Re: Low Power Output for Hendricks BitX20A - Watt meters and Scope readings do not agree....
#bitx20
Leonard
Very good video.? For those who were not around several years ago, Leonard KC0WOX
played a large part i popularizing the BITX and in helping others build and fix their own BITX
transceivers.? His videos are as relevant now as they were back then.?
During the past few years the QRPKits company of Doug KI6DS has been transfered to
Pacific Antenna, and the BITXxxA series seems to have been dropped from production.?
The BITXxxA assembly manuals are still available from Pacific Antenna/QRPKits
Arv
_._
On Tue, Aug 14, 2018 at 3:42 PM Leonard < dredger@...> wrote: Here's a video of a Hendrix BITX20a looking at the modulation, carrier balance and harmonics rejection. I'm not an expert but I believe my way of testing is relatively accurate.
I start out with 16 watts power out. The 20a has push-pull output so gives more power and good second harmonic rejection.
This was made 10 years ago or so. The 20a is available from It is considerably more expensive though. Arv had a big hand in the design and testing of the kit.
Leonard
kc0wox
|
On Wed, Aug 15, 2018 at 05:21 AM, ajparent1/KB1GMX wrote:
I'm starting a new clean sheet
project
HI Allison. I was wondering if you were up to something along these lines... uBitx V2,0? I hope you would share you design so others could reproduce. I am dying to scratch build a uBitx type radio.? You definitely appear to have an excellent grasp on what needs to be done to build on the existing uBitx to create an even better multiband QPR radio. 73 Nick VK4PLN.
|
Re: Low Power Output for Hendricks BitX20A - Watt meters and Scope readings do not agree....
#bitx20
Here's a video of a Hendrix BITX20a looking at the modulation, carrier balance and harmonics rejection. I'm not an expert but I believe my way of testing is relatively accurate.
I start out with 16 watts power out. The 20a has push-pull output so gives more power and good second harmonic rejection.
This was made 10 years ago or so. The 20a is available from It is considerably more expensive though. Arv had a big hand in the design and testing of the kit.
Leonard
kc0wox
|
|
|
Allison
Re.? the Elliptical filter...moved spur trap to 23.8.? I moved the trap frequency to 23.8 by changing value of L3.? Then R2 was changed
from 3 ohms to 0.5 ohms to give more attenuation.? This might work if the trap is not
too narrow to cover possible spur frequency range.? Attenuation is now 45 DB.?
Arv
_._
On Tue, Aug 14, 2018 at 9:08 AM ajparent1/KB1GMX < kb1gmx@...> wrote: Arv,
Interesting filter.? However how effect is it? at 23.8mhz (dial frequency of 21.2)?
Looks to be maybe 18db loss at that frequency.? It may be enough.
Allison
|
What's the difference between the Nextion and the TJC LCDs? Is one better or is it just name brands vs clone? I didn't see any TJCs over 2.8", are there 3.5" screens?
Thanks!
Vince - K8ZW.
--
Michigan VHF Corp.
|
Jerry,
All the info is there.??
As to mic gain being a poor solution.? I'll apply your logic.
For the people using them it was a easy solution.? They?
got the power they wanted and are flying blind and really?
don't care as the solutions require them to do work.
Myself I don't like the choices, all of them.? As I've literally
sliced it up to measure and isolate issues the whole thing
has become moot to me.? I'm starting a new clean sheet
project that?will have the filters and will work.? The power
amp is done.? It performs from from 1.8Mhz to 30mhz flat
to 2db at 10W, useful to 50mhz at 6W, and 70mhz at 4W
using IRF510 and has no failure modes or instability.?
Low pass at the output, band pass at? the input and it will
be better than a lot of commercial ham gear.? ?A clean
sheet design.
Allison
|
Allison,
This is just some armchair engineering, I don't have gear to easily
measure harmonics and spurs at 40dB down.
But mostly, I'm kind of lazy.
You have been in the trenches, measuring and hacking.
That said:
I doubt we need the 6dB pad on the LO into the mixers.
Perhaps a series resistor is sufficient, or two series resistors to ground with a tap in the middle.
If we do need the pad, then so be it.?
Add a $0.50 MMIC to each of the three clocks.
