Date   
Re: uBitx Modulation only lows no highs in frequency response

Jerry Gaffke
 

Allison is suggesting that the 100pf caps at C217, C218, C219, C220, C221, C222
be swapped out with something smaller.

The board is laid out for 1206 sized surface mount caps, though 0805 sized parts could be used.
These sizes are in imperial units, something near that size in metric should work fine.
    https://en.wikipedia.org/wiki/Surface-mount_technology#Rectangular_passive_components
Dielectric should be C0G or NP0.
Voltage rating doesn't matter much here, anything 25v or more should be fine.
Use caps of 5% tolerance (preferably better), or measure them with a capacitance meter.
    https://groups.io/g/BITX20/message/52471https://groups.io/g/BITX20/message/52471
Standard values that might be tried include the current 100pf, or Allison's 91pf, or  82pf.
they lower the value the wider the bandwidth.
Though changing those capacitance values may change the shape of the filter response
with frequency, ideally we would sweep the filter shape somehow to make measurements
before and after the mod.

As you know, crystal filters in an SSB transceiver like this are a trade-off.
A wider filter may sound better, but may not be suitable when there are many
stations operating on nearby frequencies.
 
Would be interesting to measure the capacitance of any 100pf caps removed,
with 10% or worse tolerance parts we would see significant variations n performance.

Jerry


On Thu, Jul 19, 2018 at 01:20 PM, Björn Pasteuning wrote:

Hi Allison,

Well I think that is the culprit.

I have tried about 7 electrets after my last posting, some sounded a minor bit better others worse.

No significant big improvement.
Also tried playing with the BFO, not much help there either.

Do you have any link regarding the parallel caps? or schematic how this could be done?

Re: S meter wiring

Bill Carpenter
 

Pat,

I appreciate it but I have no idea what a Nextion screen is.

73,Bill NZ0T

Re: uBitx Modulation only lows no highs in frequency response

Björn Pasteuning
 

Hi Allison,

Well I think that is the culprit.

I have tried about 7 electrets after my last posting, some sounded a minor bit better others worse.

No significant big improvement.
Also tried playing with the BFO, not much help there either.

Do you have any link regarding the parallel caps? or schematic how this could be done?

--
73' Björn de PD5DJ
www.pd5dj.nl

Re: Unbuilt uBITX Ver4 and Blue Cabinet for sale.

SM6MOJ
 

The G4HUP buffer amplifier is connected to the 45 MHz IF that is available from C12. I have obtained an SMA "pigtail" that will connect the buffer amplifier output to the SDR dongle.

Re: uBitx Modulation only lows no highs in frequency response

ajparent1/kb1gmx
 

You may have to move the BFO down more for better audio. 
Its the first thing everyone tries, 100 to 200 cycles may help greatly. 

Also more than a few have narrower than expected 12mhz filters.  
Mine swept on the analyzer at under 1700hz wide and reducing
the parallel caps from 100pf to 91pf got it out to over 2100hz.

Allison

Re: uBITX v3 - Wiring in a 6 pin Mini-Din for Data

Kevin Rea
 

Hi Andy,
did you ever do this mod ?

if so, how did it do ?

Kevin rea
lancaster, calif.
k6rea

Re: RF power chain mods and improvements..

ajparent1/kb1gmx
 

This string is 275 entries and counting long for those that use email rather than web site you loose a
huge amount of context and replies never mind the ability to look back.

I stopped writing on improvements over 20mhz as any increase in power makes
the over 20mhz spur a greater issue. Do so at your own risk.

For Q90 the BFR106or a similar high FT part is a winner.  Keep Ie under 20ma.

For the pre-driver and driver....

THe whole point is to get more gain at higher frequencies as the 3904s can be
pretty dismal at 10M.  The 2n2222s are better that but for better 10M you need
2n3866 or 2n5109 and transformer optimizations.  Even with that it wants to
do stupid high power at 80m and less than half at 10M.  So the C81/r83 mod
is needed to tame down 80m (470pf/8.2ohms from memory).

If your not interested in over 20mhz 2N2222A(to18). Ie 20ma max per device.
If you are interested in over 20mhz 2n3866 or 2n5109. Ie can be higher but take care for heating.

