Don Cantrell ND6T documented this adjustment to the Bitx40 LPF in January of 2017:
? ??
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On Mon, Aug 6, 2018 at 09:14 PM, Arv Evans wrote:
With all the filter discussion regarding uBITX I decided to take a look at design of
the output filter on the BITX-40.
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Hello Bill,
Its very unfortunate that a well intended kit that was assembled with questionable quality parts, circuit and several other anomalies beyond my comprehension, is in its present quandary. The principals it appears, had good intentions and are to be commended for that. However, they have no authority in North America. In fact the Border agencies of both our countries are probably raising their eyebrows over the entire fiasco, ?If not they soon will be. As I said earlier in my position As XO on board ship I can¡¯t afford to run afoul of the authorities so my bitx 40 and ubitx have been destroyed. Sad really, I will be looking at the kits from QRP LABS. Or maybe I should purchase a good used FT817.
As an aside I had SIGINT techs look at the harmonic signature on the Harris, Wolfsburg and Bendix King gear and found them to exceed requirements by 30%, but of course again I¡¯m comparing caviar to peanuts. My wife chastises me for my attitude ergo I¡¯m at sea for 6 months of the year. I¡¯m trying to do better hi hi. It¡¯s no wonder I¡¯m not allowed in the house before dark.
The sheer number of builders, the responses in this group, would suggest that there is a strong need for a simple affordable all band QRP rig, that is a fact, It will be interesting to see what happens in the next while.
In the research I have done there are some kits available from China, Russia and also Malaysia , they may be more in cost but perhaps ???
On a final observation you can buy all kinds of brands of test gear but there are only certain brands that are deemed to be certification instruments when operated by a certified knowledgeable technician, just because you go out and buy a Rigol
doesnt mean that now you are instantly an industry expert.
Early day tomorrow, anchors aweigh at 0400
cheers and 73
WRS
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Glen VK3PE
That is something that can be tested.? It doesn't show in the simulator, but real-world
may be different.? When I get to actually wiring this it will be easy to test.
Thanks for the info.
Arv
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On Mon, Aug 6, 2018 at 10:18 PM Glenn < glennp@...> wrote: Arv,
I read somewhere that its a good idea to drop the inductor value by 25% or so, (cant recall exact %) then calculate the parallel Cap value for the required notch.? Otherwise i think the RL is compromised.
Or my memory is suspect, quite possible........
vk3pe
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Arv,
I read somewhere that its a good idea to drop the inductor value by 25% or so, (cant recall exact %) then calculate the parallel Cap value for the required notch.? Otherwise i think the RL is compromised.
Or my memory is suspect, quite possible........
vk3pe
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Hello
With all the filter discussion regarding uBITX I decided to take a look at design of
the output filter on the BITX-40. This LTSpice run shows that the stock LPF starts to roll off at about 8 MHz, which is
pretty good.? Problem is that the magic -43 db point does not come until about 21 MHz
or about the 3rd harmonic area.? Can this be imporoved...maybe. By adding just one capacitor across the output inductor we now get much more
attenuation at the 3rd harmonic point of 21 MHz.? By changing the value of C3
it is possible to move that point up or down in frequency.? This might be a way
to attenuate a specific harmonic or spur if it does not move about too much.
Next step is probably to scan the BITX-40 output to see if it really needs this type
of modification (how clean is it?).
It should also be possible to add a similar capacitor across the L6 inductor to have
another attenuation point.? That is a test for tomorrow because it is late and us old
guys need their beauty sleep.??? 8-)
NOTE: The upper trace in the pictures is frequency response.? The lower trace is phase
shift, which could be important if oscillation is encountered.? Note the sharp phase
shift at the parallel resonance point in the 2nd picture.
Arv? K7HKL
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On Monday, August 6, 2018, 4:37:38 PM EDT, bdunk@... <bdunk@...> wrote:
Thanks Jack,
I'm not sure what you are talking about, I just assumed I install the replacement encoder and it should work.
Where do I fine the 4.3 software?
