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Over the past 24 hours, Jack and I have been in contact off-group about the possibility of setting up a VK source for the W8TEE BITX40 VFO etc pcb, one that could also be accessed by our cousins in NZ.

I am pleased to advise that Jack and I have been easily able to reach agreement. As a result, I will buy a quantity of boards from him at US$7.50 each, plus shipping on whatever quantity I end up ordering. In turn, I will make the boards available to builders here downunder at their cost to me. In other words, the individual board price will be based on equally sharing my costs by simply dividing my total payment to Jack by the number of boards involved.

The price to each participant will then be that unit price per board, plus the actual costs of my posting the order to the builder. Obviously, the final cost will depend upon how many boards the builder requires and the postage cost to that address from VK7 but we confidently predict that ther will be a saving on the cost of ordering directly from Jack. Fortunately, the Australian customs declaration is comparatively simple document and there is never a queue at my local Post Office and we have a free trade agreement, so ZL orders won't be any hardship at this end.

I am travelling over the next 3 days but will reach my home QTH on Wednesday 14 June. I hope to be able to place the order with Jack within a day or so of getting home. If you would like to take part in this group buy please email me direct at vk7mx@wia dot org dot au, removing the spaces and the dots, obviously.

I intend to buy a few spare for future builders, so don't be too concerned if you come across this post later than 14 June.

73

Bill, VK7MX & VK1MX

So in order to know which value I should use i should have equipment such as an oscilloscope...
i may return to previous values...
a shame i already removed the smd cap

You can still get rosin core solder.
Using that stuff is like burning incense.?

If vaporized lead has been an issue all these years, I'm done for.
Could explain a lot.

Jerry, ?KE7ER

Changing the capacitance at C102/C103 will adjust the frequecy of the BFO, , typically at 11.998500 mhz.
Farhan found that with 47pf at C102 and with all five 12mhz crystals matched, the BFO was placed correctly with respect to the crystal filter for LSB use.
There are reports that some get better audio if the frequency of the BFO is adjusted a few hundred hz from that point.
However, the value that worked for Peter may not be the value you need on your rig.

If you wish to vary the BFO frequency for better audio, I suggest you change out C102 and add a trimmer capacitor at C103.
The 47pf Farhan settled should be within the range of C102+C103, your setting for best audio might be above or below Farhan's 47pf value.
For example, perhaps remove C102 and put a 100pf trimmer at C103.
Or put a 20pf cap at C102 and a 50pf trimmer at C103.



A better solution would be to drive the BFO from CLK0 of the Si5351 as is done on the uBitx,
then we could add code to the sketch to adjust the BFO frequency from the calibration routine.?

Jerry, KE7ER

if you have place your Bitx40 for 7.0000 on display and you han a reading about 5 MHz just say ( reading*5 )
and place result in this line :

?si5351.init(SI5351_CRYSTAL_LOAD_8PF, 24994650L,0); ( 24994650 is my result line normal say 25000000L

diff. from display readout an "real" freq. is less then 100hz?

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These are the best "cheap" filters I've seen--adequate for casual
work. I've got models similar to both of these.






They're certainly better than just a fan!


73, David KB4FXC

Any suggestions for a cheap, effective benchtop solder fume filter. ? Currently I use my bench in the garage but I'd like to move into the house. Of course to do this I have to be smoke and odor free. ?

I have noticed that when intouched with the tester probe into the the sound from the speaker become louder.
So, i decided to try this mod that Peter showed o his video


Although all I could get was this 33+18p caps it sounds good to me

Jonathan KK6RPX wrote...

Just curious, how many West Coast BITX operators
are on this list?

I ordered a BITX40 on June 2. It will be used on
Salt Spring Island, BC.

It was after ordering a hot air soldering station
that I started looking for SMD QRP kits that I came
across the BITX40.

I almost sent my first post off yesterday. I had
downloaded the Raduino INO file and was attempting
to compile it but kept getting error messages. I
finally figured out I needed the Si5351 library,
although from what I've read, I might have go
looking for an older version. This will be my first
time doing anything with an Arduino.

