Date   

Re: Simple spur fix

Gordon Gibby <ggibby@...>
 

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

Cheers!
Gordon



On Sep 8, 2018, at 07:13, Warren Allgyer <allgyer@...> wrote:

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.

<Screen Shot 2018_09_08 at 7.10.48 AM.png>


Re: Simple spur fix

 

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:
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.

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Re: New Website ubitx.com

freefuel@...
 

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 


Re: Simple spur fix

Warren Allgyer <allgyer@...>
 

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.


Re: Simple spur fix

 

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:

It turns out I did have time for one pass of spur measurement. Here are screens for each of 17 through 10 meters. Conditions of the test: Audio input: 100 mVrms, 1.5 kHz tone. RV1 adjusted in each case for 2 watts output.

So far it looks really good with the eBay filter in place of R27. No other changes.

Yet to be verified: 100 mV audio drive, without the filter in place, gave very unacceptable IMD performance. It may well be in the case of the added filter that the stages preceding the filter have enough dynamic range to work at that level and it is simply compensating for the insertion loss of the filter itself. That can and will be confirmed with two tone IMD testing that will indeed have to wait. Also, we simply have to listen to the recovered voice quality and decide if it is adequate. Adding the filter has introduced low frequency rolloff for LSB and high frequency rolloff for USB. The change is less than 6 dB and may not be objectionable but that will be a subjective judgement.

Overall, very promising as a cure for the spurs.

[] [] [] []




Re: Simple spur fix

Warren Allgyer <allgyer@...>
 

And finally, here is a wider span showing 15 through 10 meters harmonic performance. My unit has the onboard filters completely removed and this scan was made with an external 30 MHz LPF plus the R27 filter. 

A clarification on the IMD comment in the last post. IMD was unacceptable at 100 mVrms audio drive before the filter was in place. It was not clear to me at that time whether the IMD was being introduced in the stages prior to the filter or after. If it was after, then increasing the audio input may be ok because it simply compensates for the insertion loss of the filter. If, though, the IMD was introduced in the SSB generator or the stages before that, then these pix may be a cure for the spurs but still have unacceptable IMD. Further testing is required to figure that out.


Re: Simple spur fix

Warren Allgyer <allgyer@...>
 

It turns out I did have time for one pass of spur measurement. Here are screens for each of 17 through 10 meters. Conditions of the test: Audio input: 100 mVrms, 1.5 kHz tone. RV1 adjusted in each case for 2 watts output.

So far it looks really good with the eBay filter in place of R27. No other changes.

Yet to be verified: 100 mV audio drive, without the filter in place, gave very unacceptable IMD performance. It may well be in the case of the added filter that the stages preceding the filter have enough dynamic range to work at that level and it is simply compensating for the insertion loss of the filter itself. That can and will be confirmed with two tone IMD testing that will indeed have to wait. Also, we simply have to listen to the recovered voice quality and decide if it is adequate. Adding the filter has introduced low frequency rolloff for LSB and high frequency rolloff for USB. The change is less than 6 dB and may not be objectionable but that will be a subjective judgement.

Overall, very promising as a cure for the spurs.


Re: Simple spur fix

Warren Allgyer <allgyer@...>
 

Raj

We may be talking "past" each other or I may not understand the intent. But as I see it the added filter is indeed a passband filter for the 45 MHz LSB/USB signal.

Referring to the attached scan: Blue trace is the filter passband measured out of the circuit with a 50 ohm in/out. Purple is measured with a 10x scope probe on the S/A input and attached to the same filter in place in the circuit. Purple is the input side of the filter. Yellow is the output side of the filter. So the screen reads top to bottom: Purple input, Blue filter, yellow filter output.

The two "humps" on the purple and yellow traces are the LSB and USB signals respectively with the audio input being swept from 0 - 5 kHz. Due to the way the 45 MHz SSB signal is generated and later heterodyned to operating frequency, the right side of both humps is the low audio frequency and the left is the high frequency. While the sweep was done from 0 - 5 kHz, the humps themselves represent only about 300 Hz (on the right side) to 2.7 kHz on the left. The 'scalloping' evident on the purple trace comes from the response curve of the 12 MHz crystal lattice filter in the SSB generator.

My comment about the shape of the newly added filter is evident by comparing the yellow output humps to the purple input. The right side of the leftmost hump and the left side of the rightmost hump are attenuated by the filter shape. This will have the effect of attenuating the low audio frequencies on LSB and the high frequencies on USB.

