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No Signal on uBit-x #ubitx-help


KM4TRT
 

After hooking up my new Nextion screen and making several great contacts, I was trying to optimize the frequency calibration and  hit the PPT switch a few times with the antenna switch in the wrong position.
I get no signal on receive or transmit.
I believe I tracked the problem down to the 45 MHz bandpass filter because:
1) I injected a 14.725 signal at 100mv at the antenna.
2) I tracked it through the first filter and the the first mixer and amp( on the scope) and
3) I get about 90 mv @ 45 MHZ just before the crystal filter with the amount of hash you'd expect to see after a mixer
4) Nothing out of the crystal filter. or out of the second amp.
Yes I did check voltages on all the concerned transistors
Can I use any of the cheap bandpass filters from Ebay as long as they are +/- 7.5 Khz pass

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313.TR0.TRC0.A0.H0.X45+mhz+bandpass+filter.TRS1&_nkw=45+mhz+bandpass+filter&_sacat=0

I looked up the WTL filters and don't see the Z 7  thats stamped on mine.
The WTL spec sheet has a 2 pole or 4 pole 45/3OT or a 2 pole of 4 pole 45/fundamental.
http://www.wtlcrystals.com/UploadFiles/31.jpg
Anyone familiar  with this?
Thanks-Andy KM4TRT


ajparent1/KB1GMX <kb1gmx@...>
 

On Sun, Sep 23, 2018 at 09:53 AM, KM4TRT wrote:
) I get about 90 mv @ 45 MHZ just before the crystal filter with the amount of hash you'd expect to see after a mixer
4) Nothing out of the crystal filter. or out of the second amp.
Yes I did check voltages on all the concerned transistors
Can I use any of the cheap bandpass filters from Ebay as long as they are +/- 7.5 Khz pass
The second amp is at ~12mhz.  if the LO to the second mixer is not correct then nothing works.
The second LO is in either 33 or 57 mhz (check the docs).

The chain from antenna in is 14.0mhz upconverted to 44.985ish mhz and then down converted to 12mhz.
If any of the oscillators are wrong you miss the 45mhz pass band or the 12mhz filter pass band
(11.995 to about 12mhz) you get nothing as in deaf.

Those 45mhz filters are not likely to fail, bad joints are possible. Any  45mhz filter should work 7.5 or the
wider 15Khz.   

I'd insure that the calibration went well and the 3 digital oscillators are indeed where they should be.
IF they are not its  going to be a deaf rock.

Allison


KM4TRT
 

Thanks for the reply.
  I realize that if nothing is going into the 2nd amp that nothing will come out.'I only said that because I have had experience where I could not find a signal at
some places because of  lead antennuation,
but was able to pick it  up further downstream in a less sensitive spot,.
To reiterate, I have the signal going into the 45 Mhz xtal but nothing reasonable coming out.  I should be getting the filtered 45Mhz signal going into the second mixer, right?
I did not change anything in the coil/cap structure, I only changed cal on the screen. (gui)
PS i was literally watching my signal disappear on the ICom waterfall display before I realized that my dummy load wasnt connected.
Andy


ajparent1/KB1GMX <kb1gmx@...>
 

On Sun, Sep 23, 2018 at 03:41 PM, KM4TRT wrote:
o reiterate, I have the signal going into the 45 Mhz xtal but nothing reasonable coming out.  I should be getting the filtered 45Mhz signal going into the second mixer, right?

If its the right frequency going in.  If not nothing.  Transmitting cant hurt the filter.
The amount of error you can have and get through the filter is about +-7.5khz!
However if the calibration software went off i space it could have stored something
totally wrong.

Now if it wasn't transmitting I'd suspect finals but no RX that a entirely different thing.

Allison


Joe Puma
 

Did you try doing a factory reset on the firmware? I use the CEC firmware and if you push the tuner knob in and turn on radio you’ll get the option to reset firmware by following on screen prompts. 

Joe


On Sep 23, 2018, at 6:41 PM, KM4TRT via Groups.Io <garello@...> wrote:

Thanks for the reply.
  I realize that if nothing is going into the 2nd amp that nothing will come out.'I only said that because I have had experience where I could not find a signal at
some places because of  lead antennuation,
but was able to pick it  up further downstream in a less sensitive spot,.
To reiterate, I have the signal going into the 45 Mhz xtal but nothing reasonable coming out.  I should be getting the filtered 45Mhz signal going into the second mixer, right?
I did not change anything in the coil/cap structure, I only changed cal on the screen. (gui)
PS i was literally watching my signal disappear on the ICom waterfall display before I realized that my dummy load wasnt connected.
Andy


KM4TRT
 

Hi Allison,
OK, I think the rust is starting to come off now.  So if I inadvertantly shifted the input frequency to the filter with the cal control, say 10K (instead of the 100 that I was looking for) then the 
signal will no longer go through the passband.  SO  whats the procedure for getting it back?
I think that the scope reading was over 45 MHZ, so I'll just adjust the calibration until I see it moving down,
Then I can find it with a dummy load and my IC7300 display.
What part of the circuit is the Cal from the Arduino actually shifting? 
Thanks
Andy


KM4TRT
 

Hi Joe,
Yes I also have the CEC firmware.  So this sounds like a better option than hunting and pecking with the calibratiion as I have nothing stored.
Andy KM4TRT


KM4TRT
 

Allison, Joe,
I do not seem to have that option for recalibration.  I'm on version 1.09 of Dr Lee's software.  
However, Allison was right on .  I recalibrated a couple of times and receive has returned and transmitting about 5 watts.
Thanks for straightening me out before I ripped the unit apart.

Has any one had trouble with the Nextion screen going off after a while?
After about 2-3 minutes, the screen goes dark.  Sometimes if I immediately turn the encoder , it comes back on,
but some time I have to reboot.
Andy