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mods to K2

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Allan Taylor

mods to K2

I unask the first question (how to raise K2 output power). But in
self-defense,
I knew that:
PAs have better distortion properties with higher supply voltages
14->20W is about 1 dB but 10->20W is 3.01 dB (3 dB MATTERS!)
operating above 10W on ssb with the K2 was not a good idea as
designed
and I would only do so in a true emergency
the PA devices would need to be replaced
the PA output network would need to be redesigned completely
the driver stage would need to at least have a huskier device
the existing K2 PA heatsink method may be marginal already
I would be barraged by nay-sayers

but I did not know that the MCU was so tightly involved in power level
control.

Purchasing the new 100W amp from Elecraft wouldn't meet my needs for at
least
three reasons:
for the same $$$ I could get a used Herc II !!
fails the one box test
would be much less efficient at 20W than a solution designed for
20W

I am still looking for a known solution to the relatively low RX audio
issue.
While buying the K2 audio filter module would work, it is an expensive
option.
(Does anyone have a used KAF2 laying around?)

Now as a well-known QRPer (KU7Y) often says

"now back into my hole"

--
73 Allan K7GT
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tnnyswy

Re: mods to K2

It seems that a K2 is not the Radio for you and your intended purpose.

((((73)))) Milverton.

>________________________________
> From: Allan Taylor <[hidden email]>
>To: Elecraft <[hidden email]>
>Sent: Friday, September 27, 2013 8:35 AM
>Subject: [Elecraft] mods to K2
>
>
>I unask the first question (how to raise K2 output power). But in
>self-defense,
>I knew that:
> PAs have better distortion properties with higher supply voltages
> 14->20W is about 1 dB but 10->20W is 3.01 dB (3 dB MATTERS!)
> operating above 10W on ssb with the K2 was not a good idea as
>designed
> and I would only do so in a true emergency
> the PA devices would need to be replaced
> the PA output network would need to be redesigned completely
> the driver stage would need to at least have a huskier device
> the existing K2 PA heatsink method may be marginal already
> I would be barraged by nay-sayers
>
>but I did not know that the MCU was so tightly involved in power level
>control.
>
>Purchasing the new 100W amp from Elecraft wouldn't meet my needs for at
>least
>three reasons:
> for the same $$$ I could get a used Herc II !!
> fails the one box test
> would be much less efficient at 20W than a solution designed for
>20W
>
>I am still looking for a known solution to the relatively low RX audio
>issue.
>While buying the K2 audio filter module would work, it is an expensive
>option.
>(Does anyone have a used KAF2 laying around?)
>
>Now as a well-known QRPer (KU7Y) often says
>
> "now back into my hole"
>
>--
>73 Allan K7GT
>______________________________________________________________
>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
>
>
>

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Dave-7

Re: mods to K2

In reply to this post by Allan Taylor

> I think there is a lot of evidence that 3dB does not matter. 10dB
matters. 6dB might matter.

My thoughts on this are that if 3 dB mattered much, then QRP, down 13
dB from 100w and 23 dB from a KW, would not work at all, or at least
not often. But we all know that QRP does work.

Now . . . contesters view this differently. If one is going
head-to-head against another station to grab a Q and run, then, yes, 3
dB can be a deal breaker. The weaker station comes in 2nd, has to wait
for the Q and loses a few seconds. Might miss another Q or even -
gasp! - a multiplier. But in the ordinary course of events 3 dB is not
terribly significant. Even in EmComm I'm not sure how significant 3 dB is.

If one is way out in the woods, where rescue time is measured in hours
or days, a few repeats would not seem to be a big deal vs carrying the
weight of the amp and needed power source.

A 100w amp will draw about 20A when key down. A 7 Ahr battery will not
last long.

I'd think that a better backwoods rig would be something like the
ATS-3, which can put out about 3w for about 8 hr using an 8 pack of AA
batteries as a power source. That combination does not take up as much
space nor weight as the K2, and so long as you use a lower freq and
run NVIS type prop, it should be loud enough.

73 de dave
ab9ca/4

On 9/27/13 10:24 AM, Walter Underwood wrote:

> My first thought on the audio was to get some efficient earbuds. Lightweight and cheap.
>
> Over on the KX3 list, people like the Chill Pill powered speakers.
>
> I know it is a second box, but the Hardrock 50 amp has been getting good reviews. You would not need to get it out except in an emergency, so it could stay deep in the pack. See: http://www.hobbypcb.com/amateur-radio/amateur-radio/hardrock-50-hf-power-amp-kit.html
>
> I think there is a lot of evidence that 3dB does not matter. 10dB matters. 6dB might matter.
>
> wunder
> Walter Underwood
> K6WRU
> CM87wj
>
> On Sep 27, 2013, at 6:35 AM, Allan Taylor wrote:

Vic Rosenthal

Re: mods to K2

In reply to this post by Allan Taylor

This argument will never die.

