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#ubitxcw #ubitxv6 More signal out on 10 meters than other bands? #ubitxcw #ubitxv6

Stephen KO4CVU
 

With a dummy load on my ubitx v6, I can see that the amplitude of the CW signal in the 10 meter band is significantly higher than on any other band when I look at the spectrum display from my RTl-SDR using AIRSPY on my laptop. In the 10 meter band, the peak of the CW signal exceeds the maximum of the scale, 0. In the 80 meter band, I am lucky to see a peak at -20. I measured the voltage across the dummy load with my old Realistic #22-204 multimeter and found the following: (frequency, voltage ac, parallel R); (28.425, 1.4, 66.184); (7.290, 1.0, 52.226); (3.885, 0.8, 52.257) I determined the values for parallel R using my nanoVNA-H to measure the dummy load. Based on what I’ve read in the posts, the power output is expected to decrease, not increase, when the frequency increases. What am I doing wrong? Thanks.

Claude VA2SOB/VE2SOB <STAC0792@...>
 

Anyone has a ubitx version 6.0 up for sale ?




Cordialement, Regards

Claude Munger Poirier. VA2SOB
LinkedIn : Claude M. Poirier



On May 18, 2020, at 1:29 PM, Stephen KO4CVU <goinfishin1952@...> wrote:

With a dummy load on my ubitx v6, I can see that the amplitude of the CW signal in the 10 meter band is significantly higher than on any other band when I look at the spectrum display from my RTl-SDR using AIRSPY on my laptop. In the 10 meter band, the peak of the CW signal exceeds the maximum of the scale, 0. In the 80 meter band, I am lucky to see a peak at -20. I measured the voltage across the dummy load with my old Realistic #22-204 multimeter and found the following: (frequency, voltage ac, parallel R); (28.425, 1.4, 66.184); (7.290, 1.0, 52.226); (3.885, 0.8, 52.257) I determined the values for parallel R using my nanoVNA-H to measure the dummy load. Based on what I’ve read in the posts, the power output is expected to decrease, not increase, when the frequency increases. What am I doing wrong? Thanks.

Dale Parfitt
 

Hi Stephen,

What is the coupling mechanism between the SDR and the Bitx? If it is  perhaps a short random wire for example, I would expect the SDR to read higher on 10M than  a lower band as the antenna appears ‘larger’ (that is, a larger fraction of a wavelength). The proper method is to measure the power on your SDR using an attenuator between the SDR and the Bitx. That way the Bitx and the SDR both see 50 Ohms and the coupling is constant across the HF spectrum. Of course, the attenuator (or a directional coupler) must have sufficient coupling loss to keep your SDR in its linear region- that is not saturating the front end.

 

Dale W4OP

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Stephen KO4CVU
Sent: Monday, May 18, 2020 1:29 PM
To: BITX20@groups.io
Subject: [BITX20] #ubitxcw #ubitxv6 More signal out on 10 meters than other bands?

 

With a dummy load on my ubitx v6, I can see that the amplitude of the CW signal in the 10 meter band is significantly higher than on any other band when I look at the spectrum display from my RTl-SDR using AIRSPY on my laptop In the 10 meter band, the peak of the CW signal exceeds the maximum of the scale, 0. In the 80 meter band, I am lucky to see a peak at -20. I measured the voltage across the dummy load with my old Realistic #22-204 multimeter and found the following: (frequency, voltage ac, parallel R); (28.425, 14, 66.184); (7.290, 1.0, 52.226); (3.885, 0.8, 52.257) I determined the values for parallel R using my nanoVNA-H to measure the dummy load. Based on what I’ve read in the posts, the power output is expected to decrease, not increase, when the frequency increases. What am I doing wrong? Thanks.

Stephen KO4CVU
 

Dale,
Unfortunately, I haven’t made any special provision for coupling. The SDR is connected via coax to a “Balun On Nine - Tiny Low-Cost 1:9 HF Antenna Balun“ located outside of the house. A long wire (about 200 feet) antenna is connected to one of the binding posts of the balun and a ground wire is connected to the other binding post. During these tests, the uBITX was on a desk within 36 inches of the SDR dongle which was lying on the floor. Could I connect a 50 ohm dummy load to the antenna connector of the SDR to achieve sufficient attenuation? I don’t have a direct coupler or real attenuator.
Thanks,
Stephen 

Dale Parfitt
 

HI Stephen,

Anything other than both the SDR and the BitX connected by an appropriate attenuator or a directional coupler will yield frequency dependent results, and not real numbers.

The correct method would be an accurate and frequency suitable wattmeter, a calibrated RF Probe and voltmeter, a scope that has the proper frequency range and a known accurate termination.

