Re: Farhan's new PA for ubitx
Is there a best and final solution yet or are we still waiting
for Allison's final comments on changes?
On 5/29/2018 9:45 PM, ajparent1/KB1GMX
wrote:
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those are .1 uf
caps, pass rf block dc.? Says so in small print on the schematic.
That is the negativefeed back to keep the mosfets tame at low hf.?
Without the cap its full
on forward bias likely will not hurt them but it will suck down
many amps as under that
condition the mosfets look like s short to ground
Chaning R97/98 to 220 ohm is going the wrong way and not advised.?
Allison
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Re: Farhan's new PA for ubitx
Yes, it's recommended you put the two pads in separate rooms.
Vince.
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On 05/29/2018 09:52 PM, Jerry Gaffke via Groups.Io wrote: That's a cap, so the zero means 0pf.
Be sure to place the two PCB pads infinitely far apart. ;-)
Farhan is disabling the negative feedback around the IRF510's.
On Tue, May 29, 2018 at 06:32 pm, Tim Gorman wrote:
Is that 0 capacitor for C261 and C262 *not* a 0ohm jumper?
--
Michigan VHF Corp.
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Re: Farhan's new PA for ubitx
That's a cap, so the zero means 0pf.??
Be sure to place the two PCB pads infinitely far apart.? ;-)
Farhan is disabling the negative feedback around the IRF510's.
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On Tue, May 29, 2018 at 06:32 pm, Tim Gorman wrote:
Is that 0 capacitor for C261 and C262 *not* a 0ohm jumper?
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Re: Oscillation problems Bitx20a
Last time I built a bitx20? PA I use a strip of copper clad (2sided) and it was about 2" by 5"?
input at one end and the PA transformer at the other.? everything evenly between.? I still
have it in a different radio runs about 7W and the final is biased at 100ma.? It was built
stock form the circuit.? Layout at that amount of gain is everything and packing it close
makes for issues.
Allison
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Re: Farhan's new PA for ubitx
those are .1 uf caps, pass rf block dc.? Says so in small print on the schematic.
That is the negativefeed back to keep the mosfets tame at low hf.? Without the cap its full
on forward bias likely will not hurt them but it will suck down many amps as under that
condition the mosfets look like s short to ground
Chaning R97/98 to 220 ohm is going the wrong way and not advised.?
Allison
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Re: Ideas for AM, NB FM Demod and CW filter board
My favorite AM radio is my Hallicrafters SX100 or the highly modded S120
of for just being odd ball my really old (1953) RCA am potable AC/DC/battery
using tubes.? ;)
I still wish I had the old RBO II shipboard AM RX.? ?It was heavy enough to
hold down a truck.
Allison
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Farhan's new PA for ubitx
I made the changes listed for the PA of changing R97 and R98 to 220ohm.
I thought the change of C261 and C262 meant going to a 0ohm jumper but
when I made that change the PA now immediately starts pulling over
5amps at turn on and blows my 3 amp fuse.
Is that 0 capacitor for C261 and C262 *not* a 0ohm jumper? From drain to
ground I get about 220ohms which is what I would expect from the two
220ohm resistors R98 and R261 in series paralleled with R97 and R262 in
series.
Any comments, suggestions, ideas?
It's not hard to replace C261 and C262 but I don't want to try any other
fixes till I have an idea of what is going on.
tim ab0wr
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Re: Ideas for AM, NB FM Demod and CW filter board
Using SSB radio for AM RX is fine I do it all the time.? Using it for TX not so much
as AM nets sort frown on it.
Building AM rx is fun in it self.
Allison?
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Re: Ideas for AM, NB FM Demod and CW filter board
I listen to AM stations all the time with the ubitx! It's not high fidelity but if you zero beat the station on SSB it is good copy, even on shortwave! Sounds at least as good as the AM stations in my old 1955 Pontiac many years ago! If you just want to station hunt give it a try! Transmitting is a different story of course. tim ab0wr On Tue, 29 May 2018 12:34:38 -0600 "Arv Evans" <arvid.evans@...> wrote: Agree with Allison. If what you want is a FM monitor receiver, then
design and build something
specifically for that purpose. If you want an AM General Coverage
receiver, then build one
specifically for that purpose. As it stands now the BITX or uBITX is
not a good choice for
either mode. Lots of modifications would be required and would still
result in a compromise
design for those modes, and could also degrade the excellent design
and performance of your
BITX or uBITX as an SSB and CW transceiver.
