Date   
Re: RF power chain mods and improvements..

Kelly Jack
 

Hi all,

Some more testing tonight.

Measured efficiency with mods per earlier post was low as follows:

Band                            Efficiency
80                  29%
             15
40                                 10                                                                         20
30                                 10                                                                         20
20                                 9                                                                           19
17                                10                                                                          22
15                                10                                                                          18
12                                8                                                                            16
10                                6                                                                            16

Re: RF power chain mods and improvements..

Kelly Jack
 

Hi all,

Some more testing and mods.

Measured efficiency of the PA only when RV1 adjusted for 10W output on each band (current measured through the PA-PWR line, current is zero during receive):
80m  29%
40m  29%
30m  33%
20m  30%
17m  34%
15m  45%
12m  41%
10m  45%

Not good.

Changed T11 to BN43-3312 same wire and turns ratio, 2 primary to 4 secondary.

Power measured using same method as above with BN43-3312 no cap across the primary, each band set to 10W by adjusting RV1.

80m  40%
40m  39%
30m  46%
20m  44%
17m  41%
15m  49%
12m  48%
10m  50%

Much better and finals are cooler but still get hot with key down for 30 seconds. Some acceptable numbers there but why is efficiency increasing with higher frequency?

Note that power efficiency measurements are for the finals only.

73



Simon
VK3ELH



 

Re: audio dropping out

Dave de WS1ETI <docame12@...>
 

On Mon, May 28, 2018 at 12:39 pm, Jerry Gaffke wrote:
Does the problem also occur when you have the volume set so low that you can barely hear it?
I want to say no it does not. It seems to be happening only when the vol pot is at half way position, or higher, and a loud station comes on.  I hear a crackling noise as the sound drops out fairly quick. Then, it will also come back the same way, by itself with no intervention from me. (Like I said earlier, sometimes if I touch the range and yellow wires the sound comes back. Now, I don't know if this was just coincidence.)   It also happens while I am tuning up on whatever band and I have the volume too high. If I turn it down, it seems to stop.

Thanks,
Dave
 

Re: Simple sound card interface #ft8

Doug W
 

here's what I did...
https://groups.io/g/BITX20/wiki/Digital-Setup
--
www.bitxmap.com

Re: A steal for Arduino Experimenters

 

Jack,

You are so right about the clones. My first was a authentic Arduino UNO that I bought from Radio Shack for 30 bucks, (so I've paid the tax), now I have maybe 40 clones of all flavors including a dozen plain ATmega328PU chips for building directly into my projects. When you get right down to it, a Arduino is nothing but a 328 chip and a 16Mhz crystal and a couple of 22pf caps, (overly simplified I know). I also agree with Jerry about using Pro Minis, it's not necessary to have all that USB circuitry sitting there running for a occasional firmware update when you can just plug a USB TTL Serial adapter in, do your update and remove it. Of course this wouldn't work if you needed CAT control, I don't. That Banggood kit is a great deal for getting started building Arduino projects.

Joel
N6ALT

Re: audio dropping out

 

Dave,

Solder a wire to the 2822 audio chip 12v in PIN 2 and monitor the voltage when this audio dropout happens.
A plated through hole may not be conducting properly if the voltage is dropping!

OTOH, your audio chip maybe bad.

Raj


At 29/05/2018, you wrote:
On Mon, May 28, 2018 at 12:39 pm, Jerry Gaffke wrote:
Does the problem also occur when you have the volume set so low that you can barely hear it?

I want to say no it does not. It seems to be happening only when the vol pot is at half way position, or higher, and a loud station comes on.  I hear a crackling noise as the sound drops out fairly quick. Then, it will also come back the same way, by itself with no intervention from me. (Like I said earlier, sometimes if I touch the range and yellow wires the sound comes back. Now, I don't know if this was just coincidence.)   It also happens while I am tuning up on whatever band and I have the volume too high. If I turn it down, it seems to stop.

Thanks,
Dave
 

Re: A steal for Arduino Experimenters

 

Oh, I forgot to add that we can make the ATmega328 even easier by eliminating the 16Mhz crystal and the two 22pf caps, and use the internal 8Mhz clock which runs a si5351 and OLED display just fine with no noticeable difference.

