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Re: Nextion TFT

 

I'm trying to buy 7" , can somebody tell me if it's ok to buy this ..

English Version Nextion 7.0" HMI Intelligent LCD Tough Screen Module Display for Arduino LCD TFT Raspberry Pi ESP8266
? to Clipboard


73,
Vu3edg


On Sun, Jul 29, 2018, 4:02 PM hirosmb <hirosmb@...> wrote:
I bought it at eBay.


Spec:

// hiro, JJ1FXF



2018/07/29 19:26¡¢Ken <chase8043@...&²µ³Ù;¤Î¥á©`¥ë:

Hi All

Could someone possibly point me to a link to purchase the Nextion TFT and spec sheets?

73

Ken VA3ABN
Re: RFI Problem related by routing audio through K3 (uBitx)?

 

The combined effect of the rely mod and? the audio switch mod do help greatly.

If the DC switching scheme also used a pair of contacts to pull the floating TX+/RX+
to ground it would help as well.? It can be done with the N3GO two transistor mod.


Allison
Re: RFI Problem related by routing audio through K3 (uBitx)?

 

ABSOLUTELY! This is a no-no and needs to be corrected on all v3 PWBs. I noticed in the new design (v4) he does not use this T/R relay audio switching scheme.I suspect it was done in part to deal with the speaker thumping everyone has complained about. There are other ways to handle that issue and many are discussed at length in other posts. You need to cut the two traces that run that audio connection near the relay. One trace can be "cut" by simply removing R70. The other trace is the one just over that trace when the PWB is positioned with R70 down at the bottom. Then, remove C51 and tombstone it on the upper pad where it formerly was. Add a jumper wire between the top exposed end of C51 and the left pad where R70 was located. Now, that will completely eliminate the RFI in your audio on your PWB. The speaker thumping may in fact become worse after you make this mod. Farhan has made an easy improvement to switch off the audio on the newest version of the PWB. I hope this helps!
N2AJX?
Re: End Fed antennas w/ uBITX #ubitx

Warren Allgyer
 

Gordon,

There is no need to do the testing at high power. I simply terminated the transformer in a 2470 ohm load made up of a 2K and a 470, 1/8th watt resistors in series. My testing is done at a maximum of 1 mW so low power is fine.

The lowest loss 49:1 transformer that I have been able to construct uses BN-43-7051 cores and I have been able to get to 0.2 dB with them. For 160-20 meters I use a 14:2 ratio and for 20 - 10 a 7:1. With a true resonant half wave wire these cores get barely warm after a full minute of key down at 100 watts.

However(!!!), that 0.2 dB loss rises dramatically if the cores feed a reactive load and are not substantially better in that case than are the big toroids.

The best case for the EFRW (random end fed wire) remains a simple tuner.

WA8TOD
Re: need a new pc ??

Vince Vielhaber
 

If you buy it, it's "new" to you.

Vince - K8ZW.

On 08/01/2018 10:57 AM, Terry Morris wrote:
omitting the word "new" is more accurate. I have purchased several
refurbished Dell box PC's with great success. $300 is a great price to
pay for this PC.
--
Michigan VHF Corp.

Re: New uBITX Raduinos for sale #ubitx

 

One has been sold and shipped, still have the other one.

W0EB
Re: experience with Sunil VU3SUA's enclosures #ubitx

Bo Barry
 

Wow. Perfectly satisfied with mine.
I did remove paint a couple places to insure the case was grounded. No biggie.
A LOT of effort and material for a tiny price in my opinion.
73, Bo W4GHV since '54
Re: End Fed antennas w/ uBITX #ubitx

 

for the parallel resonant see:



Also:


As to what toroid for tuned usually iron powder type -2 or -6

However I use a L-network for monoband EFHWS.? I grind the number in a spreadsheet
make a coil using iron-powder or conventional solenoid coil and a capacitor with enough?
voltage rating (at least 2000V) and I'm off to the races.? One trick is if I don't have the
exact capacitor value needed I go with the next lower and parallel it with a section of
teflon coax (about 29.4pf/foot good to 2500V).? Also if vibration is not an issue the
Arco trimmers work.

