Warren,

That IMD could be in the IF amps (Too much gain for 2n3904's at 45mhz?? Mixer overload?)
or in the power amp.? If IMD gets worse when RV1 is cranked up, that would suggest it's in the PA.
If it's in the 45mhz IF, the new filter will help but is too wide to clean up the immediately adjacent channels.
Seems it should be straightforward to clean up this IMD on v5, but may take lots of small hacks to?
clean up existing rigs.? Fortunately, at 5 or 10 watts out it seems to not be just too bothersome as
I don't recall any reports of trouble in the forum.? But it should be fixed on v5, and v3,v4
should not be used with an external high powered linear.

Jerry

Sorry: +/- 7.5 kHz 3 dB

Hi all, good job.?
1.The output? of 45-2pole in C22 position needs transformer 50/600 and small C <10 pF- it will have close to flat responce.
2.As I wrote befor as main filter I used SMD: DSF753SDF 4POLE marked as D45015GQ +/-7.5 dB. I put it on board on the back side and used transformers 4t/10t in small binocular 2402.
Best to all George.

All three relays are de-energized during received, so contacts are as shown in the uBitx schematic
with a path through the 10m filter.
At the start of transmit, the following routine gets called (file ubitx_20.ino of the stock HFSignals firmware)
Should be readable enough even if you've never seen C code before.

Jerry


#########################################
On Sat, Sep 8, 2018 at 09:33 AM, Brent Seres/ VE3CUS wrote:

Just a question, and I apologize if it's been covered before.
Could someone tell me the LPF relay sequencing for the existing ubitx configuration? What relays are energized for what frequency ranges? I want to figure out the logic for building an off board LPF solution using a cleaner layout and switching (ie..1 relay path only per filter...or separate relays at the input and output of each filter....basically a more symetrical, conventional layout.

Thanks for everyone's help

Brent

More data...... Comparison of CW power out with SSB power out using the added 45 MHz filter:



The chart was made by adjusting RV1 to maximum key down CW power, and then keying PTT with an input tone at the specified level. There are a couple of caveats here:
1) 120 mVrms is far above the audio level that caused unacceptable IMD before the filter mod. IMD must be checked and the audio levels adjusted to make it acceptable.
2) 120 mVrms is also far above the output level of most microphones, at least without shouting. If IMD is bad at this level then the audio level must be reduced. Before the mod the radio showed terrible IMD at any input level higher that about 25 mV and, at that level, the radio produced less than 2 watts. If it turns out the filter is a 'magic bullet' and the radio can actually sustain this level of input with acceptable IMD, then the input audio stages need more gain.

Kees, I have no plan to change out the original filter at this point. It is pretty moot until we know what the IMD is.

WA8TOD

Allison,

I'm afraid if you tested the way you described in your original post on this thread, you weren't testing for crosstalk.? I believe what you measured wasn't cross-talk at all, but rather ground bounce due to current starvation of the Si5351 output buffers.

I've attached the Si5351 datasheet.? On page 5, Silicon Labs gives the following specs:

Vddox, output buffer voltage => 3 ranges, 1.8V +/- 0.9V (5%), 2.5V +/- 0.25V (10%), and 3.3V +/- 0.3V (9.09%).? ?The Raduino uses a 3.3V supply for Vddox.

Iddox -? output buffer supply current per output => 2.2mA typical, 5.6mA max

Zo, output impedence @ 3.3V => 50 ohms

Note this is output impedence, which is very misleading.? The spec is not saying to use an output load of 50 ohms (Rload).? It is saying we need to drive thru a 50-ohm impedence to reach the destination Rload.? So we need to calculate the mimimum output load (Rload) that the output driver can drive.

Rload = Vddox/Iddox = 3.3 / 0.0056 = 589.3 ohms.? This is the minimum load the output can drive, as it gives the maximum allowed output supply current.? Exceed this spec and you enter current starvation on the power supply to the output buffer.

You stated that you used both a 50-ohm load (not impedence) and a 25-ohm load (not impedence) for your cross-talk testing.

