Re: [Elecraft] PBSK31

[David Giles]

Hello Phil,

My K2's serial number is in the 5000s so it has the temperature 
stability circuit built in.  I have only just recently started using it 
on JT9 after some time on JT65.  I don't start transmitting until it has 
warmed up after 5 minutes or so.  I first used it outdoors at my remote 
site (see VK3TUN on qrz.com) and had to shield it from the wind.  Now 
that the shed is up, that is no longer an issue.  I don't know if it 
helps that much with dissipating the heat, but I always have the bail 
extended.


73 de David VK5DG / VK3TUN


On 25/04/2016 7:53 AM, Phil Wheeler wrote:

David,

Do you do anything special to ensure frequency stability in those 
modes with your K2?


Phil W7OX

On 4/24/16 3:02 PM, David Giles wrote:
I've made hundreds of contacts using JT65 and JT9 with my K2 at 5W. 
Most of these portable on a 12v battery with solar charging. With a 
48 second transmit period, it's probably more of a stress test than 
BPSK31.


73 de David VK5DG / VK3TUN

On 24/04/2016 2:07 PM, Bruce Rattray wrote:

What is the safe level to operate the K2 at for the PBSK31 mode?  I'm
thinking 2 or 3 watts.  tnx 73 Bruce ve5rc


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Re: [Elecraft] PBSK31

[Don Wilhelm]

Phil and all,

Yes, those mods can do a lot for temperature stability of the K2. Adjust 
the Thermistor board RA value if necessary to achieve the best stability.
The KX3 can achieve good temperature stability if the Extended 
Temperature Compensation procedure is completed - I would not attempt 
any of the JT data modes without doing that first.


73,
Don W3FPR

On 4/24/2016 7:28 PM, Phil Wheeler wrote:
I've done all those mods to #380, Don. I didn't realize they were that 
effective!  And after reading of thermal stability issues some have 
had in JT65 (e.g., using a KX3) I assumed the K2/10 would have even 
larger issues in those modes, given the age of the design.


Your message is good news indeed!

73, Phil W7OX



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Re: [Elecraft] PBSK31

[Phil Wheeler]

I've done all those mods to #380, Don. I didn't 
realize they were that effective!  And after 
reading of thermal stability issues some have had 
in JT65 (e.g., using a KX3) I assumed the K2/10 
would have even larger issues in those modes, 
given the age of the design.


Your message is good news indeed!

73, Phil W7OX

On 4/24/16 3:52 PM, Don Wilhelm wrote:

Phil,

I cannot say if David did anything special for 
frequency stability, but any K2 above SN 3000 
had the BFO stability mod and the PLL 
Temperature compensation mod installed which can 
achieve the necessary stability.  K2s below SN 
3000 can be upgraded with those upgrade kits.


The stock PLL Temperature Stability Mod has 
resistor RA as a 33k resistor.  That resistor 
value can be modified to achieve closer 
temperature stability for any particular K2.  
The K2 manual does not contain information about 
how to vary and check the compensation, but that 
information is contained in the instructions for 
the PLL Temperature Stability Mod - download 
from Elecraft.


The temperature change in the K2/10 is not 
likely to be very much even for long periods of 
transmit because the PA transistors and heatsink 
are not close to the VFO/PLL and BFO areas and 
there is a lot of 'air space' inside the enclosure.
With the KPA100 added, that air space is much 
more confined and the heat from the KPA100 PA 
transistors will have an influence.
In other words, while the stock K2/10 may be 
sufficiently stable, the K2/100 may need some 
'tweaking' of the RA resistor value for 
equivalent stability.


73,
Don W3FPR

On 4/24/2016 6:23 PM, Phil Wheeler wrote:

David,

Do you do anything special to ensure frequency 
stability in those modes with your K2?


Phil W7OX

On 4/24/16 3:02 PM, David Giles wrote:
I've made hundreds of contacts using JT65 and 
JT9 with my K2 at 5W. Most of these portable 
on a 12v battery with solar charging. With a 
48 second transmit period, it's probably more 
of a stress test than BPSK31.


73 de David VK5DG / VK3TUN





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Re: [Elecraft] PBSK31

[Don Wilhelm]

Phil,

I cannot say if David did anything special for frequency stability, but 
any K2 above SN 3000 had the BFO stability mod and the PLL Temperature 
compensation mod installed which can achieve the necessary stability.  
K2s below SN 3000 can be upgraded with those upgrade kits.


