Topics

weird tx rx cycle #ubitx #v6


eb2elu
 

I would like to use my ubitx in portable operations so I bought a wonderband wonderloop antenna. It is a tiny magnetic loop  that seemed to be great for this radio but something really weird happens when I use it with my ubitx. If I tune wonderloop antenna on the right frequency  I am using and push ptt, ubitx starts to do a very fast TX/RX cycle. If antenna is not tuned for that frequency ubitx and I push PTT normal TX operation happens.

https://youtu.be/vG_MR4AtKkU

Does anybody have any idea about it could be happening?


Gordon Gibby
 

RF interference? 


On Jul 31, 2020, at 18:11, eb2elu@... wrote:

I would like to use my ubitx in portable operations so I bought a wonderband wonderloop antenna. It is a tiny magnetic loop  that seemed to be great for this radio but something really weird happens when I use it with my ubitx. If I tune wonderloop antenna on the right frequency  I am using and push ptt, ubitx starts to do a very fast TX/RX cycle. If antenna is not tuned for that frequency ubitx and I push PTT normal TX operation happens.

https://youtu.be/vG_MR4AtKkU

Does anybody have any idea about it could be happening?


eb2elu
 

But only happens with that antenna and only when antenna is tuned for the ubitx operating frequency.


Dale Parfitt
 

This is most certainly RFI or the PA going nuts because of high SWR. How far is the antenna from the rig? Have you attempted to pretune the loop with an antenna analyzer and then putting the antenna   on the uBitx at the same frequency? For a loop of a given diameter, the narrower the BW the more efficient it is. The gain of this antenna is far below a half wave dipole- a poor choice for QRP work, albeit convenient.

 

Dale W4OP

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of eb2elu@...
Sent: Friday, July 31, 2020 6:11 PM
To: BITX20@groups.io
Subject: [BITX20] weird tx rx cycle #v6 #ubitx

 

I would like to use my ubitx in portable operations so I bought a wonderband wonderloop antenna. It is a tiny magnetic loop  that seemed to be great for this radio but something really weird happens when I use it with my ubitx. If I tune wonderloop antenna on the right frequency  I am using and push ptt, ubitx starts to do a very fast TX/RX cycle. If antenna is not tuned for that frequency ubitx and I push PTT normal TX operation happens.

https://youtu.be/vG_MR4AtKkU

Does anybody have any idea about it could be happening?


Dale Parfitt
 

Again, how far is the antenna from the rig? Have you attempted choking the feedline to reduce common mode? Do you pretune the antenna before putting it on the rig?

 

Dale W4OP

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of eb2elu@...
Sent: Friday, July 31, 2020 6:24 PM
To: BITX20@groups.io
Subject: Re: [BITX20] weird tx rx cycle #v6 #ubitx

 

But only happens with that antenna and only when antenna is tuned for the ubitx operating frequency.


Bob, N1KPR
 

Sounds like RF is getting back into the rig. How far away is the loop? Does it do that without the mic plugged in and just a shorted plug in the key jack?

Bob, N1KPR




NOTE Pls add backup address to your phone book: rwbetts@...

http://www.bobsamerica.com  http://www.youtube.com/n1kpr

Engineering: Where Enigma meets Paradox


On Friday, July 31, 2020, 6:41:29 PM EDT, Dale Parfitt <parinc1@...> wrote:


Again, how far is the antenna from the rig? Have you attempted choking the feedline to reduce common mode? Do you pretune the antenna before putting it on the rig?

 

Dale W4OP

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of eb2elu@...
Sent: Friday, July 31, 2020 6:24 PM
To: BITX20@groups.io
Subject: Re: [BITX20] weird tx rx cycle #v6 #ubitx

 

But only happens with that antenna and only when antenna is tuned for the ubitx operating frequency.


Arv Evans
 

RF output is higher when the antenna is tuned to resonance.  This causes RF to
enter the microphone, the mike cable, and the mike amplifier.  Can also enter via
the key lead if it is fairly long.  Power supply regulators can also be modulated by
RF if not well filtered.  Wall warts are typically not bypassed for HF.  Computer
power supplies are typically not well bypassed for HF.

This type problem usually occurs with antenna systems that operate with a
floating ground, or that claim no ground is needed.   Can also occur if the ground
is too small wire, or is not making a good connection.  Basic problem is voltage
radiation too close to the rig.  A metallic (shielded) case can help in some situations.

Arv  K7HKL
_._


On Fri, Jul 31, 2020 at 4:24 PM <eb2elu@...> wrote:
But only happens with that antenna and only when antenna is tuned for the ubitx operating frequency.


eb2elu
 

Hi, antenna is attached directly to the rig. I have used that antenna with a yaesu 857 directly attached and that tx rx x cycle didn't happened. My ubitx has a metallic case but may be poorly shielded compared to yaesu 857. I will try to get a coaxial cable to put antenna as far as I could from radio.
Thank you very much for your help


Dale Parfitt
 

Different rigs have different RFI immunity. In any case, having the antenna right at the radio is poor practice and  your body movement will detune the antenna.

If you will accurately measure the  1.26:1 SWR points (bandwidth) say on 40M,  tell me the diameter of the  man loop and its diameter, I will respond with its gain below a dipole.

 

Regards,

Dale W4OP

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of eb2elu@...
Sent: Saturday, August 1, 2020 5:02 AM
To: BITX20@groups.io
Subject: Re: [BITX20] weird tx rx cycle #v6 #ubitx

 

Hi, antenna is attached directly to the rig. I have used that antenna with a yaesu 857 directly attached and that tx rx x cycle didn't happened. My ubitx has a metallic case but may be poorly shielded compared to yaesu 857. I will try to get a coaxial cable to put antenna as far as I could from radio.
Thank you very much for your help


eb2elu
 

Well,I have tried to separate antenna from the radio about 2 meters and sometimes is happening the same as before. It seems that this radio is affected a lot by RFI. @Dale, I have a 55 cm diameter loop http://www.wonder-wand.co.uk/WonderWand/WW_Photos.html and I am sure that is much more less effective than a dipole,but it is a tiny one and very portable.


Dale Parfitt
 

Thanks- so what I still need is  the diameter of the wire comprising the loop and  for you to measure the bandwidth either side of  where the loop is tuned, above and below until the SWR rises to 2.62:1- or even 2:1 on 40M or 20M- tell me the frequencies and also the value of the best SWR when you’re making the  measurements.

 

Tnx,

Dale W4OP

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of eb2elu@...
Sent: Wednesday, August 5, 2020 6:49 PM
To: BITX20@groups.io
Subject: Re: [BITX20] weird tx rx cycle #v6 #ubitx

 

Well,I have tried to separate antenna from the radio about 2 meters and sometimes is happening the same as before. It seems that this radio is affected a lot by RFI. @Dale, I have a 55 cm diameter loop http://www.wonder-wand.co.uk/WonderWand/WW_Photos.html and I am sure that is much more less effective than a dipole,but it is a tiny one and very portable.