Author Topic: Low-noise and low-budget 13.8VDC ham radio power supply for 100W HF transceiver  (Read 821 times)

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Offline Kalvin

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Hi,

I am looking for a low-noise and low-budget 13.8VDC power supply for a 100W HF transceiver (ie. 13.8VDC 300W). Most of the inexpensive power supplies on the market to be used with a 100W transceiver seem to be switching-mode supplies, and I do not really want to struggle with the possible switching noise problems. Some switching power supplies offer an option to adjust the switching frequency so that possible switching noise can be moved away from the frequency of interest, but I really do not want to play with the power supply in that way either. The other option is to go for a traditional, bulkier linear power supply. The switching-mode supplies are inexpensive, small and lightweight compared to the linear power supplies, however.

I was thinking that would it be possible/practical to combine a switching-mode power supply with a small linear power supply as follows:

- When the transceiver is receiving, the linear power supply would provide the power to the transceiver up to 2A/13.8VDC, and the switching-mode power supply is disabled, thus no switching-noise while receiving.

- When the transceiver is transmitting, the switching-mode power supply would be enabled and would provide the power to the transceiver, and the switching noise wouldn't be an issue during transmitting anyway.

- The power supply would be monitoring the current consumption of the transceiver and perform the switch-over between the power supplies when the current consumption exceeds the set limit (say 2A for example).

Some switching-mode power supplies, for example from Meanwell, provide external "remote on/off"-control signal which is used to control the power supply on/off. However I was not able to find any information how fast the switching-mode power supplies will react to this "remote on/off" signal, and will this "remote on/off" signal also disable the switching elements of the power supply completely.

Does anyone know a suitable switching-mode power supply (13.8VDC, min. 300W) which has a built-in support for this "remote on/off" control which would disable the switching elements completely and which would react to the "remote on/off" signal within say 10ms or less.

Br,
Kalvin
 

Offline Kalvin

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In order to make this switch-over from the 2A linear power-supply to the switching-mode power supply possible without dropping the output voltage too much when the transceiver switches from receive to transmit 100W full power, it may be required to use a lead-acid battery to provide the required power during switch-over. The 2A linear power-supply can keep lead-acid battery topped all the time. Of course a super capacitor could also be used instead of a lead-acid battery. The bonus of using lead-acid battery is to get an emergency power supply as well [for QRP operation].
 

Offline TheMG

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As mentioned, you would need a battery or super-capacitor in circuit to provide power while the switching supply turns on. Switching power supplies don't fire up instantly.

I think a small linear supply (current limited!) float-charging an AGM lead acid battery would be best for your situation. Battery will provide the current during transmit. As long as the battery is of sufficient capacity and you don't transmit so much in one sitting as to discharge it completely.

Keep on the lookout on the used market for larger linear power supplies, occasionally you can find one going for a low price.

Switching power supplies that are RF-quiet on HF do exist (I have a couple) but they are most certainly not cheap (paid around $400 CAD +taxes and shipping, each). Well worth it if you can afford one though. https://www.ict-power.com/products/intellicharge-series/
 

Online vk6zgo

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Bite the bullet & pick up a linear supply.

They aren't really that big or heavy.
Mine is:
W:- 150mm (roughly 6")

H:- 140mm (roughly 5.5")

D:- 330mm (roughly 13")

(By comparison, the depth & height are about the same as my transceiver, which is, of course, much wider.)

You can pick it up with one hand, but I wouldn't like to carry it far like that.
 Two hands? ---No drama!
They usually spend their life sitting in one place, anyway.
 

Offline David Hess

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A 200 watt linear power supply is not that large or expensive.  Keep things simple.
 

Offline imo

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I would also recommend a good linear PSU.
My own experience has been even with a cheapo switching PSU (ie SEC-1223 with a few ferrite rings added inside) you may almost* fully eliminate the switcher's noise at lower bands provided the antenna is far away off your hamshack, the signal path with good matching, and you are using a robust grounding scheme.

* "Almost" means I was not able to find the switcher noise at 160/80/40m by listening. I was comparing my rig+PSU used at home QTH (strong switcher noise at lower bands) with my rig+PSU used in a professional club station environment (no switcher noise).

PS: http://oz1db.dk/samlex/start_eng.html
« Last Edit: April 10, 2020, 01:16:19 pm by imo »
 
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Offline Kalvin

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Thanks guys for your replies. As suggested, keeping things simple, biting the bullet and buying a linear power supply is a right thing to do. Yes, a linear power supply weighs somewhat more and costs more than a switching power supply, and avoiding the RFI will outweigh the extra cost.
 