Some good news is the eBay filters appear to be a good match for the SSB generator as both humps are centered in the filter passband. So I think I am in good shape to do some testing on the effect the added filter has on the spurs. That will have to wait until the afternoon as our club technical breakfast is in about an hour.


Re: Simple spur fix

 

Glenn,

The intention of the filter is not the passband. I wanted to get rid of all the HF 3-30MHz that was
being picked up from messing with the mixer and BiDi amp. So a 45M30 say 30KHz filter may be
fine or better if any center freq is off.

The need as I see it is the ultimate rejection beyond 1MHz is -90db which is great!

Raj

At 08-09-18, you wrote:
the sweep at 50R is in relationship to the mod suggested in this thread, which I understand is a '50R' impedance area. I swept it exactly the same as Warren for comparisons sake only..

vk3pe


Re: Simple spur fix

iz oos
 

Gosh, I have received now the comment by Ray, so mine is a kind of repetition of it.


Il 08/set/2018 10:07, "iz oos" <and2oosiz2@...> ha scritto:

You measured the filter at 50ohm but the terminating impedances should have been 650ohm/3pf. I am not sure whether the impedance of the stock filter is similar and the matching in the Ubitx might be adequate as is.


Il 08/set/2018 03:16, "Warren Allgyer" <allgyer@...> ha scritto:

My filters arrived earlier than expected. These are from eBay at 

https://www.ebay.com/itm/Tellurian-Technologies-45MHz-Crystal-Bandpass-Filter-T45U15BG-Matched-Pair/181956516605?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Immediate results are disappointing so I have put them on the S/A to see what is going on.

Center frequency: 44.987166 MHz, about 13 kHz lower than expected
Insertion loss: 6-10 dB across the bandpass at 50 ohms in/out
Corner points: 15 kHz across center

This filter is going to play havoc with SSB because of the variance across the filter passband and because 45 MHz is centered on the extreme high side of the filter. 

When I put it in in place of R27 the results were not good. But it is early and I have lots to verify yet. Tomorrow I will pull the 45 MHz filter supplied with the uBitx and check it in the same way. I have no point of reference but I am not excited about these filters at this point in the testing.

WA8TOD




Re: Simple spur fix

iz oos
 

You measured the filter at 50ohm but the terminating impedances should have been 650ohm/3pf. I am not sure whether the impedance of the stock filter is similar and the matching in the Ubitx might be adequate as is.


Il 08/set/2018 03:16, "Warren Allgyer" <allgyer@...> ha scritto:

My filters arrived earlier than expected. These are from eBay at 

https://www.ebay.com/itm/Tellurian-Technologies-45MHz-Crystal-Bandpass-Filter-T45U15BG-Matched-Pair/181956516605?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Immediate results are disappointing so I have put them on the S/A to see what is going on.

Center frequency: 44.987166 MHz, about 13 kHz lower than expected
Insertion loss: 6-10 dB across the bandpass at 50 ohms in/out
Corner points: 15 kHz across center

This filter is going to play havoc with SSB because of the variance across the filter passband and because 45 MHz is centered on the extreme high side of the filter. 

When I put it in in place of R27 the results were not good. But it is early and I have lots to verify yet. Tomorrow I will pull the 45 MHz filter supplied with the uBitx and check it in the same way. I have no point of reference but I am not excited about these filters at this point in the testing.

WA8TOD



Re: Simple spur fix

Glenn
 

the sweep at 50R is in relationship to the mod suggested in this thread, which I understand is a '50R' impedance area.  I swept it exactly the same as  Warren for comparisons sake only..

vk3pe


New Website ubitx.com

Sunil Lakhani
 

A new website ubitx.com has been opened for providing info of building the ubitx into our universal case, sold on amateurradiokits.in
Presently info is limited but we shall keep on adding more info on various accessories that can be added with ubitx.
This is an effort to help builders with their construction.

Any suggestions are welcome.

Regrads

Sunil VU3SUA
 


Re: Simple spur fix

 

The filter is 650 ohms and not 50 ohms. It is a roofing filter in this application
so I will not expect SSB filter results!

Change your span to 2MHz and look. Ultimate rejection is 910KHz.

