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Is there a circuit for the BITX40v3

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The circuit diagram has not been updated.
Also, those transistors are 2n3904's, not BC849's.

? therefore it will not work without them? ?Can you/we notify the producers of it? ?Why is this apparently not ?written about, in the instructions? ?-without a pile of geek knowledge, how could I possibly find out?!
? ? ?I can certainly see these blank places, on the board I ordered and received barely a week ago!??? One of the reasons! = This is significantly why I hesitated this long, following many of the BITX threads, to get even one of these, among several other build and directions serious weaknesses...
? ? ?from Steve K7EW ??

Steve,

The Bitx40 should just work as shipped if you follow the instructions on hfsigs.com under WireUp.
It will work better if you download Allard's improved firmware for the Raduino.
You get some extra features (such as support for CW and RIT) if you implement the hardware mods that Allard describes, but this is not required.


Here's all the changes to the schematic as posted on

Boards shipped with the Raduino do not have L4 stuffed (to disable the analog VFO).
C103 in the BFO is not stuffed.
Farhan found that by using a Bat54s diode array instead of the original 1n4148's at D15, D16 the diodes were well matched and there was no need for the balancing pot at R106.
The transistors could be BC849's or 2n3904's in the Sot23 package, but 2n3904's are what get stuffed into the board.?

The schematic does not clearly show how U3 is wired up as some schematic wires lie on top of other wires.
In particular, U3-3 connects to TX 12v, and the junction between R144, C142 and T6-4 does not connect to anything else.
Also , RV1-2 connects to C151 and R150.


The rig works as shipped, but there are a few things that could be done better (of course). ?
Most people don't bother, and the rig works fine. ?Here's a partial list:

The heatsink for the IRF510 could be bigger, and should be insulated from the IRF510 tab which is tied to the PA-PWR1 supply.
The grounded end of C130 and D7 should instead be connected to K1-9, so they are across the relay coil.
Q13 and R141 are running kind of hot, should have higher dissipation parts there. ?(a 2n3904 in a TO92 package, a 1/4 watt resistor)
Q13 blows if a high powered transmiter is operating nearby, back-to-back 1n4148's from K1-12 to ground would solve this. ?/g/BITX20/topic/4415405
Loud signals can blow your ears off, there are several AGC circuits proposed in this forum. ??
You might want to remove C113 to reduce the audio gain. ? ?
An RF gain control would be nice ?/g/BITX20/topic/4238539The transmit LPF lets through a 2'd harmonic that is close to the legal limit: ??

This rig was built for the purpose of encouraging people to hack at it. ? Many do, and this forum might be difficult to navigate if you are not the hacking sort. ?But the above outline should tell you all you need to know about the rig and adjustments to the schematic. ?Yes, it would be good if somebody at hfsigs could update the schematic, but at $59 most of us are more than happy to deal with that. ?

OK, back to your question:
> ?? therefore it will not work without them?

Not work without what?

Jerry, KE7ER

?

On Sun, Jun 25, 2017 at 02:27 pm, Jerry Gaffke wrote:

"The grounded end of C130 and D7 should instead be connected to K1-9, so they are across the relay coil."

Hi Jerry, even though I have been following most of this stuff and understand most of it, I have forgotten the reference to the above statement. ?Was this to stop that pause and click when you hit the transmit button? ?If not what is is for, and how do you stop that pause.?
Thanks
Andy

The reverse diode across most relay coils is to short out the back EMF from the coil (inductor) when the current suddenly stops flowing. ?Without the diode, there's likely some arcing across the PTT switch.

You're right, my list missed out on the pop fix, though many don't find it all that annoying.
There are two, one that winds up in the headphones, and one that goes out on the air at the start of each transmission.
Here's a thread about the transmit pop, also has a solution to the receive kerchunk: ?/g/BITX20/topic/5142279
I like Raj's addition of a cap to cure the transmit pop, though there is interference with Allard's CW scheme as discussed in the thread.
Here's another thread discussing the problem: ?/g/BITX20/topic/4105232#22950
And another: ?/g/BITX20/topic/4105485
And ?/g/BITX20/topic/ptt_pop_hack/4460108

Do we have a consensus on the best solution for the rx kerchunk yet?
I'd go with Raj's cap for the transmit pop, and if CW is wanted along with the pop fixe then maybe hack the rig to inject CW at the first mixer like the uBitx does.

Jerry, KE7ER

Thanks Jerry, I'll chew on these for a while. ?The pop is not only irritating, but slows the natural transition. ?Its like: transmit- wait-talk.
Andy