Date   
Installing BCI and Kit-Projects AGC

Joel Trenalone
 

Hello All,
I have been working on a UBITX V5 and am installing both a BCI filter and the Kit-Projects AGC. According to what I have read regarding the BCI FILTER and the Kit-Projects AGC, both are installed by cutting in the RF receive path between K3 & K1. 

The way I read the schematic, the receive path travels from the antenna through K3 to K1 and on to the receiver. All the instructions (Kit-Projects and UBITX.net) show the AGC installed immediately after K3, then install the BCI then onto K1 (in that order). 

My my question is for the AGC to work properly, shouldn’t it be installed after the BCI filter (So the AM broadcast is filtered out)?

Please excuse my ignorance, but before I cut the trace and install these two modifications, I want to make sure they are in the right order,

Thanks in advance,
Joel KD6AGW :)

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

Jerry Gaffke
 

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

Re: RX of uBITx V3 fried - which components to change? #ubitx

Jerry Gaffke
 

Yes, on the uBitx, K1-14 is shorted to ground for DC by T2 pins 1 and 6 by way of L1,L2,L3,L4.
At DC, T2,L1,L2,L3,L4 are all just a few centimeters of magnet wire, and present very little resistance.
At an RF frequency of 3.5mhz and more where our ham bands are, they present significant impedances.

Jerry, KE7ER



On Sun, Jun 9, 2019 at 05:26 PM, Sascha Bohnet | DL5SMB wrote:

So I am at home again and the troubleshooting begins :-)

Maybe thats's a stupid question, but should there be a DC short within the antenna line between the relais K1 (14) and ground in the signal path?

I first thought Q3 in ND6DTs AGC was dead as I had a short between Ground and RF-Out. I then replaced it and noticed hat that did not help and Q3 had again a short between Source and Drain.

So i took took out the AGC, tried to find the problem on the small PCB and noticed that the short (about 3 Ohm) was in fact on the uBITX itself. I am a bit bad at reading schematics,
but then i found T2, where the signal path 1 is connected to 6 GND . So this is normal beaviour, am I correct?

Re: Mounting Low Pass Filter Relays On Bottom of Circuit Board

Jim Sheldon
 

Already tried that a long time ago - didn't make much, if any difference on my Siglent SSA 3021X spectrum analyzer so not really worth the trouble IMO.

W0EB

------ Original Message ------
From: "wishbone_aaa" <@Wishbone>
To: BITX20@groups.io
Sent: 6/9/2019 7:51:42 PM
Subject: [BITX20] Mounting Low Pass Filter Relays On Bottom of Circuit Board

While replacing the four low pass filter relays with Axicom units, a thought occurred to mount the relays on the bottom side of the circuit board. The bottom side is mostly a ground plane. Wonder if there might be any advantage in isolation of signals ? Have no way of measuring. Perhaps someone with more RF experience can comment.


Mounting Low Pass Filter Relays On Bottom of Circuit Board

 

While replacing the four low pass filter relays with Axicom units, a thought occurred to mount the relays on the bottom side of the circuit board. The bottom side is mostly a ground plane. Wonder if there might be any advantage in isolation of signals ? Have no way of measuring. Perhaps someone with more RF experience can comment.

Re: RX of uBITx V3 fried - which components to change? #ubitx

Sascha Bohnet | DL5SMB
 

So I am at home again and the troubleshooting begins :-)

Maybe thats's a stupid question, but should there be a DC short within the antenna line between the relais K1 (14) and ground in the signal path?

I first thought Q3 in ND6DTs AGC was dead as I had a short between Ground and RF-Out. I then replaced it and noticed hat that did not help and Q3 had again a short between Source and Drain.

So i took took out the AGC, tried to find the problem on the small PCB and noticed that the short (about 3 Ohm) was in fact on the uBITX itself. I am a bit bad at reading schematics,
but then i found T2, where the signal path 1 is connected to 6 GND . So this is normal beaviour, am I correct?