Joel
N6ALT

I would like to chat with someone that has set there ubtx up with a raspberry pi and is using fl digi,

Tony D'Angelo <tony_d_33931@...>
 

I would like to chat with someone that has set there ubtx up with a raspberry pi and is using fl digi,

I think this may be a good way to go as I have most of the parts. Not sure if I need an external sound card or diarwolf or both. I do have a pi tnc but I don’t think that would be much help here. Please I want to chat with some one who has done this no please no “helpful guys with a bunch of links.”  We all know what I’m talking about! LOL

Thanks

Re: A steal for Arduino Experimenters

Jack, W8TEE
 

Mornin' Joel:

Agree 100%. The CAT people do need the interface and the reason I push that more than the non-USB versions is because much of my work is done with people who don't have much (any?) programming experience and the familiar USB connector lowers the hurdles in their minds. After I put JackAl to bed, I'm going to do a project with the new Protoneer board, which is about the same size as the Nano, but with a 3x clock and 32K of SRAM.

Jack, W8TEE

On Tuesday, May 29, 2018, 10:11:53 AM EDT, Joel Caulkins <caulktel@...> wrote:


Jack,

You are so right about the clones. My first was a authentic Arduino UNO that I bought from Radio Shack for 30 bucks, (so I've paid the tax), now I have maybe 40 clones of all flavors including a dozen plain ATmega328PU chips for building directly into my projects. When you get right down to it, a Arduino is nothing but a 328 chip and a 16Mhz crystal and a couple of 22pf caps, (overly simplified I know). I also agree with Jerry about using Pro Minis, it's not necessary to have all that USB circuitry sitting there running for a occasional firmware update when you can just plug a USB TTL Serial adapter in, do your update and remove it. Of course this wouldn't work if you needed CAT control, I don't. That Banggood kit is a great deal for getting started building Arduino projects.

Joel
N6ALT

Re: Instruction Manual needs revision #ubitx

W7PEA
 

Yes! There's a wiki on doing a vanilla buid I started for the same reasons you mention.  https://groups.io/g/BITX20/wiki/uBITX-Assembly

It's not mine, it's the groups, so feel free to improve it. 
W7PEA

Re: Oscillation problems Bitx20a

Arv Evans
 

FOKO

The "Miguel" mod that you are talking about has become a de-facto standard for the QRP-Kits version of BITX.  It decreases higher frequency gain of the IRF510's and makes them less suceptible to oscillation if the antenna feedpoint impedance is too high.  These components are usually just soldered across the indicated points on the bottom of the PCB.  

Arv K7HKL
_-_






Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------
From: Fokko PH0KKO <kaapstad1@...>
Date: 5/29/18 12:46 AM (GMT-07:00)
To: BITX20@groups.io
Subject: [BITX20] Oscillation problems Bitx20a

I built a Bitx dead-bug-style for 40 meters based on the Bitx20a schematic but I have some oscillation problem. I set the driver bias and both final biases to 50 ma and the drive adjust about a quarter of the way up. Sofar nothing wrong.

But as soon as I connect the signal generator it starts oscillating, even after disconnecting the signal and turning the drive adjust all the way down. I use a 40A switching PSU so that should be able to handle it, my amp meter does not show any fluctuation.

There are some suggestions in the Bitx20a manual but I don' t quite know hoe to interpret them: "mounting a 220 ohm resistor between C6/R13 and the collector of Q3", does that mean leave everything else as it is and add an extra resistor between these points? Or does it mean: cut the connection going from C6/R13 to T3 and put a 220 ohm resistor in between?

The same goes for "mount a 1k resistor between the drains of Q18 and Q19". Also here, should I leave it as it is and simple add a 1k resistor over the drains of these MOSFETs or put them in line between the MOSFETs going to T2? This is not clear to me. I hope someone can advise me.

 

Re: W8TEE vft/tft questions

tom.mccobb@...
 

Thanks for this.  I downloaded the code and will take a look.

Re: RF power chain mods and improvements..

ajparent1/KB1GMX <kb1gmx@...>
 

Increasing efficiency with frequency usually indicates not enough inductance
or over coupling (too high a tranformation ratio).  I'd expect the efficiency to peak
around 10mhz  and what finals are used have less influence safe for what the
ideal combo is.  I'd expect the peak to be better than 55% based on experience.  

Right now the Drivers are 2n2222A(to18) and heating there is noted only when
pushing power.  The 4 of them easily push  1 watt.   They seem better than
mpsh10s in that spot.  still not flat for power but at 12W on 80M I can see 6W on 10M
and RV1 full up on 10 is easily 10W and saturating (clipping) at 15W on 80.
With that I find the IRF510s run cool with a 2:2 transformer using BN43-302 
running cold.

