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.

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.

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.

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

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

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.

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

A new website has been opened for providing info of building the ubitx into our universal case, sold on
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
?

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:

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

very much same as yours.

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

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

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

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

Kees, your thinking of K3 relay bypass?

It works but you must have some form of audio switch like V4 or the board you make up.
Tried that back in june, likely wrote about it here along with a modified
2n7000 anti-pop-thump switch.

Allison

Glen,

Generally I used one 5109 for ever pair of 3904 due to what I had on hand.

However there are a raft of other parts in the CATV class of 1-3W, 800ma Ic,
and FT greater than 1200mhz.

Did not say copy this so like I said your on your own.??

BN 43-202? typo, old stiff fingers.

Allison

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

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

开云体育

I’m not exactly familiar with this master calibration. ? I found a way to simply measure the offset of the 25 MHz Crystal by having the system send a 25 MHz signal and measure it with accurate ?receiver. And then I simply edited the code to make it be the correct frequency. ?

开云体育

All great ideas! ? Goal here is to be helpful. ? We may not always reach that, but we can certainly do better each day. ?