Re: [QRPLabs] Preliminary results -- W8TEE/AC8GY Mag Loop Testing

vajra guru
 

I would like to call attention to the work of members of the Elmira Radio Club in refining the EH antenna... Paul VE3PVB and Al VA3TET among others were leaders in the project, taking Ted Hart's work as their starting point, and got some very encouraging results... You can read more here:
Best, Calvin VE3EIT 



On Saturday, June 1, 2019, Alan de G1FXB via Groups.Io <g1fxb=yahoo.co.uk@groups.io> wrote:

Hi Alison,

I recall you done antenna R&D.

RE my comments: feeder radiation?? etc,?? and one of the examples I was eluding to:-

Ever have reason to look at the work of Ted Hart?? W5QJR ? EH antennas in either their or your commercial or hobby capacity?

Perhaps 5, never as many as 10 vearment supporters & no one else in the world could get them to work however "tweaky" the MKII / MKIII designs evolved

Had a massive US Mil. grant for their R&D, nothing. Failed to convince the IEEE with all their techno babble papers as to the theory?

However I bet they have nice retirement homes......


Maybe I'm an old fashioned dinosaur?

Way off topic... but "Do they work?"

a quick yes or no will suffice.?? :-)

--- .???? --- --- ---

regards Alan

??

On 01/06/2019 21:28, ajparent1/KB1GMX wrote:
Alan de G1FXB,

Your correct.?? any testing and I've done a lot with small loops you need lots of??
"shield breakers" or choking to remove the COAX shield as a possible secondary
coupling making it an undesired array and often clouding results or minimally
distorting patterns greatly.

If the RF source is small and self contained it can be at or very near the
feed point and make the problem easier.?? Same applies for receivers
as well.

Generally Loops, large or small, are considered self contained antennas not
requiring ground planes or counterpoises.?? However in the real world those
will exist.?? As a result supports or cables and the very existence of the
ground below it do influence the results.

Allison

Re: Wanted

Adrian Chadd
 

Heh, hit me up privately (adrian.chadd@...) - I'll give you a
radio for your club. :)


-a
(kk6vqk)

On Sun, 9 Jun 2019 at 13:36, Martin KM6TCD <peaceofandalus@...> wrote:


We're a bunch of newbies, most still studying for the exam. We've got a budget of $100. Perhaps could raise a bit more.
So a buit and tested kit would be a good option.
km6tcd
Sent: Thursday, June 06, 2019 at 9:39 AM
From: "iz oos" <and2oosiz2@...>
To: BITX20@groups.io
Subject: Re: [BITX20] Wanted

The ubitx might scare the majority... being too educational. There are by the way really good (low phase noise, good blocking etc) and durable transceivers, like the IC-765. Of course I would vote for the ubitx, but consider the 'hey teacher we don't need education' .


Il 06/giu/2019 08:51, "Balasubramanyan Cp" <bsnvu2yc73s@...> ha scritto:

Dear CLUB MEMBERS/OM/YL,
Why not to get uBITX VERSION 5 LSB & CW MULTIBAND 10W QRP from OM Farhan, INDIA ? It is very very very good IN ALL RESPECT !!!!!!
73s. Email bsnvu2yc73s@....


On Wed, Jun 5, 2019 at 8:55 PM Adrian Chadd <adrian@...> wrote:

Yeah, hit me up. I'm local to you (east oakland) and can help you get
a HF transceiver.



-adrian

On Wed, 5 Jun 2019 at 10:38, Martin KM6TCD <peaceofandalus@...> wrote:

Our club is looking for a built, tested, and working transceiver.

Anyone got one they might sell?

km6tcd



Re: uBitx V3 transmit probles.

