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Author Topic: Modified Sine Wave Power Supplies for POTA/SOTA  (Read 321 times)

K1KIM

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Modified Sine Wave Power Supplies for POTA/SOTA
« on: February 19, 2022, 02:19:18 PM »

Does anyone use modified sine wave generators for 120VAC power supply to their radios in the field for NON 12VDC operating systems? I would think this to be unacceptable.

Or are batteries the best way to go using only 12VDC equipment.?

Most of the reasonably priced Inverters 12VDC-120VAC are modified sine wave also.

Haven't done POTA as of yet.

Thoughts?
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VE3HIX

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Re: Modified Sine Wave Power Supplies for POTA/SOTA
« Reply #1 on: February 19, 2022, 04:53:01 PM »

At our repeater site we have normal AC input through an Uninterruptable Power Supply, and the whole thing is backed up by an automatic AC generator. The UPS passes all good AC through it, and instantly switches to a battery backed modified sine wave output when the power fails. When the generator comes up to speed 20 seconds later, the UPS passes power from the generator through to the equipment. The generator has an acorn-shaped sine wave due to its built-in voltage regulator.

We have run all of our equipment for extended periods on the UPS and on the generator with no ill effects. We did not test the UPS for harmonic interference to the radios. Please let me know if there are any genuine cases of equipment problems due to a modified sine wave.

Cheers and good luck,
Bob VE3HIX
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WB6BYU

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Re: Modified Sine Wave Power Supplies for POTA/SOTA
« Reply #2 on: February 19, 2022, 08:33:46 PM »

Quote from: K1KIM

Does anyone use modified sine wave generators for 120VAC power supply to their radios in the field for NON 12VDC operating systems? I would think this to be unacceptable.



Why are you imagining it would be unacceptable?

I'd think a power transformer in a 12V power supply for the radio
would act the same as one for a different voltage.  Or are you
thinking of just using the generator to charge batteries directly?
Mine doesn't put out nearly as much power that way.

Many of them do have a problem with conducted noise, often
radiated by the extension cords.  I'm planning to put a big
ferrite filter on mine to see if that fixes the problem.

G4AON

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Re: Modified Sine Wave Power Supplies for POTA/SOTA
« Reply #3 on: February 20, 2022, 04:10:52 AM »

What do you mean by “sine wave generator”? Most of us refer to either a 12V to mains inverter, or an internal combustion engine powered generator…

Unless you are running a QRO amplifier, direct battery power should suffice. Especially useful are lithium iron phosphate batteries (LiFePO4), which are vastly superior to lead acid in terms of weight and terminal Voltage. Casual logging can be done on paper, tablet computer or on a phone.

For portable contests I use a 68 Ah LiFePO4 battery and a 12 Volt to 19 Volt “car adapter” for my Asus laptop that is used for logging. I can run a 100 Watt radio for 6 to 8 hours quite comfortably. For casual operating, a smaller and cheaper battery would suffice, especially if not logging with a laptop.

73 Dave
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W9IQ

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Re: Modified Sine Wave Power Supplies for POTA/SOTA
« Reply #4 on: February 20, 2022, 04:51:21 AM »

Or are batteries the best way to go using only 12VDC equipment.?

When you use an inverter, you are adding another level of inefficiency that changes your battery's energy to heat. This is in addition to the power lost from the radio's power supply.  The result is you need to carry a battery with at least 25% more capacity to attain the same operating time as powering a radio directly from a 12 volt battery.

So, if you can, operating directly from a battery increases operating time, decreases carried weight and volume and reduces RFI.

- Glenn W9IQ

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

WA2EIO

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Re: Modified Sine Wave Power Supplies for POTA/SOTA
« Reply #5 on: February 20, 2022, 07:07:23 AM »

The OP mentions "....radios in the field for NON 12VDC operating systems."

What type of equipment and operating are you thinking about?   Can you offer any more details on your intended field station?

Ron   WA2EIO
« Last Edit: February 20, 2022, 07:10:40 AM by WA2EIO »
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K1KIM

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Re: Modified Sine Wave Power Supplies for POTA/SOTA
« Reply #6 on: February 20, 2022, 09:35:28 AM »

The OP mentions "....radios in the field for NON 12VDC operating systems."

What type of equipment and operating are you thinking about?   Can you offer any more details on your intended field station?

Ron   WA2EIO

It's more of a hypothetical question perhaps than a practical one.

What about old heavy 120VAC equipment. Drake, Kenwood, Collins etc?

What did portable stations do back in the 50's-60's?
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N6YWU

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Re: Modified Sine Wave Power Supplies for POTA/SOTA
« Reply #7 on: February 20, 2022, 09:44:20 AM »

For FT8 ops, logging, and some SDRs, the computers and OEM laptop chargers usually require non-12V power inputs to keep them going overnight.  If you use only Raspberry Pi's, I suppose one could get away with using only 12V-to-5V regulators with 12V batteries.  I wonder how RFI clean those units are.
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WB6BYU

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Re: Modified Sine Wave Power Supplies for POTA/SOTA
« Reply #8 on: February 20, 2022, 11:31:00 AM »

Quote from: K1KIM

What about old heavy 120VAC equipment. Drake, Kenwood, Collins etc?

What did portable stations do back in the 50's-60's?