The various transformers need help too.  Look back for specific winding info.  
Memory test of what I used: 
T8 (q90) 5t #30 bifilar on FB43-2402  
T9 FB43-302 4t trifilar #28
t10 FB43-302 4t trifilar #26
T11 FB61-202 3T/4T #24

To take advantage of the transformer mods you needs ot make other changes....
See the progression!

2n3866 kitsandparts. com 6.00$ for two.  RFparts.com 1.95ea
2n2222A RFparts.com  65 cents

Biggest issue with RFparts is I believe the have a 25$ minimum, for me I take advantage of that and
stock up on various other pats like Arco trimmers, metal clad mica caps and other itms useful to a
VHF/UHF RF person.

Other suppliers Mouser, Digikey, Jameco.

FYI MPSH10 kits and parts have them for 25/$5.00 and BS170 25/$5.00  reliable source and they have
Ferrite and toroids!

Allison

Re: uBitx Modulation only lows no highs in frequency response

Björn Pasteuning
 

Hi Joel,

Thanks I will try that, I think I have a little bag of gathered electreds lying around somewhere.

Will keep you posted.
--
73' Björn de PD5DJ
www.pd5dj.nl

Re: QST review of the Bitx40

Richard Spohn
 

Farhan, taking a quote from one of our most beloved movies here in the
States, "...you're gonna have to get a bigger boat!" -- Rich WB2GXM

On 7/19/18, Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:
Just now got my August 2018 copy of QST, a ham publication by the ARRL here
in the states.
Has a very positive review of the Bitx40 starting on page 44, built with
Sunil's enclosure.

Expect a wave of new forum members.

Jerry, KE7ER



Re: uBitx Modulation only lows no highs in frequency response

 

Björn, If you are using the electret element that came with the uBitx, I would try a different one. I haven't been able to use the mics that came with any of my Bitx kits because of bad audio quality. I bought a whole bag of them from a eBay vendor for just a few dollars that work perfect.

Joel
N6ALT

Re: RF power chain mods and improvements..

Jer Tres
 

On Wed, Jul 18, 2018 at 07:02 PM, ajparent1/KB1GMX wrote:
In context they worked in that they were marginally better than the 2n3904s, but compared
to the 2n2222A or 2n2219 they were not very good.   Compared to 2n3866 they were poor.
Hi Allison,
So it sounds like you found the 2n3866 superior to the 2n2222a  at some point in the chain. To avoid having to repeat what you have already tried could you share with us at which point in the chain, i.e. driver, predriver & did you use one or two or four? 2n3866’s are pretty pricey but not unobtainium from a reliable source. And do tnis superiority apply to all bands or just to the higher frequencies?

If this is obvious or you have already stated it, I apologize for having missed it (and it’s obviously not obvious to me...) please do not give up, your opinions knowledge and findings are well respected here

and elsewhere.

Thanks. And thank you for your patience.

Sincerely,

Jerry aa1of

Re: S meter wiring

pat griffin
 

I am away so this is from memory.  If you are using the Nextion screen and click on the data display with version, etc you will get a display with an option to monitor the ADC voltage, i.e., the input on the purple wire to A7.  This will give you an idea of the voltage levels.  I think I set the low end and the high end and let the system figure out those in between and it looked kind of decibel/logarithmic to me. I didn't try to make it reflect precise, textbook s units.

Pat AA4PG 


Pat Griffin
http://www.cahabatechnology.com


From: BITX20@groups.io <BITX20@groups.io> on behalf of Bill Carpenter <nz0tham@...>
Sent: Thursday, July 19, 2018 12:41:08 PM
To: BITX20@groups.io
Subject: Re: [BITX20] S meter wiring
 
So, what I need to do is measure the voltage at J1 on the AGC at very low and high signals and then guess for what is between those two extremes?  How did you come up with a setting of 217 for the high end based on your 4 volt measurement?

Re: S meter wiring

Ralph Mowery
 

Most of my settings was just so the s-meter responded like I wanted it to.  I have a service monitor so (if I remember correctly) I set if for 50 u Volts ( the often stated reference to s-9)and started with all the bars but not the + displayed.  That did not give the response I wanted.  I did run the signal level up very high and the most the AVC circuit put out was about 4 volts.  Safely under the 5 volt max of the Arduino.  I think that may  have been where the 217 came from.  That gives the ++ at the end of the bars on my ubitx.

