Hello
I finally assembled my next QDX and configured it to work 40m, 30m, 20m, 17m and 15m bands.
That was not easy. As the QDX design is brilliant giving max from the min, the same time any band modification means a lot of struggle with the parasitic resonances. I was fed up with fighting for the one band and afterwards seeing I ruined another... I think I now know what Hans feel during development :)
Ok, but the result is:
Band configuration:
?+---Band configuration-------------------------------------------------------+
?|? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? |
?|? Band name (m)? ? ? 4? ? ? ? 30? ? ? ?20? ? ? ?17? ? ? ?15? ? ? ?0? ? ? ? ?|
?|? Audio gain (dB)? ? 54? ? ? ?54? ? ? ?54? ? ? ?54? ? ? ?54? ? ? ?0? ? ? ? ?|
?|? Frequency min.? ? ?7000000? 10100000 14000000 18068000 21000000 0? ? ? ? ?|
?|? Frequency center? ?7074000? 10136000 14074000 18100000 21094600 0? ? ? ? ?|
?|? Frequency max.? ? ?7200000? 10150000 14350000 18168000 21450000 0? ? ? ? ?|
?|? Sweep start? ? ? ? 5000000? 8000000? 10000000 16000000 18000000 0? ? ? ? ?|
?|? Sweep step? ? ? ? ?50000? ? 50000? ? 120000? ?200000? ?200000? ?0? ? ? ? ?|
?|? BPF number (0-3)? ?0? ? ? ? 1? ? ? ? 2? ? ? ? 3? ? ? ? 3? ? ? ? 0? ? ? ? ?|
?|? LPF number (0-2)? ?0? ? ? ? 0? ? ? ? 1? ? ? ? 1? ? ? ? 2? ? ? ? 0? ? ? ? ?|
?|? PIN fwd bias (mA)? 30? ? ? ?30? ? ? ?30? ? ? ?30? ? ? ?30? ? ? ?30? ? ? ? |
?|? Transmit? ? ? ? ? ?ENABLED? ENABLED? ENABLED? ENABLED? ENABLED? DISABLED? |
?|? TX PTT +5V? ? ? ? ?DISABLED DISABLED DISABLED DISABLED DISABLED DISABLED? |
?|? TX PTT grounded? ? DISABLED DISABLED DISABLED DISABLED DISABLED DISABLED? |
?|? RX PTT +5V? ? ? ? ?DISABLED DISABLED DISABLED DISABLED DISABLED DISABLED? |
?|? RX PTT grounded? ? DISABLED DISABLED DISABLED DISABLED DISABLED DISABLED? |
?|? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? |
?
Hardware modifications:
15m
L4, L10 - Blue-Yellow core, 13 turns
C7 220p
C20 200p
C14 330p
C11 18p
?
20m/17m
L3, L8 - Yellow core, 11 turns
C6 220p
C19 220p
C13 330p
C10 68p
?
40m/30m
L2 - Yellow core, 14 turns
L6 - Yellow core, 15 turns
C5 510p
C18 560p
C12 680p+100p
C9 82p
?
?
C30 100p
C28 82p
C31 33p
C29 47p
?
L12 40m 4.7uH
L12 30m 3.3uH
L12 20m 2.2uH
L12 17m/15m 1uH
I?used four discrete high-Q coils for the L12, firstly it was much easier for the development and secondly it made resonances fight easier. See photo.
Capacitors used were 0805 SMD, C0G, 50V, 5%, different manufacturers. They fit very well on the THT capacitor pads.
I have no equipment other than SDR to measure the LPF parameters. I did only some simulations. Anyway I think it should be ok in respect to the harmonics attenuation. You can check it by yourself.
QDX configuration is 9V supply. Output power is 3-3.5W on all bands, reduced from the original design by inserting two silicon diodes in series as L14 replacement.
73
Pawe? SO8FM?