For wide band trasnformers I tend to do a lot of build and test to see what works.
Depenign on how its would and the type (transmission line, hybrid or....) wire used
and many other parameters it may use different materials.? But its been measured
and tried a few ways for best result.? For the 1:49 I've had better result with
mu=125 (61ish material) or sometimes 43.??

One I have copied many times with good results is a multi ratio design by K3MT.
ITs part of his grasswire antenna but generally useful for many things.? The article
attached.? It would be a good 1:9 transformer for those wanting to try the
non-resonant 53ft or longer approach with a counterpoise.? Try the Grasswire
while your at it, its easy to install!

Allison

grasswire.pdf
grasswire.pdf

Re: need a new pc ??

 

omitting the word "new" is more accurate. I have purchased several refurbished Dell box PC's with great success. $300 is a great price to pay for this PC.
Re: End Fed antennas w/ uBITX #ubitx

Gordon Gibby
 

¿ªÔÆÌåÓý

Chuck, Alyson, and others: ?could I get a schematic of your parallel resonant tuning system? And could I get Alyson and or Warren to come yet on what permeability toroid is optimal?

Warren, I¡¯m not bright enough to know if your method of trying to figure out the results of the poor load is correct or not but it seems like a good first cut. ? ?

With a bunch of series/parallel resistors it should be easy to make a 2450 load, one could even do it with surface mount devices and have very little inductance I believe. ? ... ? 40 100,000 ?half watt resistors in parallel would give a really low inductance 20 W load.? ?Cost would probably be five dollars. ?No reason not to give it a try! ?

I dimly understood Alyson¡®s concerns about the back to back system, seems like it wouldn¡¯t be too hard to try it without the connection and with the connection and see if there¡¯s any difference. ?She knows way more than I ever willabout this kind of stuff

I¡¯m trying to see if I can work up the guts to put two of our off-center fed homebrew Balun ?systems back to back and figure out what our losses were! ?I¡¯m not sure I really want to know! ?

Gordon



On Aug 1, 2018, at 10:41, ajparent1/KB1GMX <kb1gmx@...> wrote:

Tim,

I did see that.? I appreciate that but I do have stock here thank you.

Allison

Re: End Fed antennas w/ uBITX #ubitx

 

I don't accept their .2db.? Also their process is only workable if they do the math to back out the?
mismatch loss.

Do I think their procedure is a good way to do it.? No.? Did that do the math to correct their data
for mismatch loss? No I see no mention or statement correcting for that.

If your argument is their test is wrongly done or has a incorrect conclusion then we do agree.

The process and procedures normally used to make that kind of measurement are likely
to disagree with their result and conclusions but will produce an accurate answer when
performed correctly.


Allison
Re: End Fed antennas w/ uBITX #ubitx

 

Tim,

I did see that.? I appreciate that but I do have stock here thank you.

Allison
Re: End Fed antennas w/ uBITX #ubitx

 

Chuck, I haven't yet built two 49:1 (one is not enough for the back to back test hi hi ), but I would use ferrites with permeability close to 800, not the powdered iron toroids like the red and the yellow you have selected (permeability is less than 10). I imagine that the inductance needed at 2500ohm needs to be very high. I might be wrong as I have not made yet one with such a high transformation radio, but I feel I am quite right, IMHO.


Il 01/ago/2018 15:56, "Chuck, N1KGY" <cwayers12@...> ha scritto:
On Wed, Aug 1, 2018 at 09:04 AM, Gordon Gibby wrote:

At any rate, it will be a huge improvement over what most of them had beforehand (NOTHING HF).? ?

