Date   
Re: External Amp

ajparent1/KB1GMX <kb1gmx@...>
 

A note: the commercial version of the 'EBY amp is the K5OOR HF packer.
the power supply is unique as it runs only on TX and does a 12 to 24V boost
to power the IRF510s to high power.  

Allison

Re: External Amp

Nick
 

Allison,

Thanks for the reply! I will read the articles regarding WA2EBY.

For the low pass filter I am using T50 the actual Fair-Rite part number is: 5961000301 which is mix 61, lower permeability and should be lower loss at HF. It could be that the whole system like you said is not stable as I have seen the distorted waveform at the input of the amp.

I will likely order some new MOSFETs and give it another go. The gate resistors might be a good addition.

I have attached what I put together in LTspice for anyone that wants to play with it. I did not put in an accurate representation for the transformers but I think the ratio is correct. What I have could be completely wrong.

--
Nick

Re: RF power chain mods and improvements..

Nick VK4PP
 

Good Morning Allison, et al.

Just thought I'd throw a few cents in the hat.

I have managed to get my uBitx to output 16w at 80m to 14w at 10m. (CW key down)
In a nutshell, Q90 changed to MMBTH10 (20 for a few $ on ebay...) 220/300  pf cap across emitter resistors of all 3904 drivers, 2:4 wind BN43-202, 330pf mica on input. and RD16 with std feed back in place. Drive RV1 at 3/4. (maybe 20w at full?)

I have yet to check IMD and such but output seems stable.

I need to do more learning/testing...

My second ubitx will get the same mods except all the driver 3904 will be changed to MPSH10... and a common power feed(L8/L9) to the RD16 via a FT50-43 Bifilar. I have worked out a neat way to implement this on the STD board... Pics to come...

73 Nick VK4PLN 

Re: RF power chain mods and improvements..

Jerry Gaffke
 

Allison,

Yes, surface mount parts into current boards would be tough.
The to-39 and to18 parts are fine for current rev boards, no point in saving 
a couple bucks and then spending hours trying to whack them into place and heatsink them.

But nice to think about what hfsignals might do in the future.
If the smt 2n5109 is cheap or an smt 2n2222a works in the driver stage,
the additional cost in parts might be held to a dollar or so.

Could be that the IRF510's and others will behave better at 30mhz if laid out differently.
And not having so much RF on the main board might even help those mixers out?
If so, a Q30-to-IRF510 daughterboard makes good sense.
And as you say, many here will prefer that to swapping out a half dozen transistors and rewinding torroids. 
Especially since with the daughterboard it could be easily reversible, back to a stock uBitx.
 
Jerry


On Sun, Jun 10, 2018 at 01:24 pm, ajparent1/KB1GMX wrote:
Jerry,

The DXT2222A-13 is a possible choice for pre-driver as the power is fairly low.  For the driver
the board layout to get the tab on enough copper is nasty space wise.  I've used that part
and its otherwise a good SOT89 2N2222A maybe a tiny bit better (lead inductance is smaller).
It would be hard to apply to the current V3 and V4 board. 

The SMT 5109 is not useful for the same reasons [board layout] for the driver. it
would work a bit better for the pre-driver. 

NOTE on SOT89 the pinout is BCE and the boards are EBC so attaching them to existing
boards would be very messy with lots of cutting and jumpers even for test reasons. They
would also need a flag to radiate the heat (copper .020 thick by .25 side and .4 tall.).
Someone else can do that for a test.

The BFR106 works for Q90 and also in the 45mhz IF amp section very well.  Its not a choice
for other parts of the radio. As more power capability is needed or 3904 is fine.

One possible layout I looked at was strip the power amp completely Q90 though IRF510s
and have a board above the main board carry the input filters, improved amp, then 
using the output  filters on the lower main board. Two pieces of coax and a few control
lines. That and other added features as there would be space.  That would make an
upgrade far easier as its a whole board and wires. 

Allison

Re: External Amp

ajparent1/KB1GMX <kb1gmx@...>
 

For low pass filter either T50-2 bekow 10 mhz and T50-6 above as that is the most
commonly used.    The 61 mix has too high mu and is prone to overloading and
heating as anything but transformers at HF.

Wire, I'd use #26 if it fits or #28 as fallback.

Allison

Re: RF power chain mods and improvements..

ajparent1/KB1GMX <kb1gmx@...>
 

For futures [HFsignals] the SMT parts are a good choice as machine stuffed
lowers cost too.