Dennis Yancey
 

Thanks, will look at that in a bit.. appreciate the suggestion.
--
72 and God bless
KD4EPG

Re: Wanted

Martin KM6TCD
 

 
We're a bunch of newbies, most still studying for the exam. We've got a budget of $100. Perhaps could raise a bit more.
So a buit and tested kit would be a good option.
km6tcd

Sent: Thursday, June 06, 2019 at 9:39 AM
From: "iz oos" <and2oosiz2@...>
To: BITX20@groups.io
Subject: Re: [BITX20] Wanted

The ubitx might scare the majority... being too educational. There are by the way really good (low phase noise, good blocking etc) and durable transceivers, like the IC-765. Of course I would vote for the ubitx, but consider the 'hey teacher we don't need education' .

 
Il 06/giu/2019 08:51, "Balasubramanyan Cp" <bsnvu2yc73s@...> ha scritto:
Dear CLUB MEMBERS/OM/YL,
Why not to get uBITX VERSION 5 LSB & CW MULTIBAND 10W QRP from OM Farhan, INDIA ?  It is very very very good IN ALL RESPECT !!!!!!
73s.  Email bsnvu2yc73s@....
 
 
On Wed, Jun 5, 2019 at 8:55 PM Adrian Chadd <adrian@...> wrote:
Yeah, hit me up. I'm local to you (east oakland) and can help you get
a HF transceiver.



-adrian

On Wed, 5 Jun 2019 at 10:38, Martin KM6TCD <peaceofandalus@...> wrote:
>
> Our club is looking for a built, tested, and working transceiver.
>
> Anyone got one they might sell?
>
> km6tcd
>


 

 

 

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

Stephan
 

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

Re: uBITx v5 - with mods

Curt
 

Ravi

Fantastic on your homebrew scratch build. Based upon all the clues, I wonder if there may be a missing connection at the crystal filter. Either try injecting a signal before and after it. If no signal source, use a wire or antenna to grab some signals and noise at the frequency. Also you might bypass that filter with a wire. If the crystal filter is the issue, then try pressing on each crystal. A smaller chance your BFO is way off, not letting signals through hear that become low enough frequency audio.

Its likely one or two simple things. Yes even touching the input of the audio should cause some buzz.

The ubitx purposely has minimal gain to make an excellent receiver. Audio level to drive a speaker is scarce even when its working well.

Curt

Re: Preliminary results -- W8TEE/AC8GY Mag Loop Testing

ajparent1/kb1gmx
 

Where I stand on loops:

Based on design work and in use.  Loop antennas are useful either in the
wide band receiving only type or tuned transmitting type.  They are not
close to full size dipoles in performance never minding beams.  However
they are self contained, compact, have a pair of very deep directional nulls.
Those features often offset the low gain and touchy tuning and on the
low bands like 80 and 160 they can be very useful even RX only for beating
local noise issues.  Often that is more important then how big your signal is.

As such Loops along with dipoles and other well understood antennas be part
of the hams box of tricks to enable communications.  

Bob/N4FBZ nails it:

"The thing is, every ham lives in a different situation... different factors that will strongly affect the performance of their antennas. 
Good ground and conductive soil (moisture) vs dry desert and poor ground, you name it.  If one has an idea for an antenna, try
it.  It might be just what is needed in that person's situation - and it's great fun trying.  That's part of learning the electronics/radio
portion of Amateur Radio... so you can have ideas of how to work around issues you may encounter (like poor grounding). 
That's just part of being a good op."

To that I'll add my three rules for antennas:
***If you want to improve any antenna raise it higher.
***If you want a better antenna add more metal (more elements
     or longer wire and so on) as bigger is often better.
***Above all else put something up or toss a wire out the window
    on the ground floor, it will be better than a bucket of wire in the shed.
    And you will then have an antenna you can compare you future work to.

Allison


Re: Preliminary results -- W8TEE/AC8GY Mag Loop Testing

ajparent1/kb1gmx
 

Alan de G1FXB

Jun 1
   

I recall you done antenna R&D.

Yes, I did for a commercial firm that was biased toward research and specialized designs.

EH antennas, based on work and research are a great way to make the coax radiate.
The antenna is often near the lower limits and radiates poorly but the coax shield is often long
enough to be effective on 160.

