Date   
Re: Arduino v1.28 for BitX40 released #bitx40

Allard PE1NWL
 

Just to avoid any confusion: Please note that this topic was for BitX40, not ubitx.
The file ubitx_cat.ino won't work on a BitX40.

Back to Praba's question:
The stock firmware v1.01 for BitX40 only provides basic LSB functionality.
So no cat control.
(v1.28 doesn't support cat control either, though)

73 Allard PE1NWL

Re: Interesting antennas for QRP

 

That's a great antenna, I have one right in front of me. The price is right also. I don't what the difference between 1:49 vs 1:64, but both seem to work the same, you just have to cut the wire to match the SWR.

Joel
N6ALT

Re: Interesting antennas for QRP

 

Let me rephrase that, I know what the difference is between the two, I just don't know if one performs better than another as I use both and can't tell any difference in performance.

Joel
N6ALT

Re: End Fed antennas w/ uBITX #ubitx

Warren Allgyer <allgyer@...>
 

Got it Jerry. I read your voltage as peak to peak rather than peak. My bad.

The resonant frequency of a wire that is multiple half wave lengths long does not occur at integer multiples of the base frequency. For example, an antenna cut to resonate at 3.6 MHz will not also resonate at 7.2 but at a higher frequency. How much higher depends on the characteristics of the wire but it will certainly not fall naturally within the 40 meter band. There will be a cyclic pattern visible from these resonances on the wide range VIA.

The fact that the antenna you have has resonances that fall at integer multiples says there is something else going on there. I suspect this is the function of the 6 turn inductor which would have the effect of electrically lengthening the wire, and lowering the resonant frequency, with greater effect at successively higher harmonics of the fundamental.

A length of 50 ohm coax attached to this adds yet another cyclic pattern of impedances that will cycle between the actual impedance at the transformer at any point where the coax length is an integer multiple of a half wave, to the transformed impedance value of the cable combined with the transformer at any odd multiple where the cable is a quarter wave.

So between the varying impedance of the transformer itself, that of the loaded wire, and the length of the cable between the rig and transformer, there is likely a brew which will give multiple resonances that fall within the ham bands. There are, however, combinations and frequencies that will present highly reactive, high VSWR loads for the transformer which will multiply its losses by a factor of 10 or more. The insidious thing about these frequency combinations is the VSWR  will remain artificially low due to those very losses. So, in operation, you actually have no way of knowing, other than transformer heating whether you are operating at a real, low loss VSWR null or one produced by high losses resulting from a mismatch.

If I could the VIA plots of the transformer/antenna with a very short cable, and again with the operating length cable, I could know which low VSWR points are real and which are simply created by loss. Short of that, if it makes contacts and the toroids don't explode (some have!), you are good to go.

WA8TOD

Re: End Fed antennas w/ uBITX #ubitx

Arv Evans
 

Seems that most EFHW impedance matching transformers are wound on ferrite
or powdered iron cores.  For experimental purposes it should be possible to use
air-core (PVC or Acrylic, or wooden cores) transformers.  The number of turns for
a given inductance is not that much different between metallic core and air core
transformers.  This is especially true if the air-cored units are wound on toroidal
forms.  Those with a lathe could easily turn toroidal formers from wood or plastic.

Possible advantage of winding one's own matching transformers is that modification
and adjustment of impedance transformation is more easily done if the transformer
is not potted inside a plastic box.  Winding one's own transformer might also allow
connection of a variable capacitor in parallel with the antenna side to make it into
a end-fed wire tuner (L-match) to achieve a more perfect match

Arv  K7HKL
_._
.


On Fri, Aug 3, 2018 at 8:24 AM Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:
Warren,

My dummy load is twenty 1k metal film resistors of 3 Watts.  So 50 ohms at 60 Watts.
With around 50 volts peak going in (100 volts peak-to-peak), that's on the order of  50*0.707 * (50*0.707) / 50 = 25 Watts of RF.
At times I cranked the RF up to 100 Watts.  The toroids are admittedly more massive than the resistors, but no discernible heating
in the toroids does give a little added confidence to the conclusion that we are not burning much power there.

