Tim,
I am one of the folks who have said the K2 audio is low - BUT
The fact is that one of the K2 design objectives was for low battery drain,
and that dictates limits on the audio reserve power available. The K2 audio
is adequate, but by comparison to most other transceivers, it is low. An
external audio amplifier is a good solution, particularly if you are
operating in a high ambient noise environment or want to operate (say) at
Field Day with the speaker (non-battery class of course). I use Tom
Hammond's amplifier with a 9 ohm speaker here and it has LOTS of output,
even though its full power output will only be realized with a 4 ohm
speaker.
As for the differences between your 2 K2s, I can recommend that you check 2
things - first is the winding of T7. The old turns ratio was 11:3 while the
new ratio is 20:5. This sets the impedance that the variable xtal filter
sees and could be even be optimized for you particular set of xtals if you
want to experiment.
The second thing that will make a difference between different K2s is the
AGC level. The AGC and the RF gain both feed the AGC input of the IF amp
chip, so that level is crutial to the overall gain of the K2 receiver. In
working on several K2s, I have noticed sthat there appears to be a slight
difference between receivers that is quite sensitive to the AGC voltage.
The 3.8 volt setting mentioned in the manual is not graven in stone, so feel
free to change the AGC threshold to match the perfomance that you want - I
usually find that somewhere in the range of 3.6 volts to 3.8 volts is the
optimum setting.
73,
Don W3FPR
----- Original Message -----
*Hi folks -
In anticipation of beginning my next K2 I have been reviewing the archives
for the many, many posts on audio - so please forgive one more! I've built
two K2's and owned 3. The one I am building now will be my 3rd. The only
thought I've ever had as a "negative" about K2's is the audio volume. At
one point two of mine seemed to have different relative volumes - even
though Gary checked out the lower volume one and said it was A-OK.
SO...in building another one I would like to ask three questions for those
of you WAY more informed than this dim bulb :-)
1 - During my build, can you suggest particular building stages and
components where I should go beyond the normal voltage/continuity checks
from the manual to make ADDITIONAL measurements to make 120% sure I have
not inadvertantly "built in" anything that might contribute to a lower
than standard volume?
2 - Have there been or are there any suggested component substitutions
that might increase overall audio? If so, what are the tradeoffs for this
experimentation?
3 - I note with interest Tom Hammond's circuit for an external amplified
Motorola speaker (see http://N0SS.net) - has anyone adopted and used this
particular setup and what do you think? Does the amplification have any
negative impacts (distortion, increased noise, etc)?
If I missed archived responses that previously addressed these questions,
I apologize in advance!!! Thanks folks!
73/Tim NZ7C
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