Date   
Re: boosting the power on 28 MHz #ubitx

Dave de WS1ETI <docame12@...>
 

Allison,

excuse the noob question. I have a handful of 2n2222's in my box. Are these anywhere near the same as your 2n222A?

Thanks,
Dave

Re: FLdigi

Bo Barry <bobarr@...>
 

Solved it yesterday. On my Raspberry pi  at least. Trying on my PC today.

Using flrig along with fldigi. Even tho the version on the pi doesn't have the flrig option. I clicked the rigcat option and it worked great.

I read that hamlib needed 2 stop bits but the code in the two firmware versions I have use only 1. I changed and recompiled but saw no change.

Anxious to start using instead of tinkering and troubleshooting.   Bo W4GHV 

Re: Dead bitx 40

MVS Sarma
 

you may have to check load side after removing the 780
 if there is a short, we need to find if the Arduino is causing?
 if so, because removal  of arduino is more difficult,  i would have a small cut in the 5V feed line to arduino and then check if the short is gone.  if it is gone, , perhaps you have to service arduino. Many of members advised how to replace an ardunio without damaging the main board. please try to read.

all the best




Regards
MVS Sarma
 

On Sat, Jun 2, 2018 at 6:24 PM, Avijit <vu3mvh@...> wrote:
Hello friends,
My friend's bitx 40 isn't powering up after few month's excellent service. No display on the raduino but the 7805 is getting hot. No sound on the speaker too. Please advise.
73,
Avijit


Re: Dead bitx 40

Jerry Gaffke
 

Is the 7805 getting hotter than it did when things worked?

Carefully measure the voltage of the 5v pin out of the 7805 to ground.
The 5v pin is on the top of the 7805, the pin nearest the blue contrast pot.
You can use one of the Raduino corner mounting holes as ground.
Do you see 5v there?  (I would guess you do.)

Any idea what happened to the rig between when it did work and when it didn't work?

There's a bunch of unused wires hanging off of the Raduino, did they possibly brush against
random points o the main board?  (Best to tape the ends of those wires up, or remove
those wires entirely by extracting the pins from the connector).


Using a shortwave receiver in SSB mode (not AM), put the antenna near the DDS wire from Raduino to main board.
With stock firmware, I believe the VFO is around 12-7.2 = 4.8mhz.
But with Allards improved firmware, it may be there, or have moved to 12+7.2 = 19.2mhz.
Can you hear that VFO carrier?    It's probably within 100khz of the stated frequency.
My guess is that you won't hear the VFO.


My best guess:  
A loose wire end from a Raduino connector brushed against 12v on the main board
and fried the Nano on the Raduino.  So you won't find that VFO using the SW receiver.
You could fix this by clipping out the old Nano and replacing it with one you buy locally.
Or you could replace the entire Raduino.

Do you have a scope?

Jerry



On Sat, Jun 2, 2018 at 05:54 am, Avijit wrote:
My friend's bitx 40 isn't powering up after few month's excellent service. No display on the raduino but the 7805 is getting hot. No sound on the speaker too. Please advise.
 

Re: µBITX Disable TC (use for CW training)

Hans Stoll
 

On Sat, Jun 2, 2018 at 06:41 am, Hans Stoll wrote:


Where to find the stock firmware (for uBITX r3) source code?
Oh sorry, found it:
https://github.com/afarhan/ubitx4
Runs with r3 as well?

Re: µBITX Disable TC (use for CW training)

Hans Stoll
 

Where to find the stock firmware (for uBITX r3) source code?

Dead bitx 40

Avijit
 

Hello friends,
My friend's bitx 40 isn't powering up after few month's excellent service. No display on the raduino but the 7805 is getting hot. No sound on the speaker too. Please advise.
73,
Avijit

Re: µBITX Disable TC (use for CW training)

Daniel Conklin <danconklin2@...>
 

The CEC firmware has a menu setting to turn off transmit  
Dan, W2DLC 

Re: µBITX Disable TC (use for CW training)

Ashhar Farhan
 

Or hack the firmware


On Sat, 2 Jun 2018, 16:19 PE1GIJ, <info@...> wrote:
Disconnect the power to the PA and only feed the logic as a kiss solution.
--
Ad, PE1GIJ

Re: The new uBITX boards are here

W8RMV
 

Thanx, Dan.  Yeah, I am drinking from the BITX firehose right now, having just jumped into this.  73 Bob W8RMV

Re: µBITX Disable TC (use for CW training)

PE1GIJ
 

Disconnect the power to the PA and only feed the logic as a kiss solution.
--
Ad, PE1GIJ

µBITX Disable TC (use for CW training)

Hans Stoll
 

Hi,

I would like to use the keyer in µBITX to for some CW excercises with a paddle but I don't want to transmit (or use a dummy load) so is it possible to disable TX while using CW and just listen to the side tone?

73

Re: RF power chain mods and improvements..

Jerry Gaffke
 

Move to a high side VFO.
Can be done by just switching to USB mode.

I believe all firmware to date uses a low side vfo, at 45mhz - OperatingFrequency.
when in LSB mode.
This was done so that the BFO was low side, to avoid interference with Nano oscillators.
If that's an issue, I think it is easily tamed.

Jerry

Re: RF power chain mods and improvements..

Gordon Gibby <ggibby@...>
 

A lot of people use a T- type tuner to connect to their feedline; these might provide a bit of filtering of the lower undesired frequency.