The Arduino takes a signal from 0 to 5 volts max on that pin so the voltage has to be in that range.  I always get the exact number confused but the range has to be from 0 to 255 or 0 to 254 on that input the way the program is written. If you set a number of over 254 or 255 strange things may happen as it over ranges the program parameters.

Feel free to use any numbers from a low of 1 to a high of 254 and just play with them so you get the s-meter to respond to your liking.  I would think everyone would use a different setting due to different antennas.  At the time I was playing with the settings I was on 80 meters with a 1/2 wave dipole up about 50 feet.  I have not taken the time to check out other bands to see how it reacts there .

de ku4pt


On Thu, Jul 19, 2018 at 2:41 PM, Bill Carpenter <nz0tham@...> wrote:
So, what I need to do is measure the voltage at J1 on the AGC at very low and high signals and then guess for what is between those two extremes?  How did you come up with a setting of 217 for the high end based on your 4 volt measurement?


Re: S meter wiring

Bill Carpenter
 

So, what I need to do is measure the voltage at J1 on the AGC at very low and high signals and then guess for what is between those two extremes?  How did you come up with a setting of 217 for the high end based on your 4 volt measurement?

Re: RF power chain mods and improvements..

Gordon Gibby <ggibby@...>
 

​So, I'm getting ready to have some number of our Alachua County ARES people built ("install" might be more accurate)  uBitx / Bitx40's.   


All these wonderful improvements y'all are developing and testing will be a huge help to us (AFTER we get their stock versions to  work.....).... so this morning I put in an order for 


10 2n2222As

10 2n3866's

100 2n3904's with an Ft of 300 Mhz --- I use these things all the time and it was cheaper to buy a lifetime supply than to buy a smaller number....


I wonder if the higher Ft-version of the 2n3904 would make any significant difference, or if the one that is already in the uBitx has an Ft that high?


Thanks for all the work y'all are doing --- it will help a bunch of Technician licensees see even more reason to graduate up to higher licensure.....we did 5 Extra's last year and hope to do a bunch of Generals this year....


gordon




From: BITX20@groups.io <BITX20@groups.io> on behalf of ajparent1/KB1GMX <kb1gmx@...>
Sent: Thursday, July 19, 2018 11:32 AM
To: BITX20@groups.io
Subject: Re: [BITX20] RF power chain mods and improvements..
 
I work with US supply vendors and in some cases ask for COC or similar documentation and get it.
Many of the companies I've dealt with for decades.

Its not a bargain if I get crap and wait twice the time to get it because I had to order and
pay for it again. In general I feel the risk and wasted time for ebay and similar is not
worth it.

I'd bet the market for leaded parts is more ripe for scams and fakes.  Solution,
use SMT parts as they are cheaper more readily available and less likely to be faked.
Yes, they are small but some offer better performance at higher frequencies.
Same for the resistors and caps.  I dead bug (ugly/manhattan construction) them too.

Allison

Re: S meter wiring

Ralph Mowery
 

You may start out something like this.

4,36,71,140,175,212,217

They should range from  1 to a max of 254.  My board only put out about 4 volts max so the 217 number was the most for me.  You can adjust the numbers to suit you. 

On Thu, Jul 19, 2018 at 11:01 AM, Bill Carpenter <nz0tham@...> wrote:
Any suggestions for the S-meter numbers to start out with?


uBitx Modulation only lows no highs in frequency response

Björn Pasteuning
 

I have the uBitx for a couple of days now, and have several "issues" with it.

One of them is modulation frequency response.

Monitoring my TX audio sounds like talking through a cloth or something, no high tones are audible.

Is this normal behaviour of this kit?

I have done all the alignments, Masterclock/BFO

 


--
73' Björn de PD5DJ
www.pd5dj.nl

Re: S meter wiring

Bill Carpenter
 

Got it working!  I tried Ian's settings which were way off for me.  Ended up at 5 on the low end to 60 on the hi end which may still be a bit "Scotch" but I want to try it at that for a while and then adjust.  Thanks everyone for all the help!

73, Bill NZ0T

Re: S meter wiring

Kees T
 

Yes, it is attached/plugged at J1 which is the positive end of C4.

73 Kees K5BCQ

Re: uBITX adjustable power supply?

Tom, wb6b
 

I just received a five pack of the same boost converters for the same purpose. I'm very interested, also, what anyone's experience has been with these. 

I'll let you know when I try it. 

Tom, wb6b