I've gone this route also, Gordon.? I bought 4 uBitX units, with the intent that I will have several HF rigs for operating activities such as Field Day, and as HF rigs to loan to new hams.? For both of those use cases, a simple and efficient antenna is needed, and I've chosen to go with EFHWs using parallel-resonant matching units built around T82 toroidal inductors - T82-2 for the 40/30/20 meter units, and T82-6 for the 20/17/15/12/10 meter units.? I used magnet wire and mica compression 'trimmer' caps which I had NOS in my parts collection, so the total cost of each matching unit for me was? ~$10.? The enclosures turn out to be the most expensive part (~$2.75 each).

one year ago these hams?didn't know a resistor from a transistor.....

and that is a real WIN.
Re: experience with Sunil VU3SUA's enclosures #ubitx

 

Mine took about 6 weeks to get to Arizona, but it was worth the wait.? Good looking cabinet.? I agree with others that paint in the openings was heavy, but a little sanding with a Dremel tool took care of that.? Isn't that why you have those fun tools.? You need something to use them on!!? Also, I had to replace the on/off switch, but a trip to my local electronics supply store and $3.00 fixed that.? Besides, I found $40 worth of other stuff that I just couldn't pass up.

Moral of the story, be patient. His case is very well made and the extra parts are useful. I don't have to go looking in the junk box for a knob.?
Re: Spurious RF at beginning of CW transmission in the uBitx

 

¿ªÔÆÌåÓý

Dexter

On further examination the problem seems more insidious than just the single capacitor in the audio section.? Each bidlrectional amplifier has its owm small capacitor and apparently contributes to the problem.? It now looks like the TX ang RX power feed lines may need some conditioning.

Arv
_-_




Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------
From: Dexter N Muir <dexy@...>
Date: 7/31/18 5:45 PM (GMT-07:00)
Subject: Re: [BITX20] Spurious RF at beginning of CW transmission in the uBitx

So for BITX40 a diode in series with R111 blocks C11 from supplying Q16 as well. Now supply that diode direct from +12, no on/off of U1 and less current through K1 pin 3. R111 can then be either reduced (to 10) or eliminated/shorted.

Re: Spurious RF at beginning of CW transmission in the uBitx

 

¿ªÔÆÌåÓý

BTW:

in the original BITX20 these diodes were in eacht RX and TX path leading to the individual amplifiers.

Henning Weddig

DK5LV


Am 31.07.2018 um 11:25 schrieb n1kw@...:

Hi Arv,

I have not played with the radio much on SSB but suspect that is probably the cause for the "BITX Click". Simply adding a diode in series with R66 (cathode toward C64) should fix the problem.

It is important to note that the possibility of brief oscillation could occur in both the 12 and 45 MHz bidirectional IF amplifier stages because of the back feeding of power from C52 and C64 during RX-TX and TX-RX transitions. Diodes added in series with R52 and R66 should eliminate that possibility. The values of remaining bypass capacitors (0.1 uF) in the IF amplifiers and associated discharge paths should result in extremely short time constants and should not be an issue.

Cheers and 73,
Bob N1KW
Re: Spurious RF at beginning of CW transmission in the uBitx

 

So for BITX40 a diode in series with R111 blocks C11 from supplying Q16 as well. Now supply that diode direct from +12, no on/off of U1 and less current through K1 pin 3. R111 can then be either reduced (to 10) or eliminated/shorted.
Re: End Fed antennas w/ uBITX #ubitx

 

On Wed, Aug 1, 2018 at 09:04 AM, Gordon Gibby wrote:

At any rate, it will be a huge improvement over what most of them had beforehand (NOTHING HF).? ?

I've gone this route also, Gordon.? I bought 4 uBitX units, with the intent that I will have several HF rigs for operating activities such as Field Day, and as HF rigs to loan to new hams.? For both of those use cases, a simple and efficient antenna is needed, and I've chosen to go with EFHWs using parallel-resonant matching units built around T82 toroidal inductors - T82-2 for the 40/30/20 meter units, and T82-6 for the 20/17/15/12/10 meter units.? I used magnet wire and mica compression 'trimmer' caps which I had NOS in my parts collection, so the total cost of each matching unit for me was? ~$10.? The enclosures turn out to be the most expensive part (~$2.75 each).

one year ago these hams?didn't know a resistor from a transistor.....

and that is a real WIN.
Re: End Fed antennas w/ uBITX #ubitx

Warren Allgyer
 

Iz,

According to the email trail the 800 ohm load was selected because that was the maximum the test fixture could produce.?

