Date   
Re: PTT Question

Tim Gorman
 

First get a 4-wire mic plug and jack and then some 3-wire + shield
audio cable. They are plentiful on the internet.

1 - wire for the mic lead from the 9814.
1 - wire for the ground lead to the mic and to the 9814.
1 - wire for the PTT lead
1- wire for the 5v to the 9814.

Which wires you use on what pins is totally up to you.

go here for more info:
cdn-learn.adafruit.com/downloads/pdf/adafruit-agc-electret-microphone-amplifier-max9814.pdf

Don't forget to put a capacitor in series with the mic lead to block
the DC from 9814.

tim ab0wr

On Fri, 08 Jun 2018 14:25:10 -0700
alexandre.polozoff@... wrote:

On Fri, Jun 1, 2018 at 11:52 am, Tim Gorman wrote:


max9814
How would one wire this up for the uBITX?


Re: RF power chain mods and improvements..

Jerry Gaffke
 

Yup, you are right.
Figure 8 on page 4 of   https://www.mouser.com/datasheet/2/348/2scr513p5t100-e-1017538.pdf
shows Ft drops below 300 for currents under 50ma when Vce is 10v on that Rohm part.

The 2n2222a datasheet just says a min Ft of 300 at 20ma with Vce of 20v, freq of 100mhz, no other data points.
No curves of nothing.
Makes me wonder what the curves for a 2n2222a would look like.


On Fri, Jun 8, 2018 at 03:51 pm, Ion Petroianu, VA3NOI wrote:
Looking at the data sheet seems to indicate that Ft=360MHz is achievable at 200 mA current. It might not work in our application.

Re: RF power chain mods and improvements..

ajparent1/KB1GMX <kb1gmx@...>
 

Regarding EB63,  Most I know had a great deal of effort trying to make it work
and behave stable.  Its not a forgiving design.  The "real RF" transistors used
are 40+ year old types that are not generally cheap.

The idea is to get part that can do about .6 watt and have an FT above 1000mhz,
360mhz is barely better than 2n3904...  

For Q90 a good solid part is easy as that stage at the extreme generates maybe a 
milliwatt or two.  So 2n5179 works fine if you stay inside the voltage limits and
never exceeds 12V (9 would be enough).  But the pads on the board are for
a SMT part and the BFR106 is a winner and cheap too.  The prime need here
is a FT of not less than 1ghz.  If any one suggest a 300mhz part you might
as well keep the 2n3905.

For the next stage we need to put out a maximum of maybe 100mW (actually 
less but headroom).  A lot of parts can do that but it must be able to keep its 
gain to 30mhz.   There are a few MMICs that can crank that kind of power
none cheap.  I think one good device is adequate.  I tried a single 5109 there it 
worked fine.

The driver stage.  That needs to deliver up to .8 watt, not a whole lot
and a pair (not 4) of 2n5109, maybe 2n3866, 2SC3052(memory test on 
the number) and long list of 20V or higher CATV parts.  Two parts of
sufficient capability results in more board space and better cooling. 
I'd like to try two 2n5109 in this stage when I get a chance.  IF 2SC2166 
was available (not fakes) it would be a likely winner here.

The IRF510 has what we need. power, gain, and price!  There are better parts
but generally at 12V... not much better and the price is significantly higher.

The biggest issue if if you diverge too far from the base design you end up
rewinding all the transformers to behave best with the new devices.

As a QRP rig it is what it is for a good price.  If I want 100W radio I have it already.
Where the uBitx fits is the QRP replacement for a monoband only radio, its 
multiband.  

Allison

Re: RF power chain mods and improvements..

ajparent1/KB1GMX <kb1gmx@...>
 

Jerry,

As and you get...

Look at the tabular data as they are not spec'ed as RF devices.
Also look at the 2n2219/2222 data sheet.  They are the same die in different packages.

Allison

Re: RF power chain mods and improvements..

Jerry Gaffke
 

I did find a 2n2222a datasheet, not the issue.
Point is, it only gives Ft for a single data point, 20ma and Vce of 20v.
The Rohm parts show a graph,of Ft over current for at Vce  of 10v at 100mhz.
I can't compare them for this application based on the data given, neither is fully characterized.
(Not that I could predict much if they were.)

Worth experimenting with.
I doubt hfsignals will be stuffing any 2n3866's 






If collector currents are up around 100ma or better, the Rohm part may be better.
But since none of these $0.15 parts are fully characterized 


On Fri, Jun 8, 2018 at 07:46 pm, ajparent1/KB1GMX wrote:
Jerry,

As and you get...