Offline Kalvin

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Offline imo

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Thanks guys for your replies. As suggested, keeping things simple, biting the bullet and buying a linear power supply is a right thing to do. Yes, a linear power supply weighs somewhat more and costs more than a switching power supply, and avoiding the RFI will outweigh the extra cost.

Switchers are good for 2m/70cm and higher bands. At those bands I never had any issue with it even with almost no grounding and the antenna 2-3m off the PSU. Even at 20m and up the noise is already acceptable with "good" grounding and antenna at least 10m off the switcher.
For lower bands I would always vote for a linear PSU even it would weight 30kg :)
« Last Edit: April 10, 2020, 02:23:51 pm by imo »
 

Offline 9aplus

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Interesting in that dilemma. Here have something similar.
Setting up SDR remote station
for wideband RX
and possible TX too on some freq
all in one pelican case.

At the moment need following sources:
5V up to 2A
-Lime NET micro & RPI CM3 (SDR serving Soapy Remote SW)
-moRFeus
-EraSynth
-Arduino

9V up to 1A
LNA4ALL
LNA4HF

12 V up to 3A in case of TX up to 10 A
-ICOM PCR 1000 used like filter bank and preselector for LimeNET RX
-ethernet hub & WiFi AP
in option:
-PA for HF
-PA for 50 / 70 MHz
-PA for Air Band
-PA for 144-160 Ham&marine bands
-PA for 430 MHz
-PA for WiFi

19 V 2 A for notebook

On or off grid
Source inside 2 x 12 V gell lead acid 7 Ah, external solar panel & charger, hand crank gen...

So 24V to 19V to 12V to 9V to 5 V
My question is:
step down switching or linear?
linear means less noise but also less efficient...

At the moment have that all running on grid like charm, but like to be able to make
switch over to 24V DC any time ;)

Yes, yes, I know that sounds like doomsday equipment  :-DD but when you have such nice time in lockdown...
« Last Edit: April 10, 2020, 04:50:39 pm by 9aplus »
 

Offline krupski

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Check out this diagram. It's the supply for my Kenwood TS590-SG:  https://s3.amazonaws.com/files.qrz.com/o/wa2sko/40_a_psu.jpg
Gentlemen may prefer Blondes, but Real Men prefer Redheads!
 

Offline imo

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Offline krupski

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My PSU was "off the shelf" and I had so much trouble with it that I had to completely redesign and rebuild it. Only original part is the metal chassis.
Gentlemen may prefer Blondes, but Real Men prefer Redheads!
 

Offline Kalvin

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I decided to go for Nevada PS-30M https://www.nevadaradio.co.uk/product/nevada-ps-30m/ , although its thermally-controlled fan is loud when it kicks in, and it is missing the important overvoltage protection at the output. I am going to implement the fan-hack and build a simple thyristor-based crowbar-circuitry as described here: https://pa0fri.home.xs4all.nl/Diversen/EP925/ep925eng.htm

I kind of liked the linear Voltcraft 13.8V units from Conrad, but I thought that the Nevada would be more versatile in the long run for my needs with its variable output voltage.
https://www.conrad.com/o/bench-power-supply-units-2110330?ATT_FX_OUTPUT_VOLTAGE_any=13.8%20V%20DC&ATT_FX_OUTPUT_VOLTAGE_any=13.8%20V%20DC&ATT_LOV_TECHNOLOGY_POWER_SUPPLY_any=Linear%20regulated%20PSU&ATT_LOV_TECHNOLOGY_POWER_SUPPLY_any=Linear%20regulated%20PSU&brand_any=VOLTCRAFT&brand_any=VOLTCRAFT
 
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Offline tkamiya

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Astron makes good linear power supplies. 

For 100 watts, you'd want RS35.  That can withstand an extended key-down, provided your radio does not explode first.  If you are exclusively SSB, you can do with RS20.  That's what I use.  I'd stay away from adjustable kind.  There is no way to LOCK the voltage, so one careless bump, you could be feeding 20V into your radio!
 

Offline StuartA

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As pointed out above, in terms of the "affordable" linear PSU's, there are a number which seem pretty good but with the proviso that they don't incorporate anything to protect your lovely rig in the event that a pass transistor shorts. I put together an external "Crowbar" device which seems to be the usual way to try and achieve an ultrafast switch-off of the 12V supply. For very little cost, I think it's it's worth doing. I own a MYDEL 304, which I suspect sells under other brand names in other countries.

Of course, a dog's danglies PSU would come with one built in.
« Last Edit: April 24, 2020, 08:07:40 pm by StuartA »
 


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