K2 carry handle and QRP TX alignment

[Ethan Miller K8GU]

All,

I breathed life into K2/10 #7372 (love that serial number) last night.
 This is going to be fun little radio despite being a 15-year-old
design!

I noticed one thing that I wanted to ask the assembled experts here:
When peaking the TX BPF capacitors, there was a perceptible and
easily-found peak; but, if I got off the peak too far, the transmitter
power would increase rapidly to >10 watts as I tuned in the wrong
direction.  This must be normal or expected?  I did not monitor the
transmitter spectrum while doing this, so I don't know if it's a loud
spur that's normally suppressed or an amplifier somewhere is
conditionally-stable?

Secondly, and perhaps most importantly since the radio appears to be
stable in the face of the previous question, any suggestions for a
side carrying strap?  In the archives, it appears that the IC-706
handle was popular.  What about the handle for the FT-450?  (I have to
place an order with Vertex Standard for some small parts for a Yaesu
HT and it would be nice to make the order worth their while by
ordering a handle at the same time.)

Thanks/73,

--Ethan, K8GU/3.

[obligatory (e) brag line: K3/100 #6714 - K2/10 #7372]
--
http://www.k8gu.com/
Repair.  Re-use.  Re-purpose.  Recycle.
______________________________________________________________
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

[Don Wilhelm-4]

Ethan,

The reason you are to first tune the BPF during receive is to get them
close to the correct settings.
You should find the peak during transmit close to the peak observed
during receive.
Certainly some of the BPF inductors and capacitors could be tuned to an
improper mixer product if adjusted farther from the correct point.  You
have the VFO frequency which is 4913 kHz away from the correct frequency
and any harmonic of the BFO that could be present in the RF content
prior to the BPF.  There will also be other mixing products that you
could tune the BPF to (but you shouldn't).  The purpose of the BPF is to
eliminate the undesired mixer products.

When tuning the BPF on TX, start with the power set between 1.5 and 2
watts.  If it climbs above about 5 watts, exit TUNE and re-enter to
bring the power down again and continue to find the peak.

73,
Don W3FPR

On 2/7/2014 9:00 AM, Ethan Miller K8GU wrote:

> All,
>
> I breathed life into K2/10 #7372 (love that serial number) last night.
>   This is going to be fun little radio despite being a 15-year-old
> design!
>
> I noticed one thing that I wanted to ask the assembled experts here:
> When peaking the TX BPF capacitors, there was a perceptible and
> easily-found peak; but, if I got off the peak too far, the transmitter
> power would increase rapidly to >10 watts as I tuned in the wrong
> direction.  This must be normal or expected?  I did not monitor the
> transmitter spectrum while doing this, so I don't know if it's a loud
> spur that's normally suppressed or an amplifier somewhere is
> conditionally-stable?
>
>

______________________________________________________________
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

[Ethan Miller K8GU]

Don,

Great---thanks for the explanation!  This is exactly the procedure I
followed, but I did inadvertently move beyond the peak on the high
bands---those caps are a bit touchy.  I resolved it by doing just as
you suggested and the peak was easily achieved.  Just noting the
curiosity, that's all.

73,

--Ethan, K8GU/3.


On Fri, Feb 7, 2014 at 10:05 AM, Don Wilhelm <[hidden email]> wrote:

> Ethan,
>
> The reason you are to first tune the BPF during receive is to get them close
> to the correct settings.
> You should find the peak during transmit close to the peak observed during
> receive.
> Certainly some of the BPF inductors and capacitors could be tuned to an
> improper mixer product if adjusted farther from the correct point.  You have
> the VFO frequency which is 4913 kHz away from the correct frequency and any
> harmonic of the BFO that could be present in the RF content prior to the
> BPF.  There will also be other mixing products that you could tune the BPF
> to (but you shouldn't).  The purpose of the BPF is to eliminate the
> undesired mixer products.
>
> When tuning the BPF on TX, start with the power set between 1.5 and 2 watts.
> If it climbs above about 5 watts, exit TUNE and re-enter to bring the power
> down again and continue to find the peak.
>
> 73,
> Don W3FPR
>
>
> On 2/7/2014 9:00 AM, Ethan Miller K8GU wrote:
>>
>> All,
>>
>> I breathed life into K2/10 #7372 (love that serial number) last night.
>>   This is going to be fun little radio despite being a 15-year-old
>> design!
>>
>> I noticed one thing that I wanted to ask the assembled experts here:
>> When peaking the TX BPF capacitors, there was a perceptible and
>> easily-found peak; but, if I got off the peak too far, the transmitter
>> power would increase rapidly to >10 watts as I tuned in the wrong
>> direction.  This must be normal or expected?  I did not monitor the
>> transmitter spectrum while doing this, so I don't know if it's a loud
>> spur that's normally suppressed or an amplifier somewhere is
>> conditionally-stable?
>>
>>
>

--
http://www.k8gu.com/
Repair.  Re-use.  Re-purpose.  Recycle.
______________________________________________________________
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