We didn't have modified sine wave generators in the 50's-60's.

They were gas motors driving an alternator, with a speed
regulator to set the frequency, so most ran at 3600 RPM.
(If you were really flush you might have an Onan that ran at
1800 RPM, and seemed much quieter.)  Electric clocks were
pretty unreliable, although the sweep second hand could be
compared to a wrist watch and used to set the regulator.

Even now, most of our equipment on a club Field Day runs from
AC power supplies plugged into a generator, including linear ones
with a transformer.  It has been a few years since I've seen a
TR-4C, KWM-2, NC-300, or Heathkit Apache plugged in at Field
Day, but I haven't seen any issues so far.

Well, except when the generators didn't receive proper maintenance,
or generated too much RF noise.  One year we started several hours
late, finally on the 4th generator we tried.

That's not to say there might not be an issue with modified sine waves,
but I haven't experienced it yet (other than possible RF noise).

AA4PB

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Re: Modified Sine Wave Power Supplies for POTA/SOTA
« Reply #9 on: February 20, 2022, 12:01:53 PM »

My linear Astron power supply does well on a modified sine wave inverter but my Icom switching power supply go nuts on a modified sine wave.
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Bob  AA4PB
Garrisonville, VA

W9FIB

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Re: Modified Sine Wave Power Supplies for POTA/SOTA
« Reply #10 on: February 21, 2022, 01:16:34 PM »

Had a couple pieces of equipment that used wall warts that didn't work well on modified sine wave. I solved the problem with a 1:1 isolation transformer and a couple of ferrites. But higher power, isolation gets expensive and heavy. But never had problems with any higher power draw equipment.
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73, Stan
Travelling the world one signal at a time.

KB1GMX

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Re: Modified Sine Wave Power Supplies for POTA/SOTA
« Reply #11 on: February 23, 2022, 08:43:48 AM »

I've used over the years modified sine to power expensive test
gear in the field with no difficulty. 

The down side was mroe stuff to carry,  bigger battery needed,
the power converter (12v to 120ac) and cables.

The caveat is if you hauling it less weight and gear is better.
So that favors 12V (nominal) gear and batteries.

Allison
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K5LXP

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Re: Modified Sine Wave Power Supplies for POTA/SOTA
« Reply #12 on: March 15, 2022, 11:58:51 AM »

There's certainly some overlap but POTA and SOTA are generally different animals.  I've never considered the issue of non-sine supplies for my SOTA station because the only rigs that are practical for that run on a battery.  In my case, a 9V one or maybe a set of AAA's.  For POTA on the other hand, you're not bound to carrying your equipment on your back and equipment choice is limited only by your wallet and GVWR of your vehicle.  I could easily carry a boatanchor station and it would run quite happily off of the sine wave genset in my RV, along with the A/C and fridge full of refreshments.  Even in my RV though my station is a 100W 12V nominal radio that I run from battery or SMPS that doesn't care what waveshape the AC input is.  So it would seem the problem is quite narrow in focus and easily circumvented through selection of equipment.

Mark K5LXP
Albuquerque, NM
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KB1GMX

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Re: Modified Sine Wave Power Supplies for POTA/SOTA
« Reply #13 on: April 08, 2022, 12:46:36 PM »

The FD The club I am part of uses a mix of gensets.

Mine is a true alternator, 1200W, quiet and no issues.

The other 4 stations  are a mix of Hondas inverter gensets of
varying sizes those are modified sine.  Again no issues.

Generally most modern radios that can used 120V directly are not fussy,
same for all power supplies tried running on the gensets are happy.

One thing we all do is include a battery so if the genset goes off line
for refuel or other reasons the station is not knocked off line. That's
more of an operating detail.

All of this is meaningless to SOTA unless the site is accessible by
vehicle as gensets and all are not easily carried unless you have
a sherpa or pack mules.   Most SOTA ops however want the "station"
to be packable as fits in a backpack  and light.

POTA that vaies all over the map from state or national parks that have
remote areas to the Local parts with trees and play areas.  Generally
they can be easier to manage for space and power.  Best and most
fun seen was someone loading a little red wagon and then dragging
it to the operating location some distance away down a trail.

The only limit may be imagination.

Allison
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G4AON

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Re: Modified Sine Wave Power Supplies for POTA/SOTA
« Reply #14 on: April 09, 2022, 01:13:08 AM »

Since the original posting, I’ve bought a Honda EU22i to replace my heavier and noisier Yamaha EF2800i generator for hill top contest QRO operating. Neither generator produces any RFI that I can detect. My linear amplifiers, an Elecraft KPA500 and a Linear Amp Gemini 4, have no problems running from either generator. My switch mode 13.8V PSU for my Icom IC-7300 is also happy with the generator supply.

While I haven’t checked the Honda on an oscilloscope, the Yamaha has a perfect sine wave output, cleaner than mains electricity in many cases.

The only RFI generation that I have had for my lower powered portable operating with a battery, was a 12V to USB converter module from eBay. It was made for installation in a car, but lacked any certifications, or even a manufacturer name. It produced S9 hash on 2m and was quickly consigned to the bin.

My 12V to 19V laptop adapter produced a low level of hash on 6m and 4m, a “clamp on” ferrite with a couple of turns through it resolved the problem.

73 Dave
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