Look at the tabular data as they are not spec'ed as RF devices.
Also look at the 2n2219/2222 data sheet.  They are the same die in different packages.

Allison

 

 

Re: RF power chain mods and improvements..

Jerry Gaffke
 

Here's an interesting part:  
    https://www.mouser.com/ProductDetail/Infineon-Technologies/BFP780H6327XTSA1?qs=0DP5yvOrqYk3T8WgQ0FT4g%3d%3d

From how it's described, I assumed it was an MMIC.
But near as I can tell, it's an NPN transistor.
Very cheap (under a buck) fairly high power (23dbm) with an Ft of 20ghz.
Designed to operate from 5v.

Jerry

Re: CW transmit bandwidth #ubitxcw #ubitx

Allan Mason
 

This email is for those interested in using the transceiver for CW. 

Being mainly a CW operator, I was concerned about the V3 board uBitx transmit CW wave shape being very hard with an almost square waveshape and as expected, key clicks could be heard on either side of the signal. A look at the circuit diagram and a little tinkering today vastly improved the situation.

All that was required was to increase the value of C1 from 0.1uf to 1uf. Attached are some CRO photos of the end result showing the leading edge and trailing edge of the transmitter output with a 1uf connected across C1. The other photo shows where a short wire was soldered to the hot side of C1 for the tests.  In reality the wave shape is now a little soft on the trailing edge, so 0.047 or 0.68uf may be sufficient for some people.   More work could possibly be done with the CW keying RC network to the 1st balanced mixer, however this one component simple fix will suit my needs.

The tests were contucted using the internal keyer set to 25wpm. The CRO connection point was at the antenna BNC connector with a 50ohm dummy load.

Regards,
Allan Mason, JP
Mobile: +61 401 324 058


On Fri, Jun 8, 2018 at 10:58 PM, Tim Gorman <tgorman2@...> wrote:
How did you measure the bandwidth?

Remember that a square wave is a infinite series of odd harmonics. Your
keying is basically a square wave unless modified to have a rounded
up-slope and down-slope. Even then you will still have some odd
harmonics that cause the bandwidth of a repeating on-off dot or dash to
have a bandwidth increase over just the carrier itself.

tim ab0wr


On Thu, 07 Jun 2018 12:37:33 -0700
"K3OS" <garysch69@...> wrote:

> Just got a v3 board running today.  I was monitoring CW on my IC7300
> and noticed that when transmitting, i.e., a string of dots or dashes,
> the bandwidth would widen to 1Khz then return to very narrow.   This
> occurred at a periodic rate if I held the dot or dash lever.
> Internal keyer was used.  When sending text the same issue occurred
> but it was more difficult to spot.  Initial test was 40 meters, 12
> watts out, but same results on 20, 8 watts out all into a dummy.
> 12.2VDC power supply. 
>
> Any clues to why this happens and what can be done?
>
> Gary K3OS






Virus-free. www.avg.com

Re: RF power chain mods and improvements..

Jerry Gaffke
 

And if you really wanted an MMIC for the pre-driver,
here's a cheap one capable of 18dBm.  $0.55 each if you get a reel.
    https://www.mouser.com/ProductDetail/Infineon-Technologies/BGA-616-H6327?qs=sGAEpiMZZMsHFhLSzabyWc6yBY9ZVzZQAmz94oaQAYo%3d

Re: CW transmit bandwidth #ubitxcw #ubitx

Jerry Gaffke
 

Cool that all it took was a larger C1, that's a good result.

From the scope traces, the rising edge is much faster than the falling edge.
This is because the CW-KEY line from the nano is rising exponentially from 0v to a 5v asymptote
it is travelling very quickly through that first fraction of a volt where the mixer becomes unbalanced.
On the trailing edge, CW-KEY is starts travelling quickly as it makes its way exponentially down from 5v,
slowing as it asymptotically approaches 0v.

If you want the rising and falling edges to be symetrical,
try adding a 1k pot across C1, this forms a voltage divider with R104 so you can adjust
the maximum CW-KEY voltage that gets presented to C1.
Adjust the pot for symmetry in your scope display, then measure the pot and replace it with a fixed resistor.
resistor across C1.   First suggested in post  https://groups.io/g/BITX20/message/50445
 


On Fri, Jun 8, 2018 at 08:48 pm, Allan Mason wrote:
All that was required was to increase the value of C1 from 0.1uf to 1uf.

