[RE-wrenches] Quietest off-grid inverter HAM radio

Sat Oct 3 22:39:14 EDT 2020

/"//Is there any inherent advantage or disadvantage to non transformer 
inverters? /

//
///Jay"/

Well, non-isolated transformer-less inverters have their own problems 
that can make common-mode EMI worse actually than isolated.

There are special (and patented) design techniques to reduce this and 
some non-patented ones that work similarly. I think SMA is one

with a patent on it.   It has to do with how the output stage of the 
inverter does its shorting of the full-bridge in-between high and low

PWM pulses.  Interesting stuff.

But engineering is always a compromise.    Audio electronic engineering 
was MUCH easier than power electronics IMO.

boB

On 10/3/2020 8:01 AM, Dave Angelini Offgrid Solar wrote:
>
> I would think if the devices meet the tested Class B spec then no 
> advantage. Engineers can design filters for the Class B requirement. 
> The radiated RF may be different between two identical specced 
> inverters of different topology. Even that can be designed in, if 
> there is a requirement and it is tested for.
>
> The basic test anyone can do is with a 10 dollar analog AM radio tuned 
> to a weak station. If you can't get 5 feet back from the inverter and 
> hear the station, then you have work to do to suppress the radiated 
> garbage. An XW is about 3 feet if it is installed correctly. My truck 
> inverter which is transformerless, will kill AM for about 50 feet.
>
> See what Bob says, my component level engineering is from the 1980's 
> and dated.
>
>   
> *Dave Angelini Offgrid Solar "we go where powerlines don't" 
> http://members.sti.net/offgridsolar/ e-mail offgridsolar at sti.net 
> <mailto:offgridsolar at sti.net> text 209 813 0060*
>
> On Fri, 2 Oct 2020 11:58:15 -0600, Jay <jay.peltz at gmail.com> wrote:
>
>> Hi Bob
>> Is there any inherent advantage or disadvantage to non transformer 
>> inverters?
>> Jay
>>
>>> On Oct 2, 2020, at 11:27 AM, "bob at midnitesolar.com" 
>>> <bob at midnitesolar.com> wrote:
>>>
>>> This is all great advice.
>>>
>>> Remember that long wires can radiate RF.  PV lines and the array can 
>>> make a good antenna for  RFI as well as the battery lines.
>>>
>>> I agree with Dave that both of those inverters are more than likely 
>>> similar.  I know that the XW has a good filter on the battery line
>>>
>>> right where it should be, at the exit point.
>>>
>>> An additional ferrite toroid core used in  common-mode filter hookup 
>>> (BOTH hot and cold wires run through the center) as close to
>>>
>>> the unit as possible on AC and DC wires as well as possibly, 
>>> communications lines exiting the units.  Battery temperature sense also,
>>>
>>> possibly.
>>>
>>> As for resources, Palomar link that Roy gave is a good resource.  
>>> Digikey or Mouser might also be a good place to look for both the
>>>
>>> parts themselves and possibly information.
>>>
>>> boB
>>> K7IQ
>>>
>>> On 10/2/2020 8:57 AM, Dave Angelini Offgrid Solar wrote:
>>>>
>>>> My advice is it is more about the installation and the distance 
>>>> from the inverter, and it's devices from the station location, than 
>>>> the make of equipment. There are other things also that I do to fix 
>>>> noise and interference. My wife is an extra class operator and 
>>>> several clients have visited to get ideas. Most any noise issue can 
>>>> be fixed later, unless you are too close to the source.
>>>>
>>>> That said I mainly use XW and I would assume Radian is similar. 
>>>> Below is the spec that XW is test for and has been since 2005.
>>>>
>>>> " EMC directive FCC and Industry Canada Class B " Below are 2 of 
>>>> the ways that the issue is defined and measured.
>>>>
>>>> So-called "*radiated emissions*" are picked-up *with 
>>>> a* test-antenna and can come from all parts of the product 
>>>> INCLUDING the cables it uses (power and module interconnects). 
>>>> *Conducted emissions* are measured directly as voltages or currents 
>>>> on the cables used by the product.
>>>>
>>>>   
>>>> *Dave Angelini Offgrid Solar "we go where powerlines don't" 
>>>> http://members.sti.net/offgridsolar/ e-mail offgridsolar at sti.net 
>>>> <mailto:offgridsolar at sti.net> text 209 813 0060*
>>>>
>>>> On Fri, 2 Oct 2020 09:35:34 -0600, Mac Lewis <maclewis1 at gmail.com> 
>>>> wrote:
>>>>
>>>>     Hi Wrenches,
>>>>     I have a HAM radio enthusiast that needs to replace their
>>>>     off-grid inverter.  He would like the inverter that puts off
>>>>     the least interference.  I don't know a whole lot about
>>>>     evaluating an inverter for this, but I am reaching out for
>>>>     recommendations.  Needing ~8kVa at 48V.
>>>>     Thanks!
>>>>
>>>>     -- 
>>>>     Mac Lewis
>>>>
>>>>     "Yo solo sé que no sé nada." -Sócrates
>>>>
>>>>
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