On Jun 2, 2018, at 01:38, Kelly Jack <kellyjack1968@...> wrote:

Not a solution but if the uppermost lpf is not going to be used could it be rengineered for 160m?

Re: RF power chain mods and improvements..

Kelly Jack
 

Not a solution but if the uppermost lpf is not going to be used could it be rengineered for 160m?

Re: FLdigi

Ashhar Farhan
 

which firmware are you using? 
- f

On Sat, Jun 2, 2018 at 10:41 AM, Dennis <dennis@...> wrote:
I have wsjt-x working fine, but I can't transmit using FLdigi. Receive works ok. Could someone share their settings with me?

73, Dennis
W7DRW


Re: RF power chain mods and improvements..

Jerry Gaffke
 

Allison, many thanks for looking into that.

The nasty spur is not a problem from 3.5mhz up to 18mhz.
So for operators that never use the 15, 12 and 10 meter bands, this is not of concern.
For many of us, a $129 rig that covers 80-17 meters is still a very good deal.

For those wishing to use the rig above 18mhz, perhaps some sort of external band-pass
or high-pass filter is in order between the uBitx and the antenna.
Some (but not all) antenna tuners might be sufficient.

If the audio from the mike amp is kept reasonable, Allison reports that the spur is 40+ dB down.
I assume it should be 43 dB below our primary signal, so it's marginal at best.
But we might avoid the worst of this problem by somehow monitoring the transmit signal level
at the mixers.  Allison has found that gain with the 2n3904's can vary on the upper bands
depending on your particular device characteristics, so it currently is not sufficient to just
check the level at one point in the chain.  However, if gains can be made more predictable,
perhaps monitoring at the top of RV1 using a diode RF probe is sufficient?
 
The uBitx has a 30mhz low pass filter between the mixers and the power amp at 
As Allison says, most multiband rigs would have switched bandpass filters in that position.
Signals are quite low level, could probably be done with analog switches rather than relays.
So yet another possibility is to add a daughterboard with switched bandpass filters to 
replace the filter at L1,2,3,4.  We only need 3 or 4 filters there and parts can be small and cheap,
so not so bad.

The spur is at the first IF frequency of 45mhz minus the operating frequency.
If the first IF is raised from 45mhz to 70mhz or more, that should remove the spur for all
frequencies from 3.5 to 30mhz.  Will definitely require something better than the 2n3904's
within that 70mhz IF strip.

Anybody see any other possible solutions?

Jerry, KE7ER



On Fri, Jun 1, 2018 at 08:18 pm, ajparent1/KB1GMX wrote:
Here is the problem...

There are a few actually.  Improving the amp leads to acknowledging other issues.

The spurs.

SSB CASE only:
For the case of transmit for 15 and 10 M the biltier used has a cutoff over 30Mhz
so effectively the amp will pass though everything it hears.  If you overdrive
the mixers especially the 45mhz output mixer you get two things. The desired
output say 28Mhz you get a second actually two others one at 11.995mhz about
50 to 60 db down and the other at about 17mhz and if the drive is low its 40+ db
down, push the audio and it can be 25db down from carrier out.  The amplifier
having no filtering below 30mhz will gladly amplify all of them and does!  This
is not an issue for 3-about 18mhz as the output low pass filter that are switched
in helps attenuate the spurs.

The math is:

Output is IF(about 45mhz) + LO (48 to 75mhz)= 3 to 30 mhz
The spur case is IF(45mhz) - Output frequency (42 to 15mhz)  Its going down while the dial frequency is going up.

For up to 18mhz the output lo pass filters and the inside 33mhz low pass filter are at work doing the job.
However for 21 and 28 mhz both filters are roughly 33-35mhz cutoff and the spur is now down around
24 and 17 mhz respectively.  They will be about 40-50db down until the 45mhz mixer overloads and
then the spurs get very much stronger at a frequency well below the cutoff of the low pass filters.
Since power output is low on 10M people will likely push the audio and the spur will get significantly
worse.

The is due to the nature of DBMs, they are three port devices and all three can receive input or deliver outputs.
Also inside the mixer all possible sums and differences for the base frequencies  and their harmonics exist.

This was determined without the amp operating by breaking the circuit at C200 for a spectrum analyzer.
We can't blame the amplifier chain  for this as it would just do its designed duty and amplify everything.

Right now I have no solution.  The usual one commercial radios implement is a switched filter 
at the point were L1 though L4 exist (and C200 to c204) and the filter would be for 15M, 12M and 10M.
I'm looking at and for other ideas.

I've stopped work on the amp (I've had success but the spur took me on a divergent path) till a
solution can be had.

This does not show up in CW mode as the way the radio is keyed there is no 45mhz contribution.

Allison

FLdigi

Dennis
 

I have wsjt-x working fine, but I can't transmit using FLdigi. Receive works ok. Could someone share their settings with me?

73, Dennis
W7DRW

Re: AGC circuit to try?

Jerry Gaffke
 

OK,
I didn't see mention of anything below 1.7ghz.
But didn't look very hard.


On Fri, Jun 1, 2018 at 07:41 pm, Michael Shreeve wrote:
Yes, may be a problem for lower freq stuff, but I claims its dc to daylight

Re: AGC circuit to try?

Jerry Gaffke
 

Not all that narrow. 
1.7-2.0 GHz means it's 300 mhz wide.
That's plenty.
Unfortunately does not cover 3.5-30 mhz.


On Fri, Jun 1, 2018 at 07:49 pm, Michael Shreeve wrote:
Yes Jerry, very narrow. Oh well, shouldn't work.