the front end diodes in the mixer will clamp any signal higher than half a volt. this should take care of the very powerful signals.

adding diodes at the open front end can lead to a very large number of spurs in ubitx. unfortunately, unlike the bitx40, ubitx does not have the luxury of a narrow, triple tunec circuit.

- f

On 13 Dec 2017 2:29 am, "Jerry Gaffke via Groups.Io" <jgaffke=[email protected]> wrote:

Not there.
Good to add two back-to-back 1n4148's from relay K1 pin 12 to ground to limit the AC voltage at the base of Q90
if the uBitx should ever be plugged into an antenna while some 100W transmitter is using a nearby antenna.
Or a nearby lightning bolt.


On Tue, Dec 12, 2017 at 11:24 am, M Garza wrote:

Looking at the schematic, it doesn't look like the diode front end receive protection was added to the uBITX.??

the front end diodes in the mixer will clamp any signal higher than half a volt. this should take care of the very powerful signals.

adding diodes at the open front end can lead to a very large number of spurs in ubitx. unfortunately, unlike the bitx40, ubitx does not have the luxury of a narrow, triple tunec circuit.

- f

On 13 Dec 2017 2:29 am, "Jerry Gaffke via Groups.Io" <jgaffke=[email protected]> wrote:

Not there.
Good to add two back-to-back 1n4148's from relay K1 pin 12 to ground to limit the AC voltage at the base of Q90
if the uBitx should ever be plugged into an antenna while some 100W transmitter is using a nearby antenna.
Or a nearby lightning bolt.


On Tue, Dec 12, 2017 at 11:24 am, M Garza wrote:

Looking at the schematic, it doesn't look like the diode front end receive protection was added to the uBITX.??

Mike - I can confirm that the address is 55 hex.? I used the Si Lab part number look-up, and the I2C address scanner routine.? This is the specific part:


The only output I see is the clock + and clock - on pins 4 and 5.? In this circuit, Clock + (pin 4) is used and 5 is left floating.? Applying the Rigol's probe across 4 and 5 shows the same 100 MHz output as that seen from clock + and ground.? The Si 570 block diagram shows a crystal inside, but there doesn't appear to be a way to probe it from outside the case.? Is there a way to check the function of the part?? The software sets the the start-up frequency to 56.32 MHz, and later moves it to 14.5 MHz.

I thought this device outputs a square wave, and I expected the software to command the Si570 to change freqs when the display changes.? So far, neither of those things happens.? I don't know if I got a bad part, killed it somehow, or have a library problem.? I guess I'll start with libraries.? A number of others have built these things and I've not found any suggestion that they didn't 'just work'.??

Andy, KG5RKP


On Tue, Dec 12, 2017 at 03:02 pm, Michael Hagen wrote:

I have made several signal generators with 2 different PCBs I designed.? Both stand-alone with level shifting.

The big one uses the SI part with 8 Clocks, I call it "Lotsa Clocks".? It has optional I2C address bit.? And 8 Clocks.

I got all my SI parts from Mouser.? Mine respond at 0x60 or 0x61 ?? I have seen them run at the outputs with crystal not correctly connected.? I have stopped using the Tiny crystals because of soldering problems.

Check for 25 MHz small sin wave on the crystal pins.? One pin has a larger sin wave than the other.? I have made a sketch that runs one or the other or both SI parts on 0x60 and 0x61.? I have bought dozens of them, always have seen those 2 addresses?

73's

Mike, WA6ISP

On 12/12/2017 12:48 PM, AndyH wrote:

Hey folks,

? ?The executive summary is that I've assembled an Si570 generator for a Sweeperino (prereq for my scratch built ?BITX) and it's emitting a 400 mV p-p sine at 100 MHz.? I cannot adjust the frequency.? I have no idea what's happening.

? ?Details...? I verified details of the Mouser-sourced Si570 from the Sil Labs database.? The address is verified (0x55) and I can talk to the Si570 with an I2C scanner and Farhan's code (as well as the Razzie code).? Voltages are good, the layout was inspired by Farhan's build as well as the builds documented by Tony Fishpool and published in Razzie (June, 2016).? Adjusting the tuning pot makes the numbers change on the LCD. There's a light square wave on the Rigol display when the frequency is actually changing.? I can't collect this signal by probing the Arduino or the comms or power pins - its only present on the output of the Si570.

? ?Does this mean anything to the Si570 experts?
? ? Thanks,
? ? ?Andy, KG5RKP

-- 
Mike Hagen, WA6ISP
10917 Bryant Street
Yucaipa, Ca. 92399
(909) 918-0058
PayPal ID  "MotDog@..."
Mike@...

what happened to the idea of using color coded cables and plugs, or just plugs that aren't reversible if you want to go the extra mile?
Adding a full bridge rectifier to everything can really bite you in the ass when you aren't used to being careful of polarity, and then fry something that isn't protected. So using a diode, so that the device just doesn't do anything when you plug it in the wrong way, is the safest option.

Imagine using a fet buffer for counter instead of present NPN transistor.

?The biasing mmethods change and we only need to have a 100k or so termination of gate.

?The dee cias could well be removed.

?try once and All the best

?regards

?sarma

?vu3zmv

?

regards
Sarma
?

On Tue, Dec 12, 2017 at 6:20 AM, <paulsmi55@...> wrote:

Well, I reduced the coupling out to the freq counter to around 20pf effective which was the lowest that would still feed adequate signal to the counter. But still I have the instability the moment I connect it up. The VFO is pulled down and sometime just runs at random frequencies. Wondering if there is something wrong with the buffer itself. I am going to try pick off a signal from the buffer stage Q6 output to the mixer and see if that perhaps works. Otherwise I may have to build another stage of buffering or maybe even try another counter. Really don't want to abandon my FLL-free VFO as it is very stable without the counter connected.

Not there.
Good to add two back-to-back 1n4148's from relay K1 pin 12 to ground to limit the AC voltage at the base of Q90
if the uBitx should ever be plugged into an antenna while some 100W transmitter is using a nearby antenna.
Or a nearby lightning bolt.


On Tue, Dec 12, 2017 at 11:24 am, M Garza wrote:

Looking at the schematic, it doesn't look like the diode front end receive protection was added to the uBITX.??

Hello everyone. Just finished my BITX40 and performed some mods. Quite happy with the rig. The receiver is hot and the transmit SSB out seems to be very good. Worked many contacts on 40 with only a small battery.

I performed the following modifications:

Installed a 10 KOHM ten turn pot for tuning. I added 130 ohm resistors at each end of the pot and installed a push button across each small resistor. This prevents tuning run away but allows you to step up or down the band to where you want to tune. The 10 turn pot really makes it easy to tune.

I mounted the radio in a case that took a lot of thought in fitting everything in. It works great and doesn't look too bad.

I have a question,

Where can I locate the firmware sketches for the Arduino in the BITX40?

73

--

Dave Robertson KD1NA