But remember the last time you called CQ and a station came back that you could hear, but
not copy. (I'm thinking CW, but it also applies to SSB).

You know he is in there, but despite struggling with the narrowest possible bandwidth and
every trick your receiver is capable of, you just can't get his call as he floats in and
out of the noise.

I maintain that even ONE dB matters in this situation.

On 9/27/2013 10:03 AM, Ron D'Eau Claire wrote:

> Quite true on HF.
>
> 3dB often matters doing weak signal work on 6 meters and up, and sometimes
> on 10 meters, but on HF there are too many other variables, QSB, etc.
>
> Back in the 30's and 40's the "Radio Engineering" texts used to list 6 dB as
> the minimum change one might expect to detect by ear on HF due to all the
> propagation variations. (Back then, 10 meters was a UHF band.)
>
> I always thought that was why Collins settled on 6dB for one S-unit on their
> receiver S-meters.
>
> 73, Ron AC7AC
>
> -----Original Message-----
>
> I think there is a lot of evidence that 3dB does not matter. 10dB matters.
> 6dB might matter.
>
> wunder
> Walter Underwood
> K6WRU
> CM87wj
>
>
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--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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Jim Brown-10

Re: mods to K2

On 9/27/2013 12:37 PM, Vic K2VCO wrote:
> This argument will never die.

As long as some of those doing the talking are ignorant of the facts,
yes. :)

> I maintain that even ONE dB matters in this situation.

And you are correct. Here are the FACTS. The 6dB and 10 dB "rules of
thumb" are based on the FACT that a 6-10 dB change in the loudness of a
sound that is well above the background noise level will be perceived by
the human ear/brain as "twice as loud," or half as loud. The key words
here are "well above the background noise level." This fact is quite
well known from the study of psychoacoustics (that is, how humans hear),
and is related to the fact that human hearing and sight are logarithmic
in their response to loudness and brightness.

The FACTS are very different if the desired "signal" is close to the
noise level, or to the level of other sounds. In that situation, a
change as little as 1-2 dB can be VERY perceptible, and make the
difference between hearing and not hearing it. One of the things I did
professionally was mix sound for live jazz performances. It wasn't long
before I learned that changes of only 2-2 dB in the balance between
instruments was often the difference between just right and not hearing
one of them.

Most serious contesters and DXers fight for every dB in their stations.
Consider that the gain of the BEST 2-el beam over a dipole at the same
height is no more than 3-4 dB, and that adding another element typically
adds 1 - 1.5 dB. And that assumes that these are well designed,
efficient antennas. Those with traps are 1-3 dB less than that. Note
that these are MEASURED numbers, not advertising numbers, and are taken
from documentation of an excellent series of tests of a dozen or so
tri-banders by N0AX and K7LXC about 15 years ago. Ward and Steve
actually measured two big antennas with negative gain as compared to a
dipole. :)

73, Jim K9YC
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John Oppenheimer

Re: mods to K2 & Propagation

In reply to this post by Vic Rosenthal

One way to quantitatively evaluate power versus probability of
communicating is to use the VOACAP Online tool:
http://www.voacap.com/prediction.html
The tool includes transmitter power at several steps, 1, 5, 10, 50, 100,
etc. Set the transmitter at your location and the receiver about 1300
miles away, optimal first hop for a 20 Degree radiation elevation angle.
Then keeping all parameters constant, run a few prediction at various
power levels and evaluate the area of the 90-100% probability on the
resulting prediction plots.

The resulting plot includes 10 lines, representing the 10% probability
steps.

John KN5L
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Bill W4ZV

Re: mods to K2

In reply to this post by Vic Rosenthal

Vic K2VCO-2 wrote

This argument will never die.

But remember the last time you called CQ and a station came back that you could hear, but
not copy. (I'm thinking CW, but it also applies to SSB).

You know he is in there, but despite struggling with the narrowest possible bandwidth and
every trick your receiver is capable of, you just can't get his call as he floats in and
out of the noise.

I maintain that even ONE dB matters in this situation.

IMHO 1 dB absolutely matters when signals are at or below the noise floor. I've lost several QSOs while activating SOTA summits for exactly the reason Vic described above. I find myself wanting my Beverages (at home) or the K3's APF, neither of which is available on a summit while using my K2.

