Date   

Re: Ubitx batteries / charger #ubitx

Daniel Conklin <danconklin2@...>
 


Re: Ubitx batteries / charger #ubitx

Arv Evans
 

George

There seems to be a potential for problems, unless I have misread what you are planning
to do.  If using only a single Li-Po or Li-Ion cell (3.8 to 4.2 volts) you can charge them with
relatively simple chargers but there must be voltage limiting in the charge scheme to insure
that the voltage never exceeds the manufacturer rated voltage (usually 4.0 volts). 

If using multiple 18650 Li-Ion or Li-Po cells you have to manage the voltage on each individual 
cell during charge to insure that no cell exceeds the rated voltage.   While I abhor the "it won't
work" and the "it will explode" scare tactics, this is one place where the nay-sayers may be
justified.  Over-voltage charging of Lithium based cells has been documented as a cause of
overheating and possibly fire. 


The small brick style cell phone auxiliary power banks usually include built-in charge control
circuitry that protects the Lithium cells from abuse.  This makes them relatively safe for most
applications. 

Most Li-Ion and Li-Po 18650 type cells include built-in FET switching that prevents discharge
to less than 2.0 volts.  If you do manage to discharge your Lithium based cells all the way to
zero they may refuse to accept re-charging current and thus become unusable. 

There are charge management boards available from several vendors.  These are needed
if you want to make up your own Lithium based battery packs that use multiple cells in series.



Maybe this helps...?

Arv
_._


On Fri, Apr 19, 2019 at 12:49 PM George Blass via Groups.Io <georgeblass=icloud.com@groups.io> wrote:
Hi All

I’m designing my case and have a question. I plan on using 18650 batteries inside the case with this voltage regulator. 

Voltage regulator

Then for charging I’ll have one of these inside the case. 

Charger

My plan is to have everything inside the case with just the charging and USB ports exposed. This way to charge up the batteries you would just plug it in like a cell phone. 

Will this work?  Am I missing something?

George


Re: Confused about how AGC works?

Jerry Gaffke
 

From 
    https://en.wikipedia.org/wiki/Automatic_gain_control
"Automatic gain control (AGC), also called automatic volume control (AVC), is a closed-loop feedback regulating circuit in an amplifier or chain of amplifiers, ..."
A google search for "AGC vs AVC" shows they are considered synonomous in radio design (but not for power grids), and that AGC is the more modern term.

In this forum, all such circuits for receivers have been getting referred to as AGC.
For some reason, the term AVC has only been used in this forum for automatic level control while transmitting
(Except for these posts from MRM.)
Works well for me, as few of us care that much about AVC while transmitting.
I suggest we keep it that way. 


Anyways, regarding the various AGC schemes:

There is this AGC kit from Sunil, it detects audio, and uses that to somehow attenuate the signal in one of the IF amps.
    https://amateurradiokits.in/product/agc-kit-for-bitx-and-ubitx/
Unfortunately, nobody seems to know how to hook it up:
    https://groups.io/g/BITX20/topic/4809028#65586
I'm sure it's easy enough to resolve with a quick email to Sunil (he monitors this forum).
And is definitely a contender, especially if you are already ordering one of the excellent Bitx40/uBitx enclosures from Sunil.

There have been several other AGC kits made available.
Let us know if any are still active, other than Sunil's and the one from   https://shop.kit-projects.com/

An AGC scheme that attenuates audio is a perfectly fine solution.
As stated in my previous post, one that attenuates RF (or IF energy) instead of audio
can give better dynamic range, but is in some ways more complicated and error prone.
An audio only AGC scheme could be mounted on the back of the volume pot, with the only
additional wire required being one to supply power.  No worries about coax and such. 
If you never hear stations so strong that they are still distorted after you turn down the volume knob
on your stock uBitx, you don't need the extra dynamic range offered by an RF (or IF) attenuated AGC.

And if you occasionally do, that could be taken care of with a manual RF gain control,
which could be just a 1k pot in the received RF from the antenna.

Jerry, KE7ER



On Fri, Apr 19, 2019 at 11:21 AM, MadRadioModder wrote:

As discussed before…

 

“An AGC circuit (automatic gain control)  turns the volume down for you when a strong station shows up like that.”

 

That’s known as AVC or “Automatic Volume Control”… not necessarily AGC.

 

MRM


Ubitx batteries / charger #ubitx

George Blass
 

Hi All

I’m designing my case and have a question. I plan on using 18650 batteries inside the case with this voltage regulator. 

Voltage regulator

Then for charging I’ll have one of these inside the case. 

Charger

My plan is to have everything inside the case with just the charging and USB ports exposed. This way to charge up the batteries you would just plug it in like a cell phone. 

Will this work?  Am I missing something?

George


Re: No Boot-Up (after spikes)

Ted
 

"If it is gets stuck at firmware version I would suspect either a defective si5351 clock generator or an issue with the i2c bus (A4/A5 from memory). Check for shorts, and if you have a scope check that you get a 3.3v swing on the two i2c signal wires."

My scope seems to be acting up and hasn't been very helpful lately. I do get ~3.2v on a DVM AC reading on the A4/A5 pins of the Nano itself.

I also found the Raduino clk2 pin grounded out to pin 4 next to it. It fails to explain a similar failure on the backup Raduino board unless I fried 4 other Nanos first (which can't be ruled out until we know).  So, while I have two brand new Nanos in packages I could build and put together, I have no further Raduino boards to try except for the one that's built into the other radio that I don't want to tear apart.

Maybe it's time to get a new spare Raduino that has not been put in a questionable circuit since repaired. Would anyone care to recommend the best aftermarket Raduino clone?

- Ted


Re: Confused about how AGC works?

Jack, W8TEE
 

Yep...seems to be a lot of confusion on this point...


Jack, W8TEE


On Friday, April 19, 2019, 2:21:43 PM EDT, MadRadioModder <madradiomodder@...> wrote:


As discussed before…

 

“An AGC circuit (automatic gain control)  turns the volume down for you when a strong station shows up like that.”

 

That’s known as AVC or “Automatic Volume Control”… not necessarily AGC.

 

MRM

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Friday, April 19, 2019 11:14 AM
To: BITX20@groups.io
Subject: Re: [BITX20] Confused about how AGC works?

 

Here's my shot at a quick summary regarding AGC circuits for the Bitx40 and uBitx
Opinions may vary.

When tuning across the band with a stock radio, you might run across a weak station
and turn the volume up to hear it.  Then a local QRO station responds and
you have to rip the headphones off to protect your ears, or be very quick in reaching
for that volume control.  An AGC circuit (automatic gain control)  turns the volume down
for you when a strong station shows up like that.

This is an early version of Don's (ND6T) AGC circuit:
    https://groups.io/g/BITX20/message/68037
Still viable, works well enough, simple and easy to build from scratch.
Really strong local signals can still be annoyingly loud, though much less so.

Don refined that FET shunt attenuator design by adding a FET series attenuator
to get additional dynamic range, keeps even the strongest stations down in volume.
    http://www.nd6t.com/uBITX/AGC.htm
It is a bit more complicated, but performs better.
Was kitted up by Kees (no longer available),
and is now available from  https://shop.kit-projects.com/

Either of the above AGC circuits will work on the Bitx40 or the uBitx.


Don's design attenuates the RF signal as it comes in from the antenna,
using a control signal derived from the audio. 

Most of the other AGC designs presented in this forum (there have been a
half dozen or so) attenuate the audio after the audio pre-amp, simple and
works well enough to protect the ears, and you avoid the tricky business of 
attenuating the RF path.  Here's a very early example of this approach:
    http://bitxhacks.blogspot.com/2016/11/agc-for-bitx.html

Attenuating the RF path is preferred, since the stock receiver dynamic range
is limited primarily by that audio pre-amp, and also to some extent by the IF amps
and mixers.  Don's design reduces the signal right where it comes in from the
antenna jack, so nothing in the radio will get overloaded and cause distortion.  