Best regards, Bert VE3TYS
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Re: Harmonic performance - SSB vs CW
mcHF Boards:- he does sell the bare 0.6 boards as? pair i think.? See order page, bottom.
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On Tue, Aug 7, 2018 at 12:24 PM, RCBoatGuy wrote:
Actually, the more I look a the mcHF RF board schmatics, the more i think its a good solution for the BPF, PA, and LPF issues. The mcHF RF board has both the BPFs and LPFs, PA with 16HVF1 push-pull PA, RX-TX switching via diodes plus an SWR bridge.? Not sure of the board layout, but he does have separate relays for the LPF inputs and outputs.
I wonder if M0NKA would consider selling the RF board as a stand-alone kit...
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Re: ND6T AGC and Click kit wiring notes
One more question, folks:
I have one of later run V3 kits with socket mounted 2822M chipset.? It works fine, and is SOCKET mounted.? Wonder if anyone has played with a substitute that pops in and might offer some (audio level albeit) AGC?? Just a thought.? I dunno what's out there, and what has been tinkered with.
Eddie
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Re: Harmonic performance - SSB vs CW
An interesting exercise is to take the values for the Lo Band 80m LPF and compare the data between Farhan's LPF, Hans' LPF and the W3NQN LPF they are basically the same design, except the W3NQN LPF has 1 extra capacitor. Use a program like "Elsie" the student version is free and look at the results ......quite a difference. Hans has the best Return Loss numbers and W3NQN has by far the best rolloff and should readily meet FCC specs.?
I'll see if I can upload the results. The actual capacitor/inductor values are readily available on the ARRL website .....just look up "Second Harmonic Optimized Low-Pass Filters" by W3NQN.?
Should be easy to rework if you are interested but it needs testing with Farhan's relay scheme. T37 or T44 toroids are fine for 10W or less and so are 100V rated Ceramic MLCs.
73 Kees K5BCQ
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Re: Harmonic performance - SSB vs CW
Actually, the more I look a the mcHF RF board schmatics, the more i think its a good solution for the BPF, PA, and LPF issues. The mcHF RF board has both the BPFs and LPFs, PA with 16HVF1 push-pull PA, RX-TX switching via diodes plus an SWR bridge.? Not sure of the board layout, but he does have separate relays for the LPF inputs and outputs.
I wonder if M0NKA would consider selling the RF board as a stand-alone kit...
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Re: BitX40 Sketch still needed....
I have that, but was hoping someone has a copy modified for use with a rotary encoder instead of the pot....
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Re: Harmonic performance - SSB vs CW
Kiss principle is good minimum changes? because you don't know how many V4 version boards A Farhan has on the shelf. .? Give away 15 m as a concept.? One reason being that $35 USD transverter boards for? 144Mhz exist.? The only work for 10 mtr? IO.? Thus 15m gets the chop.
NB the -38 Db noted on that specific? 30m filter is no so much of a worry. The Japanese guy was driving 2x2 RDHH16 in parallel to get 50W out (so he said).? He should have expected 35W maximum for reasonable harmonics level. Hence harmonic production would have been much worse than a safe design. What his test set up was and calib. aspects I have no idea.
regards, Timothy E. Fidler : Engineer BE Mech(1) Auckland , NDT specialist AINDT UT /RT3 , MT2?
Telephone Whangarei?? 022? 691 8405
e: Engstr@...
----- Original Message -----
To: <[email protected]>
Cc:
Sent: Mon, 06 Aug 2018 19:01:10 -0700
Subject: Re: [BITX20] Harmonic performance - SSB vs CW
Thanks Tim.
I will Implement the diode switching to reduce IO ports required.. or even go i2c bus? hmm...
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Re: ND6T AGC and Click kit wiring notes
Nick,
Hi, any eta on the AGC kits?? Just finished the V3 ubitx: it needs AGC or I will need new ears.?
Thanks.
Eddie
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Re: Harmonic performance - SSB vs CW
Thanks Tim.