AB7E made a very useful set of recordings which demonstrates differences in weak signal copy in background noise. They also demonstrate why you should not send at QRQ speeds when signals are weak (an exception to this is when lightning crashes are prevalent).

http://www.ab7e.com/weak_signal/mdd.html

It's interesting to note significant differences in various SOTA activators ability to copy my signal from a summit (i.e. Summit-to-Summit QSOs). I usually hear other SOTAs well but some are deaf as stones. I believe this is due to inexperience by some in copying weak signals.

73, Bill W4ZV

drewko

Re: mods to K2

In reply to this post by Allan Taylor

I was curious to determine what a 3 db increase in power output might
mean in terms of total number of possible contacts. So I set up my K3
to run WSPR on 20 meters for a while today:

At regular intervals over the course of 9 hours the power output was
toggled back and forth between 5 and 10 watts, logging some 2,000
signal reports for the entire period.

So, how much is a 3 db increase in power output worth? According to my
WSPR log data, about 40% more contacts. (At that rate a 6 db increase
would give nearly twice as many contacts. And a K3/100 should have
about three times as many QSOs in it than a K3/10...)

Anyhow, the original intention to mod the K2 might be justified. It's
not an insignificant improvement, though it might be good to log a few
thousand more reports to make sure.

73,
Drew
AF2Z

On Fri, 27 Sep 2013 08:24:39 -0700, you wrote:

>My first thought on the audio was to get some efficient earbuds. Lightweight and cheap.
>
>Over on the KX3 list, people like the Chill Pill powered speakers.
>
>I know it is a second box, but the Hardrock 50 amp has been getting good reviews. You would not need to get it out except in an emergency, so it could stay deep in the pack. See: http://www.hobbypcb.com/amateur-radio/amateur-radio/hardrock-50-hf-power-amp-kit.html
>
>I think there is a lot of evidence that 3dB does not matter. 10dB matters. 6dB might matter.
>
>wunder
>Walter Underwood
>K6WRU
>CM87wj
>

Vic Rosenthal

Re: mods to K2

One BIG problem which I should have mentioned before is that while you
might get away with it on CW, doing this would increase IMD for SSB or
digital modes a great deal.

On 9/28/13 7:19 PM, drewko wrote:

> I was curious to determine what a 3 db increase in power output might
> mean in terms of total number of possible contacts. So I set up my K3
> to run WSPR on 20 meters for a while today:
>
> At regular intervals over the course of 9 hours the power output was
> toggled back and forth between 5 and 10 watts, logging some 2,000
> signal reports for the entire period.
>
> So, how much is a 3 db increase in power output worth? According to my
> WSPR log data, about 40% more contacts. (At that rate a 6 db increase
> would give nearly twice as many contacts. And a K3/100 should have
> about three times as many QSOs in it than a K3/10...)
>
> Anyhow, the original intention to mod the K2 might be justified. It's
> not an insignificant improvement, though it might be good to log a few
> thousand more reports to make sure.
>
> 73,
> Drew
> AF2Z
>
>
>
>
>
>
> On Fri, 27 Sep 2013 08:24:39 -0700, you wrote:
>
>> My first thought on the audio was to get some efficient earbuds. Lightweight and cheap.
>>
>> Over on the KX3 list, people like the Chill Pill powered speakers.
>>
>> I know it is a second box, but the Hardrock 50 amp has been getting good reviews. You would not need to get it out except in an emergency, so it could stay deep in the pack. See: http://www.hobbypcb.com/amateur-radio/amateur-radio/hardrock-50-hf-power-amp-kit.html
>>
>> I think there is a lot of evidence that 3dB does not matter. 10dB matters. 6dB might matter.
>>
>> wunder
>> Walter Underwood
>> K6WRU
>> CM87wj
>>
>
> ______________________________________________________________
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Eric Swartz - WA6HHQ

Re: mods to K2

Administrator

In reply to this post by drewko

We've beaten this subject to death with lots of good info.

Thread now closed in the interest of improving list SNR :-)

73,

Eric
You're intrepid Elecraft list moderator, who is waiting for his flight home at Heathrow. I hate jet lag..

elecraft.com
---
Sent from my iPhone 5S

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Geoffrey Downs-3

Re: Eric Flies Home

Happy Landings Eric. Thanks for coming to the UK National Hamfest. It was
very good for so many of us here to be able to meet you in person and to
have the opportunity to hear your interesting talks.

73

Geoff
G3UCK

-----Original Message-----
From: Eric Swartz WA6HHQ - Elecraft

Eric
You're intrepid Elecraft list moderator, who is waiting for his flight home
at Heathrow. I hate jet lag..

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