So an AGC design with attenuation in the audio stage works to protect the ears,
but strong signals may be distorted enough to be unintelligible.  With RF 
attenuation, strong signals remain undistorted.

All successful AGC circuit designs presented in the forum thus far detect the
incoming signal level just before the volume control.  Signal detection must occur
after the 12mhz crystal filter, otherwise we would also detect strong nearby stations
that the crystal filter rejects.  Detection of audio is not quite ideal since it takes time for
the signal to arrive there, so there will be a brief pop when a strong signal shows up
before it is properly attenuated.  But detection of 12mhz RF between the crystal filter and the
demodulator is difficult, because the unshielded 12mhz BFO on CLK0 will sneak into
our AGC signal detector and look like a very strong signal.

Here's an example of a well regarded AGC scheme for a high performance receiver:
    http://www.ka7exm.net/hycas/hycas_200712_qst.pdf
It's about as complicated as an entire uBitx receiver.

Jerry, KE7ER



On Thu, Apr 18, 2019 at 06:43 PM, Curt wrote:

check this out - this is a similar version of the same circuit

http://www.nd6t.com/bitx/AGC

the main idea is sampling the audio, feeding the transistor to boost this signal.  the 2 diodes develop a rectified signal based upon the audio, and this is used to bias a MOSFET used as a variable resistor. 


Virus-free. www.avg.com

--

…_. _._


Re: Confused about how AGC works?

MadRadioModder
 

As discussed before…

 

“An AGC circuit (automatic gain control)  turns the volume down for you when a strong station shows up like that.”

 

That’s known as AVC or “Automatic Volume Control”… not necessarily AGC.

 

MRM

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Friday, April 19, 2019 11:14 AM
To: BITX20@groups.io
Subject: Re: [BITX20] Confused about how AGC works?

 

Here's my shot at a quick summary regarding AGC circuits for the Bitx40 and uBitx
Opinions may vary.

When tuning across the band with a stock radio, you might run across a weak station
and turn the volume up to hear it.  Then a local QRO station responds and
you have to rip the headphones off to protect your ears, or be very quick in reaching
for that volume control.  An AGC circuit (automatic gain control)  turns the volume down
for you when a strong station shows up like that.

This is an early version of Don's (ND6T) AGC circuit:
    https://groups.io/g/BITX20/message/68037
Still viable, works well enough, simple and easy to build from scratch.
Really strong local signals can still be annoyingly loud, though much less so.

Don refined that FET shunt attenuator design by adding a FET series attenuator
to get additional dynamic range, keeps even the strongest stations down in volume.
    http://www.nd6t.com/uBITX/AGC.htm
It is a bit more complicated, but performs better.
Was kitted up by Kees (no longer available),
and is now available from  https://shop.kit-projects.com/

Either of the above AGC circuits will work on the Bitx40 or the uBitx.


Don's design attenuates the RF signal as it comes in from the antenna,
using a control signal derived from the audio. 

Most of the other AGC designs presented in this forum (there have been a
half dozen or so) attenuate the audio after the audio pre-amp, simple and
works well enough to protect the ears, and you avoid the tricky business of 
attenuating the RF path.  Here's a very early example of this approach:
    http://bitxhacks.blogspot.com/2016/11/agc-for-bitx.html

Attenuating the RF path is preferred, since the stock receiver dynamic range
is limited primarily by that audio pre-amp, and also to some extent by the IF amps
and mixers.  Don's design reduces the signal right where it comes in from the
antenna jack, so nothing in the radio will get overloaded and cause distortion.  

So an AGC design with attenuation in the audio stage works to protect the ears,
but strong signals may be distorted enough to be unintelligible.  With RF 
attenuation, strong signals remain undistorted.

