[MRCA] PRC10 Inverter

[J Mcvey]

Look familiar? This is a prototype for the PRC-10 using cheap modules from ebay.You have to use 12V because virtually of of these modules will LV lock out at 8V,so that adds a layer of complexity. A buck regulator is needed to produce -6V instead of working directly off the 6V  battery as as the Italian inverter  does.
There is the HV module, a buck module for  -6v and a boost module that works off of the 6V output because it has to reference to  +6 ..The HV is set to 141V to get 135V with respect to  radio ground since it is actually referenced to -6V. 
Radio ground and battery negative are two different things in this configurationand never the twain shall meet or bad things will happen.. Radio ground is +6 ,  -6 is used for the tx final filliment.
The 3300 ohm is a dropping resistor for the 67.5 screen V. The 180 ohm is a ballast load for the buck regulator .
I don't trust this stuff, so I have crowbars accross the 1.5V and the -6 supplies. So far so good.
It did radiate some EMI , but I think it might be OK if I put it in a metal box shield.
Jim AC2EU
    On Wednesday, January 30, 2019, 2:17:54 PM EST, Robert Nickels <ranickel at comcast.net> wrote:  
 
 On 1/30/2019 7:41 AM, Ray Fantini wrote:
> Why build when you can buy? Look at EBay item:
>
> https://www.ebay.com/itm/DC-DC-10-32V-to-45-390V-High-Voltage-Boost-Converter-Step-up-Booster-Module-JKHW/152787389030?hash=item2392d68a66:g:rZUAAOSwPWRZXF4g:rk:28:pf:0

After buying and evaluating many boost converters for use powering 
radios, I can say they do indeed work.  Or I should say, "can be made to 
work in an RF application".   Just be prepared to spend some time  
mitigating EMI, both conducted and radiated from the input and output 
wires and from the board itself.   It's not rocket science, just the 
usual kind of  filtering, grounding, and shielding, but each one seems 
to take a little tweaking as there is essentially no configuration 
control so the board you buy today might be similar to but not identical 
to the one you bought a month ago,  depending on where the eBay reseller 
got his stuff. And it's rare but some do provide schematics and 
manufacturer's reference designs for the SMPS ICs are helpful.   I've 
always had to add LC filtering on the HV output at a minimum as the 
switching frequency harmonics extend well into the HF range.   Conducted 
noise on the 12 volt lines that gets into other equipment also usually 
is an issue.     I had to remotely mount  the converter in a steel box 
for my last project because the magnetic field from the transformer was 
inductively coupling to the receiver IF coils when they were in close 
proximity.

On the plus side, they can produce a usable amount of power, are well 
protected, very efficient - and cheap.    Just remember TANSTAAFL and 
you'll be on the right track.

73, Bob W9RAN

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