[Elecraft] A couple of KPA1500 remote operating questions

[Bob Wilson, N6TV]

On Wed, Jun 10, 2020 at 4:33 PM Peter Dougherty <lists at w2irt.net> wrote:

> 1.      The area it will be going into is dusty.


Dust is not good for amplifiers.  They must move lots of air through the
amplifier.  Do you really have to put it there?  Is it because you can't
stand the fan noise?  Or the heat?


> I suspect it's particulate dropping down from the insulation in the
> ceiling.


Any way to fix that?  Maybe a HEPA room filter?


> I plan to put a shelf about 10 inches over top of the amp but I'm
> wondering if
> this might be a problem.


Well, it won't keep the dust out.  Cool air is blown *into* the amplifier
from the rear fans, and out the top (and also through gaps in the front
panel if the fan speed gets high enough).  A shelf over the amp. could
force the hot exhaust air to circulate back down close to the intake.  Not
good.

If so, how often should I get down there with a compressor to blow the crud
> out of everything? Or maybe put a piece of fine
> air filter material over the fan inlet?
>

A filter will probably reduce air flow, and put more stress on the fans.
Not good.

2.      The crawlspace is not heated and probably gets into the 40s or even
> 30s during the winter. Would this be a risk?
>

Cold is good.  Amps like to be cold (KPA1500 has more gain when cold than
when not).  But if moisture or condensation is a problem down there, not
good.


> 3.      I'm using the amp with a K3s. At the moment I have a Y-box from the
> accessory port, and a cable from the Y-box to the amp. Since this won't be
> on the same floor as the radio, how can I get this working with the radio?
>

A long M/F DE-15 cable should work.  I don't know what the length limit
is.  10 to 15 feet should be OK if you have 2.5' from the K3 ACC to the
Y-BOX.   But use a well shielded cable.  I recommend this one for extra
long runs:

https://www.cablesondemand.com/category/HD15/product/CS-DSPMHD15MF/URvars/Items/Library/InfoManage/CS-DSPMHD15MF.htm



> If I site the amp immediately below where it is now I could probably run a
> 10' DB15 extension cable down from the Y-box to the amp, but I'm pretty
> sure
> that will violate all kinds of fire regs. Not sure how I can do this.
>

Fire regs?  Can't comment on that, but there is no more than 13V on any
pin, and very little current, so it's hard to imagine how that cable could
cause a fire.

But once the amp. is down there, how will you monitor it?  Are you planning
to run a long USB or Ethernet cable down there as well?  A long USB cable
will probably need ferrites.  A long Ethernet cable should generate RFI if
you use the unshielded type.

Or are you going to keep a PC in the crawlspace, connected by WiFi, and use
KPA1500 Remote software?

73,
Bob, N6TV