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FSK power

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Nr4c

FSK power

First I want to thank all who responded to my FSK question earlier
this week. The information was helpful and appreciated.

Now, one more. How much power can I safely use with FSK? I have made
several contacts so far at about 50 watts. Can I use more? there is a
RTTY contest this weekend, and I don't want to damage the radio, but
don't want to start off with a weak signal if I can do better.

Thanks

...bc nr4c

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Richard Ferch

Re: FSK power

The specifications for the transmitter in the Owner's Manual say 100% 10
min 100W key-down at 25 C ambient, so RTTY at 100 watts is within spec
even for extended transmissions, and an RTTY contest with its short
transmissions should be no problem at all at 100 watts.

You can monitor the temperature of the finals by tapping the DISP key
and rotating the VFO B knob until you see PA xxC (where xx is the
current temperature). I believe there is a protective thermal shut-down
somewhere up around 80C, but I doubt whether you will come anywhere near
that. Mine gets into the mid-50s near the end of long transmissions
during digital mode ragchews, but it doesn't get that hot during
contests. The ambient temperature has a significant influence, too.

If you do monitor the PA temperature, don't be surprised if you observe
temperature readings that are slightly higher during receive than during
transmit periods. The voltage drop in the power cable at the high
transmit current draw results in lower voltage at the rig, which in turn
causes the temperature indication (not the actual temperature) to drop
slightly. In digital modes I often observe the fans speeding up in
receive and slowing down in transmit when the PA temperature reading
happens to be close to the threshold for a fan speed change. I found
this disconcerting at first, until I realized what was happening!

73,
Rich VE3KI

NR4C wrote:

> Now, one more. How much power can I safely use with FSK? I have made
> several contacts so far at about 50 watts. Can I use more? there is a
> RTTY contest this weekend, and I don't want to damage the radio, but
> don't want to start off with a weak signal if I can do better.

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Mark n2qt

Re: FSK power

I've become a firm believer in air flow during rtty contests. I use a 24
volt 5 inch muffin fan
blowing air down into the K3 across the PA fins. I run the fan with about
12 volts which
cuts the noise down somewhat. Looking at the PA temp while doing this, it's
hard to get
it up much over 35C during a contest.

Mark n2qt

>
> NR4C wrote:
>
>> Now, one more. How much power can I safely use with FSK? I have made
>> several contacts so far at about 50 watts. Can I use more? there is a
>> RTTY contest this weekend, and I don't want to damage the radio, but
>> don't want to start off with a weak signal if I can do better.
>
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Guy, K2AV

Re: FSK power

The K3 has the best heat dissipation scheme I have ever seen in a 100W
transceiver. Though Wayne and co. don't want to hear about us doing it,
some of us have done the brick on key thing at 110 watts for a long time,
and watched the temp level out in the 50's. Fan comes on, goes to high, and
blows a lot of reasonably warm air out.

Yes, you CAN muck up the top cover and blow more air in if that makes you
feel good. But the prevailing opinion will be that's unnecessary. It would
not be accurate to tell anyone that a top fan is necessary.

73, Guy.

On Thu, Sep 23, 2010 at 3:10 PM, Mark n2qt <[hidden email]> wrote:

> I've become a firm believer in air flow during rtty contests. I use a 24
> volt 5 inch muffin fan
> blowing air down into the K3 across the PA fins. I run the fan with about
> 12 volts which
> cuts the noise down somewhat. Looking at the PA temp while doing this,
> it's
> hard to get
> it up much over 35C during a contest.
>
> Mark n2qt
>
> >
> > NR4C wrote:
> >
> >> Now, one more. How much power can I safely use with FSK? I have made
> >> several contacts so far at about 50 watts. Can I use more? there is a
> >> RTTY contest this weekend, and I don't want to damage the radio, but
> >> don't want to start off with a weak signal if I can do better.
> >
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> >
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> >
>
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Joe Planisky

Re: FSK power

There seems to be some variation in this. I often run around 70W and
the temp usually tops out around 60 - 65C. It's gone as high as 72C
on a warm day.

73
--
Joe KB8AP

On Sep 23, 2010, at 1:03 PM, Guy Olinger K2AV wrote:

> ...
> some of us have done the brick on key thing at 110 watts for a long
> time,
> and watched the temp level out in the 50's. Fan comes on, goes to
> high, and
> blows a lot of reasonably warm air out.
> ...