With a 50-ohm load, Iddox = V/R = 3.3 / 50 = 66mA, which is more than 10x the maximum allowed output buffer supply current.

With a 25-ohm load, you subjected the part to 132mA Iddox!?

In both cases, the output buffers are so power starved that the chip internally can't supply enough Vddox to control the output buffers.? The result is ground bounce on all the outputs, not cross-talk.? This is typical behavior for digital chip output drivers whose output specs are violated in such a manner.? It also explains why you didn't see as much signal on the Si5351 outputs as you expected.?

The Zo spec was meant to say that the chip was designed to drive thru a 50-ohm impedence (either a 50-ohm coax or a 50-ohm micro-strip line on a PCB) to its load (Rload), not that you could use a 50-ohm or 25-ohm termination as the Rload.? An example of this appears on page 22 of the Si5351 datasheet.? Here the datasheet describes using the part to drive 2 clock outputs with 180 degree phase difference, but the example circuit shows driving the Si5341 clock outputs thru a 50-ohm coax to a voltage divider for the receiving circuit that presents an Rload of 511 ohms + 240 ohms = 751 ohms to each? Si5351 output buffer.? This gives an Iddox = 3.3 / 751 = 4.4mA, well within the 5.6mA max Iddox spec.

I suggest you repeat your cross-talk tests using an appropriate Rload value at the end of a 50-ohm line for each clock output and see how much cross-talk you see.

73,

Carl,? K0MWC

Hi;
The paragraph description on modifying the Beofeng mic connections to the uBITX is vague. Can a schematic please posted a schematic diagram as to how the mods actually are done. 'Thank you '73?

Great data Warren. Are you also going to replace the other 45MHz filter with the matching one you received ? Sure shows what all working together can accomplish........ Good Soup for everyone.?

73 Kees K5BCQ

Raj,

Doesn't leaving R27 in place give you better impedance matching ? Did you try cutting the trace in between and just putting the filter between C22 and R27 ?

73 Kees K5BCQ?

Sorry Bill.? I didn't mention that I do set it with the PTT switch, then exit the setup mode.? This set has exhibited this symptom since day 1.? I thought changing out the Arduino would have helped.? Before that I was adding caps to the reset.? Thanks anyway.

Bob

Hi Bob,

I do not see the part where you save the setting after you have set it. Press the push to talk button to save it while you are still in the calibration mode. Otherwise it does exactly as you describe and will be back to the original next time you turn it on.

Before you leave the calibration and after you have it where you want it, press push to talk. Not your CW key. Not later after you have left the calibration mode. Before you leave calibration.

73,

Bill KU8H

--
bark less - wag more

When the set is first powered on, there is a tinny, high frequency audio.? When you enter the setup mode and enter calibration, pressing the menu button, the audio is normal tone. Then I adjust the calibration level and set it, then exit, all is well.? Until I turn it off. I have tried other software with no luck. So I re-loaded the original factory software. I thought with all the issues you have seen with the various ubitx versions that you people may have come across it. Thanks anyway.

Bob

开云体育

Wow! ?Very nice work, Warren!!!! ?Extremely helpful for many, many people!!

Warren,

Try with both matched filters.. that should get further reduction.
I don't have a pair right now..

Raj

At 08-09-18, you wrote:

Hi Sunil,

Transformer isolation is VERY useful for eliminating ground loops and Galvanic isolation for the audio circuits. should you design a revised digital interface board provisions for installing audio isolation transformers would be much appreciated.??

-Justin N2TOH?

And finally, finally (for real this time) a pic of the filter in place. The center ground lead of the filter is not visible but it bend under the case and picks up the R13 ground.

Good work !

I have been using 3 to 31MHz as my span as you will see these dancing deverishes darting in and and out of the lower end
of the spectrum.

I got better results by replacing C22 with filter and leavening R27 intact!

Have a nice meeting and catch you later!

Raj

At 08-09-18, you wrote: