Date   

Re: ubitx v4 - CLK0,1,2 signal levels?

Adrian Chadd
 

hi!

On Wed, 17 Mar 2021 at 09:12, Jerry Gaffke via groups.io
<jgaffke=yahoo.com@groups.io> wrote:

A minor addendum:

When we say that these are 7dBm mixers, that means they work best when
the clock port is driven from a sine wave generator with a 50 ohm source resistance,
at an amplitude such that if it were instead driving a 50 ohm resistor the resistor
would be getting 7dBm of power.

The actual power into the mixer is a fair bit more complicated, as those diodes
are non linear devices. For this reason I recommended putting a scope at
the input of the 6dB attenuator and subtracting 6dB, not the input of the mixer.
Thanks for replying! I'm more curious about whether it's being pushed
too hard, rather than trying to improve things right now.

I'm thinking of making a VFO for an old tentec radio as its mechanical
VFO is busted, so I'm looking into impedance, loading, current, etc
right now and I'll need a buffer/match/attenuator setup here to match
the expected levels for the tentec.

Thanks!



-adrian
(kk6vqk)


Re: ubitx v4 - CLK0,1,2 signal levels?

Mark Erbaugh
 

FWIW, my personal uBTIX firmware has an option to set the output of CLK 2 (1st mixer) to 2mA or 8mA (which is the default in the stock firmware). I found that there wasn't much difference at 4 mA or 6mA, but between 2mA and 8mA, the radio had a slight reduction in receive level that made stronger signals easier to listen to.

73,
Mark, N8ME


Re: ubitx v4 - CLK0,1,2 signal levels?

Jerry Gaffke
 

A minor addendum:

When we say that these are 7dBm mixers, that means they work best when
the clock port is driven from a sine wave generator with a 50 ohm source resistance,
at an amplitude such that if it were instead driving a 50 ohm resistor the resistor
would be getting 7dBm of power.

The actual power into the mixer is a fair bit more complicated, as those diodes
are non linear devices.  For this reason I recommended putting a scope at 
the input of the 6dB attenuator and subtracting 6dB,  not the input of the mixer.

Jerry, KE7ER


Re: ubitx v4 - CLK0,1,2 signal levels?

Jerry Gaffke
 

Adrian,

Good question.
And one that has been pondered by quite a few people.

SiLabs AN619 says each Si5351 output can be programmed for 2,4,6 or 8 ma.
A square wave of 3v pk-pk centered on ground (dc blocking cap) has an rms voltage of 1.5v.
But 1.5v into the 50 ohms presented by the 6dB resistive attenuator on the uBitx
is 1.5/50=30ma, way more than the 8ma max the Si5351 can provide.
The 50 ohm output impedance spec in the Si5351 datasheet means that it can terminate
a reflection coming back to it, not that it can effectively drive a 50 ohm load.

Exactly how much power the mixers get would best be evaluated by looking at
the Si5351 side of the 6dB resistive attenuator with a good scope,
and subtracting 6dB from how much power you think you see there.
But what you see with the scope will not be square or sine, and may
vary with frequency.
Assuming an 8ma square wave into 50 ohms (8ma out when hi, 8ma in when low),
that works out to 8ma*8ma*50ohms = 3.2mW, or 2dBm of power into the attenuator.
It could be more, that 8ma is not very well spec'd.

The Si5351 may not be programmed for the highest level of 8ma.
As we increase the programmed output current, we see more crosstalk
between outputs since they are all powered from a single Vddo pin.
And that can create birdies and spurs.

>  The si5351 datasheet says its 2.2mA to 5mA

I assume you are looking at Iddox in table 3, page 5 of the datasheet,
the output buffer supply current going into the chip when driving a 5pf load.
That doesn't tell us how much current comes out of the clock pin
when driving a 50 ohm load.

The mixers use Schottky diodes, and so would want about 7dBm of power,
and we would want to see 6+7=13dBm of power going into the attenuator
from each Si5351 output.  We're well short of that.

The attenuators are necessary to terminate mixer products coming out of the clock port,
preventing them from reflecting back into the mixer and creating more mixer products.
More mixer products means more birdies and spurs.

Folks have tried adding buffers to the Si5351, didn't help uBitx performance much.
The mixers seem to work well enough as they are, somehow.   
Dynamic range on receive is limited by the audio preamp stage at Q70, not the mixers.
Mixer dynamic range on transmit is not really an issue.

I may not have all the above correct, let me know of any errors.

Jerry, KE7ER


On Tue, Mar 16, 2021 at 11:37 PM, Adrian Chadd wrote:

On Wed, 10 Mar 2021 at 05:54, Jerry Gaffke via groups.io
<jgaffke@...> wrote:

Sounds like an output cell on the Si5351 got (mostly) blown.
Looking at the upper left corner of the uBitx schematic,
CLK2 is adjacent to the 12v supply pin to the Raduino.
Any chance that the Raduino got shifted over one pin and power applied?

The series cap for CLK2 on the Raduino would have mostly blocked that 12v,
but just charging the cap could blow that IO cell.

I don't recall other reports here of Si5351 outputs getting blown like this.
I mean, anything is possible!

Out of curiousity, how much current are the clocks supposed to supply
into the three mixers? The si5351 datasheet says its 2.2mA to 5mA, but
eyeballing those mixers, it looks like it could be a bit more?


-adrian
(kk6vqk)


Re: Good place to tap for PTT-OUT #v5

Zvi Segal
 

I added additional relay and drove it from the Tx (+12V).   Use its contacts to deliver ground PTT to PA and isolate the uBitx.

Good practice is adding a reverse diode on the relay's coil to protect from surge voltage on disconnection.


Zvika 
4Z1ZV


Re: What is the BEST fist microphone to use the BITX 6.0

kg9hfrank@gmail.com
 

Pacific Antenna http://www.qrpkits.com/microphone.html

--
Frank, KG9H


Re: Good place to tap for PTT-OUT #v5

Dean Souleles
 

Hi Rob - look here...

BITX Hacks: Adding an External Linear Amplifier Control circuit to your uBitx

Use PTT to trigger a relay - then you can switch to whatever you need.  Important thing is to keep the amp isolated from the transceiver.

Dean
KK4DAS


Re: What is the BEST fist microphone to use the BITX 6.0

Jay - WS4JM
 

Stephen,

I use a D104M6 on my V3 µBitx. I get great reports with it, usually have the gain around 6-7. YMMV

Jay
WS4JM


Re: 1940 Sears Ham Radio Catalog

 

Classic..thanks for posting!


Re: Let the upgrades begin! #ubitxv6

Evan Hand
 

On Wed, Mar 3, 2021 at 08:28 PM, Evan Hand wrote:

I will keep looking and post it to the files section of the board if I find it.  You could also search there and on ubitx.net, though I have not found it yet.
Justin,

I finally got a backup 3.5" Enhanced Nextion display and was able to test the different versions of screen files.  Attached is the one that I am using.  You can see if it is more to your liking.

73
Evan
AC9TU


1940 Sears Ham Radio Catalog

Bob Lunsford
 

I never knew Sears had a Ham Radio oriented catalog
 

1940 Sears Ham Radio Catalog

 

https://www.waynekirkwood.com/images/pdf/Sears_Roebuck_1940_Radio_Amateur_Test_Equipment_Sound_Systems_Catalog.pdf

Enjoy a nostalgic look at the past



Re: 5.0" Nextion for uBitX V6 #ubitxv6 #nextion #ubitx6-help

Gyula Molnar
 

Hi Aaron,

You should read Ian’s KD8CEC page because he’s dealt with this display a lot in previous years.
Type in the search engine: http://www.hamskey.com/search?q=nextion

73, Gyula HA3HZ


UBitX/V0.20+ a nextion screen to be installed

Lal Jayasinghe
 

Dear Robert/AG6LK

Not-@-All,  Not-@-All,  Dear Robert & it  was rather a good gesture of you.
unfortunately we've, the  Govt.Supply of 220V A.C.  input so it is a separate power supply which I've to worry my head-over.

There was another Good Samaritan on the same group who wanted to know the version of my UBitX but then I shall go through the removing-the-cover and to have a peep on the board.

Hey Guys forgive me for not being Lazy,(Ha.....Ha....) Shall call back, but I am monitoring the  Group becoz I am a QRP Buff, though I have a TS430-S donated to me by Israel Amateur Radio Club/4X4WN. 

Be seeing you Dear Guys.

Thank You Mr. Farhan/VU2ESE for giving an affordable Txcvr

Good Day
73's
de 4S7LP/LAL J.


Re: ubitx v4 - CLK0,1,2 signal levels?

Adrian Chadd
 

On Wed, 10 Mar 2021 at 05:54, Jerry Gaffke via groups.io
<jgaffke=yahoo.com@groups.io> wrote:

Sounds like an output cell on the Si5351 got (mostly) blown.
Looking at the upper left corner of the uBitx schematic,
CLK2 is adjacent to the 12v supply pin to the Raduino.
Any chance that the Raduino got shifted over one pin and power applied?

The series cap for CLK2 on the Raduino would have mostly blocked that 12v,
but just charging the cap could blow that IO cell.

I don't recall other reports here of Si5351 outputs getting blown like this.
I mean, anything is possible!