There are several ICs that can be used as the back-end of a AM/FM
receiver. They come
in WBFM or NBFM models, and some are suitable for both wide or narrow
FM. It should be
easy to design and build a simple down-converter to go ahead of one of
those chips and
follow it with an audio amplifier stage. For FM you would probably
want AFC, and lots of
gain followed by a limiter ahead of the FM detector. For AM you will
probably want to include
some sort of AGC.
What does seem to be useful for AM and FM and related to the uBITX or
BITX-40 would be to
use a Raduino board as the frequency and mode control for a new
design for AM, FM, or both.
The Si5351a is inexpensive and could be a good source of LO signals
for the down-converter.
Software for the Arduino Nano could be written to specifically
support this layout.
If your goal is VHF or UHF operation on SSB or CW, then a transverter
might be the most
cost effective way to go. Doing this would only require that the
BITX or uBITX output be
attenuated enough to match input level requirements for the
transverter.
My 2-cents worth.
Arv K7HKL
_._
On Tue, May 29, 2018 at 12:10 PM ajparent1/KB1GMX <kb1gmx@...>
wrote:
On Tue, May 29, 2018 at 10:26 am, Ashhar Farhan wrote:
TDA1220
Superregen at 45mhz as AM/FM detector... I can't go there. ;) I
did it 40 years ago at 10.7mhz
I learned a lot. I wanted a RX that could hear Aircraft (118 to
136mhz) and 2M fm (144-148).
Its a great way to go for low power consumption and poor
selectivity, not a no tune design!
Took a bit of digging to find a data sheet.
Yes, but try to buy them from non questionable sources. It went
EOL years ago so the only
parts are NOS (new old stock that have been sitting). However
something like that would
solve the RX problem and needs to work at the 12mhz IF and its upper
frequency for the
TDA1220 is 30 mhz. It was a 1994 part and I even have two of
them. That and two filters
plus three tuneable cans to add fun to ones life. Look for the
TDA-7000 (also EOL) as
that works easily at 45mhz for FM rx.
That type of part goes in and out of fashion rather quickly but
there is always something
new to replace it.
It still leaves generating AM and FM. Double sideband AM is easy,
sum the 45mhz though
a 6DB pad and a DBM and you get perfect low level modulation. Gain
down stream
becomes critical as the carrier has to be 1/4 peak power or it
sounds distorted.
For AM and power do a class E rig. Using switching fets its fairly
easy to do
Monoband AM at 50W or more (with switchmode class D modulator).s
FM in the current scheme means audio to digital and feed that to the
SI5351. I think
a bigger MPU might be needed. The alternate is 12mhz crystal osc
and FM it using
a varicap diode, not a no tune approach. That also requires audio
processor
(preemphasis and clipping/limiting).
Both AM and FM will easily pass through the 45mhz filter and its
wide enough.
I cut my teeth on AM (marine radio pre VHF and aircraft) and FM
(Land mobile
and Marine VHF) commercial stuff must be 50 years ago. It was fun.
Allison
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Re: What does zero-beat sound like?
#ubitx
Hi Don,
Thank you for confirming this!
I purposely asked the questions as uninformed as possible. I was assuming the best sound would be zero beat but given the fact that this uBitx has thrown me a couple of curve balls I stated to doubth myself and was looking for a confirmation on my assumption ;-)
There are quite a few errors and assumptions in the manual that are easilly been overlooked by those who grew up with this project or are wizards of the eletrons. Hoping that this little tread might help.
Smiles across the wires,
Rogier
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Re: RF power chain mods and improvements..
Jerry,
Its not that much an issue as the current result is lower than normal power.
Just something to think about.??
I
t could be an add using a second cpu to manage on a separate add on board.
Allison
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Re: uBITX - Aligning the master clock
Looks like the software has a bug.? I experienced the same thing during the alignment.? The display shows, say 1.080.00 (1080 on the AM dial). When I tune to a lower frequency, the frequency should drop to 0.900.00 (900 on the AM dial).? Instead it shows 9.000.000.? It would be best to show 900.000. This bug will confuse people just as it did you and me.? I'd like the option to change periods to commas or vice versa in the setup menu.? The world uses the comma more than the period.