The first step will be to get it all put together
and working, but adding CW and AGC might be nice
additions.

I'll try and listen on 7277 KHz this evening, but
it won't be on a BITX40 yet. I can turn the power
down, but I will be guessing at the actual power
level.

--
73 Keith VE7GDH

I have this one
good on rx but poor on tx

whizz loop antenna by moonraker
there are two versions starting from 7 or 14mhz

The NPN's powered from the "TX" 12v rail do not get power unless the PTT switch is pressed to transmit.
I suggest you concentrate on the receiver first.
When checking out the transmitter, no need to apply power to the IRF510 ?until everything else is working.
Should be able to hear a 40m transmission from just the Q14 driver, using?a nearby shortwave receiver.

Ola amigos

Estou pensando em comprar esta fonte portatil? para um linear de 40m ...já cansei dos QRPps com esta propaga??o...rerere



73 de py2ohh miguel

You may be very lucky here, everything could just work.?
The transistors are all protected by a diode or resistor or both.
I suggest you just put everything back together and see if the receiver works.
If it does not work, try following the procedure Farhan outlines here: ??
(His piece of wire has nothing on the other end, it is just an antenna to pick up local QRM)

Forget D7 ever existed.
D7 doesn't really do anything at all due to a mis-wire in the schematic (the PC board follows the schematic).
It is supposed to be across relay K1, just like D8 it scross K2.
The diode D7 would give the reverse EMF of the K1 coil someplace to go when the PTT switch opens up.
Without D7 properly installed, there may be arcing across the PTT switch, with some impact on reliability.
Plus spikes on the main 12v rails into the radio.
But that is not your main concern. ?
Just know that D7 never did much of anything for anybody because it was wired up wrong.

On mine, the entire radio takes 150ma from my 12v supply to receive.
If I unplug the Raduino, the main Bitx40 board takes 73ma.?

Raj's advice to check the base-emitter voltage across all those NPN transistors is a good one,
just unplug the Raduino and look for around 0.7 volts on each NPN with a DC voltmeter.

Also check to see if U2 pin 1 has 9 volts.
When you get around to checking the transmitter, U3 pin 1 should have 5 volts when PTT is pressed.

If you get stuck, try finding somebody with a scope.

Jerry

It is certainly possible that I reversed the supply leads - all of the other wiring looks ok but I might have simply put the spade connectors on the wrong way round. I used the battery because it's what was to hand but good point about monitoring the voltage on transmit.

Matt 2E1HNK

Is it possible that you did reverse the power supply wires into the Bitx40?

That battery is quite small.
Could be the battery didn't have enough power to blow the LM7805,
but was able to blow D7.

When you get to where you are trying to transmit, I suggest monitoring the?
battery voltage. ?With such a small battery it may have trouble maintaining 12v.

Jerry

That's very interesting!
Many thanks for testing.
I will try on my own BitX and see if I can reproduce this.
Will keep you posted.

73 Allard PE1NWL

Arv,

I've been looking into what might happen if somebody reversed the 12v power supply leads into the Bitx40.
Have found that the LM78* regulators would not protect what lies behind them. ?(But an LM2940* would)

I guess I'm confused too. ?Not sure what a diode in front of an LM340 would do about shorted inputs,
except maybe act as a cheap fuse. ?The diode would protect things if power supply leads going in were reversed though.

Yes, -almost- neighbors. ?About 170 miles if could fly.
An all day trip if driving, as we have the Wallowas and Hells Canyon between us.
Friends driving 84 often suggest they might drop by, but it's not so simple.
Wallowa Co is walled off on all sides by canyons and mountains.
"I know where you want to go, but you can't get there from here."

On the plus side, we have a nice radio quiet location.
Especially if I shut down our off grid power inverter, and the fence chargers.
Nearest neighbor is over a mile away.
Almost need an outside antenna to catch anything on the AM broadcast band.

Let me know if you ever have reason to come out this way.
I can recommend the Buffalo Burger at Terminal Gravity, paired with their Breakfast Porter.

Jerry, KE7ER