Nothing like having some good test equipment if  you are  homebrewing, testing, aligning etc.

 

During these tests, the uBITX was on a desk within 36 inches of the SDR dongle which was lying on the floor. Could I connect a 50 ohm dummy load to the antenna connector of the SDR to achieve sufficient attenuation? I don’t have a direct coupler or real attenuator.

 

99% of the 9:1 and 4:1 Baluns are not baluns at all- they are simply transformers, still allowing the outside shield of the coax to be part of the antenna. And as above, the antenna’s response is frequency dependent and just as bad, the output power of the Bitx is likely all over the map as it is seeing widely ranging SWR.

Secondly, with the 2 rigs that close to one another, direct radiation pick up may be the coupling mechanism, or a good part of it.

Just not a good situation.

 

Dale W4OP

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Stephen KO4CVU
Sent: Monday, May 18, 2020 2:41 PM
To: BITX20@groups.io
Subject: Re: [BITX20] #ubitxcw #ubitxv6 More signal out on 10 meters than other bands?

 

Dale,
Unfortunately, I haven’t made any special provision for coupling. The SDR is connected via coax to a “Balun On Nine - Tiny Low-Cost 1:9 HF Antenna Balun“ located outside of the house. A long wire (about 200 feet) antenna is connected to one of the binding posts of the balun and a ground wire is connected to the other binding post. During these tests, the uBITX was on a desk within 36 inches of the SDR dongle which was lying on the floor. Could I connect a 50 ohm dummy load to the antenna connector of the SDR to achieve sufficient attenuation? I don’t have a direct coupler or real attenuator.
Thanks,
Stephen 

Stephen KO4CVU
 

Dale, Thanks for the suggestions. I am really getting frustrated with this thing. I hooked the unit to a fan dipole in the second story attic of this house (in a HOA-restricted subdivision) with both 10 meter and 40 meter dipoles. I used my nanoVNA to adjust the dipoles to length. The 40 meter dipole resonates at 7.235 MHz with a VSWR of 1.389 and parallel resistance of 36.033 ohms. The 10 meter dipole resonates at 28.34 MHz with a VSWR of 1.198 and a parallel resistance of 50.059 ohms. I have run a 75-foot length of RG-8X coax to the attic to directly connect to the antenna without any balun. The other day, I tried to communicate with a local ham operator who is less than 3 miles away from my location as the crow flies and over flat ground. He has a 50 watt transceiver. Fortunately, I was able to talk to him on my 2 meter Yaesu FT-65 HT connected to one of Ed Fong's DBJ-1 antennas during the attempt. I could just barely copy his faint CW signal on 40 meters. He could not copy my CW or phone signal on either 40 meters or 10 meters. I never could hear his signal on 10 meters. Am I being unrealistic in attempting to contact someone in the neighborhood with a QRP radio?
Unfortunately, I do not have a RF watt meter although I have some parts on order to build a poor-boy's version of one. Maybe they’ll get here one of these days and I will be able to tell if the uBITX is putting out any signal.

Dale Parfitt
 

Hi Stephen,

I think you should be able to make that path. I hope he is using a horizontal antennas also. The ground wave penalty for  being cross polarized can be as much as -20dB. Likely you have some vertical radiation from  your coax  because of no balun- that is, the coax is p[art of your antenna.

So Evan and others on the list  can likely give  you some pointers on making sure the Bitx is calibrated etc I am assuming you  do hear other stations on 40, 80M etc on the correct sideband. Is WWV pretty much spot on?

 

Regards,

Dale W4OP

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Stephen KO4CVU
Sent: Monday, May 18, 2020 4:09 PM
To: BITX20@groups.io
Subject: Re: [BITX20] #ubitxcw #ubitxv6 More signal out on 10 meters than other bands?

 

Dale, Thanks for the suggestions. I am really getting frustrated with this thing. I hooked the unit to a fan dipole in the second story attic of this house (in a HOA-restricted subdivision) with both 10 meter and 40 meter dipoles. I used my nanoVNA to adjust the dipoles to length. The 40 meter dipole resonates at 7.235 MHz with a VSWR of 1.389 and parallel resistance of 36.033 ohms. The 10 meter dipole resonates at 28.34 MHz with a VSWR of 1.198 and a parallel resistance of 50.059 ohms. I have run a 75-foot length of RG-8X coax to the attic to directly connect to the antenna without any balun. The other day, I tried to communicate with a local ham operator who is less than 3 miles away from my location as the crow flies and over flat ground. He has a 50 watt transceiver. Fortunately, I was able to talk to him on my 2 meter Yaesu FT-65 HT connected to one of Ed Fong's DBJ-1 antennas during the attempt. I could just barely copy his faint CW signal on 40 meters. He could not copy my CW or phone signal on either 40 meters or 10 meters. I never could hear his signal on 10 meters. Am I being unrealistic in attempting to contact someone in the neighborhood with a QRP radio?
Unfortunately, I do not have a RF watt meter although I have some parts on order to build a poor-boy's version of one. Maybe they’ll get here one of these days and I will be able to tell if the uBITX is putting out any signal.