For the RD16HHF, K5BCQ has the receipe with his 20W amp. 

NOTE breadboard/deadbug will behave better.  The traces on the ubitx in the final
area are too narrow for the RF currents and impedance.  This is worse at high power.
It adds inductance that cannot be tuned out in the drain path.

Watch the harmonic output.  Second should be about the same as third with the filters.
At some point I have to look at the filters too but being as there are only four its a
tough haul to do 3.5 to 30. 

Here's a detail...  While testing I found the 45mhz IF amp I noted low in gain.  Replaced the 2n3904
with a BFR106 for Q10 and Q20 and saw a big increase in TX drive (about 6DB before mixer
compression) and it also helped the RX on 10 and 15M.  A 2n3904 at 45mhz is really asking too
much for the device in common emitter service while the emitter followers are ok as is.


Allison

Re: RF power chain mods and improvements..

ajparent1/KB1GMX <kb1gmx@...>
 

Periodic message and note...

The work I'm doing for the power chain is centered on getting about 10W and some level
of uniformity to 10M.  Not all the things I'm doing will help if your goal is 13W or more.
I'm shooting for 10W and to stay within 2w or less of that through 10M (less than 2db
differential).  Getting to a 3db drop 12W at 80 and 6W at 10 is easier.  

Why do this?  Because mine was one that did 13W on 80M, barely 7w on 40M and
1.6W on 10M.   As a RF modder from way back, this can be better.

As I work I may find other things as well and have.

Those working toward higher power...
I would strongly suggest if your trying to do 13W or more to pull the finals off the board
optimise the driver for a 50 ohm load and put the final amp off board connected by coax
from the driver to the final and back.  I'm neither pro or con to IRF510 or RD16HHF as
both work depending on what power your want.   You will have more room
for big ferrite, optimal  RF conductor paths, better heat sinking and keep the
high power stages further away from the lower power stages for RF stability.

Note on low pass filters.  To go 3.5 to 30mhz is a problem for engineering as they
must suppress harmonics of harmonically related bands.  It pretty much means
a filter for 3.5 to 6  (60M note in the USA the spec is higher for spurious signals),
The next has to be effective for 7 through about 10.5mhz, the third must pass 20 and 17M,
and the 15 and 10M filter must be a hard stop for harmonics of 15M as well as 10M.
That is a tall order and depending on tolerances I see bumps and wiggles that make
gain flatness hard to achieve that is if the amp does but the filters mess with it.

It is a lot to achieve on a small board and I consider uBITX really doing a great
job of achieving it.  Getting it to work well is in engineering terms abou managing
compromise well.


Allison

Ideas for AM, NB FM Demod and CW filter board

Rahul Srivastava
 

Hi!

I was discussing with Farhan on this topic for an add on demod board to add more versatility to uBitx.  CB radios often used a common chip for AM as well as NBFM receive. I enquired here and TDA1220 is available in mkt for slightly more than a $.

With the parallel XF mod maybe we can have an add on board with this chip and a 6 pole Cohn CW xtal filter. 2nd IF's now being 12MHz SSB, 10.7MHz + 455KHz for AM/FM and possibly 8.xx MHz or some other for CW. 

Guys what to suggest..

73

Rahul VU3WJM 

Re: A steal for Arduino Experimenters

Jerry Gaffke
 

I find the Arduino clones easy enough, but the CH340 trips up lots of folks, especially those with a Mac.
Doing away with or disabling the CH340, then coming in with a UART through D0,D1 allows a choice
of the various USB-to-UART devices, perhaps FTDI or CP2102.  Having D0,D1 come to the front
panel at a stereo 3.5mm jack allow D0,D1 to be used with a keyer paddle when not used for CAT
or firmware downloads.  No need to mess with getting a USB cable into the Arduino.
Having the USB-to-UART a separate cable assembly allows an easy UART loopback test
of the host port before trying to mess with talking to an Arduino.  And if using it for CAT,
a UART at 9600 baud is going to be a lot easier to filter out RFI cruft from than a 12mhz USB port.

I don't think this is a slam dunk either way, it's nice to be able to plug a USB cable into an Arduino
and not worry about obtaining some other thingie to put between your PC's USB port and the Arduino.
Just presenting an alternate view here. 