I will Implement the diode switching to reduce IO ports required... or even go i2c bus? hmm...
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Re: Harmonic performance - SSB vs CW
That last message on the Japanese LPF board? was supposed to be Just to Nick but I stuffed up...
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Re: Harmonic performance - SSB vs CW
ps The PCB includes C/O relay and attenuator relays.
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Re: Harmonic performance - SSB vs CW
Overkill maybe, I have a 3 band version PCB of the G4TZR version used in Picastar, rated 100+ watts.?? Made for a personal HF rig project where 3 bands is all i need although the board can be stacked for 6 bands.? Schematic is on G6ALU's web pages, but cut down for 3 bands.? Layout identical. glenn vk3pe  
On Tue, Aug 7, 2018 at 11:31 AM, Gordon Gibby wrote:
Sure seems like it would be fairly simple and inexpensive, to make a small additional board to which you would route the transmitter signal, and relay ?control voltages, buffered if necessary ¡ª-as Nik is working on.?
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With the relays at opposite ends, even in expensive one should work. ?
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Reuse ?as many components as reasonable from the existing filters. ? The inductors at least!
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Fairly simple upgrade! ?If someone builds it , I¡¯ll buy several boards, if not, I¡¯ll lay out my own! You guys are busy explaining exactly how it needs to be done! ?And I mainly care for just a few bands?
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Cheers
Gordon
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On Aug 6, 2018, at 20:35, ajparent1/KB1GMX < kb1gmx@...> wrote:
Nick,
Best layout is similar,? Bus down one site to the NO contacts
and the wiper is the end of the filter and when in the off poistion the
wiper sits on the NC contacts to ground shorting the filter.? So a filter pick?
enables the relay and filter and no pick the filter is shorted.? Reduces
the effects of stray capacitance.
That and copper pour under everything and opposing side. lots of vias to?
tie them together especially along signal tracks.
Allison
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Re: Harmonic performance - SSB vs CW
Nick have a look at the "Jap"? 5 bands with three outputs and diode OR LPF suggestion that I just posted before you go too much further.. just a heads up.? THe design needs rework for lower power ,? but it is not too bad.? It can be just std double Pi design without all the magic bypass cappies - there must be books that cover that but I don't have one.
Remember too that a BPF board looks as if? required to cut right into the cct . thought it may be with a well designed LPF board that latter may be dispensed with.? That may affect your layout to produce a one size suits all.
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Re: Harmonic performance - SSB vs CW
On the subject of adding BPFs in place of the 30MHz LPF between T2 and the PA, has anyone considered using M0NKA's mcHF transceiver's solution for BPFs using multiplexer I/Cs?? The IC's are pretty cheap, only 48 cents in quantities of 10.
His schematics can be downloaded here:?.? The first page of the RF schematics shows the BPF and multiplexers.
Not sure what kind of impedance matching would be required to use these, but thought I'd mention it.
73,
Carl, K0MWC
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Re: Harmonic performance - SSB vs CW
Proposed filter switching fr the rework.
BEfore everyone rushes off into filter relay config as in electrical this one can do 80m,? 40 (10 with changes) and 20-30m. And all on three outputs because of the cunning diode "Or.? Moreover it shorts the unused filter to GND (except for the 20-30 one) as per AJP suggestions . This of course is a LPF design and the power level at 50W and therefore input Z is not correct for uBit X use.??
Not beyond the wit of man /or women ! to fix that. What is really cunning is that the design is zero load when used on the 20m daylight service,? ie out and about on a battery.? "It's got a Cop motor before unleaded so it runs good on regular gas ....".? Perhaps worthy of consideration though all the relay select firmware has to change.? You lose 15 m tx but still need only three o/p as before . what the heck...I kept this on file for a rainy day.? ?Allison .. am I forgiven..? please. No metric fishing...from now on.
Personally I dislike the the idea of zero means a valid state from an electrical Pof View.. ie wire falls off . no fault occurs but a logic state changes . But on a PCB it seems acceptable.
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AA9GG
Nick VK4PP
