[Elecraft] (no subject)

[Edward R Cole]

Good points:

JT-65 is 100% duty cycle unlike CW or SSB that are much lower duty 
cycle.  The issue is dissipation power in your finals.  I run JT-65 
with 1300w and theoretically the 8877 can dissipate 1500w so I am 
fine (the caveat is the 8877 needs very good air cooling).  With no 
air the 8877 quickly fails with only filament voltage applied (5v-11a).

QRP on 2m eme is generally considered anything under 600w or less 
than two yagis.  That is a very weak signal when transmitted 
half-million miles roundtrip to the Moon.  I have made JT-65 eme 
contacts using four 10-element yagis and only 150w...definitely QRP.

Likewise, I can run 20m psk at 12w out of the native K3/10 into a 
triband yagi with good results.  But the dissipation area in the KX3 
is so small I would lower this to 3w.  The Elecraft radios will 
quickly tell you if you are exceeding their abilities!

On the other hand I over-built my 300w PA by adding a fan to it can 
be run "to the wall" at max power.

73, Ed - KL7UW

From: Jim Brown <jim at audiosystemsgroup.com>
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] KPA100 recommended max power for digital
         modes?
Message-ID: <53084C05.5060806 at audiosystemsgroup.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

On 2/21/2014 7:43 PM, WA7SPY wrote:
 > I was looking at the operating manual online and did not see any 
recommended power setting for operating the amp with digital modes.

Elecraft output stages are very well protected. In general, I feel
comfortable running them "balls to the wall" with keydown modes, with
all the lights lit. With well matched antennas, I run keydown modes at
full power. If the output stage gets warm, the fan will run faster, and
if that isn't enough, the rig will back off the drive.

Remember that the WSJT modes are "weak signal" modes, NOT low power
modes. There is a big difference. We may get lots of distance per watt
and be happy with QRP for easy paths, but for the most difficult paths
(EME, transcontinental 160M), great digital ops pile on the watts and
use their best antennas. I do a lot of QRP, but I also know when to turn
on the big amp. :)

73, Jim K9YC


73, Ed - KL7UW
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