The stock PLL Temperature Stability Mod has resistor RA as a 33k 
resistor.  That resistor value can be modified to achieve closer 
temperature stability for any particular K2.  The K2 manual does not 
contain information about how to vary and check the compensation, but 
that information is contained in the instructions for the PLL 
Temperature Stability Mod - download from Elecraft.


The temperature change in the K2/10 is not likely to be very much even 
for long periods of transmit because the PA transistors and heatsink are 
not close to the VFO/PLL and BFO areas and there is a lot of 'air space' 
inside the enclosure.
With the KPA100 added, that air space is much more confined and the heat 
from the KPA100 PA transistors will have an influence.
In other words, while the stock K2/10 may be sufficiently stable, the 
K2/100 may need some 'tweaking' of the RA resistor value for equivalent 
stability.


73,
Don W3FPR

On 4/24/2016 6:23 PM, Phil Wheeler wrote:

David,

Do you do anything special to ensure frequency stability in those 
modes with your K2?


Phil W7OX

On 4/24/16 3:02 PM, David Giles wrote:
I've made hundreds of contacts using JT65 and JT9 with my K2 at 5W. 
Most of these portable on a 12v battery with solar charging. With a 
48 second transmit period, it's probably more of a stress test than 
BPSK31.


73 de David VK5DG / VK3TUN


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Re: [Elecraft] PBSK31

[Phil Wheeler]

David,

Do you do anything special to ensure frequency 
stability in those modes with your K2?


Phil W7OX

On 4/24/16 3:02 PM, David Giles wrote:
I've made hundreds of contacts using JT65 and 
JT9 with my K2 at 5W. Most of these portable on 
a 12v battery with solar charging. With a 48 
second transmit period, it's probably more of a 
stress test than BPSK31.


73 de David VK5DG / VK3TUN

On 24/04/2016 2:07 PM, Bruce Rattray wrote:
What is the safe level to operate the K2 at for 
the PBSK31 mode?  I'm

thinking 2 or 3 watts.  tnx 73 Bruce ve5rc


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Re: [Elecraft] PBSK31

[David Giles]

I've made hundreds of contacts using JT65 and JT9 with my K2 at 5W.  
Most of these portable on a 12v battery with solar charging. With a 48 
second transmit period, it's probably more of a stress test than BPSK31.


73 de David VK5DG / VK3TUN

On 24/04/2016 2:07 PM, Bruce Rattray wrote:

What is the safe level to operate the K2 at for the PBSK31 mode?  I'm
thinking 2 or 3 watts.  tnx 73 Bruce ve5rc

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Re: [Elecraft] PBSK31

[Matt Maguire]

Wouldn't want to go much higher than 5W though -- you want to maintain 
linearity, and PSK31 has a peak-to-average-power-ratio of 3dB.
73, Matt VK2RQ

Envoyé d’Outlook Mobile




On Sun, Apr 24, 2016 at 6:18 AM -0700, "lstavenhagen" 
 wrote:










I agree with Don, the K2 should be brick-on-key at 5 watts at least. On m 12V
batteries, mine are almost that way at full power, the heat sink at the
bottom definitely gets warm but seems to go forever without getting hot.

On a regulated PS, though, that doesn't drop into the 11v range like my
batts, that may not be true

73,
LS
W5QD



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Re: [Elecraft] PBSK31

[lstavenhagen]

I agree with Don, the K2 should be brick-on-key at 5 watts at least. On m 12V
batteries, mine are almost that way at full power, the heat sink at the
bottom definitely gets warm but seems to go forever without getting hot.

On a regulated PS, though, that doesn't drop into the 11v range like my
batts, that may not be true

73,
LS
W5QD



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http://elecraft.365791.n2.nabble.com/PBSK31-tp7616597p7616600.html
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Re: [Elecraft] PBSK31

[Don Wilhelm]

Bruce,

I always operated mine at 5 watts.  The K2/10 has a large heatsink area.
You may want to try even higher than 5 watts - if you want to check to make
sure it is OK, feel the bottom rear panel of the K2 enclosure.  It will 
be warm,
But you should still be able to hold your fingers on it.  If it is too 
hot to

touch continually, it is too hot.

73,
Don W3FPR

On 4/24/2016 12:37 AM, Bruce Rattray wrote:

What is the safe level to operate the K2 at for the PBSK31 mode?  I'm
thinking 2 or 3 watts.  tnx 73 Bruce ve5rc



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[Elecraft] PBSK31

[Bruce Rattray]

What is the safe level to operate the K2 at for the PBSK31 mode?  I'm
thinking 2 or 3 watts.  tnx 73 Bruce ve5rc

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