[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
>
>