Do they work, for some measure of "works" yes sorta.  Hint do not choke the shield.
A better statement is that better antennas are likely possible in the same volume.

Every time I see that I go back to first principles and examine the system.

Allison

Re: Preliminary results -- W8TEE/AC8GY Mag Loop Testing

Robert D. Bowers
 

A friend of mine reported very good results with one of the loop antennas sold by MFJ (40-6 coverage as I remember).  He liked it because of the noise problem - here it can be a huge issue (not unusual to have S9 noise at least a couple hours out of the day, and some days 20-40db over the whole day).  He got out fine - but the big difference is that he could hear others.  (I've been thinking about building a loop - because of the noise, but even more so because they're small and work without being high up - and this area IS bad for lightning (a couple of direct hits on the tower over the years and many strikes within a couple of hundred feet at most, only a few repairs needed in the shack due to very good grounding, a disconnect 'patch board', and careful layout).

This thread reminds me of what I was told about a person wanting to run 40m (I think it was for a contest, but for something 'special').  He made up a quicky dipole and just threw it across the tops of some bushes, a few feet off the ground.  He said it worked GREAT, so much so that a couple of other hams were going to try it.  You wouldn't think it would work so good, but he said he did really well with it.

Another story - there was a huge sinkhole that suddenly formed here in Florida.  A ham lived just outside of the danger zone, and reported differences in how his antennas operated as the water level (immediate water table) rose in the sinkhole.  (I don't remember if his setup worked better or worse - just that it changed.)

The thing is, every ham lives in a different situation... different factors that will strongly affect the performance of their antennas.  Good ground and conductive soil (moisture) vs dry desert and poor ground, you name it.  If one has an idea for an antenna, try it.  It might be just what is needed in that person's situation - and it's great fun trying.  That's part of learning the electronics/radio portion of Amateur Radio... so you can have ideas of how to work around issues you may encounter (like poor grounding).  That's just part of being a good op.

Bob

N4FBZ

On 6/9/19 10:14 AM, EI4GNB wrote:
I knocked up a 3-turn loop, with an old soviet era vac-cap, total length was 10m of copper tube, and it covered 160m thru' 30m and did work very well, although the bandwidth was so skinny on topband, it did not allow for use of the internal tuner in my rig, tuning slightly off the SSB frequency as auto-tuners do when using a carrier. It just weighed so much that it was impractical. Did manage trans-atlantic on FT8 on Topband using it, so not all bad.

Next i tried using LM400 coax instead of the copper in a single loop, with 2 favourite lengths in the kit and a much smaller Vac-Cap, and i can work 40m thru' 6m by swapping out the coax (basically a long patch lead) and doing a slight tweak to the vari cap. I housed everything in an ABS box with SO239 for the coax loop connected to the cap, and i mount it on a small fibreglass pole, strapping it to whatever is available with luggage/shipping straps when out & about. Sure beats end-feds or tryign to support a vertical or inverted V etc.

I feed all my loops with a ferrite ring BTW, just dangling on the coax loop opposite the cap which is in the ABS box the loop hangs from.

Sure, this ain't no 'Cloudburn 5000 XL-DX Superblast multi-element face-melter' of an antenna, but it punches WAY above it's weight, and if You get lucky, You may even catch something to eat with it.

Re: Preliminary results -- W8TEE/AC8GY Mag Loop Testing

EI4GNB
 

I knocked up a 3-turn loop, with an old soviet era vac-cap, total length was 10m of copper tube, and it covered 160m thru' 30m and did work very well, although the bandwidth was so skinny on topband, it did not allow for use of the internal tuner in my rig, tuning slightly off the SSB frequency as auto-tuners do when using a carrier. It just weighed so much that it was impractical. Did manage trans-atlantic on FT8 on Topband using it, so not all bad.

Next i tried using LM400 coax instead of the copper in a single loop, with 2 favourite lengths in the kit and a much smaller Vac-Cap, and i can work 40m thru' 6m by swapping out the coax (basically a long patch lead) and doing a slight tweak to the vari cap. I housed everything in an ABS box with SO239 for the coax loop connected to the cap, and i mount it on a small fibreglass pole, strapping it to whatever is available with luggage/shipping straps when out & about. Sure beats end-feds or tryign to support a vertical or inverted V etc.

I feed all my loops with a ferrite ring BTW, just dangling on the coax loop opposite the cap which is in the ABS box the loop hangs from.

Sure, this ain't no 'Cloudburn 5000 XL-DX Superblast multi-element face-melter' of an antenna, but it punches WAY above it's weight, and if You get lucky, You may even catch something to eat with it.

Re: uBITx v5 - with mods

Ashhar Farhan
 

ravi,
which firmware version are you using? it might help to trace a signal. inject a 100mv signal and trace it with a scope on the rx path..
- f

On Sun, Jun 9, 2019 at 11:35 AM MVS Sarma <mvssarma@...> wrote:
Ravi jee, 
Just use kd8cec , select the lcd type in ubitx.h, select ver5 on main file, just compile. 

Later pwer on Nd while calibrating  change bfo to 1105550 and click ptt and save. Also power cycle.
Later select wwv and complete calibration.if needed few steps of bfo.

You should succeed. Atb
Sarma vu3 zmv



On Sat, 8 Jun 2019, 8:14 pm Ravi Miranda <ravimiranda@... wrote:
Hi All,

Apologies for the long post.

Background
I built a V5 using the circuit here:
http://www.hfsignals.com/wp-content/uploads/2019/02/ubitx_v5.pdf

I have also included the mods (BFR106) and changed the resistors as
specified. Only the RX stage has been enabled.
For the stages I used :
http://w7zoi.net/bidirectional_matched_amplifier.pdf keeping the
original values intact

The ladder crystal filter has been built with 11.0592 Mhz Crystals.

The voltages for the RX side (only) transistors are as follows:
Q10 [C] (9.33)     [B] (2.02)      [E] (1.31)
Q11 [C] (11.69)    [B] (9.33)     [E] (8.62)
Q12 [C] (11.69)    [B] (8.62)     [E] (7.89)


Q30 [C] (9.12)     [B] (2.06)      [E] (1.38)
Q31 [C] (11.69)    [B] (9.12)     [E] (8.45)
Q32 [C] (11.69)    [B] (8.45)     [E] (7.75)

I have not used the AGC circuit as given in the original V5 but opted
for the LM324 version. However, this is not  enabled.

I have taken the Panadapter out from just before the ladder filter
(post the stage 2 TIA). This is connected to SDRSharp to check signals

For the software, I used the V1.2  with frequencies calculated based on KD8CEC:
http://www.hamskey.com/2019/02/whats-new-with-ubitx-v5-1-changed-if.html

I  used the following values:
#define SECOND_OSC_USB (56054200l)
#define SECOND_OSC_LSB (33940800l)

#define INIT_USB_FREQ (11059250l)

According to the notes in KD8CEC's blog the firstIF has been set to
45005000L due to L7 and L5 pulling the crystal filter by 5KHz

Using the PanAdapter tap point that has been provided for I can see
that the signal passes through at just about 45.000.000 MHz, but at
times (start up) the signal can be heard on SDR# on 44.993.400.


Going backwards, I have used a signal injector from the input of the
audio amp to the output of the crystal stage and have a good noise
injection level at the speaker. If I use the signal injector at the
input side of crystal filter there is no sound.

I am using a local MW station on 1458KHz as this is the only station
that I can hear via SDR# (AM). The beat seems correct.

I can hear this station on the uBITx speaker very faintly (if I put my
ear next to it).

I am unable to copy any Ham stations or WWV or any other HF broadcast stations.

On start up I can hear a slight crackling noise through the speaker,
but have no clue where this is being generated.

To ensure that the SI5351 was calibrated correctly I used :
https://groups.io/g/BITX20/wiki/Si5351-Calibration-Sketch

and saved the value in the program

I have a RF milivoltmeter (homebrew) using a AD8307 and LM358
(uncalibrated), this is showing signal levels at testpoints. I haven't
done a thorough test at all points yet.

I have injected a 20mV(approx) using a AD9851 into the antenna input I
can hear the zero beat (14.150). With a stronger signal injection the
speaker jumps around quite a bit :-)

I have the following few questions ( few)
1. How do I know that the uBITx is tuned correctly
2. The volume level through the speaker is very poor.
3. Are the voltage levels on the transistors correct?
4. Shouldn't the Pandadapter (RTL dongle + SDR#) show the spectrum of
a larger bandwidth rather than just the tuned frequency at 45MHz?
5. Are the stages amplifying correctly?
6. How do I locate the source of the crackling? This dies down in a few mins.

I have access to a DSO, what checks can I do to verify the working and
improve the sound level?

Thoughts suggestions and comments welcome.

Sorry once again for the long post and thanks for reading. Have a great weekend.

Best 73,

Ravi/M0RVI










--
I'm here to add more value to the world than I'm using up.



Re: uBitx V3 transmit probles.

 

If the blue bias pot is slightly skewed then one lead could be cut. Replace.

Remove Q95 and check gate voltage as you vary the associated preset RV2. It should go from
0-5V. If not replace and set the bias again.

Raj

At 09-06-19, you wrote:
I have a V3 that just quit transmitting. It appeared the finals just went out. I replaced the finals (used sockets per advice from another user) and still no output. It is a good thing that I put them in sockets as now one of the new finals is bad. I decided to leave the finals out and test all the Transmit test points per the Diagnostic guide. When I test all the test points, the values are good both in transmit and receive mode, the transmitter section seems to be working as it should.

I hooked up my straight key and tested it in cw mode. The transmit section again looked good as far as the voltages go. Remember there are no finals and on pin 2 of the IRF510 I am getting a voltage reading when transmitting and a constant voltage of 12 volts on pin 2 all the time. Nothing of course on pin 3 as there is no 510 in place.

When I put an IRF510 in each socket, the one in Q94 looks normal but immediately the one in Q95 goes to 10 volts on pin 1. Where is this coming from and why? I have gone through 3 IRF510s in that location now, testing each one on my tester before installation.

Any ideas? Kind of at my wits end (actually that happened when I turned 13, but that's another story).....

Thanks in advance for the always helpful and illuminating ideas.

God bless
Dennis, KD4EPG

Re: uBITx v5 - with mods

MVS Sarma
 

Ravi jee, 
Just use kd8cec , select the lcd type in ubitx.h, select ver5 on main file, just compile. 

Later pwer on Nd while calibrating  change bfo to 1105550 and click ptt and save. Also power cycle.
Later select wwv and complete calibration.if needed few steps of bfo.

You should succeed. Atb
Sarma vu3 zmv



On Sat, 8 Jun 2019, 8:14 pm Ravi Miranda <ravimiranda@... wrote:
Hi All,

Apologies for the long post.

Background
I built a V5 using the circuit here:
http://www.hfsignals.com/wp-content/uploads/2019/02/ubitx_v5.pdf

I have also included the mods (BFR106) and changed the resistors as
specified. Only the RX stage has been enabled.
For the stages I used :
http://w7zoi.net/bidirectional_matched_amplifier.pdf keeping the
original values intact

The ladder crystal filter has been built with 11.0592 Mhz Crystals.

The voltages for the RX side (only) transistors are as follows:
Q10 [C] (9.33)     [B] (2.02)      [E] (1.31)
Q11 [C] (11.69)    [B] (9.33)     [E] (8.62)
Q12 [C] (11.69)    [B] (8.62)     [E] (7.89)


Q30 [C] (9.12)     [B] (2.06)      [E] (1.38)
Q31 [C] (11.69)    [B] (9.12)     [E] (8.45)
Q32 [C] (11.69)    [B] (8.45)     [E] (7.75)

I have not used the AGC circuit as given in the original V5 but opted
for the LM324 version. However, this is not  enabled.