> The cyclic VSWR pattern is very likely the result of the 100 feet of coax

As I've said earlier, when I measure my antenna system with just a few feet of coax between the matchbox and the vector impedance analyzer,
I get the same peaks and valleys in the VSWR as shown on the website but the peaks are more pronounced.   
The peaks and valleys are due to resonance in the wire, not something about the coax.  
Adding coax primarily affects frequencies at which the matchbox has a high VSWR, when losses in the coax become significant.
On a positive note, the coax does lower the VSWR at somewhat off resonant frequencies, allowing use there without a tuner.
Most non-WARC bands are usable across the entire band without a tuner even with a short coax, 80m and 10m are the primary exceptions

> It is a puzzle to me that the antenna shows resonant characteristics on non-harmonically related bands like 30 and 15 meters.

30m is near the third harmonic of 80m:  3.6*3 = 10.8mhz       Though far enough away that you still want to use a tuner with this antenna
21mhz is near the 6'th harmonic of 80m:   3.6*6 = 21.6mhz    That one's usable without a tuner.

> Additionally, you were using the "2K" model 

These are both rated at "1kW ICAS".   Danny (and his competition) does offer 2kW transformers, I have no idea what's inside them.
I have nothing here capable of more than 100W, reports are that at 1kW the toroids do heat up badly if you hold the key down too long.
Since the box is sealed and up on the roof somewhere, your primary indication is that the SWR starts rising.
On bands such as 30m where the wire is not quite resonant, you definitely don't want to go more than a few hundred Watts.


>  And this combo was terminated in a perfect resistive load. When terminated in the wire the load will be very different
>  and highly reactive on some bands. As such the transformer losses will rise dramatically but the apparent VSWR
>  will not due to the losses. I sure would like to see a VIA plot of the wire itself through the transformer.

At any integer multiple of the fundamental, the wire is resonant and purely resistive.
I'd guess that this is closer to 3000 ohms than 2500 ohms.
At resonance the measured SWR of the antenna system when using just a few feet of coax
is down at 1.2 or less, suggesting negligible losses.  (See the published charts).
Losses do rise when somewhat off resonance, as is the case with 30m.

Jerry, KE7ER


On Fri, Aug 3, 2018 at 04:46 AM, Warren Allgyer wrote:

Jerry and Gordon

Great data Jerry! I too am scratching my head over some the entries but it is a start and good to know.

I don't understand the impedance variation of the terminated pair and the terminated transformers individually. My test did not show that and it raises a bit of a red flag. I also looked more closely at the SWR table published by the manufacturer. Having stared at similar VIA outputs in my lab I noted two things. The cyclic VSWR pattern is very likely the result of the 100 feet of coax, very close to a half wave at 80 meters, alternating between a quarter wave transformer and a half wave at harmonics of 80 meters or whatever is the actual length of the coax. Notice that these peaks are attenuated as you approach 30 MHz. That is indicative of the loss in the system at those frequencies. The lower the loss of the transformer the higher and more uniform would be these peaks.

A final note on the heat: the numbers you show indicate losses on each individual transformer between 0.2 and 0.8 dB which is significantly better than I measured using the spectrum analyzer/tracking generator. As such I would not expect much heating from the 5-8 watts of input power you used. Additionally, you were using the "2K" model which uses a double stacked transformer for additional heat dissipation capability. And this combo was terminated in a perfect resistive load. When terminated in the wire the load will be very different and highly reactive on some bands. As such the transformer losses will rise dramatically but the apparent VSWR will not due to the losses. I sure would like to see a VIA plot of the wire itself through the transformer.

