Hallo Dave,
> http://www.astromag.co.uk/k3/
Very nice indeed!!!
Close to what we have seen on my K3, but we have not been as extensive.
> not convinced of the benefit of several roofing filters for the K3.
This is something I think we will be looking at, when we do another
round of measurements.
> an anomaly at 2 KHz signal spacing where my 400 Hz
We did not see this on my K3 using the 400Hz roofing filter.
> My measurements give a 3rd order dynamic range of around 100 dB at
> 2 KHz signal spacing with a 400 Hz 8 pole filter and slightly better
> with a 2.8 KHz 8 pole filter (around 105 dB).
We measured a dynamic range of c. 106db (+/- a few dB) from 100kHz down
to 2kHz with the 8 pole 400Hz filter on 20m. So both measurements (by
DK4YJ with K3 #00067 and G4AON with K3 #00080) are in the same ballpark.
vy 73 de toby
PS: http://www.astromag.co.uk/k3/ -> distributors in Germany and Japan
I seem to remember Peter Zenker writing several months back that his
company would not be selling the K3 in Germany. They do offer other
stuff by Elecraft.
Dave G4AON wrote:
> Having spent a few hours conducting measurements of the 3rd order
> mixing products with my K3, I'm not convinced of the benefit of
> several roofing filters for the K3. If other owners with access to two
> signal generators and a hybrid coupler would like to try their K3 with
> whatever filters they have I would be most interested in the results.
>
> Try as I might with very strong dual signals into the K3 from two
> signal generators and a hybrid coupler, changing the bandwidth by
> altering the width control between 400 Hz and 450 Hz there is mostly
> no difference in the 3rd order products except for an anomaly at 2 KHz
> signal spacing where my 400 Hz 8 pole filter seems to be about 10 dB
> worse!
>
> I've tried the shift control, very careful measurements at higher
> signal levels with spacings from 1 KHz to 20 KHz, etc. There is a
> difference of perhaps 3 or 4 dB where the narrower filter has the
> advantage with 3rd order products in the spacing range 5 to 20 KHz
but > it's so small as to be insignificant and gives no measurable
> difference near the noise floor, only being apparent with signals
> some 10 dB higher than the standard ARRL test levels to measure the
> 3rd order products. The levels required to produce the small
> difference are hitting the end stop of the K3 and are - 20 dBm, levels
> not likely to be encountered in practice for most of us. The only
> filters I have at the moment are 2.8 KHz 8 pole and 400 Hz 8 pole.
>
> I also noticed the dynamic range appears better by a small margin with
> the pre-amp turned on... Although it should be pointed out that using
> a pre-amp improves the MDS (minimum discernible signal) and raises all
> signals by around 10 dB, so it's not increasing "signal handling".
>
> My measurements give a 3rd order dynamic range of around 100 dB at
> 2 KHz signal spacing with a 400 Hz 8 pole filter and slightly better
> with a 2.8 KHz 8 pole filter (around 105 dB).
--
DD5FZ (ex 4n6fz, dj7mgq, dg5mgq, dd5fz)
K2/10 #885
K2/100 #3248
K3/100 #67
DOK C12, BCC, DL-QRP-AG, JN58td
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