--
Jon Titus, KZ1G
Herriman, UT USA
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Re: The new uBITX boards are here
Farhan,
I'm keenly aware of volume lock in and pricing to build.? I looked at the data sheet BFR93.
Using the V3 schematic for Q10, Q20 and Q90 that is a good smt part.? Maybe for?the
predriver as a pair.? Unsuitable for the driver as power handling is too low even as pairs.
The pre driver I'm using is the MPSH10 and its ok for the predriver but not stiff enough
as driver using four of them.
Right now the best part I've tried for driver is 4x 2n2222A (to18 part).? Not a cheap part
the 2n2219 is the same die in the thermally better to5 but cheaper and more common
than 2n3866 and 2n5109.? I'm still looking at high Ft CATV parts for high bandwidth
and power (.8 to 2W range).??
FYI the emitter resistors are high, too much voltage drop and the devices go into current
limiting.? Initially 11 ohms then 5.6 ohms worked better with 2n2222A.? Bias had to be
adjusted for about 20ma?per device idle.??
A note 2n3904s can work but the gain has to be kept to about 10-12db per stage to keep
the power flatter. The cost is one more stage like q90 after the gain pot RV1.? Keeping the
gain low suppresses the low frequency gain rise.
Allison
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Re: What does zero-beat sound like?
#ubitx
Rojier,
I am tempted to reply "the sound of one hand clapping" but that would only be partially true. You hit the nail squarely when you surmised the best sound on an AM station. When you tune so that the carrier decreases in frequency to the point to where it can no longer be heard then you are approaching zero beat. Now if you listen to the modulation content, particularly if it is music, you continue to tune for the most natural sound. If you have an ear for music, there will be a point where everything is "in tune". That's the point where you are truly tuned to frequency. Some folks can pick up just a Hertz or two! 73, Don
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Re: Instruction Manual needs revision
#ubitx
I'm willing to start with the "MBITX TUNEUP instructions if anyone is interested. I can post it for comments.
--
Jon Titus, KZ1G
Herriman, UT USA
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Re: What does zero-beat sound like?
#ubitx
I have no idea what the various software releases for the uBitx are doing.
But during calibration, the BFO should be placed in the center of the 12mhz crystal filter?
so a zero beat can be heard.
Also, the accuracy of that zero beat is proportional to the frequency of the signal.
So a zero beat to WWV at 15mhz is 15 times more accurate than a zero beat of a 1.0mhz AM broadcast station.
The three local oscillators are each a strict ratio of the 25mhz reference,? ?and from post 44515
the operating frequency of a stock uBitx in LSB mode is:? ? vfo - (clk1-bfo)?
By the distributive law of algebra, a 100ppm change in vfo, clk1 and bfo will result in a 100ppm change in the operating frequency.
Jerry
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On Tue, May 29, 2018 at 03:38 pm, Glenn Anderson wrote:
When tuning in an AM station when your rig is listening on SSB, you will hear a carrier tone... This will vary depending on whether you change your frequency up or down... When you tune so that the frequency you hear gets so low that it "disappears" then you have "zero-beated" on the station... Most commercial rigs have a tune button that typically is at every 25 or 100 khz on the dial...
Once you no longer hear the tone then that's when you calibrate your dial... A good frequency on air is WWV @ 10.000Mhz...
I hope that helps,
Glenn VE3JAU
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Re: What does zero-beat sound like?
#ubitx
Rogier KJ6ETL
Might also mention that if you are zero-beating against WWVB or WWVH there is
modulation on the carrier that will interfere with getting a proper zero-beat.? This
modulation is shut off at 43 minutes past the hour and turned on again 52 minutes
after the hour.??
This means that to get a true zero-beat you need to do it between 43 minutes after
the hour and 52 minutes after the hour.
Arv K7HKL
_._
Rogier
Have you ever tuned across a steady carrier with a CW receiver and listened to the tone
as it starts high (difference between the two signals), then goes lower as you get closer to
the same frequency, and then goes back higher as you move to a higher difference between
signal frequencies?? Near the center of this tuning range the difference signal will go lower
and lower until it becomes less than 1 Hz.? If your receiver has an S-meter you can probably
see the meter waving back and forth at a few tenths of Hz difference.? Continue fine tuning to
minimize this slow frequency difference and you will find a place where there is no difference
between LO+/- BFO and received signal.? That is "Zero-Beat".? I guess the term "zero" means
"no beat note"...maybe...?
