Hi

If you take a look at the picture of that module, you can pretty much figure out a rough schematic. You can then ask: what’s missing here?

Simple answer is that nothing on that board is focused on RFI / EMI. It’s all just a very basic set of parts to get the voltage conversion done and not much else.

What should be there?

Coils that work at RF. They also (obviously) need to handle the current involved. Some multi hole ferrite beads just might be useful as well. Put at least one in series with the input and probably more than one in series with the output. 

Capacitors that work at RF. Electrolytic's really are not great for RF. Ceramic X7R parts would be a much better choice. Several (at least one on both sides of each of your coils ) would be ideal. 

As insane as it sounds, you probably get more RF back out of the *input* to the device than from the output. Both sides need some attention. 

As always, check the junk box before you head out and spend money. It’s a pretty good bet you already have the sort of parts you will need. No need to go insane looking for a 68 uH part because some random dude named Bob suggested it. That 47uH or 100 uH you already have will do just fine. 

One thing to watch out for: Most of these run at something in the 20 to 100 KHz range. 60KHz is quite common. Hash up at least to the 5th harmonic of the operating frequency is still going to be pretty substantial. If your gear gets down that low, there will be a bit more fun killing all the birdies. 

Bob
KB8TQ

On Sep 12, 2025, at 1:05 PM, Dave Merrill <[email protected]> wrote:

These on Amazon Haul appear to be the same design and are less expensive:


__... ...__ Dave N9ZC 



On Fri, Sep 12, 2025, 10:40 AM <[email protected]> wrote:

Amazon is you friend.  There are all manner of DC-DC boost and buck converters that will do yeoman service for you,  the buck converters are a few bucks ($3-6), and there is a nice 45-390V boost converter from several sources for around $10.00. (There are two versions- a bi-polar, and a positive only, don’t get the bipolar unless you need it, as it is half the current) They will deliver up to 30W over the output voltage range.  I have used them as dynamotor replacements, literally fitting the converter in a gutted dynamotor case. I have used literally dozens of these over the last 5 years, and find they work very well, with quite high efficiency.

 

Regards,

Scott W7SVJ

 

From: [email protected] <[email protected]> On Behalf Of Mark K3MSB
Sent: Friday, September 12, 2025 09:25
To: Ray Fantini <[email protected]>
Cc: [email protected]; List Milsurplus <[email protected]>
Subject: Re: [MRCA] DC-DC Up Converter

 

Ray and "Milrad" --

 

Thanks for the info.

My initial goal is to provide a field solution for my BC-221.  It now has a 110 VAC power supply, and I'd like to convert it to 12 V DC.

I need 6.3 V AC/DC and 150V @ 20 mA.      A single battery with the DC-DC converter should work.

I use LiFePO4 batteries for POTA (Parks On The Air) activities and can run my IC-7300 at 100W for 2 to 3 hours (which is why I typically run it at 50W).    Since the 211 will only be on intermittently, a single battery should easily last for 2 days.    

I'd generate some heat for the filament dropping resistor, but that doesn't matter.

 

73 Mark K3MSB

 

 

 

 

 

On Fri, Sep 12, 2025 at 9:21 AM Ray Fantini <[email protected]> wrote:

Just finished a DAG radio direction finder using this same converter. Its providing 90 volts and replacing a B battery. Built a small box that takes the output of a twelve volt SLA Battery and provides 1.5 and 90 volts for the direction finder. Found that the inverter was fairly quiet but is almost completely lacking any output filtering. It also produced noise on the input buss to the battery but keeping everything in a meatal box and short it was not an issue. Regulation was ok but did notice there are some points where the PWM system on the board will produce weird noise at some settings. Think the little inverter is good for low power things like replacing B Batteries but would not trust it for things like 225 B+ supplies in a big radio.

 

Ray F/KA3EKH

 

 

From: [email protected] <[email protected]> On Behalf Of MilRad via MRCA
Sent: Thursday, September 11, 2025 9:30 PM
To: Mark K3MSB <[email protected]>; ARC5 <[email protected]>; List Milsurplus <[email protected]>; Military Radio Collectors Association ([email protected]) <[email protected]>
Subject: Re: [MRCA] DC-DC Up Converter

 

 

I have had good luck with this one.

 

On 09/11/2025 7:39 PM EDT Mark K3MSB <[email protected]> wrote:

 

 

Hi Folks

 

A while back (perhaps a few weeks)  there was a thread on DC to DC up converters in which there was one particular unit that quite a few people liked.

 

I thought I saved that info but didn't.  If anyone has the info, please forward.

 

Thanks

 

Mark K3MSB

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