All successful AGC circuit designs presented in the forum thus far detect the
incoming signal level just before the volume control.  Signal detection must occur
after the 12mhz crystal filter, otherwise we would also detect strong nearby stations
that the crystal filter rejects.  Detection of audio is not quite ideal since it takes time for
the signal to arrive there, so there will be a brief pop when a strong signal shows up
before it is properly attenuated.  But detection of 12mhz RF between the crystal filter and the
demodulator is difficult, because the unshielded 12mhz BFO on CLK0 will sneak into
our AGC signal detector and look like a very strong signal.

Here's an example of a well regarded AGC scheme for a high performance receiver:
    http://www.ka7exm.net/hycas/hycas_200712_qst.pdf
It's about as complicated as an entire uBitx receiver.

Jerry, KE7ER



On Thu, Apr 18, 2019 at 06:43 PM, Curt wrote:

check this out - this is a similar version of the same circuit

http://www.nd6t.com/bitx/AGC

the main idea is sampling the audio, feeding the transistor to boost this signal.  the 2 diodes develop a rectified signal based upon the audio, and this is used to bias a MOSFET used as a variable resistor. 


Virus-free. www.avg.com

--

…_. _._


Re: No Boot-Up (after spikes)

Ted
 

Sam,

Yes.  See earlier response. I thought I had wired up a virgin screen cord but it was late.   it must have been, because some other time during the night I destroyed the 2.8" screen that goes in this project. So a new one, the enhanced model this time, is somewhere between who knows where and where I am, in the mail. Let's hope i don't blow up the redundant screen while trying to troubleshoot, and I'll re-do those wires.  If that doesn't work, it's haunted,  and I have plenty of gas for chainsaw and a box of 20 gauge shells.


Ted


Re: No Boot-Up (after spikes)

Ted
 

That's that's about the only thing that's left course, and it may just be a case of denial that I would bother to check them. Guess I'll get on that.


Tnx,

Ted


Re: Confused about how AGC works?

Jerry Gaffke
 

Here's my shot at a quick summary regarding AGC circuits for the Bitx40 and uBitx
Opinions may vary.

When tuning across the band with a stock radio, you might run across a weak station
and turn the volume up to hear it.  Then a local QRO station responds and
you have to rip the headphones off to protect your ears, or be very quick in reaching
for that volume control.  An AGC circuit (automatic gain control)  turns the volume down
for you when a strong station shows up like that.

This is an early version of Don's (ND6T) AGC circuit:
    https://groups.io/g/BITX20/message/68037
Still viable, works well enough, simple and easy to build from scratch.
Really strong local signals can still be annoyingly loud, though much less so.

Don refined that FET shunt attenuator design by adding a FET series attenuator
to get additional dynamic range, keeps even the strongest stations down in volume.
    http://www.nd6t.com/uBITX/AGC.htm
It is a bit more complicated, but performs better.
Was kitted up by Kees (no longer available),
and is now available from  https://shop.kit-projects.com/

Either of the above AGC circuits will work on the Bitx40 or the uBitx.


Don's design attenuates the RF signal as it comes in from the antenna,
using a control signal derived from the audio. 

Most of the other AGC designs presented in this forum (there have been a
half dozen or so) attenuate the audio after the audio pre-amp, simple and
works well enough to protect the ears, and you avoid the tricky business of 
attenuating the RF path.  Here's a very early example of this approach:
    http://bitxhacks.blogspot.com/2016/11/agc-for-bitx.html

Attenuating the RF path is preferred, since the stock receiver dynamic range
is limited primarily by that audio pre-amp, and also to some extent by the IF amps
and mixers.  Don's design reduces the signal right where it comes in from the
antenna jack, so nothing in the radio will get overloaded and cause distortion.  

So an AGC design with attenuation in the audio stage works to protect the ears,
but strong signals may be distorted enough to be unintelligible.  With RF 
attenuation, strong signals remain undistorted.

All successful AGC circuit designs presented in the forum thus far detect the
incoming signal level just before the volume control.  Signal detection must occur
after the 12mhz crystal filter, otherwise we would also detect strong nearby stations
that the crystal filter rejects.  Detection of audio is not quite ideal since it takes time for
the signal to arrive there, so there will be a brief pop when a strong signal shows up
before it is properly attenuated.  But detection of 12mhz RF between the crystal filter and the
demodulator is difficult, because the unshielded 12mhz BFO on CLK0 will sneak into
our AGC signal detector and look like a very strong signal.

