Re: Rig ergonomics and performance comparison


Eric Swartz - WA6HHQ, Elecraft
 

The K3 transmits through both bandpass filters (before the final
amplifier stages) and through low pass filters after the PAs.

The bandpass filters do an excellent job of removing out of band noise
generated in earlier stages. The low pass filters afer the PA remove
any hamonic energy generated in the final PA stages.

73,
Eric WA6HHQ
Elecraft

--- In Elecraft_K3@yahoogroups.com, "CR" <vk3he@...> wrote:

Hi Chris

I was incorrect, the K3 uses lowpass filters and not bandpass filters
in the TX chain, so they are still needed. However with the great
IMD dynamic range figures that most are expecting its only in cases
where you have 2 transmitters on the same band where the receiver will
be challenged. Until we see what the phase noise performance of the K3
is like we can only presume that it will be good and this wont be a
issue.

I do believe that the W3NQN filters have very good performance, they
are so good in fact that its possible to use a dual band yagi on the
same boom and receive on one band while another station is
transmitting on another band.

Most people use the bandpass filters to null the second harmonic.
Several stations use stubs along with these filters for added
attenuation. Phase noise especially if its very bad will also be
reduced, however i would think that most multi multi contest stations
would avoid using radios with poor phase noise performance. If
a receiver is phase noisy it follows that the transmitter would
probably also have a bad case of phase noise on transmit.


I feel confident that the K3 will deliver.

Craig

--- In Elecraft_K3@yahoogroups.com, G3SJJ <g3sjj@> wrote:

Craig, I think I am correct in saying that the various bandpass
filters
available, eg ICE, Dunestar were created to reduce tx phase noise
from
adjacent current design radios in MO and SO2R setups. I have a
pair of
the Dunestar 600s here and they do just that, although antenna
separation plays a big part also. We used them for several years
in our
GU8D operation in the IOTA Contest and they were very effective.

One of the things that has impressed me in the K3 discussions was the
in-band close-in figures. A couple of years ago we did some in-band
checks here using 2 FT1kMPs with roofing filters and tx amps. I
haven't
got the actual data to hand but with mono band antennas on 20m
separated
by 70m, we were able to operate SSB and CW to within about 100KHz. I
wouldn't have thought the Dunestars would have made any difference
but I
honestly cannot remember.

I'm looking forward to getting my K3 shortly to do some more
tests. In
particular at the beginning of October we have the RSGB 21/28MHz
Contest
which I won last year using just the MP. This year I am intending to
run
SO2R with the MP and K3 and will be looking to do in-band dual
mode as
well as dual band. That should be interesting.

73 Chris G3SJJ


CR wrote:

It will be interesting to see if the Elecraft K3 needs external
bandpass filters when used in a multi multi contest environment.
Considering what the cost is for a full set of W3NQN filters, it
certainly make the K3 a popular if you dont have this additional
cost
or weight to carry around on an expedition or in contest station.

I also wonder if a Tracking Preselector will become a future option
for the K3. The Yaesu U tune preselector is a great feature although
old hat! However if the K3's front end is bullet proof it would be
hard to justify the additional expense and marginal performance gain
from a preselector. When bad IMD, Keyclicks and phase noise dominate
the value of such filters is questionable. However it might be handy
in places like Europe. Its going to be torturous operating a perfect
receiver like the K3 and hearing the good, the bad and the ugly
knowing very well its not your receiver when you hear the bad!

Such is the price of perfection!

Craig
VK3HE

--- In Elecraft_K3@yahoogroups.com
<mailto:Elecraft_K3%40yahoogroups.com>, "Jon Pellant" <w1jp@> wrote:

Thanks for your feedback. I trust my gut instincts sometimes and
my gut
made me blindly order a K3. I trust I won't be dissappointed.

Jon
w1jp

--- In Elecraft_K3@yahoogroups.com
<mailto:Elecraft_K3%40yahoogroups.com>, Rick <mrfarm@> wrote:

Assuming you like the ergonomics of a given rig, the one
parameter
that
I look at the most is the close-in IMD3 (Third Order
Intermodulation
Distortion).

Currently <snip/>

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