[TowerTalk] Low RFI diesel generator?

[Patrick Greenlee]

As is everything practically in any engineering situation, tradeoffs are the 
essence of decision making. Requirements vary so solutions vary. Given the 
statistics on outages in my area, I do not anticipate having frequent power 
outages in excess of a few hours.  Since installing a propane fueled backup 
generator a few years ago we had one outage nearly 4 days long and a few of 
a couple hours or less.  We have 2 each 1000 gal propane tanks.

I chose propane fuel over diesel, not because I don't appreciate diesel's 
strong points, I have two diesel trucks and a diesel tractor.  Diesel 
gensets, especially slower turning ones at 1800 RPM or less can be excellent 
long term power sources. I would have been happy to have found an 
appropriate 1800 RPM propane genny but didn't.  My understanding is that 
short runs and many starts and stops are not good for diesels. Propane burns 
super clean and short weekly runs (15 min) do not contaminate the oil as can 
be the case with short runs on a diesel. Maintenance issues are much less 
with propane. One exception is arctic conditions such as in Minnesota or 
North Dakota etc. where temps dip to -40F and lower.  Anti-gel and kerosene 
can keep a diesel operable in low temps but propane's vapor pressure goes to 
zero at about -40F so there is no pressure to deliver fuel to the genset.

Whatever the choice of fuel, having a backup genny of any stripe is far 
superior to not having one even if it is a small portable gasoline fueled 
unit.  Backup is good.  When outfitting my welding trailer I opted for a 
gasoline powered generator running conventional 240 volt plasma, MIG, stick, 
etc. as opposed to a motor driven welder (which is not as good of a backup 
genny.) This 17,500 watt genny is the backup to my propane fueled backup 
generator.  I realize not everyone's situation is similar to mine but even a 
small portable backup genny  is a great piece of insurance and a super boost 
toward being able to take care of yourself when the fabric of civilization 
wears a bit thin during storms, floods, grid glitches, etc..  My experience 
with small hand portable gensets indicates low RFI but surely there will be 
variations model to model and brand to brand. I did fine with Honda units. 
Worst case for radio use you might be able to shroud a generator with light 
weight galvanized sheet metal (paying attention to cooling air, exhaust, and 
air intake) to reduce interference.

When the chips are down, how do you power your ham station?  Are you ready 
to handle emergency traffic or are you one of those for whom others will 
have to offer care and assistance?

Semper Paratus  Be a good scout.

73

Patrick AF5CK


--Original Message----- 
From: Grant Saviers
Sent: Wednesday, March 27, 2013 12:21 AM
To: Rick Kiessig
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] Low RFI diesel generator?

Many of the home backup gens here are 3600 rpm, not a bad compromise IMO
considering the very low duty cycle.  However, when I bought my Kohler
the advice was to not go 3600 as the very low loading on the engine
during the weekly test/exercise cycle frequently causes cylinder glazing
and that leads to high oil consumption.  So I ended up with a larger gen
(40kw) than I wanted at 1800 rpm.  1200 and 900 rpm gensets are
available for continuous duty and last nearly forever.  I talked to a
mechanic in Bora Bora who had a pair (100kw?) running for 15  years 24/7
with only injectors replaced.

I use propane (1000 gal tank) as fuel as diesel is tricky to store for
long periods.  In the US, the environmental codes for any useful gallon
quantity require double tanks and special permits, a hassle and
expense.  A little moisture (tank condensation) and you get bacterial
growth.  I had a boat with 750 gallons on board and periodic pumpouts
and filtering were needed in warm climates if the fuel wasn't used.
Also the cetane rating deteriorates with time. Propane (or natural gas)
is the cleanest least hassle least wear fuel, and propane is stable for
long term storage with no maintenance. Natural gas might not be
available in certain disaster situations.

As for RFI, none noticed from my spark plugged Kohler which is 50' from
one tower, but I've heard that the newer diesel electronic injectors in
light trucks can cause RFI in mobile applications.

As a suggestion, if diesel power is a must, you might ask the marine gen
dealers/installers/mechanics near you for some advice, they all need to
be RF quiet.  Some other marine/commercial brands - Northern Lights,
Caterpillar, Kohler, John Deere.  Larger Onans are Cummins/Onans.
Detroit Diesel makes bigger ones. Huge numbers of the legendary 71
series diesels (2 to16 cylinders) powered gensets in all sorts of
applications and are available surplus.

Grant KZ1W


On 3/26/2013 6:45 PM, Rick Kiessig wrote:
> I'm in the market for a new genset - probably a low-RPM diesel generator,
> with 240VAC, clean sine wave output, audibly quiet / "silent" canopy, in 
> the
> 10 to 20 KW range. It will be located fairly close to my radio equipment, 
> so
> I'm particularly interested in finding one that won't also create a bunch 
> of
> RFI.
>
>
> Reliability is key. Low fuel consumption is also important. I may end up
> adding a transfer switch to have it run my home in the event of a power
> failure, along with an external fuel tank to increase maximum run time to
> about 14 days.
>
>
> I'm currently looking at Cummins, Kubota, UK Perkins and Lister Petter. I
> would appreciate any recommendations for brands or models that you've 
> found
> to be good, as well as ones to avoid.
>
>
> Thanks and 73,
>
> Rick ZL2HAM
>
>
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