Evan Hand
 

I have been following the thread, however not sure I have any good suggestions.  The first thing that threw me off was the measurements given in the first post:  The resistance measurements do not make sense.  A true dummy load would always measure 50 ohms, as it is all resistance that is supposed to be independent of frequency.  The second thing that does not make sense is the voltage readings.  For 10 watts in 50 ohms, you should have about 22 volts RMS.  Assuming the meter is reading RMS (NOT a good assumption at 28 MHz) then 1.4 volts would be 0.04 watts.  That means the PA is not working, or more likely the measurements are not valid.

The fact that you can bearly hear the other radio suggests that the BFO is off from the SSB filter.  I would start work on the receiver with the adjustments in the Ashhar Farhan video on calibration.  
https://www.youtube.com/watch?v=t6LGXhS4_O8  using the BFO Tuning Page: https://www.hfsignals.com/index.php/bfo-tuning-aid/

The BFO does affect SSB transmission.  It is turned off during CW transmission.  Still, get the receiver working before you start on the transmitter.

When the receiver is working, then I would do the initial test in the v5 instructions: https://www.hfsignals.com/index.php/ubitx-tuneup/  Here you are interested in the PA bias adjustment.  Does your VOM measure DC current up to 2 amps?

I would also be interested in the current draw when transmitting.  Might explain the low output if the finals are not really working.

There is a possibility that something was damaged when you were trying the transmitter out, especially if the load is not very fay off in impedance (More than 2:1 SWR).  That is why I am suggesting the PA bias run.

Dale had some other suggestions for the difference in signal strength that could explain what is happening with the SDR measurements.  Another possibility is that you are detecting the signal of the driver and that the finals are not working.  If that is the case, then any data would be suspect. 

Hope this helps.
73
Evan
AC9TU

Stephen KO4CVU
 

Dale,
I am glad to hear that my expectations are reasonable in the neighborhood.
Yes, WWV at 15 MHz show up at 15 MHz on the dial although it is pretty weak for me right now. Last night, I heard several stations from East Texas on 80 meters. One fellow in Ackworth, GA sounded like he was right next door hollering through the window. I am located just east of Nashville, TN.
Thanks,
Stephen

Evan Hand
 

So it seems you have the receiver working.  As stated in the other post from me, I would now do the bias adjustments of the PA.  That would also tell you if the finals are working., though not the drivers.

73
Evan
AC9TU

Stephen KO4CVU
 

Evan,
Yes, I think the receiver is functioning now. I followed the #1 PA BIAS section of the MBITX Tune-Up procedure on the hfsignals website. I was able to set the two bias adjustments to add 100 ma per each to the total current consumption as the instructions indicated. Unfortunately, there was no significant change in the current when I yelled into the microphone. I tapped on it and even tried putting my cell phone on it while the signal generator app played a 1500 Hz tone. There was no change in the current. As a last resort, I set the mode to CW. The current consumption jumped up to about 2.5 amps when on the 80 meter band and about 1.1 amps on the 10 meter band.
Previously, and after reading other posts, I have drilled 8 more small holes in the front of the mIcrophone housing to allow more sound into the cavity for the small microphone element. (And I did the drilling with the housing disassembled and microphone element removed.)
Do you think I have a bad element in the microphone? Or perhaps there is a wiring issue in the plug?
Thanks for your help,
Stephen

Evan Hand
 

I would agree that the most likely candidate is the mic element.  I would look into another source to connect to the mic input.  Remember that the sleeve is connected to the PTT line, so you would need to make a breakout cable with the tip going to an audio source (PC or Phone) and the ring to a switch to ground the PTT line (you can also just short the connector with the lid off of the rig).  You will also need a 1 to 10 micro F cap to isolate the electret bias voltage on the mic input.  The rig side would be the positive lead if using an electrolytic.

For background, there have been a LOT of complaints on this board with supplied mic issues for the v6.  More so than the 2 years prior and all of the version 4 and 5.  The Baofeng mic looks really good but has had quality issues even with the ones supplied with their handhelds.  Honestly, a $20 CB mike with a preamp would be a better choice.  You can then adjust the volume for the best sound with full output.  I bought this one on Amazon:
https://smile.amazon.com/gp/product/B0077PS0UI/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1  (looks like the price went up a few dollars).