Here's an example of a well regarded AGC scheme for a high performance receiver:
    http://www.ka7exm.net/hycas/hycas_200712_qst.pdf
It's about as complicated as an entire uBitx receiver.

Jerry, KE7ER



On Thu, Apr 18, 2019 at 06:43 PM, Curt wrote:
check this out - this is a similar version of the same circuit

http://www.nd6t.com/bitx/AGC

the main idea is sampling the audio, feeding the transistor to boost this signal.  the 2 diodes develop a rectified signal based upon the audio, and this is used to bias a MOSFET used as a variable resistor. 


Re: Attenuator function in CEC firmware #nextion #ubitx #firmware

Tom, wb6b
 

On Fri, Apr 19, 2019 at 06:10 AM, Jack Brabham - KZ5A wrote:
looks like the ideal "effector" location for an RX AGC scheme
Hi,

Yes, that looks like it could be a good choice. Just be certain that the power level at that point, on transmit, is within the limits of the attenuator. Off hand I think it is, but there many folks here that may have a more accurate assessment. There have been some issues with Q90 being blown by nearby transmitters and lightning strikes. It may be a good idea to add one of the protection mods, like diodes, that have been suggested in other threads, to protect the attenuator chip input.

I may do the same with my attenuator module, enhance my uBitx, rather than my original reason for buying is as a piece of test equipment. I'll watch your progress.

Tom, wb6b


Re: Confused about how AGC works?

Don, ND6T
 

Hi Digger,

Often the simplest of things are revealed as complex. As Jerry says, the delays are important. The values used allows the attenuation to smoothly increase and track the signal level variations such that the response is fast enough to produce a pleasant result but not so fast that it will oscillate. Your confusion may be that you perceive that the end result is a tightly controlled output. It is not. Stronger signals result in slightly stronger audio levels. A S9+40 dB signal will be a bit louder than a S9 signal, just not horribly so. That increase is designed to be slight and gradual. This simple circuit is almost (but not quite) linear in that respect. Fortuitously, the shunt resistance takes over as the series resistance nears maximum conduction and it is a nice, gentle, transition. Close but not perfect. Good enough.

To get a better AGC, especially one that tames the initial burst, you would need a much more complex circuit. The better ones include an additional detector and multiple additional gain control points throughout the RF and IF amplifiers. If we had a carrier to use as a signal strength reference then it would be easier. Without the carrier we have to rely on the modulated signal. Tricky.

I use a compromise circuit. Even then, it seems that it is so complex that the majority of builders need kits or completed boards. This circuit is the best that I can do (so far) in keeping it simple yet effective.

Did this help?
73, Don


New V5 build results and calibration issues. #ubitx-help #nextion #ubitx #calibration

derek (G4VWI)
 

The following observations may be of interest to others having just got round to completing my V5 build.

1) For safety I made use of the SMT reverse polarity protection circuit by KC9ON to simplify the power supply fuse circuitry which worked very well. Two separate fuses used.