Out of curiousity, how much current are the clocks supposed to supply
into the three mixers? The si5351 datasheet says its 2.2mA to 5mA, but
eyeballing those mixers, it looks like it could be a bit more?


-adrian
(kk6vqk)


What is the BEST fist microphone to use the BITX 6.0

mister35mm <mister35mm@...>
 

Hello boys and girls...

What I want to know is:-

1. What is the BEST fist microphone to use the BITX 6.0 ? Ideally, I want something I can use, WITHOUT modifying the radio. I have an Astatic D104 fist microphone, which has amplification, but no speech processor or compression.

2. Has anyone installed an internal ATU or a battery pack.

Regards

Stephen
G7VFY


Re: Good place to tap for PTT-OUT #v5

_Dave_ AD0B
 

An easy place is  the the TX/rx relay driver transistor I went from the base of that transistor and added in a second driver transistor and relay. You might just need the transistor and drive the output to your amp or what ever. 
--
73
Dave
ADOB
Raduino bracket and Ham_Made_Keys


Re: Let the upgrades begin! #ubitxv6

Robert AG6LK
 

Hi Justin,

I really like your setup. It's pretty sweet looking. I just ordered a v6 yesterday from Gigaparts. It'll be here on Friday. I  just ordered the Mic that you suggested from Amazon thanks for the tip.
I also ordered a 3.5" Nextion enhanced display last week and it was just delivered yesterday. what's enhanced about it I don't know yet, I guess I'll see, I'm not sure how the Nextion sets up to the v6. I've seen that other people have put the 3.5" Nexton in their v6, so I know that it can be done. The only problem is they never explain in their post how they installed it. I was hoping you would explain how you installed yours, Can you also point me in the right direction for the correct tft file? I would greatly appreciate it. 

Thanks in advance, 73.

Robert, AG6LK


Re: Good place to tap for PTT-OUT #v5

Jerry Gaffke
 

Yes, the TX rail has 12v on it whenever the rig is transmitting, 0v when it is not.
Probably your best choice, and easy to tack a wire on it.

Does your amplifier really want a 12v signal, or something more like 5v?
How much current will the amplifier draw from this signal?

I would think about limiting the current somehow, perhaps a series resistor inside the uBitx.
Otherwise a miss-wire in the cable could cause 10 Amps to flow, and lots of smoke.

Jerry, KE7ER


On Tue, Mar 16, 2021 at 10:38 AM, Rob French (KC4UPR) wrote:

I'm looking to add a PTT-OUT to the back panel of my uBITX, to control e.g. an amplifier or a switch to isolate an external SDR during transmit.

My thought is to grab C154/D11 or one of the other filter-switching relay circuits.  Those look like easy places to tack a short wire to without having to completely disassembly my uBITX.

Two quick questions:
(1) Dumb question... but that junction does provide what I want, right?  i.e. +12V on transmit.
(2) Any downsides to tapping the +12V on transmit, from that location?  e.g. some RFI effect

Thanks,
Rob KC4UPR


Re: 5.0" Nextion for uBitX V6 #ubitxv6 #nextion #ubitx6-help

K2ICC
 

Upgrade the regulator to feed the screen needs.


On Tue, Mar 16, 2021 at 6:28 PM Aaron K5ATG via groups.io <k5atg=yahoo.com@groups.io> wrote:
I'm wanting to upgrade to a larger Nextion and I came across this 5" one.
5.0" Nextion NX8048T050 TFT HMI USART Intelligent Touch Display LCD Module 16M

5" Nextion Display

Would it work with the uBitX v6 and would it be much harder to use than the 2.8 Nextion? 
Also, would a 5" Nextion be able to display more than the 2.8" or is everything on the screen is magnified? 
--
'72
Aaron Scott
QRPARCI# 16443
GQRP# 16389
4SQRP # 1080


Re: 5.0" Nextion for uBitX V6 #ubitxv6 #nextion #ubitx6-help

Evan Hand
 

Aaron,

I have not used a 5" screen.  I have used a 2.4", 2.8", 3.2", and a 3.5" Nextion.  They have all worked the same to the most extent, though some of the Nextion programs have more features than others.  I could not see any issue with going to the 5" display as long as you can find the right Nextion files for it.  There are some in the files section here and on ubitx.net.

One key thing to consider is the supply for the larger screen.  I would recommend adding a second 5volt regulator just for the larger screen.  I have seen them mounted to the case for heat transfer and then run the power to the screen with a common ground for the data lines.

To get a feel for what is in the Nextion program, you can use the Nextion editor and load the .hmi file then run in debug mode.

Above are my thoughts, you may want to wait to hear from someone who has used the larger screen.
73
Evan
AC9TU

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