I have taken the Panadapter out from just before the ladder filter
(post the stage 2 TIA). This is connected to SDRSharp to check signals

For the software, I used the V1.2  with frequencies calculated based on KD8CEC:
http://www.hamskey.com/2019/02/whats-new-with-ubitx-v5-1-changed-if.html

I  used the following values:
#define SECOND_OSC_USB (56054200l)
#define SECOND_OSC_LSB (33940800l)

#define INIT_USB_FREQ (11059250l)

According to the notes in KD8CEC's blog the firstIF has been set to
45005000L due to L7 and L5 pulling the crystal filter by 5KHz

Using the PanAdapter tap point that has been provided for I can see
that the signal passes through at just about 45.000.000 MHz, but at
times (start up) the signal can be heard on SDR# on 44.993.400.


Going backwards, I have used a signal injector from the input of the
audio amp to the output of the crystal stage and have a good noise
injection level at the speaker. If I use the signal injector at the
input side of crystal filter there is no sound.

I am using a local MW station on 1458KHz as this is the only station
that I can hear via SDR# (AM). The beat seems correct.

I can hear this station on the uBITx speaker very faintly (if I put my
ear next to it).

I am unable to copy any Ham stations or WWV or any other HF broadcast stations.

On start up I can hear a slight crackling noise through the speaker,
but have no clue where this is being generated.

To ensure that the SI5351 was calibrated correctly I used :
https://groups.io/g/BITX20/wiki/Si5351-Calibration-Sketch

and saved the value in the program

I have a RF milivoltmeter (homebrew) using a AD8307 and LM358
(uncalibrated), this is showing signal levels at testpoints. I haven't
done a thorough test at all points yet.

I have injected a 20mV(approx) using a AD9851 into the antenna input I
can hear the zero beat (14.150). With a stronger signal injection the
speaker jumps around quite a bit :-)

I have the following few questions ( few)
1. How do I know that the uBITx is tuned correctly
2. The volume level through the speaker is very poor.
3. Are the voltage levels on the transistors correct?
4. Shouldn't the Pandadapter (RTL dongle + SDR#) show the spectrum of
a larger bandwidth rather than just the tuned frequency at 45MHz?
5. Are the stages amplifying correctly?
6. How do I locate the source of the crackling? This dies down in a few mins.

I have access to a DSO, what checks can I do to verify the working and
improve the sound level?

Thoughts suggestions and comments welcome.

Sorry once again for the long post and thanks for reading. Have a great weekend.

Best 73,

Ravi/M0RVI










--
I'm here to add more value to the world than I'm using up.



uBitx V3 transmit probles.

Dennis Yancey
 

I have a V3 that just quit transmitting. It appeared the finals just went out. I replaced the finals (used sockets per advice from another user) and still no output. It is a good thing that I put them in sockets as now one of the new finals is bad. I decided to leave the finals out and test all the Transmit test points per the Diagnostic guide. When I test all the test  points, the values are good both in transmit and receive mode, the transmitter section seems to be working as it should. 

I hooked up my straight key and tested it in cw mode. The transmit section again looked good as far as the voltages go. Remember there are no finals and on pin 2 of the IRF510 I am getting a voltage reading when transmitting and a constant voltage of 12 volts on pin 2 all the time. Nothing of course on pin 3 as there is no 510 in place. 

When I put an IRF510 in each socket, the one in Q94 looks normal but immediately the one in Q95 goes to 10 volts on pin 1. Where is this coming from and why? I have gone through 3 IRF510s in that location now, testing each one on my tester before installation. 

Any ideas? Kind of at my wits end (actually that happened when I turned 13, but that's another story)..... 

Thanks in advance for the always helpful and illuminating ideas. 

God bless
Dennis, KD4EPG
--
72 and God bless
KD4EPG