2) I  used the Kit-Projects version of the ND6T gain control. Out of three versions used this one is by far the easier to fit and is recommended as it has a 5v regulator working from the 12v line. I have used a tiny mil. spec. rotary switch instead of the DP3T switch provided. Adjust for a little more gain to allow for compensation when switching in a narrow CW filter.
 3) I have used Murata T filters with .01 caps to ground in the power lines. I was getting noise from a small brushless fan. If anyone has used a SMALL temperature switch circuit let me know. If not where have others wired their fans to? I am not keen to solder directly onto the IC.
Initial tests:
1) Out of the box the VFO was out by 1.2Khz! Others mention this but as yet no explanation has been given. To calibrate make sure you have a dummy load connected. Go into "settings" >"calibrate". Connect the PTT orange wire to ground and a carrier should be visible on your analyser, SDR or second radio display. Mine was set to under 1K bandwidth centered on 10Mhz. and no trace was visible! Widening the bandwidth still no trace until the relay was activated for the third time. Possibly a sticky relay I hope? First attempt I ended up with the tuning high. Second attempt zooming in it was near enough. The BFO calibration agreed with other published settings and was straight foward.
2) Checking the CW output on a spectrum scope  showed the resistor values were not ideal and the keying will need adjusting when CEC firmware is installed. IAMBIC B produced better results. Suggestions?
On 20Mtrs. a burst of RF appeared after the keying had completed. I am not sure if this was due to the exposed circuitry on the bench or if this is a known issue with a solution? Let me know.
3)
Checking the power output the meter (not calibrated) showed an average between 5-8 watts depending on band.
4) This V5 example appears to be much more sensitive than my V4.
5) The LM386 audio amp gives adequate output into a small Visaton FRWS-5 4 Ohm speaker.
NB: The PA's get quite warm to the touch with key down even with a larger heat sink so a small fan is advised.

I intend to add a Nextion 3.2e display. Will the saved parameters and calibration be read when updating the firmware? Has anyone added a RTC to the display yet?

Please let me know how you have got on with your V5 build and comment on any points raised.

Best wishes. Derek G4VWI.


Re: No Boot-Up (after spikes)

Joe Puma
 

It will do that if one of the yellow or blue wires are not connected forgot which one. Probably the RX line. So maybe that connect is damaged at the Raduino. 

Joe


On Apr 19, 2019, at 9:10 AM, Sam Tedesco <stedesco619@...> wrote:

Nextion shows callsign/ver and all zeros on freq?


Re: Attenuator function in CEC firmware #nextion #ubitx #firmware

Jack Brabham - KZ5A
 

Tom,

The 4302 or the newer 4312 (which seems hard to find) are the modules I'm thinking of.    I think the 4302 was mentioned in ZL1AXG's article.

The placement between the LPF and the pre-driver puts the ATTN in the antenna path on RX which is presumably 50 ohm and I assume is also 50 ohm on TX considering the by-directional LPF.

This placement, to non-engineer me, looks like the ideal "effector" location for an RX AGC scheme, ahead of any active devices.    Or it could just be setup as a manual RF gain control on RX.   It is also looks like a very straight forward way to control drive levels per band on TX, either via pre-sets or an ALC setup.

I'm also thinking that this approach should be largely free of "unintended consequences".

In any case it looks like an enjoyable experiment.

73 Jack KZ5A




On 4/19/2019 5:10 AM, Tom, wb6b wrote:
On Thu, Apr 18, 2019 at 04:26 PM, Jerry Gaffke wrote:
You could easily control that attenuation from a processor, perhaps
These may be a little overboard for the purpose but I have one of each of these digitally controlled attenuators that I bought to build up my tool set for making RF measurements. 

This one had the part number of the attenuator chip ground off. Depending on the manufacture of the part, the specified low frequency cutoff could be 9Khz, 1Mhz or 10Mhz. For HF measurements a possible 10Mhz cutoff is an issue.
https://www.ebay.com/itm/New-OLED-6G-Digital-Programmable-Attenuator-30DB-step-0-25-RF-Module-Micro-USB-/263584061842
However, the construction with the machined aluminum body is impressive.

This one specifies the part number in the description and the number on the attenuator chip matches. It is a 9Khz to 4Ghz attenuator. It doesn't have a display, so would be a better choice for installing into the uBitx. 
https://www.ebay.com/itm/PE4302-Digital-RF-Step-Attenuator-Module-High-Linearity-0-5dB-50-ohm-RF-DSA/121830578745

You can also buy the current version of the Peregrine attenuator chip from Digikey, mount it on a SMD adaptor board and add it to your uBitx IF chain. But, the modules are easier to work with.

These parts have an actual 50 ohm impedance (when the other end is 50 ohm terminated). It might be that the 50 ohms is a bit more load that the IF chain was designed for. 