Re: CW transmit bandwidth #ubitxcw #ubitx

Jerry Gaffke
 

These are inverse exponential responses, it won't be symmetrical.
But the pot should help move it toward vaguely similar rise and fall rates.

The integrator mentioned in post 50445 is capable of creating a very nice trapezoid.
We had a discussion on this going in the AT-Sprint group over a decade ago:
    https://groups.yahoo.com/neo/groups/AT_Sprint/conversations/messages/1086
where we found a way to make the rise and fall slopes of the trapezoid equal,
and also how to make the slopes constant when the power supply voltage varied.
Way overkill, most of us should just stick with the cap and resistor.

 

On Fri, Jun 8, 2018 at 09:17 pm, Jerry Gaffke wrote:
If you want the rising and falling edges to be symetrical,

Re: RF power chain mods and improvements..

rcbuck@...
 

Allison, thanks for the heads up on EB63 design. I will avoid it and think about something similar to the Hardrock-50. It is a modern design and the parts are inexpensive. I will probably build the amp just to cover 40 and 20. Low pass filters at the input to the amp and 3 section LPFs on the output should be sufficient. An attenuator for each band on the input would take care of the difference in output levels of the uBitx.

Out of curiosity I will look at the uBitx output with the DSA-815 sometime this weekend.

Ray
AB7HE

Re: pcb for modifications ver3 to ver4

Ashok Khachar
 

Sprint layout file uploaded to file folder GL

Re: Spurs for Dummies? #ubitx-help

iz oos
 

Many tuners are rudimentary highpass filters, especially at 28mhz, the spur may be far away to be attenuated somehow. Also a monoband may further attenuate that spur. To keep it as simple as possible I would use an external high pass filter. Just plug and play.


Il 09/giu/2018 01:06, "Arv Evans" <arvid.evans@...> ha scritto:
Once you now what the probable frequency of spurs it is relatively easy to monitor
them with another receiver.  Even something as simple as the Pixie circuit will work
if you provide stability and accuracy with a DDS or Si5351 as its local oscillator. 
Well shielded auxiliary receiving devices can be calibrated by inserting a step
attenuator in the antenna input and measuring audio beat note level of the output. 
This could be the basis of a poor-man's spectrum analyzer. 

Arv
_._


On Fri, Jun 8, 2018 at 3:04 PM <davedt1e@...> wrote:
Wow!...All the feedback here has exceeded my expectations.

Alyson,  I'm truly impressed that you were able to "Dumb" this down to an understandable level.  I've learned quite a few things in this thread that have been pestering me for a long time.

I'll consider trying a filter,  but not until I figure out how to monitor for the spurs. What's the point unless I can confirm that it's working, right?!  But I won't pester you all with that right now.  I'm sure the answer to that is somewhere on the board.

I'll keep watching for a consensus on the issue.

Thanks to everyone!

Maybe some other noobs will benefit  from this as well.

David

Re: Spurs for Dummies? #ubitx-help

iz oos
 

Here is a filter designed with SVCFilt (at least a 20 years old ARRL programme) under Windows95 (hihi). Capacitors can be any ceramic (usually are rated at 50v) and inductors may be built with or without a toroid.


Il 09/giu/2018 08:31, "iz oos" <and2oosiz2@...> ha scritto:

Many tuners are rudimentary highpass filters, especially at 28mhz, the spur may be far away to be attenuated somehow. Also a monoband may further attenuate that spur. To keep it as simple as possible I would use an external high pass filter. Just plug and play.


Il 09/giu/2018 01:06, "Arv Evans" <arvid.evans@...> ha scritto:
Once you now what the probable frequency of spurs it is relatively easy to monitor
them with another receiver.  Even something as simple as the Pixie circuit will work
if you provide stability and accuracy with a DDS or Si5351 as its local oscillator. 
Well shielded auxiliary receiving devices can be calibrated by inserting a step
attenuator in the antenna input and measuring audio beat note level of the output. 
This could be the basis of a poor-man's spectrum analyzer. 

Arv
_._


On Fri, Jun 8, 2018 at 3:04 PM <davedt1e@...> wrote:
Wow!...All the feedback here has exceeded my expectations.

Alyson,  I'm truly impressed that you were able to "Dumb" this down to an understandable level.  I've learned quite a few things in this thread that have been pestering me for a long time.

