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V5 uBitx CW issues

Dennis Yancey
 

I have a V5 uBitx with CEC v 1.22 firmware and using a straight key. It works great on everything from 40 meters and below, however on all bands from 20 meters to 10 meters, when I press the key,  it locks in transmit and you have to push the TX stop button or power off to reset the radio. Any ideas?
--
72 and God bless
KD4EPG

Curt
 

Dennis

Sounds maybe like RF feedback. If you have or can make a dummy load that would confirm it. Or dial back transmit power to see if that cures it. If you have only one antenna I am suspicious.

God bless you and yours.

Curt

Evan Hand
 

I would agree with Curt.  I have run into this issue when I had RF on the shield from an OCFD (off center feed dipole).  Solved it with snap on ferrite on the coax both at the entrance to the shack and at the output of the SWR/PWR meter that I keep in line.   Solved it for me.

73
Evan
AC9TU

Dennis Yancey
 

Using ladder line from random wire antenna to the tuner. Tunes perfect 1.1 to 1 SWR, where would I put the ferrite? in the coac between the tuner and the radio? Or between the tuner and the meter? This antenna setup works fin with other radios up to 125 watts.. that is the biggest I have.. 

--
72 and God bless
KD4EPG

Dennis Yancey
 

Thanks for the help folks. As always, you come through with great ideas. I will try these tomorrow.

--
72 and God bless
KD4EPG

Evan Hand
 

Dennis,

The SWR reading will not be a true indication of RF on the coax shield or in the shack.  The problem could also be just stray RF in the shack. First of all verify that it is RF getting into the rig by transmitting into a dummy load as Curt suggested.  If the problem goes away, then it most likely is an RF issue getting back into the Raduino (actually the Nano in the Raduino) that controls the uBitx.

Based on your setup, I would first make sure you have proper ground on the rig and the tuner.  If that  doesn't solve the problem, then I would place the ferrite between the uBitx and the tuner.  I would also place a small ferrite on the key line.  For my uBitx I used shielded wire for the CW key line.

Is the rig mounted in a metal enclosure?  If not shielded, then adding copper foil and grounding to a plastic case might solve the issue. 

Just suggestions.  My case of the RF in the shack is a known issue with OCFD antennas.  Not sure on your setup. 

Please use the above ideas at your own risk.  It is very difficult for me to diagnose through descriptions.
73
Evan
AC9TU

Dennis Yancey
 

Evan, 
Thanks for the info and suggestions. The uBitx is in a metal case designed for it, one of Sunhil's cases. I also use shielded wire between the key and the radio. I will run some tests with the dummy load and see and report back. Here is a new symptom, I took the radio off the 13.8 v power supply and put it on my battery, 11.8v fully charged. The issue subsided a great deal but the sidetone sounded really bad on 20 meters and let me fine tune the adjustment of SWR which cleaned up the sidetone a great deal. On the other bands going up, it was still doing the same thing..  I will keep posting my findings. 
Thanks,
 
-- 
72 and God bless
KD4EPG

Dennis Yancey
 

I took the antenna off and tested the uBitx straight into a 50 ohm dummy load and it performed flawlessly on the upper bands as well. I don't have ferrite beads I can use at the moment but will get some soon. This also gives me a reason to rework my ground system, as i have felt it has needed reworking for a bit.. will  keep you informed as to progress. 
Thanks again, everyone for your gracious thought and suggestions. 

--
72 and God bless
KD4EPG

 

Dennis,

Initially I had instability on the test bench with Bitx boards from HFsignals. I solved it by using
a 50 ohm shielded cable similar to RG174 and all issues went away.

I suggest that you cut the original 2 wire for antenna as short as possible (1/2") and
solder a thin coax or even a shielded wire till the BNC so that this piece does not radiate
inside the box.

My setup is not unstable even at high SWR of 4. This happened when my 40M dipole
dropped on the concrete roof when the tree that it was tied to fell in the storm.

Raj

At 12/07/2019, you wrote:
I took the antenna off and tested the uBitx straight into a 50 ohm dummy load and it performed flawlessly on the upper bands as well. I don't have ferrite beads I can use at the moment but will get some soon. This also gives me a reason to rework my ground system, as i have felt it has needed reworking for a bit.. will keep you informed as to progress.
Thanks again, everyone for your gracious thought and suggestions.

--
72 and God bless
KD4EPG

Evan Hand
 

I strongly believe that your issue is RF in the shack.  The Ferrite clip on worked for me.  When I got the ferrites, I bought an assortment, as I did not know what size exactly.  It also gave me the option to add more than one on a line/coax.

Here is what worked for me:
https://smile.amazon.com/gp/product/B0757H1SBZ/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

I am sure you can find them for less.  I tend to be lazy.

73
Evan
AC9TU

Don, ND6T
 

Since the path from tuner to ground becomes more significant at higher frequencies I have found that tuning the ground with a variable series LC circuit helps incredibly. Otherwise it is frequent that the wire from your tuner to actual outside ground is a quarter wave length and thus high impedance.
Fashion a simple LED RF indicator and touch it to the case of your radio. You might be surprised.
73, Don

Ashhar Farhan
 

The ringing could be due to a race around the bidirectional amplifiers when for a brief moment, both directions are powered during transition from rx to tx.
- f

On Fri 12 Jul, 2019, 9:18 AM Dennis Yancey, <Kd4epg@...> wrote:
Thanks for the help folks. As always, you come through with great ideas. I will try these tomorrow.

--
72 and God bless
KD4EPG

Roman
 

Regarding ferrites, this is only for the desperate: If you have old VGA or DVI cables laying around you can sometimes harvest the ferrite beads from them, though it does involve larger cutters and sharp bigger size box cutter blade. Cut the cable 1" (2cm) from each end with the pliers, slice down through the plastic about 2mm from the end towards the cable from all sides without hitting the ferrite (it can crack) but try to expose the face end of the ferrite possibly with multiple cuts, and go all the way around until you cut through the cable shield but not the cable, do on both ends. Using pliers, pull the remaining wires out. Slice down the length of the ferrite jacket until you barely touch the ferrite, pull the jacket off. Carefully using pliers pull the jacket out of the center of the ferrite. Most of these will fit RG58 cable. Don't lose part of a finger doing this! I think it is smarter to purchase what you need and get the right size/material.