Your antenna appears to accept power much better than I suspected. The strategically positioned 6 turn air wound coil has a lot to do with that because it is what allows the wire length to change electrically and let harmonically related bands fall into the integer related even harmonic. It is a puzzle to me that the antenna shows resonant characteristics on non-harmonically related bands like 30 and 15 meters. That may be the witchcraft element of the coil combined with a strategic length of coax feedline.

Thank you for doing and reporting on all of that work! Great job.

WA8TOD

Re: experience with Sunil VU3SUA's enclosures #ubitx

Kevin Rea
 

Hi Sunil,
Do you have any plans to make a case that will House a 3 1/2" or 5" Nextion display ?
Kevin Rea
K6REA

Re: Interesting antennas for QRP

ajparent1/kb1gmx
 

There are some general reasons for that.  One being the 1:64 transformer is more difficult
and most installed wires are at a lower height so the feed point resistance is lower.

Also 50*49 is 2450,  50*64=3200  most wires are in that general range such that
there is overlap.    If the wire is thinner and higher the 64 transformer may be better
but for most installations the 49 will do fine.

Also 1:36  (50*36=1800) is a doable transformer (2t:12t wire) as even for a nominal
2500 ohm wire the mismatch is 1.4:1.  And low wires as would be typical for
field installs at lower frequencies like 80 and 40M are lower in feed point resistance.

Allison

my mic

hirosmb <hirosmb@...>
 

This took for a hour. :)

// hiro, JJ1FXF

Re: End Fed antennas w/ uBITX #ubitx

Jerry Gaffke
 

With a short coax, I saw the same pattern of VSWR peaks and troughs as a long coax, 
just that the peaks were higher with the short coax.  As expected.
 


On Fri, Aug 3, 2018 at 08:43 AM, Warren Allgyer wrote:
If I could the VIA plots of the transformer/antenna with a very short cable, and again with the operating length cable, I could know which low VSWR points are real and which are simply created by loss. Short of that, if it makes contacts and the toroids don't explode (some have!), you are good to go.

Re: Interesting antennas for QRP

ajparent1/kb1gmx
 

For some reason there is a religion for squares of integers 6/7/8 yielding
one to 36, 49 and 64.

There is no reason why the winding could not be 2t:13t for 6.5 turns ratio or 1:42.5 or
2 to 15 turns for 7.5 ratio or 1:56.25.  The latter  would match 2813 ohms well.

Transformers can be used in a compound series arrangement like to 1:9
in parallel for primary and series for secondary to get 1:36.  Many other
possible configurations can be configured.

Allison

Re: Front Panel Stereo Socket Board Wiring Layout

Dave New, N8SBE
 

Sunil,

Thanks for the update.

An issue: I found on my front panel PCB that pins 2 and 5 on the headphone jack were not connected together (tip and ring), so that I only heard audio in the left side of my headset.  I jumpered those two pins together, and now I have audio in both sides.  It still properly disconnects the speaker when the headset is plugged in.

Have you made an update to the front panel PCB, since I received mine (a few weeks ago)?

Connector discussion: I ended up ordering and using a Dupont kit for the female bodies/sockets and right-angle pins.  They worked OK, but the volume connector hits the main PCB standoff, and the mic connector is a very tight fit against the chassis-mounted round 4-pin XLR connector body.

Would the TVS connectors be lower-profile?  Suggested US source for those connectors?  Any model/order numbers? I got my Dupont kit:


and Inwiss crimper tool:


from Amazon US, free two-day prime shipping.

We have a group of folks here that ordered a quantity buy of uBitxes, and some have ordered and/or received cases, but I'm one of the first to actually assemble one and get it on the air.  We are having a meeting in September to address uBitx build hints and kinks, and I'm putting together a log of issues/fixes to help them get their uBitx boards up and installed in cases properly.  I thought to share my Dupont kit to anyone that needed connector shells and sockets, but if a TVS kit is better, I'll go that route.  So far, searching for TVS connectors on Amazon hasn't turned up a kit similar to the Dupont connector kit I have.

