Date   
Re: Amateurradiokits Chassis and Grounding

Ian Reeve
 

Hi, I have just completed a build using the case designed for the 3.5 inch nextion.I did carefully with a counter sinking bit take off the minimum of paint surrounding the antenna,and front jacks. I used a single point on the chassis to take the power Jack negative,the antenna Jack return and the earth returns from the Jack panel.This ties together electrically the back panel,the front panel and the main chassis.The lid is earthed via one screw to the back panel.   Ian M0IDR


From: BITX20@groups.io <BITX20@groups.io> on behalf of Curt via Groups.Io <wb8yyy@...>
Sent: Tuesday, June 11, 2019 6:17:14 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Amateurradiokits Chassis and Grounding
 
Ravi, Joe - good info - I remember doing something to expose some metal on the nice case. 

remember this is a DIY project -- Sunil would be happy to have us expose some metal wherever we deem suitable!  we have the technology (use a drill bit slightly larger than the hole or whatever one might have). 

enjoy the nice hardware, from India and other parts of the globe! 

Curt

Re: AGC Circuit for uBITX Featured in July 2019 QST Magazine

Jerry Gaffke
 

If in your location you get stations you want to hear that are strong enough
to still sound distorted when the volume control is turned down, then
you do need the dynamic range that RF attenuation gives you.
If not (or if your primary concern is that you not damage your ears),
then a simple AGC with audio attenuation is perfectly fine.
Many many many *Bitx* owners are perfectly happy with audio AGC,
and perhaps a pot where RF comes in from the antenna for use as a manual RF gain control.

Mad and I have had this argument before over what "true AGC" might be:
    https://groups.io/g/BITX20/topic/31238211
It's AGC regardless of the frequency at which attenuation takes place.  Period.
There have not been any takers yet to this challenge:
    https://groups.io/g/BITX20/message/68083

Jerry, KE7ER



On Tue, Jun 11, 2019 at 09:08 AM, MadRadioModder wrote:
The advantage of the JackAL is that it is a true AGC, controlling the gain of the AF and RF stages of the radio… and thus preventing overload and distortion of the RF stages before the audio gain adjustment.  The circuit in the in QST is just a simple volume control/ limiter that could work on “any audio line” to keep the volume below a specified point.

Re: AGC Circuit for uBITX Featured in July 2019 QST Magazine

MadRadioModder
 

Or…. Just turn the volume down.

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Tuesday, June 11, 2019 2:04 PM
To: BITX20@groups.io
Subject: Re: [BITX20] AGC Circuit for uBITX Featured in July 2019 QST Magazine

 

If in your location you get stations you want to hear that are strong enough
to still sound distorted when the volume control is turned down, then
you do need the dynamic range that RF attenuation gives you.
If not (or if your primary concern is that you not damage your ears),
then a simple AGC with audio attenuation is perfectly fine.
Many many many *Bitx* owners are perfectly happy with audio AGC,
and perhaps a pot where RF comes in from the antenna for use as a manual RF gain control.

Mad and I have had this argument before over what "true AGC" might be:
    https://groups.io/g/BITX20/topic/31238211
It's AGC regardless of the frequency at which attenuation takes place.  Period.
There have not been any takers yet to this challenge:
    https://groups.io/g/BITX20/message/68083

Jerry, KE7ER



On Tue, Jun 11, 2019 at 09:08 AM, MadRadioModder wrote:

The advantage of the JackAL is that it is a true AGC, controlling the gain of the AF and RF stages of the radio… and thus preventing overload and distortion of the RF stages before the audio gain adjustment.  The circuit in the in QST is just a simple volume control/ limiter that could work on “any audio line” to keep the volume below a specified point.


Virus-free. www.avg.com

--

…_. _._

Re: AGC Circuit for uBITX Featured in July 2019 QST Magazine

Jerry Gaffke
 

Mad is right.
Just turning down the volume is good enough for the majority of *Bitx* owners.
And how designer meant for this minimalist rig was meant to be used.

But if you got the gain way up to hear a weak station
and then suddenly some +40dB local steps on top of him,
it can be hard to tear the headphones off fast enough.

Jerry


On Tue, Jun 11, 2019 at 12:10 PM, MadRadioModder wrote:

Or…. Just turn the volume down.

 

Re: AGC Circuit for uBITX Featured in July 2019 QST Magazine

Curt
 

As we almost started to debate this, ubitx works with no agc, and somewhat better with audio AGC. Glad I figured out finally the vk3ye agc, its nice enough. Those adding the jackal get something even better, Jack invited me to look at it a while back. It has some elements of the hybrid cascode IF AGC. We can each manage our degree of addiction in modifying this nice rig.

I don't miss agc much sitting on a frequency,  but in tuning its nice. While I have an agc off switch I find no reason to turn it off. My tweaks to the vk3ye agc are on the k3pzn website, but I confess I see a resistor value is off, the same one in Peter's schematic. Need to fix that.

Curt

Re: AGC Circuit for uBITX Featured in July 2019 QST Magazine

Curt
 

Back to topic -- I see it uses a LM386 output with a JFET input conditioning stage.  A MOSFET is across the differential input of the LM386 to provide attenuation.  audio is sensed by a diode, that directly biases the MOSFET gate with a little RC conditioning.  It does require a little more surgery than the ND6T (minimal surgery) or VK3YE (no surgery) designs.  Useful solution perhaps for someone who has or wants to remove their audio amplifier. 

I confess my ubitx currently feeds a NESCAF with a LM386, now external. 

73 Curt

Updated Nextion 5" screens

Mark Hatch
 

Hi,

Just added to the files sections an updated version of the KD8CEC Nextion code for the 5" screens (Basic and Enhanced). (Only the 5" Enhanced has been tested, I don't have a 5" basic) This work is an extension to the "heavy lifting" already done by Joe Puma (KD2NFC). 

I couldn't help myself and did some "improvements" to the user interface that Joe and probably others may or may not like. So I have included the HMI file in the directory too so you can make it look your way. If you have a 7" or 9" screens, you should be able t load up the HMI, set the device to match your screen and regenerate the tft file. If you have one of these screens and can't figure it out, let me know.

Files: AJ6CU Nextion 5-inch files/5inch June 10

So summary of major changes that i made from Joe's original effort
  1. Home page
    • Correction of scale for histogram (have more space, so let's use it!)
    • Addition of direct access to memory STO/LOC screens (had to eliminate the Radio tower logo, sorry)
  2. Various
    • In case you had not noticed, the button to get "Home" was in various locations, although not done, I am in the process of moving it to a consistent place (upper right)
    • Scaling changes to Bandscan and Spectrum
    • Various pages required you to hit "read" or "refresh" to go get the data. I made this happen on page entry. Kept the refresh button as this seems to be a little flakey.
    • Tried to introduce a consistent color scheme. Blue background, white letters where you can change, yellow for titles.
    • All screens (except home screen) will eventually have the name of screen in upper right in red.
    • Button pushes go green when pushed and return to grey when released
    • Added a few more scrollbar slider sizes so that the slider fit the slide bar better.
  3. Frequency entry (touch the middle 3 numbers on home page) is now a little more obvious. When you are in direct frequency entry, you only see numbers, When you are in Band select, you only see the bands. 
  4. Memory to VFO redesigned. Seemed easier to use for me. 
  5. VFO to Memory - still don't like this one. Want to make it more like Memory to VFO where you can see all 10 memory slots and then select the one you want to overwrite. For now, just replaced the keyboard with a standard one that pops up when you click in the name and some fancy arrows to spin the mem#.
  6. Although it is against my better judgement, I did make available KD8CEC's debug screen. Tried to warn you off, but i am sure someone will do something awful to his/her poor ubitx using this screen. ;-)
  7. CW setup screen redesign (and it automatically fetches data on startup)

There is some issues... The biggest issue being that when you go into a submenu (e.g. CW setup/MemtoVFO, etc.) the Spectrum Histogram in lower left corner doesn't always automatically restart. If you change any control VFO/Freq, mode, etc.) it restarts.  This is going to be a pain to debug because of the extensive use of timers and state machine in the Nextion code.... Would welcome anybody that can make a suggestion here.

I have also not tested it on a Basic 5". There maybe performance issues, especially where I increased the scale of the graphs.

Still lots of work, want to get rid of some of those background pictures in the control screens that really don't match the others. The bandscan is something I would really like to "adjust" because it was really not obvious to me how it worked. And perhaps even a "?" in upper right of some screens for a little help?  Probably put together another update in a couple weeks.

73
Mark
AJ6CU




  1.  

Antuino and SWR

Michael Aiello
 

Has anyone experimented with the Antuino as an SWR meter?
I have noticed it reads consistently high, even after repeated return loss calibrations.

Using a set of calibrated dummy loads, I get these readings:
1:1, 50 ohms  - Antuino reads 1.0
2:1, 100 ohms - reads 3.0
5:1, 250 ohms - reads 8.7
100:1, 5000 ohms - reads 99.9

So we have good agreement at each end of the scale, not so much in the middle. Using my commercial SWR analyzer, these loads read exactly as marked.

Anyone have a similar experience?

73,
Mike N2HTT

Re: Oscillation problems Bitx20a

Sajid Rahum
 

Hi Howard.

I am about to start building the minipa70 kit;  have ordered also irf520s.  any pictures on how to mount them will be helpful.  I did found the video below very helpful but he skips on the mounting of the IRFs; additionally the resistor mount that is recommended to drop the swrs will also be appreciated; i still am not clear where it needs to be put.

https://www.youtube.com/watch?v=a2PEWpgIoCY

Heat sink is ready, additional fan, waiting for the band pass filter.  aluminium box is ready.  Time to give the ubitx a boost; i was able to make a qso over to mid NY from Ontario with a 4/5 report.


Sajid

Add S-meter to VK3YE AGC

Curt
 

I have been pleased with this unusual AGC circuit as it nicely removes the top of large signals.  VK3YE has suggested measuring current in parallel with the LED that drives the AGC action, but I found this gave little indication of relative signal strength.  it works much better measuring current in series with the LED. 

I am using a small meter movement supplied by Sunil, about 250 uV peak current.  A shunt resistor across the meter is necessary since the LED current at peak is at least 20 mA per my research.  The approximate value of the shunt resistor Rsh = ( Im x Rm ) / Ish

Rm was unknown but I am able to measure it with my DVM at around 500 ohms.  Inserting these values gives 6.25 ohms.  i found a resistor around 5 ohms and it working nicely.  Its not a real S-meter response - let's call it a signal strength meter.  I sense I can discern signals from approx S5 to S9 with it.  Now if someone does not have a meter movement, the LED itself could be observed to sense signal strength - but the meter is a nice touch. 

I have previously tried s-meter sensing circuits but the action of this particular AGC circuit prohibits them from functioning - so this simple current meter does decently. 

73 Curt

Re: External Amp

Sajid Rahum
 

Hi Richie

Were you able to get the 22ohm 1 watt resistor added?  can you share the exact place you soldered over from the gate to target solder point.  That is where it is not clear.

Sajid

Re: AGC Circuit for uBITX Featured in July 2019 QST Magazine

Richard Spohn
 

Jack, any luck with your website? I am starting to take a serious
look at the JackAl board, would love to find out more info before
buying...as in the BOM and Prices, etc. - Rich WB2GXM

On 6/11/19, Jack Purdum via Groups.Io <jjpurdum=yahoo.com@groups.io> wrote:
The JackAl circuit has both audio and IF AGC, is Open Source, and designed
for the µBITX. The manuals can be downloaded from QRP Guys. Anyone who wants
to build it is free to do so. See attached.
Jack, W8TEE

On Tuesday, June 11, 2019, 9:59:21 AM EDT, pat griffin
<patgriffin@...> wrote:

I have only glanced at the circuit but it appears similar to the various
ubitx agc circuits we have seen with some nice enhancements.  In fact, the
author, K1BQT (email: k1bqt at arrl dot net), built it for a ubitx.  It uses
2n5486, 2N7000 and LM386.73, AA4PG
_._,_._,_



Re: AGC Circuit for uBITX Featured in July 2019 QST Magazine

Jack, W8TEE
 

We have not worked on the site, mainly because I was spending time on my FDIM talk and now our club hamfest is Saturday and Al and I are working on the book. One chapter is a different mag loop and controller, so the site has fallen down on the priorities list. However, we have moved everything to our group web site:


Check that out and see if it helps.

Jack, W8TEE

On Tuesday, June 11, 2019, 10:05:00 PM EDT, Richard Spohn <wb2gxm@...> wrote:


Jack, any luck with your website?  I am starting to take a serious
look at the JackAl board, would love to find out more info before
buying...as in the BOM and Prices, etc. - Rich WB2GXM

On 6/11/19, Jack Purdum via Groups.Io <jjpurdum=yahoo.com@groups.io> wrote:
>  The JackAl circuit has both audio and IF AGC, is Open Source, and designed
> for the µBITX. The manuals can be downloaded from QRP Guys. Anyone who wants
> to build it is free to do so. See attached.
> Jack, W8TEE
>
>    On Tuesday, June 11, 2019, 9:59:21 AM EDT, pat griffin
> <patgriffin@...> wrote:
>
>  I have only glanced at the circuit but it appears similar to the various
> ubitx agc circuits we have seen with some nice enhancements.  In fact, the
> author, K1BQT (email: k1bqt at arrl dot net), built it for a ubitx.  It uses
> 2n5486, 2N7000 and LM386.73, AA4PG

> _._,_._,_
>
>
>
>


Re: Antuino and SWR

Ashhar Farhan
 

Mike,
This is unusual. Do you have a signal source that can be used to provide variable level signals such as a step attenuator or an amplitude controlled signal generator?
It could be that the frequency calibration is off. Have you checked the frequency calibration too?
What frequency are you using for swr measurement?
- f

On Wed 12 Jun, 2019, 6:23 AM Michael Aiello, <n2htt.mike@...> wrote:
Has anyone experimented with the Antuino as an SWR meter?
I have noticed it reads consistently high, even after repeated return loss calibrations.

Using a set of calibrated dummy loads, I get these readings:
1:1, 50 ohms  - Antuino reads 1.0
2:1, 100 ohms - reads 3.0
5:1, 250 ohms - reads 8.7
100:1, 5000 ohms - reads 99.9

So we have good agreement at each end of the scale, not so much in the middle. Using my commercial SWR analyzer, these loads read exactly as marked.

Anyone have a similar experience?

73,
Mike N2HTT

Re: Antuino

KE2GKB
 

has anyone gotten a chance to test this? It seems there are quite a few of us with this problem. I need to get an attenuator set on hand to try this my self but I have noticed this problem with my antuino as well mostly where the the SNA measures -15 with a short piece of Coax hooked up.

-- Tim Keller - KE2GKB https://shop.kit-projects.com

Re: Amateurradiokits Chassis and Grounding

Dexter N Muir
 

Modern wood-drills (used to be called 'bits' for brace-and-bit use) might help, in an ordinary drill (hand- or low-speed) to 'peel off ' a circular 'land' of paint (or whatever). They have a flat 'cutting' edge with a centralizing peak that ought to be the right size/proportion.

Re: bitx40: low RF ower an dead part in RX path?

Stephan Lauffer
 

Dear Jerry,

thanks for your help!

For Pwr I use diode to prevent wrong polarization. Then into the LM2940 12V with 0.1uF on input and 100uF on output side. The PA is connected after the diode. I will add another, bigger C at input for some tests.

Yesterday I noticed an other "funny" thing: If the input power is lower than about 12.9V I can hear strong the tuning ticks. But I have no high freq hiss. If I increase the voltage the ticks went of and the hiss begings. (:

Ok, my RF input part seems to be OK I guess. I checked it out with a ~2m wire like Farhan in the video below. The sound here is not that loud (f.e. at C11) and not that high and crispy but I guess this is in the specs. I can hear weak signals, thats good, my bitx has good ears. Just could a bit more louder. Hm... Checked four different small speakers.

Would ne nice to fix the hiss and tuning click thing... some day! :)

Am 10.06.2019 um 04:43 schrieb Jerry Gaffke via Groups.Io:

Stephan,
Driving 1khz into C31 is not going to give much response because the amplifier at Q3
is operating at 12mhz, and the 0.1uF at C33 will mostly block the 1khz audio frequency.
The signals through Q3 remain at 12mhz until after going through the mixer at D15,D16,T4,
after which they are at audio frequencies.
Here's an easy way to do a rough check of the gain of each stage of a receiver:
http://bitxhacks.blogspot.com/2016/12/troubleshooting-bitx40.html
Farhan uses a piece of wire that's maybe a meter or two long as an antenna, nothing attached to the far end of the wire.
Your household environment will have 60hz power hum and lots of RF signals from digital clocks and light dimmers
and natural atmospheric disturbances, all of which get picked up by the wire to provide the test signal.
If the Bitx40 is getting signals strong enough that you need the AGC circuit to prevent the audio from distorting,
that distortion is probably coming from too large of a signal into the Q12 audio pre-amp stage.
The LM386 audio amplifier should then give plenty of volume.
I suggest you triple check the way the volume control and speaker have been wired up,
perhaps try a larger speaker.
The three terminal Low-Dropout-Regulator should work fine if used with the recommended bypass caps.
You don't say which LDO you are using, here's a datasheet for the popular LM7812 (and many variants of it).
They recommend a 0.22uF cap to ground at the input pin of the regulator to avoid oscillation,
which may very well be the source of your noise problem.  (Maybe just two common 0.1uF caps in parallel.)
A 0.1uF cap from output pin to ground is not a bad idea.
Jerry, KE7ER
On Sun, Jun 9, 2019 at 09:32 AM, Stephan Lauffer wrote:
Hello!
With the AGC mod from Don nd6t I have a lot of fun with my bitx40
again. Without this strong signals overdrive my RX path somewhere
(in LM386?) that much that I had strong distortion with volume poti
in round about the middle position and above.
But there are two other problems (maybe default bitx40 behaviour or
a broken part??):
1st: My RX signal is very weak.
I checked out several small speakers but I need to set volume to max
in any case. The bitx is then not as loud as a normal human voice
nearby you. Maybe a transistor in the RX path is a problem? I feed a
nf signal ~1kHz with some few mV into C116, C107 and C33. Everytime
I get a loud and strong signal. On C31 I did not get a good/strong
signal. Maybe in this stage is a problem? Is there a paper/wiki how
I could nail this problem down? First I thought about another NF
stage witha LM380. But after I get the loud signal with my
testsignal I guess this is not needed.
2nd: "White noise"/hiss in the NF signal:
I tried to power the PA independend with > 12V for more HF output.
This means: After the power plug I split the PWR IN with a LDO for
the main 12V circuit and another wire without the LDO into the PA
in. So fare, so good. The very interesting part is that I get high
freq hiss in the RX signal path as soon as the input voltage exceeds
the 12.0V out plus the drop voltage of the LDO. F.e. this means:
Clear RX signal up to 12.7V and high freq noise up from here. The
noise reaches its max volume about 13.0V. Is this a general problem
as soon as I drive the PA with higher volume or is there a change to
solve this issui with better groundings/shields..?
Best regards, 73 an thanks for help,
Stephan dc8lz
--
Liebe Gruesse, with best regards,
Stephan Lauffer

Telefon: +49 7661 905216
Mobile: +49 172 7145197
Ham Radio: DC8LZ, QTH JN37XX
Schulstr. 1c
79252 Stegen
Germany

Re: bitx40: low RF ower an dead part in RX path?

 

Your in out voltage is getting close to its lower limit + diode drop.

Raj

At 12-06-19, you wrote:

Yesterday I noticed an other "funny" thing: If the input power is lower than about 12.9V I can hear strong the tuning ticks. But I have no high freq hiss. If I increase the voltage the ticks went of and the hiss begings. (:

Re: bitx40: low RF ower an dead part in RX path?

Stephan Lauffer
 

Jerry,

Am 10.06.2019 um 04:43 schrieb Jerry Gaffke via Groups.Io:
[...]

If the Bitx40 is getting signals strong enough that you need the AGC circuit to prevent the audio from distorting,
that distortion is probably coming from too large of a signal into the Q12 audio pre-amp stage.
The LM386 audio amplifier should then give plenty of volume.
I suggest you triple check the way the volume control and speaker have been wired up,
perhaps try a larger speaker.
You mean Q16 not Q12, right?

At Q12 I changed R123 and R126 a bit to get a stronger MIC signal.

73, Stephan
--

Re: bitx40: low RF ower an dead part in RX path?

Stephan Lauffer
 

Hello Raj,

yes. I thought it shouldn't be a problem to work with some few volt below 12 (f.e. with 10V).

I found this fix https://www.youtube.com/watch?v=_7q7nG-awsc and it works very fine. :)

So now no more tuning ticks below 12V (12,9V). That's nice because I'd like to power it with 3S Lipo cells sometimes.

Am 12.06.2019 um 10:14 schrieb Raj vu2zap:
Your in out voltage is getting close to its lower limit + diode drop.
Raj
At 12-06-19, you wrote:

Yesterday I noticed an other "funny" thing: If the input power is lower than about 12.9V I can hear strong the tuning ticks. But I have no high freq hiss. If I increase the voltage the ticks went of and the hiss begings. (:
--
73, Stephan dc8lz