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#qdx Middle band QDX 30m - 15m
#qdx
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Hello?
Just playing with my newly assembled 80-20 QDX. In the past I had an idea to make something similar from the TX frequency generation point of view, but Hans was faster. The only solace for me is that brilliant minds works similar :). Anyway, to the topic: As 30m is my favourite band, and I plan to erect a QDX dedicated antenna for 30m and 15m, the question is if anyone experimented already with "middle band" configuration? I know that the main topic will be RX filtering, It would be nice to wind a single coil? (with taps) as it is in the original design, just shifted to cover 30m-20m-17m-15m. L12 for 20-10m version looks like it can take few more turns to go down to 30m. Or at least I can put in two separate coils for 30m and 15m only, if the single core will not do. Just wondering if anyone tried that, before I will start doing mess with the windings. Thanks for the info Pawe? SO8FM |
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Hello Pawel, I changed my HB-QDX to 30-20-17-15-12-10m. I took the LP filter 20/30m from the LB-QDX, wound the RX filter for 30-20-17/15-12/10. You have to make a compromise, the transmission curve is not wide enough on all bands. I wound and tuned the RX coil band by band, a calculation didn't work well for me, and only installed it properly at the end 73 Reiner |
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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? |
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Hello Jonatan
I have an old sample box (more than 10 years) of Wurth coils and I used them. It may happen they are already obsolete :) Similar coils you can get at any bigger parts supplier (Mouser, Digikey, Farnell, etc), ebay or Chinese part suppliers.? Link example: I prefer to choose wire wound inductors (usually better Q, looks like little tantalum capacitors - like in my case - or you can even see the windings), not multilayer (higher resistance, lower self resonance frequency, looks like ceramic capacitor). Not saying multilayer is a crap, you just need to know where it can be used and where is better to get something better :) 73 Pawe? SO8FM |
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Pawel, That looks great!? Can you post your BPF sweeps? Thanks & 72, 73? JZ KJ4A On Thu, Aug 17, 2023 at 1:53?AM Pawe? H <pawel@...> wrote: Hello Jonatan |
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40m
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? ? ----------------------------------------------------------------------------
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-5 |.. . . . . . . *** ... . . . . . . . . ... | . . . . . . . ... . . . . . . .
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-7 |****? ? ? ? ? ? ? ? .? ? ? ? ? ? ? ? ? ?.? |? ? ? ? ? ? ? ? .
? ? ----------------------------------------------------------------------------
? ? 8? ? ? ? ? ? ? ? ? ?9? ? ? ? ? ? ? ? ? 10? ? ? ? ? ? ? ? ? 11
20m -8 |.? ? ? ?.? ? ? ? .? ? ? ?.? ? **.? ? ? ?.? ? ? ?.? ? ? ? .? ? ? ?.
-10|.. . . ... . . . . . . . . . * . .|. . . .***. . ... . . ... . . . . . . . .
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-15|.. . . ... . . . . . * . . . . . .|. . . ... . . ... . . ... . . . . . . . .
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? ?|.? ? ? ?.? ? ? ?*.? ? ? ?.? ? ? ?.|? ? ? ?.? ? ? ?.? ? ? ?.? ? ? ? .? ? ? ?.
-20|.. . . ... . . * . . . . . . . . .|. . . ... . . ... . . ... . . . . . . . .
? ?|.? ? ? ?.? ? ?*? .? ? ? ?.? ? ? ?.|? ? ? ?.? ? ? ?.? ? ? ?.? ? ? ? .? ? ? ?.
? ?|.? ? ? ?.? * *? ?.? ? ? ?.? ? ? ?.|? ? ? ?.? ? ? ?.? ? ? ?.? ? ? ? .? ? ? ?.
? ?|**? ? ? **** *? ?.? ? ? ?.? ? ? ?.|? ? ? ?.? ? ? ?.? ? ? ?.? ? ? ? .? ? ? ?.
? ?|. *.? * *? ?.? ? ? ?.? ? ? ?.|? ? ? ?.? ? ? ?.? ? ? ?.? ? ? ? .? ? ? ?.
-25|.. . . ... .*. . . . . . . . . . .|. . . ... . . ... . . ... . . . . . . . .
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-27|.? ? ? ?.? ?*? ? .? ? ? ?.? ? ? ?.|? ? ? ?.? ? ? ?.? ? ? ?.? ? ? ? .? ? ? ?.
? ? ----------------------------------------------------------------------------
? ?10? ? ? 11? ? ? ?12? ? ? 13? ? ? 14? ? ? ?15? ? ? 16? ? ? 17? ? ? ?18? ? ? 19
17m 7? |.? ? .? ? |? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .
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-5 |.. . **. .|. . . . ... . . . ... . * . ... . . . ... . . . ... . . . ... . .
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-10|** . . . .|. . . . ... . . . ... . . . .*. . . . ... . . . ... . . . ... . .
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-20|.. . . . .|. . . . ... . . . ... . . . ... . . . ... . . . ... . . . .***. .
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-23|.? ? .? ? |? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? *
? ? ----------------------------------------------------------------------------
? ?16? ?17? ?18? ?19? ?20? ?21? ?22? ?23? ?24? ?25? ?26? ?27? ?28? ?29? ?30? ?31
15m -2 |.? ? .? * .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .
? ?|.? ? .**? .? ? |? ? .? ? .? ? .? ?*.? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .
-5 |.. *** . ... . | . ... . . . ... . * . ... . . . ... . . . ... . . . ... . .
? ?|.**? .? ? .? ? |? ? .? ? .? ? .? ? .*? ?.? ? .? ? .? ? .? ? .? ? .? ? .? ? .
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-15|.. . . . ... . | . ... . . . ... . . . ... . . . ... . . .*... . . . ... . .
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? ?|.? ? .? ? .? ? |? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? **.? ? .? ? *
-20|.. . . . ... . | . ... . . . ... . . . ... . . . ... . . . ... . * . ... .*.
? ?|.? ? .? ? .? ? |? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .*? ?.? * .
? ?|.? ? .? ? .? ? |? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? . ** . *? .
-23|.? ? .? ? .? ? |? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ? .? ?***? ?.
? ? ----------------------------------------------------------------------------
? ?18? ?19? ?20? ?21? ?22? ?23? ?24? ?25? ?26? ?27? ?28? ?29? ?30? ?31? ?32? ?33
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Very Nice!...JZ
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On Thu, Aug 17, 2023 at 9:08?AM Pawe? H <pawel@...> wrote:
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Hello Reiner,
Did you use all the values of the low band LP filter 20/30 for HB-QDX?? Were you able to look at the harmonics from this modification?? I did not make any changes to my HB lpf and the second harmonic did not meet FCC requirements on 30m.? I have been toying with changing out the filter, but wasn't sure it was worth the effort. .Andy W3SW |
dl8lrz Reiner
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