Mike gain is not a good solution to low power out if we have trouble with signal levels at the mixers.
Better to bite the bullet and add a gain stage to the power amp.
As per posts 51172, 51211
And distribute gain across stages appropriately,
maybe invest is something better than the $0.03? 2n3904's.
?
Jerry, KE7ER
toggle quoted message
Show quoted text
On Tue, Aug 14, 2018 at 11:09 AM, ajparent1/KB1GMX wrote:
Jerry,
>>I'm bucking the complexity of all the added filters.
The uBitx has been popular because it is simple, would be nice to keep it so.<<
Question how are you going to increase the LO/2nd-lo/BFO levels?? Knobs full
up (5351 levels) are far from enough.
You might but with maybe 2 or 3W I'm certain the spur will be much less an issue once you
get bored not talking to anyone on 15M and move to another band.
I am not telling anyone what to do.? Only what I've measured in a sample size growing
greater and a few of them totally unmodified.
Every one wanted more mic gain, and had a ICom or Turner mic.
All were disappointed with 20m and up power out.
I don't like the solution either.
Allison
|
What about Farhan's summary statement, on another thread, that "?The harmonics at 14 Mhz and below can be controlled by backing off the drive level" and "I guess that we really need a good ALC to cut the drive on the lower bands".
73 Kees K5BCQ
?
|
Jerry,
>>I'm bucking the complexity of all the added filters.
The uBitx has been popular because it is simple, would be nice to keep it so.<<
Question how are you going to increase the LO/2nd-lo/BFO levels?? Knobs full
up (5351 levels) are far from enough.
You might but with maybe 2 or 3W I'm certain the spur will be much less an issue once you
get bored not talking to anyone on 15M and move to another band.
I am not telling anyone what to do.? Only what I've measured in a sample size growing
greater and a few of them totally unmodified.
Every one wanted more mic gain, and had a ICom or Turner mic.
All were disappointed with 20m and up power out.
I don't like the solution either.
Allison
|
It's a uBitx. I had this probem since it arrived and when I made first tests with it. A few days later, I built a case from copper plated FR4 circuit board material for it to ensure the shielding is good enough. I shortened and twisted most wires in the uBitx, like the antenna wire and the audio wires to avoid rf-coupling to them as much as possible. This made my problem much better, but it still occurs at some antennas, like the mentioned endfed halfwave.
With my IC726 I used this endfed halfwave antenne quite often and had just a few problems with ist, so I like it. At home I'm not able to put up a wire antenna, so I'm trying to use a magnetic loop.
73,
Ludwig
|
As Jerry has noted, on my unit at least, the 15 meter ¡°45 MHz-Carrier¡± spur at 24 MHz is below the -43 dBc limit and therefore not a problem. I checked it again this morning to confirm and found it at -47 dBc¡¡ still not great but acceptable as is with the existing filter.
WA8TOD
|
Yes, I understand the cruft is unwanted mixer products, makes sense.
I'm hoping that limiting mike levels, reducing IF gain, and increasing LO injection levels
will take care of that cruft.
I'm bucking the complexity of all the added filters.
The uBitx has been popular because it is simple, would be nice to keep it so.
Jerry
toggle quoted message
Show quoted text
On Tue, Aug 14, 2018 at 10:31 AM, ajparent1/KB1GMX wrote:
Now The cruft you see... look at that long explanation in #57038 about mixing and
making mush.? I only went the 4th harmonic.? The usual is not less than the 7th or 11th.
|
Allison,
Hmm, post 57037
Guess you were talking to Kees then.? ?;-)
Good summary of the pitfalls in single conversion.
My Swan 100MX has lots of band specific filters and lots of shielding to do what it does.
Not something I want to duplicate.
?
We're very close to usable, would be nice to build something bulletproof
with regard to compliance without adding additional band specific filters.?
I'm still favoring a bump up from 45mhz for first IF, there are zero additional parts involved.?
Reduce IF gain, increase LO power levels, standardize on mike construction,
all with the aim of getting a consistent and clean signal out of the first mixer into the 30mhz LPF.
Add one more stage to the power amp (ouch!) since?levels going into Q90 will be reduced.
?