There's another thread on here with my notes, in case you've not come across it, yet:


Volume control connections: I figure I'm not the only person that even after doing some head-scratching trying to figure out which pins where the 'high" and "low" pins on the volume control, that I managed to get it backwards, and was rewarded with a VERY load noise when I first powered the radio on with the control turned completely CCW.  It would be helpful to have a photo of the actual back of the volume control, showing which pins are "high" and "low" ("mid" is hopefully kind of obvious).

XLR Mic connections:  There is no information as to which pins on the XLR jack are to be assigned to Gnd, PTT, and Mic.  I did a Google search, and found a few which seemed to agree that Pin 1 is GND (natch), and that Pin 2 is Mic, and pin 3 is PTT.  At least that's how I wired it.  I haven't found a pre-wired 4-Pin XLR mic to try, but it appears that Cobra CB mics were wired this way, and there may be some some of industry standard for wiring 4-pin XLR PTT mics, but I haven't found it.

Thank for all your effort to bring us a really nice case for the uBitx.  Mine is dark green, and sets off the green LCD display nicely.

73,

-- Dave, N8SBE

-------- Original Message --------
Subject: [BITX20] Front Panel Stereo Socket Board Wiring Layout
From: "Sunil Lakhani" <vu3sua@...>
Date: Fri, August 03, 2018 1:03 am
To: BITX20@groups.io

The front panel stereo socket board wiring layout for universal case for ubitx has been published. 8 pin relimate female to female connectors are used for digital and analogue connectors on ubitx board and the front panel board.
For mic ptt, volume, encoder, speaker TVS connectors have been used with right angle pins.The case comes now complete with these accessories too.Those that want the wire kit or complete kit with board can get from our website amateurradiokits.in

Pictures for front panel board.

https://groups.io/g/BITX20/photo/6439/7?p=Name,,,20,1,0,0

https://groups.io/g/BITX20/photo/6439/8?p=Name,,,20,1,0,0

use any wire but follow the wire sequence. 
Kindly report if any mistake found.

best of 73s
Sunil  VU3SUA

Re: Interesting antennas for QRP

 

Allison,

I can't speak for others, but the reason I use squares of integers is because I can do the math in my head:-) You are right, no reason why it can't be a different ratio, just means trimming the antenna length a little. Still, it would be best to keep the length of wire close to a theoretical 1/2 wave length for best efficiency, I would guess.Anything in the 1:36-64 range should be good for the transformer.

Joel
N6ALT

Re: any tips for debugging RFI issue? #ubitx-help

ajparent1/kb1gmx
 

That is a 1:9 random wire box.  Expect RF on the coax if the ground lug is not used with a .25 wave wire.

The SWR may be good with the wires in use but you have an off center fed antenna and RF on the coax
is not much better.    

For both grounding the braid and using a Air or ferrite choke at the ground point to the radio is advised.

Using a choke at the match box will require a counterpoise to be used or the antenna may be ineffective.
I also expect the SWR will change.  You need a .25 wave counterpoise with that matchbos and the coax
is not a good choice to do that service for the problems you are already having.

Your likely have a lot of RF on the coax and that is a source of the problem.
You are up against the wall (townhouse and all) for antennas and I get that.  

Things to try...

First and foremost use a counterpoise wire at the matchbox they provide a lug for that
the hanger hook is that in the picture.   The wire should be around 16.5ft for 20M.

Try attaching to the radio chassis itself a wire maybe 16-17ft (quarter wave) to force
the case to a current node (sorta ground).  Just lay the wire out straight on the floor
or ceiling (if ground floor) as a test.  See if that helps 20M (likely makes other bands worse)

One thing you might try is replace the matchbox with a vanilla 20M center fed dipole (two 16.5ft wires)
even if temporary.  If your high enough one of the wires can just dangle (forms a center fed inverted L).

Or replace the matchbox with a 1:49 type and use a 66-68ft wire (half wave end fed and working on harmonics)
You may still have RF on the coax but a lower magnitude and maybe less troublesome.