Raj


At 08-09-18, you wrote:

My filters arrived earlier than expected. These are from eBay at

https://www.ebay.com/itm/Tellurian-Technologies-45MHz-Crystal-Bandpass-Filter-T45U15BG-Matched-Pair/181956516605?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Immediate results are disappointing so I have put them on the S/A to see what is going on.

Center frequency: 44.987166 MHz, about 13 kHz lower than expected
Insertion loss: 6-10 dB across the bandpass at 50 ohms in/out
Corner points: 15 kHz across center

This filter is going to play havoc with SSB because of the variance across the filter passband and because 45 MHz is centered on the extreme high side of the filter.

When I put it in in place of R27 the results were not good. But it is early and I have lots to verify yet. Tomorrow I will pull the 45 MHz filter supplied with the uBitx and check it in the same way. I have no point of reference but I am not excited about these filters at this point in the testing.

WA8TOD


Re: install 20x4 I2C Display - Problem without 3.3v ?

Jerry Gaffke
 

Fabian,

> By the way i should ask "what ist an PULLUP Resistor?"

Just a normal fixed resistor.

The i2c bus has two open collector signals named SDA (data) and SCL (clock).
Each of those two signals has a pullup resistor to 3.3v or 5.0v, with a value of perhaps 2k or 5k.
So when nothing is happening, both of those signals get pulled high.
But any device on the i2c bus can pull them low, then release the signal to allow it to go high again.

I am not familiar with your display, or with the i2c bus interface on your display.
I don't see any pullup resistors in the photo you showed.
They could be on the back of the i2c bus interface board.
Or they may not be present at all.
You could try measuring the resistance from the SDA and SCL pins to the upper power rail (with power off)
using an ohmmeter.
It is possible there are no pullup resistors at all on that board.

You might just try hooking up the SDA and SCL lines to the Raduino, see if it works.
The worst that will happen is that it will damage the si5351 chip on the Raduino,
but I doubt that will happen.

Getting i2c devices to work can be difficult.
Ii you need assistance you might be best off attending a local amateur radio club meeting,
see if someone there can help you get it going.

Jerry


On Fri, Sep 7, 2018 at 03:01 PM, sdr freak wrote:
when i was reading your post then i dont understand my I2C panel that's on my I2C Display in here. that is not the same i see at other pics by ubitx users they have showed.. and by the post pics above, you can see my I2C Display and there is nothing like an capacitor or resistor.. By the way i should ask "what ist an PULLUP Resistor?" i dont know this word, or is it the variable resistor that looks like a blue quadrat with a with plastic screw, to adjust the displays brightness, ..is that mean for pullup resistor? others not at my I2C panel and i dont know what you think about the KD8CEC website.. there would be a tutorial an there nothing was say about any 3.3v or desolder resistor.. that is making me crazy.. here ( http://www.hamskey.com/2018/04/various-lcd-support-in-ubitx-with.html ) have you an idea for that website tutorial wasn't give information to the point of voltage on these pins using?

and what you say about my other idea, to desolder the I2C panel from Display and use it by put in the orignal display pins place? was that an option or there is an hiding problem too?

thanks


Re: Simple spur fix

Glenn
 

very much same as yours.


Re: Simple spur fix

W0PWE
 

I keep thinking back to the 2nd post on this topic where  HA5OGL suggests modifying the Termination Insensitive Amplifier to make it a tuned amplifier. I don't have a uBitx board so I don't know how difficult that would be to implement on a real uBitx. I intend to build from scratch so I could easily add the tuned circuit. 

Has anyone considered the tuned amplifier approach? I might try it in LTSpice if it seems like a viable solution.
W0PWE


Re: Simple spur fix

Warren Allgyer <allgyer@...>
 

How do they look for insertion loss? I think 6 dB may be manageable but 12-20 is going to be too much.
WA8TOD


Re: Simple spur fix

Glenn
 

Warren, Just measured one of mine from junk box also, with almost identical results to yours. Very slightly narrower BW.
.
Mine are 45E2BF  made by Toyocom. Actually part of  a pair. If i series (pair) them up, BW is a little narrower as expected and ripple just slightly less.

glenn
vk3pe


Re: Pa Drivers Biasing

Glenn
 

Thats ok on parts.  Although getting them might be another story. I have  a pretty good 'junque box' from years of playing radio, but never deep enough with whats 'wanted'.

And typos.

glenn