> 73, Guy.
>
> On Thu, Sep 23, 2010 at 3:10 PM, Mark n2qt <[hidden email]> wrote:
>
>> I've become a firm believer in air flow during rtty contests....
>> Mark n2qt
>>
>>>
>>> NR4C wrote:
>>>
>>>> Now, one more. How much power can I safely use with FSK? I have
>>>> made
>>>> several contacts so far at about 50 watts. Can I use more?

Mark n2qt

Re: FSK power

In reply to this post by Guy, K2AV

Necessary no, but I am eager for my K3 to have a long and productive life, and cooler
semiconductors are always better. I put some plastic press on feet on the bottom of the
fan I use, and a screen on the top to keep fingers out so no changes to the K3 cover.

Feeling good is not a bad reason to do things.....

73,
Mark
----- Original Message -----
From: Guy Olinger K2AV
To: Mark n2qt
Cc: [hidden email]
Sent: Thursday, September 23, 2010 4:03 PM
Subject: Re: [Elecraft] FSK power

The K3 has the best heat dissipation scheme I have ever seen in a 100W transceiver. Though Wayne and co. don't want to hear about us doing it, some of us have done the brick on key thing at 110 watts for a long time, and watched the temp level out in the 50's. Fan comes on, goes to high, and blows a lot of reasonably warm air out.

Yes, you CAN muck up the top cover and blow more air in if that makes you feel good. But the prevailing opinion will be that's unnecessary. It would not be accurate to tell anyone that a top fan is necessary.

73, Guy.

On Thu, Sep 23, 2010 at 3:10 PM, Mark n2qt <[hidden email]> wrote:

I've become a firm believer in air flow during rtty contests. I use a 24
volt 5 inch muffin fan
blowing air down into the K3 across the PA fins. I run the fan with about
12 volts which
cuts the noise down somewhat. Looking at the PA temp while doing this, it's
hard to get
it up much over 35C during a contest.

Mark n2qt

>
> NR4C wrote:
>
>> Now, one more. How much power can I safely use with FSK? I have made
>> several contacts so far at about 50 watts. Can I use more? there is a
>> RTTY contest this weekend, and I don't want to damage the radio, but
>> don't want to start off with a weak signal if I can do better.
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
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N5GE

Re: FSK power

In reply to this post by Joe Planisky

On Thu, 23 Sep 2010 14:28:41 -0700, Joe Planisky <[hidden email]>
wrote:

The variation is probably due to a difference in ambient shack
temperature.

All of my ham radio equipment runs cool due to it's being in a
computer/server room with it's AC system set to 75F.

BT 73 ES GUD LUK
DE N5GE,
QCWA LIFE MEMBER 35102,
LICENSED SINCE 1976 AR SK

[hidden email]
http://www.n5ge.com

>There seems to be some variation in this. I often run around 70W and
>the temp usually tops out around 60 - 65C. It's gone as high as 72C
>on a warm day.
>
>73

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Amateur Radio Operator N5GE

Ray Sills

Re: FSK power

In reply to this post by Richard Ferch

The difference in power between 50 watts and 100 watts is essentially
insignificant. If you can't work 'em at 50 watts with the antenna
you have... 100 watts ain't gonna make the difference. Period. 500
watts... 1KW.. OK.. maybe that'll help.

Just because the rig can "take it"... the extra power and dissipated
heat is just wasted.

My opinion.

73 de Ray
K2ULR
FN20kg
Warrington, PA

On Sep 23, 2010, at 3:02 PM, Richard Ferch wrote:

> The specifications for the transmitter in the Owner's Manual say
> 100% 10
> min 100W key-down at 25 C ambient, so RTTY at 100 watts is within spec
> even for extended transmissions, and an RTTY contest with its short
> transmissions should be no problem at all at 100 watts.
>
> You can monitor the temperature of the finals by tapping the DISP key
> and rotating the VFO B knob until you see PA xxC (where xx is the
> current temperature). I believe there is a protective thermal shut-
> down
> somewhere up around 80C, but I doubt whether you will come anywhere
> near
> that. Mine gets into the mid-50s near the end of long transmissions
> during digital mode ragchews, but it doesn't get that hot during
> contests. The ambient temperature has a significant influence, too.
>
> If you do monitor the PA temperature, don't be surprised if you
> observe
> temperature readings that are slightly higher during receive than
> during
> transmit periods. The voltage drop in the power cable at the high
> transmit current draw results in lower voltage at the rig, which in
> turn
> causes the temperature indication (not the actual temperature) to drop
> slightly. In digital modes I often observe the fans speeding up in
> receive and slowing down in transmit when the PA temperature reading
> happens to be close to the threshold for a fan speed change. I found
> this disconcerting at first, until I realized what was happening!
>
> 73,
> Rich VE3KI
>
>
> NR4C wrote:
>
>> Now, one more. How much power can I safely use with FSK? I have made
>> several contacts so far at about 50 watts. Can I use more? there is a
>> RTTY contest this weekend, and I don't want to damage the radio, but
>> don't want to start off with a weak signal if I can do better.
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html

n7ws

Re: FSK power

Well, you know what they say about opinions.

If you're jabbering away with some locals across town they might never know the difference. But three dB can make a difference, especially on RTTY and in contests.

Try telling a contester that the Kilobucks he just spent to stack another Yagi on his tower was a waste of money.

--- On Thu, 9/23/10, Ray Sills <[hidden email]> wrote:

> The difference in power between 50
> watts and 100 watts is essentially
> insignificant. If you can't work 'em at 50 watts with
> the antenna
> you have... 100 watts ain't gonna make the
> difference. Period. 500
> watts... 1KW.. OK.. maybe that'll help.
>
> Just because the rig can "take it"... the extra power and
> dissipated
> heat is just wasted.
>
> My opinion.
>
> 73 de Ray
> K2ULR
> FN20kg
> Warrington, PA

Guy, K2AV

Re: FSK power

In reply to this post by Joe Planisky

No, I don't think that is normal variation. 72C is 162F. I think that is
too high and reflects something else. You would be well served to chase
that down.

Are your fans running at max at that temp? Do the fans blow out to the rear
or pull air in? What is your supply voltage showing on DISP under full
load. Have you done the temperature calibration per the manual, and the
power calibration. (One soul due to an error was putting out 110 when he
was set to 60. He too was getting over temps besides his power woes of only
going up to an indicated 90 watts.)

73, Guy.

On Thu, Sep 23, 2010 at 5:28 PM, Joe Planisky <[hidden email]> wrote:

> There seems to be some variation in this. I often run around 70W and the
> temp usually tops out around 60 - 65C. It's gone as high as 72C on a warm
> day.
>
> 73
> --
> Joe KB8AP
>
>
> On Sep 23, 2010, at 1:03 PM, Guy Olinger K2AV wrote:
>
> ...
>>
>> some of us have done the brick on key thing at 110 watts for a long time,
>> and watched the temp level out in the 50's. Fan comes on, goes to high,
>> and
>> blows a lot of reasonably warm air out.
>> ...
>>
>
> 73, Guy.
>>
>> On Thu, Sep 23, 2010 at 3:10 PM, Mark n2qt <[hidden email]> wrote:
>>
>> I've become a firm believer in air flow during rtty contests....
>>>
>>> Mark n2qt
>>>
>>>
>>>> NR4C wrote:
>>>>
>>>> Now, one more. How much power can I safely use with FSK? I have made
>>>>> several contacts so far at about 50 watts. Can I use more?
>>>>>
>>>>

William H. Droeger, Jr.

Re: FSK power

In reply to this post by n7ws

Hi folks- 3 db in my qrp world is HUGE.
On Sep 23, 2010, at 7:15 PM, Wes Stewart wrote:

> Well, you know what they say about opinions.
>
> If you're jabbering away with some locals across town they might
> never know the difference. But three dB can make a difference,
> especially on RTTY and in contests.
>
> Try telling a contester that the Kilobucks he just spent to stack
> another Yagi on his tower was a waste of money.
>
> --- On Thu, 9/23/10, Ray Sills <[hidden email]> wrote:
>
>
>> The difference in power between 50
>> watts and 100 watts is essentially
>> insignificant. If you can't work 'em at 50 watts with
>> the antenna
>> you have... 100 watts ain't gonna make the
>> difference. Period. 500
>> watts... 1KW.. OK.. maybe that'll help.
>>
>> Just because the rig can "take it"... the extra power and
>> dissipated
>> heat is just wasted.
>>
>> My opinion.
>>
>> 73 de Ray
>> K2ULR
>> FN20kg
>> Warrington, PA
>
>
>
> ______________________________________________________________
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Jack Smith-6

Re: FSK power

In reply to this post by n7ws

If the RTTY demodulator is of the FM type, i.e., a limiter followed by
a discriminator (or, more likely these days, the software version of a
limiter and discriminator) 3 dB difference between two signals could
well cause the stronger signal to capture the limiter and suppress the
weaker signal.

Exactly what happens with some of the more exotic DSP-based demodulation
algorithms when the input is two signals differing by 3 dB but on the
same frequency and with asynchronous data is a more difficult question.

Jack

On 9/23/2010 8:15 PM, Wes Stewart wrote:

> Well, you know what they say about opinions.
>
> If you're jabbering away with some locals across town they might never know the difference. But three dB can make a difference, especially on RTTY and in contests.
>
> Try telling a contester that the Kilobucks he just spent to stack another Yagi on his tower was a waste of money.
>
> --- On Thu, 9/23/10, Ray Sills<[hidden email]> wrote:
>
>
>> The difference in power between 50
>> watts and 100 watts is essentially
>> insignificant. If you can't work 'em at 50 watts with
>> the antenna
>> you have... 100 watts ain't gonna make the
>> difference. Period. 500
>> watts... 1KW.. OK.. maybe that'll help.
>>
>> Just because the rig can "take it"... the extra power and
>> dissipated
>> heat is just wasted.
>>
>> My opinion.
>>
>> 73 de Ray
>> K2ULR
>> FN20kg
>> Warrington, PA
>
>
> ______________________________________________________________
> Elecraft mailing list
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Jim Brown-10

Re: FSK power

In reply to this post by Ray Sills

On 9/23/2010 4:37 PM, Ray Sills wrote:
> The difference in power between 50 watts and 100 watts is essentially
> insignificant.
Any contester or DXer will tell you from experience that this is NOT
TRUE. When you're 20 dB over the noise and QRM, 3dB doesn't matter, but
when you're on the edge of making a contact, 1-2dB can matter a LOT.
MANY times, I've been working a contest by running up and down the band,
with the amp tuned at one end. When i get to the far end, I'm running
less power. I'll work the guys who hear me well, but I've often had to
retune the amp for another 2dB make the contact. Also, I often run my
legal limit Ten Tec Titan at 1kW to save the tubes, but when I'm not
getting through, I'll kick it up that extra 1.7dB to 1500 watts to make
the contact.

One of the big misunderstandings about dB and audibility is that when
the desired signal is close to the noise level, a dB or so can be quite
obvious.

73, Jim Brown K9YC
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Kok Chen

Re: FSK power

In reply to this post by Ray Sills

On Sep 23, 2010, at 4:37 PM, Ray Sills wrote:
> The difference in power between 50 watts and 100 watts is essentially insignificant.

Whether 3 dB of power difference is important depends on band conditions.

Alex (Mr. CW Skimmer) VE3NEA has a nice set of measurements that he'd made a few years ago at

http://www.dxatlas.com/RttyCompare/

The AWGN (Additive White Gaussian Noise) condition is basically the case of a quiet band (single path with no Watterson spreading). Notice that a 3 dB change in SNR can take you from practically perfect printing to no printing at all. The blue curve is what you see in textbooks for binary FSK. The others are three amateur software modems that he'd measured.

On the other hand, in the presence of selective fading or flutter, a 3 dB power change won't improve the character error rate by very much, you need 10 dB of power change to transition the RTTY decoding threshold.

73
Chen, W7AY

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Joe Planisky

Re: FSK power

In reply to this post by Guy, K2AV

Do note that the 72C reading was on a day when it was probably around
32C (90F) in the shack. Normal summertime temps in the shack are
closer to 27C (80F). Otherwise:

> Are your fans running at max at that temp?

Oh yes. They kick into "leaf blower mode" around 55C.

> Do the fans blow out to the rear or pull air in?

Blows out the back.

> What is your supply voltage showing on DISP under full load.

13.6V

> Have you done the temperature calibration per the manual,

Yep. The rig and a thermocouple in my DMM usually agree within +/- 1C
at startup.

> and the power calibration.

Yes, but just to make sure I ran it again just now. 70W requested
gives me about 63W into a dummy load (as measured with my oscilloscope.)

You didn't ask, but yes, I'm adjusting my audio input for 5 bars on
the ALC meter.

Someone else asked about restricted airflow. The rig sits on an open
shelf by itself with about 18 inches of clear space behind it and
nothing but the ceiling about 4 feet above it.