Tom, wb6b


 



Re: No Boot-Up (after spikes)

Sam Tedesco
 

Nextion shows callsign/ver and all zeros on freq?


Re: No Boot-Up (after spikes)

Ted
 

Thanks for the tip, John.  Thing is that I've tried no fewer than four Nano replacements and two other, known operational Raduino boards.  That's the part that makes no sense. Bad outputs or clock readings should have been eliminated by now due to component-swapping.

But I will look at readings for the experience & to learn more about these things.


Tnx agn,

Ted
K3RTA


Re: No Boot-Up (after spikes)

John (vk2eta)
 

Hello Ted,

Sorry about the mishap, but it has happened to quite a few of us before.

I would try the Raduino off the main board but connected to a PC for supply via USB.

If it is gets stuck at firmware version I would suspect either a defective si5351 clock generator or an issue with the i2c bus (A4/A5 from memory). Check for shorts, and if you have a scope check that you get a 3.3v swing on the two i2c signal wires.

73, John


Re: Attenuator function in CEC firmware #nextion #ubitx #firmware

Tom, wb6b
 

On Thu, Apr 18, 2019 at 04:26 PM, Jerry Gaffke wrote:
You could easily control that attenuation from a processor, perhaps
These may be a little overboard for the purpose but I have one of each of these digitally controlled attenuators that I bought to build up my tool set for making RF measurements. 

This one had the part number of the attenuator chip ground off. Depending on the manufacture of the part, the specified low frequency cutoff could be 9Khz, 1Mhz or 10Mhz. For HF measurements a possible 10Mhz cutoff is an issue.
https://www.ebay.com/itm/New-OLED-6G-Digital-Programmable-Attenuator-30DB-step-0-25-RF-Module-Micro-USB-/263584061842
However, the construction with the machined aluminum body is impressive.

This one specifies the part number in the description and the number on the attenuator chip matches. It is a 9Khz to 4Ghz attenuator. It doesn't have a display, so would be a better choice for installing into the uBitx. 
https://www.ebay.com/itm/PE4302-Digital-RF-Step-Attenuator-Module-High-Linearity-0-5dB-50-ohm-RF-DSA/121830578745

You can also buy the current version of the Peregrine attenuator chip from Digikey, mount it on a SMD adaptor board and add it to your uBitx IF chain. But, the modules are easier to work with.

These parts have an actual 50 ohm impedance (when the other end is 50 ohm terminated). It might be that the 50 ohms is a bit more load that the IF chain was designed for. 

Tom, wb6b


 


No Boot-Up (after spikes)

Ted
 

It came to pass that,  in the process of inserting a 7809 between the Raduino daugterboard and its B+ pin-to-mainboard, that I failed to notice a solder blob shorting out the 7809. I made a 90-degree header change at the Raduino mounting point on this build, making this relatively painless [or not].

It was realised, when turning on the (1-metre-long) remote power switch whereupon an added power relay chattered on and off [due to low relay supply voltage for the instant of the short],  graciously saving my 5-amp fuse.   Don't ask....

Since then, the radio powers up but the Nextion screen would not get past simply powering on and showing the basic screen graphics (as if in the PC editor). The obvious have been performed:

- Replace Nano.
- Try different brand of Nano
- Try Nextion screen from redundant uBitx radio
- Replace Raduino (in stock, known)
- Replace 5-volt regulator on oruginal Raduino.
- Swap Raduino from redundant uBitx radio
- Try swapped Raduino with different Nano
- Restore Raduino with original, 2-line LCD display (shows opening call sign and firmware edition, nothing more)

So: should not a Raduino board power up by itself when given 12v & (-) , and respond to the original LCD display or a Nextion screen, that is, respond to manual display inputs even without a mainboard present? 

If a mainboard is required for Rauino/screen operation past initial lighting, what might fail specifically which will stall further brain function like that? 

V3 board; whole rig seen in my Photos folder.


73,

Ted
K3RTA