Hope that helps. Sometimes us ancient old geezers assume that newer hams already know all the radio language.
Arv? K7HKL
_._
On Tue, May 29, 2018 at 4:14 PM kj6etl < pa1zz@...> wrote: Ok this might be the most newbie queastion in the century but I am not sure what Farhan means in the Tune-Up instructions to calibrate the uBitx to "zero-beat" on a known AM station.
Doest this mean turning for best sound? No sound? A 1000rz tone?
Seriously what is this "zero beat" on an AM broadcast station supposed to sound like ?-)
Thanks!
Rogier
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Re: What does zero-beat sound like?
#ubitx
Hi Arv,
Thanks again!
Yes I am an old ham myself by now and am familliar with the turning across a CW signal ;-)
Problem is that the uBitx doesnt have an s meter so your advice is hard to implement. So should the new ham tune for best audio or what ?-)
Alternatively I can ask a friend to transmit in SSB or CW so I can calibrate to that.
Now the question is should he transmit in CW or the appropriate sideband for that frequency?
I don't know what in what mode the calibration is taking place and using the wrong sideband could cause the rig to be off by a couple of khz..
Hoping this will also serve other people who might be puzzled with the instructions..
Smiles across the wires,
Rogier
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Re: What does zero-beat sound like?
#ubitx
When tuning in an AM station when your rig is listening on SSB, you will hear a carrier tone... This will vary depending on whether you change your frequency up or down... When you tune so that the frequency you hear gets so low that it "disappears" then you have "zero-beated" on the station... Most commercial rigs have a tune button that typically is at every 25 or 100 khz on the dial...
Once you no longer hear the tone then that's when you calibrate your dial... A good frequency on air is WWV @ 10.000Mhz... I hope that helps, Glenn VE3JAU
On Tue, May 29, 2018 at 6:11 PM, kj6etl <pa1zz@...> wrote: Ok this might be the most newbie queastion in the century but I am not sure what Farhan means in the Tune-Up instructions to calibrate the uBitx to "zero-beat" on a known AM station.
Doest this mean turning for best sound? No sound? A 1000rz tone?
Seriously what is this "zero beat" on an AM broadcast station supposed to sound like ?-)
Thanks!
Rogier
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Re: The new uBITX boards are here
?ordered? 10 of one, 15 of the other.
gordn
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?Well I'll be doggoned --- I found BOTH those transistors at mouser.? ?Tonight I'll order some.? ?This is starting to get INTERESTING.
Gordon
What did I say about using a high FT transistor?
Since I don't have KST10s but know the MPSH10s and you say its the same save for package
my first shot would be go for it, can't be worse.? MPSH10s are 650mhz minimum so its better
by two.? Looking at the data sheet make sure the pins for base and emitter fall on the right
pads.? Likely do but, check.
The kst10 FYI is 650mhz FT device so it will likely be better by a factor of two but not as good as
the BFR106 is a 5ghz device.? For feedback amps like that a FT according to the spreadsheet?
needs to be good to more than 2000mhz.? I'd suspect any 1ghz or better device should work well.
when compared to a 300mhz device.? The spreadsheet off the disk EMRFD gives 18db for
a 5ghz device and 13.6db for a 300mhz device and 15.8 for a 650mhz device.? You get
2.3db for he effort.? ?In reality it may be better.?
I have to comment did you check the FT for that device?? For the BFR106?? The idea is
not to flail wildly but to do some basic calculation and the easy one is:
B=Ft/F? where FT is the stated datasheet number and F is the working frequency.
if we take 300 and divide by 45 we get 6.67 a very low gain.? 650/45 is 14/44 better
but barely twice.? Work it backward, a desired gain of 17db or 50 so 45*50=2250
that's the desired FT.? The only thing somewhat magic is that 17db happens to be 50
but that is easily calculated as the antilog.? 17db=10(log50) or for those that want a
weird backward explain...
17db gain is:? 10db or 10x plus 7db or 5x, so we multiply and get 50.
Why use logs (aka? DB)?? it saves multiplying big numbers in your head that you can otherwise add.
The magic is that I can remember the logs of 10 for integers at age 65 but, not what day it is. ;-)
Hint I grew up with and still have a slide rule.? The calc in the iphone is decent in scientific mode
(turn it landscape).
Allison
Allison
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atouk
kj6etl
Don, ND6T