. Works beautifully.
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Michael Walker, Employee

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What do they do to prevent RFI suppression on each port?   I know they mention it, but I would like to know under the covers what is there?

Ray, the voltage sagging may not be a powersupply issue, but ohms law issue.  Somewhere you have a slight bit of resistance that is causing the voltage to drop either at a connector, fuse or even the powerpolls.  You can use a voltmeter to measure the voltage drop while under full load.

You can increase the powersupply up to about 15V without harming the radio.  

Is the powersupply sagging or is it that the power cables and connection causing some voltage loss.  To test for sagging, measure the full load voltage at the power supply lugs and then at the radio and see if there is a difference.

Find the voltage drop and make sure you clean all the connections to insure there is a 0 ohm connection (aka, a deal short).

Lastly, from 80 to 100 watts is less than 1 db less of RF power and yes, you might be able to measure that in FT8 (a -10db signal will now be -11db) you might ask yourself if it is worth the effort.

BTW, I get full power out on FT8 on 20M with an RS20A on a 6600 and I just checked on 40 by setting Tune to 100 and it was 102 watts out.  My RS20 doesn't sag at all.

Are you sure what you want to do is going to fix your problem?  How much power out do you get with Tune set to 100?

Mike va3mw
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Varistor

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Since the station has been built as a SO2R, M/S, or M/2 station from the grounds up, RFI management is a multi-prong solution.

The shack is physically separated from the main house and has its own 60 amp service and electrical panel. The entire panel is fed using a commercial EMI filter- and a Siemens FS140 whole house 140 KA surge protector- to ensure nothing comes from the main house. This also ensures that the amplifiers are somewhat protected.

Specifically for the DC bus, the full RFI prevention chain is as follows:

1) Commercial EMI filter directly before the power supply.
2) 100 amp power supply
3) 3 x commin mode chokes made by looping 9 turns thru Ferite Rite material 31 Big Clamp On right before the DC distribution box.

The overall strategy is to bring clean AC into the shack and then deliver clean DC to each operating position.

A strict “clean desk” policy is in enforcement and the power supply, the chokes, and the DC bus are all attached to the bottom of the shack desk and nothing is visible on the top of the desk. Note that the DC bus also feeds the fans for the 3 KW bandpass filters and the 2x8 antenna switch; they also have CM chokes.

On the RF side, every antenna feedline has its own CM choke and goes thru a 3 KW bandpass filter before connecting to the 2x8 antenna switch. Every antenna also has its own CM choke at the feed point. Due to proximity a couple of verticals require their own coax stubs at the base.

It’s pretty straightforward actually and there is nothing groundbreaking, just being disciplined to follow established best practices. The key is to resist the temptation to improvise and hit the textbooks before doing anything; then develop a complete design and execute it all at once.
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Johan / SE3X

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Using two MAAS 25A PS one each for my 6500 and 6700. 6500 with an Expert Amp, so drive only around 35W max. 6700 with my Acom, more drive power 80 watt. None of them sags a single volt when running in contest. I have both PS on top of each radio. No RFI, and very short cables, max 25-30cm. I'm mainly on SSB, some CW, but no HP FT8 or RTTY, so not comparable perhaps? But long power cords, IMHO, a recepie for trouble ;)
(Edited)