The 6 dB figure comes from a simulation that I did in my lab. I calibrated the spectrum analyzer/tracking generator combination to 0 with a test cable assembly. I then shunted the S/A input with a 22 ohm resistor, resulting in about a 16 ohm load for the tracking generator. This reduced the displayed power level by 6.5 dB.

What the displayed value on the source RF meter in the test setup would be determined by the output characteristics of the RF source and the probe characteristics of the power meter, neither of which I have access to. I can be assured however that the reading would be wildly inaccurate.

WA8TOD
Re: End Fed antennas w/ uBITX #ubitx

 

We need an update in QST!? Was the 800ohm load selected to test the off-frequency characteristics of the 49:1 transformer? Il the load becomes 16ohm because of the transformer, the mismatch loss should be 2db, why you say over 6db?


Il 01/ago/2018 15:18, "Russ Hines" <russ@...> ha scritto:
Noticing this thread is taking on the epic proportions of a similar thread involving baluns on another forum some years ago.? It resulted in this paper:



Gentleman and lady, write a paper.
Russ Hines
JMS & Associates, Inc.
SBE CSRE
WB8ZCC
--
Reply to: russ@...
On 8/1/2018 9:04 AM, Gordon Gibby wrote:

?Do you know why they didn't use 49*50 ohms as their termination?? ?


I didn't read the email trail (sorry, just not enough time in this world) but it seems like you could make a dummmy load for that if necessary.? ?


What I have gleaned out of all this argumentation back-and-forth is that these things can have single-digit losses if working into a resonant piece of wire.? ?And that using a tuner is preferable. [I always work for lowest losses personally.]? Some of our newer hams locally are very limited in their "radio assets".? ?We'll be building uBitx's beginning in a bout 3 weeks.? We have already built 11 knockoffs of the Buckmaster off-center fed antenna and I hope to high heaven we built baluns etc with single-digit losses!!? ?At any rate, it will be a huge improvement over what most of them had beforehand (NOTHING HF).? ? Their skills are growing and I've learned a lot from all the discussions of various "issues" on this forum.? ?


After we get the "stock units" working, hopefully with v4 factory software and setting the oscillator numbers precisely in the code itself, we will begin on some of the most important improvements, which I haven't had time to get to quite yet....one year ago these hams?didn't know a resistor from a transistor.....


cheers,


gordon



From: [email protected] <[email protected]> on behalf of Warren Allgyer <allgyer@...>
Sent: Wednesday, August 1, 2018 8:53 AM
To: [email protected]
Subject: Re: [BITX20] End Fed antennas w/ uBITX
?

I have been asked by private message what it is about the QST Review test methodology that I found invalid. I constructed this explanation of their test in response and I would like to share it with the group.

The testers used a setup that is used by the ARRL Lab to test the loss of Antenna Tuners. When testing an Antenna Tuner the tuner itself converts whatever load is presented by the "Load Box" back to 50 ohms as a termination for the RF Source. The inline HP RF Power Meter is working in its natural 50 ohm domain and should be accurate within the specification of the meter.

When testing a 49:1 transformer however, there is no way to adjust the termination to 50 ohms. So, with an 800 ohm load selected in the load box as the authors specify in the email trail, the RF Source and the source power meter are operating in a 16 ohm environment. What the actual power out of the source is, and what power is indicated on the source power meter with a 16 ohm load, are determined by the characteristics of each box. It most certainly cannot be assumed to be 10 watts. The error in this step can easily be over 6 dB.

When the test therefore shows the transformer to have a loss of 0.2 dB, the actual loss could be as much as 6.2 dB.

The two transformer back to back test that I have documented does not suffer from a load mis-match and is therefore a far more appropriate way to do this measurement.
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