Glossary:
The Nano and Protoneer are particular flavors of Arduino processor boards, and the Raduino is a board built by 
hfsignals that has a Nano mounted on it plus a display and the si5351 to create our local oscillators. 
CAT is an acronym for "Computer Aided Transceiver", where you use a desktop/laptop/RasberryPi to control
your amateur radio transceiver instead of twiddling all the knobs and switches on the transceiver.
RFI is Radio Frequency Interference.  USB is what comes out of that little rectangular port of your laptop
(Universal Serial Bus), and it not Upper SideBand in this context.  UART is Universal Asynchronoous 
Receiver Transmitter, a fairly primitive and easy to debug way of moving data around that predates USB
by about 40 years.  D0,D1 are two generic digital pins on the Arduino that also connect to
the Arduino's internal UART hardware.  The CH340 chip on the Nano listens to the USB interface from
your laptop, translates it into UART signals that get presented to D0,D1 through two 1k resistors, the
resistors allow you to talk to D0,D1 from some other device besides the CH340 such as a CP2102
or FTDI cable assembly of your choosing when the CH340 is not being used.
http://www.ftdichip.com/Products/Cables/USBTTLSerial.htm
http://www.oddwires.com/cp2102-serial-adapter-module-usb-to-rs232-with-jumper-wires/

Jerry, KE7ER


On Tue, May 29, 2018 at 07:58 am, Jack Purdum wrote:
Agree 100%. The CAT people do need the interface and the reason I push that more than the non-USB versions is because much of my work is done with people who don't have much (any?) programming experience and the familiar USB connector lowers the hurdles in their minds. After I put JackAl to bed, I'm going to do a project with the new Protoneer board, which is about the same size as the Nano, but with a 3x clock and 32K of SRAM.
 

Banggood front panel template

brad martin
 

Figured I would share my design of the front panel of the Banggood (https://www.banggood.com/Electronic-Plastic-Shell-Cartridge-Handle-Project-Case-Desk-Instrument-200x175x70mm-p-1035473.html?cur_warehouse=USA) that I have seen a lot of people using.  Im not a graphic designer or a designer of any sort so please edit this as you like or see fit and contribute your edits as you want.  Currently the basic design of this is that the uBITX mainboard, raduino, and LCD all just drop in.

Re: Instruction Manual needs revision #ubitx

Kevin Timm
 

Too bad the pictures aren't clickable (for enlarging). Only the schematic gets bigger

73 
K5KDT

On Tue, May 29, 2018 at 10:04 AM W7PEA <patrick@...> wrote:
Yes! There's a wiki on doing a vanilla buid I started for the same reasons you mention.  https://groups.io/g/BITX20/wiki/uBITX-Assembly

It's not mine, it's the groups, so feel free to improve it. 
W7PEA

Re: Oscillation problems Bitx20a

ajparent1/KB1GMX <kb1gmx@...>
 

Several things:

The IRF510 is a very good RF device in that it achieves a lot of gain and at respectable power.
That translates to about 16dB in the HF range with 50 -200ma of bias. 

That also means keeping it away from the low power part of the amplifier chain preferably
a straight line from input to output.  I usually cut the drain lead off the IRF510 at the case
and use the tab (with suitable lug and insulators) for connection.  That allows the input
Gate to be further from the output  Drain and the source lead to be as short as possible
with mounting the transistor to a heat sink that is grounded (use insulators and thermal grease).
List that as tribal tricks.

Other considerations is that power conductors can propagate signals to places not desired
so by pass well (to excess).

If the input circuit or output circuit is not well controlled for impedance the high gain devices
(includes the drivers and before) will become oscillators.  The resistor to the gate of the
IRF510 should be kept to a low value such as 47 ohms.  Also keep the toroids well apart
as despite claims they do couple to the one next to it, just not as well as open coils will.

Dead bug means short leads are a very good practice!


Allison

Re: I would like to chat with someone that has set there ubtx up with a raspberry pi and is using fl digi,

ajparent1/KB1GMX <kb1gmx@...>
 

It has been discussed here before.

I have a RPi3b running FLdigi and its ok with a external usb sound card and a FTDI RS232-3v3 serial cable.
the serial cable provides DTR keying(externa or PTT)  for my Tentec 6n2 rig and the sound card with
isolation transformers handle the audio.  NOTE use the RPi 3 or higher and make sure you max the
clock for the version as FLdigi use a lot of the CPU.  Also tune Linux for minimum process activity
so FLdigi has sufficient resources.  Try to not use software modem or pWM as it s resource intensive
the external sound card I use were cheap USB stereo units 7-8$ off Amazon.

I'd use the exact same interface for the uBitx as it works fine with my all of my HB SSB radios and the
kd1jv 20M SlopBucket, KNQ7A as well.

Allison