73
--
Joe KB8AP

On Sep 23, 2010, at 6:48 PM, Guy Olinger K2AV wrote:

> No, I don't think that is normal variation. 72C is 162F. I think
> that is
> too high and reflects something else. You would be well served to
> chase
> that down.
>
> Are your fans running at max at that temp? Do the fans blow out to
> the rear
> or pull air in? What is your supply voltage showing on DISP under full
> load. Have you done the temperature calibration per the manual, and
> the
> power calibration. (One soul due to an error was putting out 110
> when he
> was set to 60. He too was getting over temps besides his power woes
> of only
> going up to an indicated 90 watts.)
>
> 73, Guy.
>
> On Thu, Sep 23, 2010 at 5:28 PM, Joe Planisky <[hidden email]>
> wrote:
>
>> There seems to be some variation in this. I often run around 70W
>> and the
>> temp usually tops out around 60 - 65C. It's gone as high as 72C on
>> a warm
>> day.
>>
>> 73
>> --
>> Joe KB8AP

John_N1JM

Re: FSK power

I run rtty at 75watts. No problems of course. Going to 100 is about 1.2 dbs. Not worth worrying about I suspect.

John N1JM

Julian, G4ILO

Re: FSK power

I normally run 50W in CW or any digi mode, because I feel more comfortable running well within the ratings, but I will always crank it up to 100W when needed.

In a contest, you're listening half the time anyway, so 50% duty cycle and the K3 will take it even at 100W output.

Julian, G4ILO. K2 #392 K3 #222 KX3 #110
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

Mike K2MK

Re: FSK power

In reply to this post by Ray Sills

Hi Ray,

Actual on the air results lead me to completely disagree with your statement. With my old rig I ran at half power on RTTY. During contests if I could not get a response from the other station by the second call I would just twist the power knob to full and 90% of the time I would get the contact. The benefit of that one single S unit was repeatedly proven to be all that I needed.

73,
Mike K2MK

Ray Sills wrote

The difference in power between 50 watts and 100 watts is essentially
insignificant. If you can't work 'em at 50 watts with the antenna
you have... 100 watts ain't gonna make the difference. Period. 500
watts... 1KW.. OK.. maybe that'll help.

Just because the rig can "take it"... the extra power and dissipated
heat is just wasted.

My opinion.

73 de Ray
K2ULR
FN20kg
Warrington, PA

Dave Hachadorian

Re: FSK power

In reply to this post by Guy, K2AV

Here is a copy of a posting I made on 20090312:

Here is a copy of a posting I made on 20090312:

I did an experiment on my two K3's - key down at 100 watts
for four minutes while noting PA Temp and fan speed. Both K3's
behaved
identically and both leveled off at PA Temp = 64C after
about 3 minutes. For the record, here are the results (best
viewed with Courier font):

Time Temp Fan
0:00 26C 0
0:26 37 1
0:44 41 2
1:19 50 3
1:45 55 4
2:40 60 4
2:50 62 4
3:15 64 4
4:00 64 4

Room temp was 77F.

According to the manual, the PA is set to drop into bypass at
84C, so it didn't even come close.

Dave Hachadorian, K6LL
Yuma, AZ

.

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Ken Chandler

Re: FSK power

I have been running 100w output using AFSK A in the RTTY contest and I have been monitoring my PA temp via the meter. I have my fan set for FN2 constantly on, and the temp has only reached 45C.

Ken..G0ORH

CW4EVER

Sent from my iPhone

On 24 Sep 2010, at 17:47, "Dave Hachadorian" <[hidden email]> wrote:

> Here is a copy of a posting I made on 20090312:
>
> Here is a copy of a posting I made on 20090312:
>
> I did an experiment on my two K3's - key down at 100 watts
> for four minutes while noting PA Temp and fan speed. Both K3's
> behaved
> identically and both leveled off at PA Temp = 64C after
> about 3 minutes. For the record, here are the results (best
> viewed with Courier font):
>
> Time Temp Fan
> 0:00 26C 0
> 0:26 37 1
> 0:44 41 2
> 1:19 50 3
> 1:45 55 4
> 2:40 60 4
> 2:50 62 4
> 3:15 64 4
> 4:00 64 4
>
> Room temp was 77F.
>
> According to the manual, the PA is set to drop into bypass at
> 84C, so it didn't even come close.
>
> Dave Hachadorian, K6LL
> Yuma, AZ
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