I'll consider trying a filter,  but not until I figure out how to monitor for the spurs. What's the point unless I can confirm that it's working, right?!  But I won't pester you all with that right now.  I'm sure the answer to that is somewhere on the board.

I'll keep watching for a consensus on the issue.

Thanks to everyone!

Maybe some other noobs will benefit  from this as well.

David


Re: THANK YOU K5BCQ

David Wilcox
 

I would like to add my kudos to Kees for the neat board and micro smd parts.  Glad I have magnified loupes and can still see them yet.  Well done my friend.  A sneeze and they will be history.  Use a raised edge cookie sheet.  Also, no cats allowed.  They stick to paws........ 

Also, if you ordered two of each they will come in separate envelopes on different days.  Two kits to an envelope.

Dave K8WPE

On Jun 8, 2018, at 4:17 PM, Mark M <junquemaile@...> wrote:

Let me add my thanks as well. I received the kits yesterday and am quite impressed. I was expecting only a set of parts so was pleased to also get the schematic, etc...even a little piece of double-sticky foam tape. Now to see if I can assemble them...those surface mount parts are really tiny.

PA transistor Heatsinking of a uBITX #ubitx

Peter LB0K
 

I can see the insulation argument to why these are installed hanging on to the IRF510s but this puts a large mechanical load on the transistor legs and increases the risks of damage, especially if one tried to use the uBITX as a portable, even as a SOTA rig.

 

One could fit a larger common heatsink that was fixed to the chassis/casing or PCB and one would then have to include rectangular insulating washers between the transistors and the heatsink.
These changes would increase the parallel drain(s) capacitance to ground, etc. etc.

 

I envisage these positive results:-

-       better mechanical strength

-       a more robust construction

-       easier to provide controlled cooling of the heatsink.

 

 

What sort of negative results should/could one expect from these measures?

 And how to fix'em?

 I envisage these negative results:-

-       a slight increase of weight

 

 

 

 Peter

Re: RF power chain mods and improvements..

Howard Fidel
 

The MMIC has a absolute maximum voltage of 4.5 VDC. Assuming you use a transformer (actually you must to get the drive level you need for the output stage) you an only use a +2 volt supply for the device for a 4 v p-p swing. So you need at least  1:2 step up transformer so the driver needs to source more current to drive it. I am completing the design of a driver that is flat to 30 MHz and will post it soon. It uses a current driver and a dual opamp replacing everything from VR1 to T10.

Howard

On 6/8/2018 11:50 PM, Jerry Gaffke via Groups.Io wrote:
And if you really wanted an MMIC for the pre-driver,
here's a cheap one capable of 18dBm.  $0.55 each if you get a reel.
    https://www.mouser.com/ProductDetail/Infineon-Technologies/BGA-616-H6327?qs=sGAEpiMZZMsHFhLSzabyWc6yBY9ZVzZQAmz94oaQAYo%3d


Re: RF power chain mods and improvements..

Howard Fidel
 

Attached is my driver it goes between VR1 and the outputs of T10 you need to remove C84 and T10 and insert this circuit. I am using the AMP signal to reduce the overall power output when driving a linear amp which needs 5W not 10W. U7 is a current driver, I chose it because I have a number of them, I probably could select something better, or use an emitter follower but it should do the job at 0 cost for me. The same with the T13-1 transformer, I have them. The opamp was selected for its speed slew rate voltage and current drive capability. C45 is there because U7 needs a minimum load capacitance for stability. I will see if I need to add something there later. TX is the switched 12 volts that is there in transmit only.
I am working on a PCB with this being one part of a daughter board for the uBitx. I would be interested in any feedback. I am not suggesting that this is a cost effective way of improving the uBitx for production. I will post the entire schematic in a few days.

Howard

On 6/8/2018 11:50 PM, Jerry Gaffke via Groups.Io wrote:
And if you really wanted an MMIC for the pre-driver,
here's a cheap one capable of 18dBm.  $0.55 each if you get a reel.
    https://www.mouser.com/ProductDetail/Infineon-Technologies/BGA-616-H6327?qs=sGAEpiMZZMsHFhLSzabyWc6yBY9ZVzZQAmz94oaQAYo%3d


Re: Spurs for Dummies? #ubitx-help

ulf.jagfors@...
 

Perhaps these practical BPF hints could be of value
https://martein.home.xs4all.nl/pa3ake/hmode/bpf_all.html
Ulf SM0CGL

Another uBITX in a wooden box

Bill Meara