Also make sure the board and the connector are electrically connected to the metal case, try putting
the cover on as well but external wires will need to be choked with ferrite.

For 1:9 baluns there are a few magic lengths that work better for some bands or all.
table attached has that info.

Also that arrangement in the all band form requires a tuner at the radio as not all bands will match well.
A tuner does not help the RF in the shack issue, its there ot keep the final intact.

Let us know her if and of it helps.  I;m sure there are others having similar issues.

Allison

Re: End Fed antennas w/ uBITX #ubitx

Doug W
 

On Fri, Aug 3, 2018 at 10:43 AM, Warren Allgyer wrote:
The fact that the antenna you have has resonances that fall at integer multiples says there is something else going on there. I suspect this is the function of the 6 turn inductor which would have the effect of electrically lengthening the wire, and lowering the resonant frequency, with greater effect at successively higher harmonics of the fundamental.
You pretty much got it.  That is how Danny (myantennas owner) explains it in a blog post at https://myantennas.com/wp/efhw-8010-is-this-the-ultimate-magic-antenna/ .  I referred to it way back in post 54967 but at the speed this thread was moving then it was easy to miss.
--
www.bitxmap.com

Re: Interesting antennas for QRP

ajparent1/kb1gmx
 

That's worked for me at least.

Of the wire is already trimmed for say 14.2  changing the transformer should show a different SWR
for the real feed point resistance.  Resonance should not change for different transformers save
for internal wire lengths.   Of course we can tweak the wire to mask that but resonance suffers
and coax shield currents rise.

What I've done is make a bridge and actually measure the antenna wire and its pretty interesting
how it can vary with height.  That was an exhausting project due to need to drag gear to the yard
and build and validate a remote bridge.  Lots of up and down, batteries, and no small amount of
retesting to validate results.

Allison

Re: Tinny sounding electric miss on uBitx

ajparent1/kb1gmx
 

Tim, your the go to then as you know know why its important. ;)

Yes the BITX (20/40/17...) are similar but not the same as uBitx.

The biggest change is the second conversion as that opens up
a few ways to alternately do things like change sideband.

Allison

Re: Tinny sounding electric miss on uBitx

ajparent1/kb1gmx
 

Its possible someone got standard HC49... not the shorter 49u like mine.  it actually does make a
difference as the quartz inside has a different cut.

Premium build, no.  It has all the bugs.

Allison

Re: Interesting antennas for QRP

SV9CVJ Nikos
 

This is my portable antenna and coupler :  https://m0ukd.com/homebrew/baluns-and-ununs/end-fed-half-wave-antenna-tuned-coupler-efhw/

73 Nikos de SV9CVJ

Re: Interesting antennas for QRP

Jerry Gaffke
 

Allison,

I haven't messed with it, but Kees' AQRP VIA includes the following feature:
"Calibration data (Open/Short/Load) is captured and recorded for all frequency steps between Start and Stop Frequency. This allows data to be recorded at the end of a transmission line, effectively eliminating the coax from the computed and displayed data. These data values are sent to the PC when requested."
That could avoid lots of trips up to the roof.  
Though I'd tend to do a direct measurement to confirm that measurements via coax are accurate enough. 
Jerry


On Fri, Aug 3, 2018 at 09:56 AM, ajparent1/KB1GMX wrote:
What I've done is make a bridge and actually measure the antenna wire and its pretty interesting
how it can vary with height.  That was an exhausting project due to need to drag gear to the yard
and build and validate a remote bridge.  Lots of up and down, batteries, and no small amount of
retesting to validate results.

Re: Additional Boards supplied with Case V3

Arvo W0VRA
 

On Thu, Aug 2, 2018 at 01:43 PM, <doncoulter@...> wrote:
...thee small pcbs that came with my kit...
Hello!

Can you post pictures of the small pcbs?  Did you mean "three pcbs" or "the pcbs"?

Thanks!