If you do go that rout you will need to make an adapter to match the 4 pin connector to the 3.5 mm jack, or cut off the end and connect a 3.5 mm jack inplace of the 4 pin connector.  I went the adapter rout, as the cases for v4 and v5 have 4 pin plugs on them.

As is the case in most new uBITX ventures, there is a set process of solving the problems one by one.  There are many others on this board that can help if you run into something that I have not seen.

Good luck on finding your last major issue.
73
Evan
AC9TU

Stephen KO4CVU
 

Evan,
As you suggested, I connected an audio (cassette player) source in series with a 1 mfd electrolytic capacitor to the microphone input. (I had recorded my voice speaking “Test Test” with my call sign on the tape.) The current consumption will exceed 1 amp on both the 10 meter and 80 meter bands at the peak volumes on the tape. Looks like a bad Baofeng microphone but I won’t know for sure until I receive the CB microphone with pre-amp. I ordered the one you suggested in your previous message the other day. Am I correct in thinking that I will need the 1 mfd capacitor with it also? I will let you know whether the new microphone solves the problem or not. 
Thank you for your help.
Stephen, KO4CVU

Evan Hand
 

I have been using that mic without the capacitor.  When I checked, there was one on the board in the mic.

You just need to make the connection with either a 3.5 mm TRS plug to 4 pin jack, or cut off the 4 pin plug and connect a 3.5 mm TRS plug.  The tip is the mic, the ring is PTT and sleeve goes to the ground/common for both.

For my rigs, the mic gain is set between 4 and 5 on the dial.  That seems to provide the correct amount of output without distortion.  

Good luck and happy QSOs.
73
Evan
AC9TU

Amie C.
 

HF signals does 😉
--
AMIE N9OXO

Stephen KO4CVU
 

Evan,
I ordered and just received the microphone with pre-amplifier that you suggested I buy. I also built a poor-man’s low power watt meter. To compare the new microphone with the original Baofeng microphone, I downloaded a signal generator app on my iPhone 6 and set it to 70% volume on a 1,000 hertz tone. I then measured the power output at the antenna connector by putting the iPhone next to the microphone being tested and moved the iPhone on the microphone until I got the maximum output. I repeated this test at a frequency on each of the bands. There was 10 fold increase on the 80 and 40 meter bands! In my opinion, if someone plans to order a uBITX v6.1 for voice use, they might as well order a microphone with a pre-amplifier at the same time and save themselves a lot of grief. Evan, thank you very much for pointing me in the right direction. Sincerely, Stephen P. S. Now, I have to do some serious searching on the posts to find the most efficient antenna for use on the 40 meter band.

Jeff Debes
 

Steven,
How much was the microphone?
Jeff


On May 27, 2020, at 8:47 PM, Stephen KO4CVU <goinfishin1952@...> wrote:

Evan,
I ordered and just received the microphone with pre-amplifier that you suggested I buy. I also built a poor-man’s low power watt meter. To compare the new microphone with the original Baofeng microphone, I downloaded a signal generator app on my iPhone 6 and set it to 70% volume on a 1,000 hertz tone. I then measured the power output at the antenna connector by putting the iPhone next to the microphone being tested and moved the iPhone on the microphone until I got the maximum output. I repeated this test at a frequency on each of the bands. There was 10 fold increase on the 80 and 40 meter bands! In my opinion, if someone plans to order a uBITX v6.1 for voice use, they might as well order a microphone with a pre-amplifier at the same time and save themselves a lot of grief. Evan, thank you very much for pointing me in the right direction. Sincerely, Stephen P. S. Now, I have to do some serious searching on the posts to find the most efficient antenna for use on the 40 meter band.

--
jeff.debes@...

Stephen KO4CVU
 

I paid $23.98 for “Barjan CB Amplified Loud Power ....” from Advanced Specialties Inc. on Amazon.

Jeff Debes
 

Sounds good,
 thanks.


On May 27, 2020, at 9:59 PM, Stephen KO4CVU <goinfishin1952@...> wrote:

I paid $23.98 for “Barjan CB Amplified Loud Power ....” from Advanced Specialties Inc. on Amazon.

--
jeff.debes@...

Stephen KO4CVU
 

Jeff, In case you need a power supply, I found a 5 watt, 12 VDC one (#PS-12005) at All Electronics for$10.95. It sure beats the nine D cells that I had lined up in a piece of PVC pipe! Stephen