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Ubitx v4 whining and swr check issue(?)

BK
 

Hi all, newbie here
Just got ubitx v4 last dec2018, installed and connected to my endfed half wave thru 3:23 ratio balun (or un-un?).

Once i powered up i notice "whining" issue which at 40m band it heard around 3-4khz (checked with spectroid) which from another thread looks like this issue will be fixed by replacing the nano board.

Once i calibrated it (to strong broadcast band) and set bfo setting, i can hear local ham band properly, with addition of the "whining".
Playing around the frequency dial, i notice that the whining change (louder) when i dial down below 7.000.050. Means 7Mhz and below had different whining sound compared to 7.000.050 and above

Well as my ordered nanos are on it's way, i set the cw key to straight key, and use that to check my antena swr. Antena was built with 20m long insulated wire(halfwave of 40m band), which theoretically should give me lower freq than 7mhz. I checked with my swr meter (and ubitx cw) and found that it dipped somewhere around 6.5mhz. Okay, i shorten the wire and test again. Playing the frequency up and down to find the new dip giving me surprise as when i reach 7.000.050 and above it gave me very high swr.

I again check 7.000.000 and below. It gave me low enough swr but when i dial 7000.050 and above the swr get very high. 

This similar with my finding on the whining issue, that 7.000.050 number seem magical. This raise question :

Is ubitx limit the tx to be only on ham band?

If so, this may justify that below 7mhz i got low swr due to "no" tx power applied, cmiiw.
I haven't check the firmware (v4.3) to see what happened on 7.000.000 vs 7.000.050. If someone can give me hints, that'd be welcomed.
Thanks for any help and sorry for my english.

d balfour
 

I got a used ubitxv4 that had that sort of a whine. Turns out the BFO was off about 2k. Go through the setup and start with the standard bfo freq of 11.9965mc, then adjust from there.

Maybe you have the same problem.

Bob Lunsford <nocrud222@...>
 

Hello. Here is my ham information and at the bottom, you can see
details of an End Fed Dipole that has worked for me. I have made
many of them but the way you place the coax is important. Check
it out:

https://hamcall.net/call?callsign=kk5r

Bob — KK5R

--------------------------------------------

On Sun, 1/13/19, <budi.krisnawan@...> wrote:

Subject: [BITX20] Ubitx v4 whining and swr check issue(?)
To: BITX20@groups.io
Date: Sunday, January 13, 2019, 8:11 PM

Hi all, newbie here
Just got ubitx v4 last dec2018, installed and connected to
my endfed half wave thru 3:23 ratio balun (or un-un?).

Once i powered up i notice "whining" issue which
at 40m band it heard around 3-4khz (checked with spectroid)
which from another thread looks like this issue will be
fixed by replacing the nano board.

Once i calibrated it (to strong broadcast band) and set bfo
setting, i can hear local ham band properly, with addition
of the "whining".
Playing around the frequency dial, i notice that the whining
change (louder) when i dial down below 7.000.050. Means 7Mhz
and below had different whining sound compared to 7.000.050
and above

Well as my ordered nanos are on it's way, i set the cw
key to straight key, and use that to check my antena swr.
Antena was built with 20m long insulated wire(halfwave of
40m band), which theoretically should give me lower freq
than 7mhz. I checked with my swr meter (and ubitx cw) and
found that it dipped somewhere around 6.5mhz. Okay, i
shorten the wire and test again. Playing the frequency up
and down to find the new dip giving me surprise as when i
reach 7.000.050 and above it gave me very high swr.

I again check 7.000.000 and below. It gave me low enough swr
but when i dial 7000.050 and above the swr get very
high. 

This similar with my finding on the whining issue, that
7.000.050 number seem magical. This raise question :

Is ubitx limit the tx to be only on ham band?

If so, this may justify that below 7mhz i got low swr due to
"no" tx power applied, cmiiw.
I haven't check the firmware (v4.3) to see what happened
on 7.000.000 vs 7.000.050. If someone can give me hints,
that'd be welcomed.
Thanks for any help and sorry for my english.

Evan Hand
 

The stock software for the uBitx does cut the VFO so that there is not any RF out.  There is a check on the VFO setting below 7.000,000.1 to shut it down on transmit.  I have not checked on where the band change to the next lower band, however it does turn back on at some point.  I am not at a terminal where I can review the code to let you know the exact frequency.

73
Evan
AC9TU

BK
 

This whining is always there even if i disconnect the antenna so i believe this is not corelate to bfo (and yes i have set the bfo properly).

When i touch around the ubitx board, nothing i touch changes the sound, but when i touch 25mhz crystal pin it does change the sound of the whining. Other than that is by moving the frequency to 7mhz and below. Anyhow thanks for the reply. Today i installed cec firmware v1.08, and do the same test around 7mhz. The same symptoms still there:
-7mhz and below makes my swr low and thw whining sound increase in volume (and or in freq)
-7.000.050 and above make my swr very high. 
I think i need an oscilloscope to see more of what happened. 

John (vk2eta)
 

The uBitx does transmit out of ham bands but the change of filters is set in relation to ham band edges.

Example for 40m, the 7-10Mhz  filter is switched ON when the frequency is set above 7,000,000Hz.
At or below that value the 3.5-5Mhz filter is ON. Therefore the available power at the antenna connection below 7,000,000Hz will be significantly reduced.

Although it is possible that an issue exist in the 7-10Mhz filter I suspect more likely an issue with the antenna.

Do you have or can you make a dummy load (example 20 x 1k ohms 1/4 watt resistors in parallel would give 50 ohms at 5 watts dissipation, usable with short burst of CW power to test the swr and confirm a very low swr on the 40m band)?

Regarding the whining, based on your "touch" test on the 25mhz crystal I strongly suspect a Nano oscillator issue. Changing the Nano fixed that issue in my rig.

73, John