Look at the EBY and HF Packer amps, also the K5BCQ for examples
of how to lay out just the IRF510 (or RD16) for performance and stability.

Allison

Re: BITX QSO Afternoon/Evening, Sunday, June 10, 3PM & 7PM Local Time, 7277 kHz in North America, 7177 kHz elsewhere.

Jay - WS4JM
 

Heard N4AYE from FL into Middle TN, Lots of lightning static from storms, rough copy

WS4JM

Re: uBitx daughter board

Andrea Contini
 

Hello Howard,

Your board is really interesting. Thank you for sharing it.

Andrea

Auto Tuner?

W2CTX
 

What is the status of the uBITX automatic antenna tuner that was discussed late last year?


rOn

Re: RF power chain mods and improvements..

Nick VK4PP
 

Just a hint for those experimenting, Jarred, VK3BL has done a great set of Vids on using an SDR as a station monitor for checking IMD...

https://www.youtube.com/watch?v=ZCdiz9Ggmh4

73 and enjoy.

Re: Auto Tuner?

K9HZ <bill@...>
 

Programming is all that is left. 

 

Dr. William J. Schmidt - K9HZ J


On Jun 11, 2018, at 7:44 AM, W2CTX <w2ctx@...> wrote:

What is the status of the uBITX automatic antenna tuner that was discussed late last year?

 

rOn

Re: RF power chain mods and improvements..

K9HZ <bill@...>
 

I have made roughly the same mods after simulating them in LTSpice and can confirm almost identical results/ power levels. 

 

Dr. William J. Schmidt - K9HZ


On Jun 11, 2018, at 5:32 AM, Nick VK4PLN <nickpullen@...> wrote:

Good Morning Allison, et al.

Just thought I'd throw a few cents in the hat.

I have managed to get my uBitx to output 16w at 80m to 14w at 10m. (CW key down)
In a nutshell, Q90 changed to MMBTH10 (20 for a few $ on ebay...) 220/300  pf cap across emitter resistors of all 3904 drivers, 2:4 wind BN43-202, 330pf mica on input. and RD16 with std feed back in place. Drive RV1 at 3/4. (maybe 20w at full?)

I have yet to check IMD and such but output seems stable.

I need to do more learning/testing...

My second ubitx will get the same mods except all the driver 3904 will be changed to MPSH10... and a common power feed(L8/L9) to the RD16 via a FT50-43 Bifilar. I have worked out a neat way to implement this on the STD board... Pics to come...

73 Nick VK4PLN 

Messed up removal of TDA2822

Sajid Rahum
 

All:
Need help. I cut the TDA2822 (WX model) and tried my best to get the pins out - used copper wick etc. no luck.  

Landed up wiring the 8 pin dil with replacement NJM chip.  When i turned around, looks like one anchor dropped out - you can see the flux showing. 

My worry where did that bit that dropped out was to go to?  I will place a wire if needed.

This was been a nightmare replacing the 2822.

Any suggestion is welcome

Re: Messed up removal of TDA2822

Sajid Rahum
 

You can see the first one on the top left where the concern is on the first photo.

2.5 MHz low pass fiilter uses no toroids, SMDs #ubitx

Peter Parker
 

I've been experimenting with various types of low pass filters to cure BCI. 

My starting point was the VK3IL design. Then I changed the values to use prewound 2.2 uH RF chokes I had.  Increasing the capacitors by a similar factor (approx 1.5 times) dropped the cut-off frequency to around 2.5 MHz.  This may offer somewhat less attenuation of the broadcast band but does mean that the uBitx will tune WWV on 2.5 MHz without too much loss.  Also 160m reception should be possible on stronger signals.  The big benefit (for some) is there's no need to wind your own toroids.  And you can use conventional components on a small circuit board that can be sawn to make the pads.  

I'm pleased with its performance. More in this video. 

https://www.youtube.com/watch?v=fgQenFJOjr4

73, Peter VK3YE

 

Re: 2.5 MHz low pass fiilter uses no toroids, SMDs #ubitx

Howard Fidel
 

You made a high pass filter, not low pass.

On 6/10/2018 9:12 PM, Peter Parker wrote:

I've been experimenting with various types of low pass filters to cure BCI. 

