[RFI] Inverters?

[Jim Brown]

Hi Warren,

Several observations. First, buying ANY generator for anything more than 
FD operation should be done as an engineering project. Some of the 
design criteria are

1) what are your loads? Grab a clamp-on Ammeter and measured them -- 
don't go by nameplate, which are always worst case. Don't have a 
clamp-on ammeter? It's a VERY important tool to own. Look for one that 
measures relatively SMALL currents -- you want 5-10A full scale, maybe 
20A or 30A. Unless you're seeing very large loads, nothing more than 50A.

2) Our average load 24/7 is less than 1kW; it goes up (a lot) when 
cooking with electricity, running A/C, contesting legal limit, and a 
bit with large fans that are part of an HVAC system.

3) Does your gen need to run well motors? My EU6500 Honda (inverter) gen 
does NOT like to run my well motors. A traditional gen half that size will.

4) How much of your loads need to be on gen? I found that I could run my 
22 cu ft fridge, computers, lighting, and moderate size home 
entertainment system on my Honda 2000i in economode. To do that, I had 
to have some of those loads redistributed between legs of 120/240 so 
that all I needed for those functions were on the same leg. Easy to do 
at the breaker panel. Our cooking is propane, so I boil water for coffee 
on the stove when on the gen. Don't try to run the microwave.

5) Consider propane. My EU6500 has been converted, W6GJB converted his 
2000i, and is going to do mine. A $22 can runs 20 hours or more in 
economode, depending on loading.

6) Doing county expeditions in very quiet places for CQP and 7QP using 
W6GJB's 2-position contesting trailer with antennas on a pneumatic mast 
and the gen on the back of the pickup it's hitched to, we found that we 
needed a good noise filter. The one that Glen and I came up with was 
added to the Handbook a few years ago. If it's not in yours, you can 
find details in the latest version of k9yc.com/RFI-Ham.pdf  I should 
plug directly into the gen -- it's the AC cable that radiates noise 
common mode, the filter kills that.

This filter is designed for HF; for 6M and above, see my recent 
recommendations for coax TX chokes for VHF/UHF, using them as a 
guideline for AC cable the size of the coax in those recommendations. 
For 6M, use two turns of RG8 through a Fair-Rite #31 1-in i.d. clamp-on; 
for best suppression, use 2-4 of these 2-turn chokes in series. See the 
photo in the pdf.

7) As others have noted, consider duty cycle. Most low cost gens, even 
the good ones, are designed for intermittent operation. My most 
demanding need when on geen is keeping the fridge cold enough to prevent 
spoiling. When running the 2000i, I typically keep the duty cycle below 
60%.

8) It's important to realize that worst case loads are usually starting 
a motor; once the motor is running, the load drops a LOT. It's starting 
my well motors that the EU6500 doesn't like. When in doubt, START your 
gen with no load on it, then connect the load, and once it's stabilized 
(usually under a minute, could be more with well motors), then kick it 
down to economode to save (a lot of) fuel.

Master DXpeditioner AA7JV, drastically reduced the amount of petrol he 
had to carry on the boat for his trips by using power amps that could 
run on batteries that were float-charged by the generators running in 
economode. George is a VERY smart engineer, and one of my heroes!

73, Jim K9YC

On 9/19/2020 9:23 PM, Warren Wolff via RFI wrote:
>    I am considering the purchase of an emergency back-upgenerator.  For the first time, I have encountered unitstagged as “inverters”.  Does this mean that some systemsare AC generators while the “Inverter-types” generateDC and then convert it to AC?    “Inverter” immediatelyprecipitates the worry of RFI.  Comments, please.
> WarrenW7WY
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