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RTTY and best IMD, cooling, etc

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Don Cunningham

RTTY and best IMD, cooling, etc

I have several amps I can use and intend to run a lot of RTTY with my K3. I
will sell off some of this "surplus", since the K3 is used more than the
other rigs I have. I would like the opinions of the group about which path
I should take. My Alpha 8410 requires VERY low drive to give 500w plus out,
in the order of 5 to 7 watts in. I have other amps, like the PW1, AL-1200,
etc that require 15w or so to give the same 500w plus out. Intuitively it
seems to me that the K3 might like the 15w or so, since the KPA3 is at the
bottom of its range and the fans can help with the cooling, even though it
is nearly 3 times the power needed to drive the 8410. Am I thinking right,
or WAY off base (as usual, hi). LS's post this morning got me to thinking
if his rig gets very warm on the bottom running 5w PSK. Any suggestions??
Thanks,
Don, WB5HAK

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lstavenhagen

Re: RTTY and best IMD, cooling, etc

You actually kind of beat me to it hi hi. But one of the stations gave me a very good IMD report with the built-in PSK encoder with the power set at 5W so I'm pretty sure it was still ok for continuous duty at the 5W setting (not knowing offhand what the true power output actually is at that setting with PSK31).

But I should think a KPA3 at 15 or 20W would really be loafing pretty good....

73
LS
W5QD

Guy, K2AV

Re: RTTY and best IMD, cooling, etc

In reply to this post by Don Cunningham

Into a well-matched load, KPA3 is capable of running 100 watts out,
brick-on-key. The cooling fins and multiple fan speeds are as good as
it gets. There is no need to pull it back to 15 watts.

Your Alpha and the K3 will be able to run 1.5 kW out RTTY until the
cows come home, assuming feedlines and antennas can take it. With
what you can get out of the AL1200 with 100 watts drive (1300-1400 on
my AL1200), that will also run contest level RTTY without issue.

73, Guy.

On Sat, Apr 10, 2010 at 1:02 PM, Don Cunningham <[hidden email]> wrote:

> I have several amps I can use and intend to run a lot of RTTY with my K3. I
> will sell off some of this "surplus", since the K3 is used more than the
> other rigs I have. I would like the opinions of the group about which path
> I should take. My Alpha 8410 requires VERY low drive to give 500w plus out,
> in the order of 5 to 7 watts in. I have other amps, like the PW1, AL-1200,
> etc that require 15w or so to give the same 500w plus out. Intuitively it
> seems to me that the K3 might like the 15w or so, since the KPA3 is at the
> bottom of its range and the fans can help with the cooling, even though it
> is nearly 3 times the power needed to drive the 8410. Am I thinking right,
> or WAY off base (as usual, hi). LS's post this morning got me to thinking
> if his rig gets very warm on the bottom running 5w PSK. Any suggestions??
> Thanks,
> Don, WB5HAK

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Dave, G4AON

Re: RTTY and best IMD, cooling, etc

In reply to this post by Don Cunningham

Don the K3 PA and driver give some 10 dB better 3rd order IMD at around
1/4 power. While that shouldn't matter on RTTY it might on other data
modes and does on SSB,. so for my money I would opt for a linear that
needs 15 ~ 30 Watts of drive.

73 Dave G4AON
K3/100 #80
----------------
<SNIP>
Intuitively it seems to me that the K3 might like the 15w or so, since
the KPA3 is at the
bottom of its range and the fans can help with the cooling, even though it
is nearly 3 times the power needed to drive the 8410.
<SNIP>
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Gary Gregory

Re: RTTY and best IMD, cooling, etc

Listening from afar, most 1Kw signals are rarely "clean" with no audible
distortion. This said, it is often caused by bad adjustment by the
operators, poor quality equipment, badly set vox and the list goes on.

Recently I worked a G3 station who claimed he was running a PW-1 set at
around 700W output and this was one of the best sounding audio stations I
have heard recently.

That said, my preference would be to use the amp that will produce the
cleanest signal over distance so I would be inclined to go along with Dave's
(G4AON) suggestion.

73's
Gary

On Sun, Apr 11, 2010 at 4:53 AM, Dave, G4AON <[hidden email]>wrote:

> Don the K3 PA and driver give some 10 dB better 3rd order IMD at around
> 1/4 power. While that shouldn't matter on RTTY it might on other data
> modes and does on SSB,. so for my money I would opt for a linear that
> needs 15 ~ 30 Watts of drive.
>
> 73 Dave G4AON
> K3/100 #80
> ----------------
> <SNIP>
> Intuitively it seems to me that the K3 might like the 15w or so, since
> the KPA3 is at the
> bottom of its range and the fans can help with the cooling, even though it
> is nearly 3 times the power needed to drive the 8410.
> <SNIP>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

--
Gary
VK4FD - Motorhome Mobile

K3 #679
For everything else there's Mastercard!!!
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alsopb

Re: RTTY and best IMD, cooling, etc

How many bad LP PSK signals have you heard? Quite a few I bet.
Admittedly, I really could care less about a terrible nanowatt PSK station.

The reality is the power war has hit PSK, like all other modes.

Sometimes high power is actually necessary, e.g. trying to work the
other side of the world at odd path times. 5 watts and a wet noodle
antenna isn't the do all station.

It is not the power level, but the equipment and the skill the the op to
use it that produces clean signals. The problem is getting people to:
1) care about it,
2) obtain the necessary skills and knowledge, and
3) exercise it

73 de Brian/K3KO

Gary Gregory wrote:

> Listening from afar, most 1Kw signals are rarely "clean" with no audible
> distortion. This said, it is often caused by bad adjustment by the
> operators, poor quality equipment, badly set vox and the list goes on.
>
> Recently I worked a G3 station who claimed he was running a PW-1 set at
> around 700W output and this was one of the best sounding audio stations I
> have heard recently.
>
> That said, my preference would be to use the amp that will produce the
> cleanest signal over distance so I would be inclined to go along with Dave's
> (G4AON) suggestion.
>
> 73's
> Gary
>
> On Sun, Apr 11, 2010 at 4:53 AM, Dave, G4AON <[hidden email]>wrote:
>
>> Don the K3 PA and driver give some 10 dB better 3rd order IMD at around
>> 1/4 power. While that shouldn't matter on RTTY it might on other data
>> modes and does on SSB,. so for my money I would opt for a linear that
>> needs 15 ~ 30 Watts of drive.
>>
>> 73 Dave G4AON
>> K3/100 #80
>> ----------------
>> <SNIP>
>> Intuitively it seems to me that the K3 might like the 15w or so, since
>> the KPA3 is at the
>> bottom of its range and the fans can help with the cooling, even though it
>> is nearly 3 times the power needed to drive the 8410.
>> <SNIP>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
>
>

Don Cunningham

Re: RTTY and best IMD, cooling, etc

In reply to this post by Dave, G4AON

Thank you, Dave, for your thoughtful and detailed response. That was
exactly what I needed. I think the PW-1 will fill the requirement you
outlined and one of the MicroHam devices will even allow auto switching. I
usually run a 4 element cubical quad at 60 plus feet, and more than 500w on
RTTY is really overkill, hi. I cannot possibly print all the responses I
get, hi.
73 and thanks for the nice response,
Don, WB5HAK

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