My starting point was the VK3IL design. Then I changed the values to use prewound 2.2 uH RF chokes I had.  Increasing the capacitors by a similar factor (approx 1.5 times) dropped the cut-off frequency to around 2.5 MHz.  This may offer somewhat less attenuation of the broadcast band but does mean that the uBitx will tune WWV on 2.5 MHz without too much loss.  Also 160m reception should be possible on stronger signals.  The big benefit (for some) is there's no need to wind your own toroids.  And you can use conventional components on a small circuit board that can be sawn to make the pads.  

I'm pleased with its performance. More in this video. 

https://www.youtube.com/watch?v=fgQenFJOjr4

73, Peter VK3YE

 


Bitx and uBitx video playlists #bitx40 #ubitx

Peter Parker
 

For those looking for a Bitx or uBitx videos but not wanting to sift through hundreds of others, I've now grouped them in a playlist. 

Either select the one you want or sit back, press play and watch them all. 

Videos in the list include a description of a scratch-built Bitx, demonstrations, Bitx and uBitx mods and more. 

https://www.youtube.com/playlist?list=PLj8-NKcZtRf7vA1dJ48bpEbTKyfoUv-4t

73, Peter VK3YE

Re: 2.5 MHz low pass fiilter uses no toroids, SMDs #ubitx

Peter Parker
 

You're quite right!  Oops! 

Re: Transmitter Mods

Tom Christian
 

I made Howard's mods on both my uBITXs with great results in spite
of myself.....:) It was a comedy of errors....  On both rigs, I didn't
have any problems with the 220pf capacitors across R87 & R88, except
the 0805 size was like working with big grains of salt. The small size
gave these mid-60s eyes a good workout!.  The resistor/inductor was
another story.  I had issues with the 1K ohm R86 teepee attempt with
the 33uH inductor.

On the first rig, I destroyed the SMD resistor with too much heat while
trying to make the solder joint (went to infinity).  I didn't have SMD
replacements, so I used a descrete 1K since the inductor I had on hand
was also descrete.  Then on the 2nd rig, the 1K resistor flew out of
the tweezers and I never was able to find it....  So this rig also got
descrete components.  Enclosed is a humbling picture......:)  I obviously
need more SMD practice!

I don't have a precision power meter for measurements, but my cheapie
analog SWR/Power meter shows before and after readings as follows:

    Band    Before    After
    -------    ---------    ------
    80        5 watts    4 watts
    60        2             3
    40        4             4
    30        2             3
    20        2             4
    17        1.5          4
    15        1             2
    12        0.8          1.5
    10        0.3          1.2

Needless to say, I'm VERY pleased with the power increase!  My reports
when testing with other hams on FT8 have been good clean signals.  This
is going to make the uBITX even more fun!

Thank you so much, Howard, for the great recommendations! 
Much appreciated!

Tom
AB7WT

Re: Transmitter Mods

Howard Fidel
 

Great news! I am 67 myself, but the 0805 parts are BIG, you should try your hand at 0201, that will drive you to drink really quick.

Howard

On 6/10/2018 9:31 PM, Tom Christian wrote:
I made Howard's mods on both my uBITXs with great results in spite
of myself.....:) It was a comedy of errors....  On both rigs, I didn't
have any problems with the 220pf capacitors across R87 & R88, except
the 0805 size was like working with big grains of salt. The small size
gave these mid-60s eyes a good workout!.  The resistor/inductor was
another story.  I had issues with the 1K ohm R86 teepee attempt with
the 33uH inductor.

On the first rig, I destroyed the SMD resistor with too much heat while
trying to make the solder joint (went to infinity).  I didn't have SMD
replacements, so I used a descrete 1K since the inductor I had on hand
was also descrete.  Then on the 2nd rig, the 1K resistor flew out of
the tweezers and I never was able to find it....  So this rig also got
descrete components.  Enclosed is a humbling picture......:)  I obviously
need more SMD practice!

I don't have a precision power meter for measurements, but my cheapie
analog SWR/Power meter shows before and after readings as follows:

    Band    Before    After
    -------    ---------    ------
    80        5 watts    4 watts
    60        2             3
    40        4             4
    30        2             3
    20        2             4
    17        1.5          4
    15        1             2
    12        0.8          1.5
    10        0.3          1.2

Needless to say, I'm VERY pleased with the power increase!  My reports
when testing with other hams on FT8 have been good clean signals.  This
is going to make the uBITX even more fun!

Thank you so much, Howard, for the great recommendations! 
Much appreciated!

Tom
AB7WT