Separate board modules laid out as strips, 4 layer boards, copper tape shielding, semiconductors more exotic
than the 2n3904, those all seem preferable to the complexity of a half dozen new switchable filters.?
With low audio levels and proper transmit LPF's? we get RF to the antenna that is nearly compliant.
That suggests using a few of these alternative measures will be sufficient.
Jerry
toggle quoted message
Show quoted text
On Tue, Aug 14, 2018 at 09:22 AM, ajparent1/KB1GMX wrote:
Jerry,
It referred to your post? #57037
Its the exercise of why DBMs look easy but make people unhappy.
Nowhere is ther e more than one conversion in that discussion or even a receiver.
its about what you get from mixers (some much worse than others) for two simple
signals.
Now to your topic:
>>>>Perhaps my vague suggestion of going back to a single conversion rig.
The thought being, if we are adding all these filters between the first mixer and the power amp,
could make them all bandpass and do away with the 45mhz IF.? <<<<
First be warned its long and goes round some covering a lot of ground for what and why.
Opening:
The problem with single conversion is the choice of IF.? Minima used 20Mhz and 15M was?
too close for simple low loss wide filters.??The Minima issues spawned HF1 which begat?
uBitx.? The underlying desire was?for low cost?continuous tuning from some low frequency?
to at least 30mhz.? ?That is its history and its important as it is why some paths and?
choices came to be.
Single conversion does work.? I have 14 radios that mange to do well on on or many
bands though 2m!.? A few are even multiband radios.
Those that come to mind are the Tempo-one (9mhz if) but 17M and 30M are near impossible.
WM20 has an 8mhz IF, which is too close to 40M to do that.
Two of my radios have nice commercial 8 pole filters at 7.8mhz which rule out 40M also too close.
The Atlas-210X a classic 80/40/20/15/10 radio uses a IF of 5.520mhz single conversion.
It might work on 30M (the 2if spur is 10.44mhz but can be trapped). All the other possible
bands are a go save for 60M (way to close to the IF to filter).
FYI the HW101 is dual conversion low IF at 3.395mhz and the second conversions is
hIghly pre-selected in the 8mhz range (tunable IF) to keep birdies down.? This was the
common technique for many radios and also KWM2, S51, HRO others many using
455khz filters in the last if.
There is a lot of history there for single and dual (even triple) conversion
and the key is those known to be great radios were big, well shielded and well?
filtered ( some with frightening mechanics to tune many stages).
At least two of the commercial radios I have Argo505 and the Triton have a 9mhz IF but are
from the 80/40/20/15/10 only era.? So bands like 17M are plagued with 2if (~18mhz) spurs,?
30M requires really good filters to keep 9mhz out of the air.? For those radios 60, 12M
are easy though.?
The only radio I have that has 500khz to 30mhz (+6M) tuning and a 9mhz HF First IF
is the Tentec Eagle first IF is 9mhz but the level of filtering is intense. You cannot tune
close to 9mhz without hearing negative effects.
So a single conversion can work but you have to jump a few hurdles.
IF it were easy everyone would have done it already.
If one is willing to dismiss with all that Phasing radios using digital IFs
are doable now with inexpensive processors and fairly simple RF to
base band conversion. That is other wise known as image rejecting
DC RX/TX where the image is the other sideband!
Allison
|
Jerry, >>>Warren's Spectrum Analyzer screenshot of 2W out on 15m shows the 23mhz spur to be 50dB down, which is fully compliant.? ?? ?? /g/BITX20/photo/65861/2?p=Name,,,20,1,0,0<<<When you get the amp flattened out so it has gain that pops up.? Note, he is normalized to 2W. Who's going to use 2W?? Who will push the mic??? Now The cruft you see... look at that long explanation in #57038 about mixing and making mush.? I only went the 4th harmonic.? The usual is not less than the 7th or 11th. There is a detailed explanation and calculator for this at: https://www.microwaves101.com/encyclopedias/spur-search Its why its called mixer products not plain old signals. Allison
|
Allison
Interesting thought...I wonder if anybody has tried using the "sub-harmonic mixer" idea in
a transceiver design?? Having the LO at half the mixer frequency might make things better
or worse.?
From limited reading it seems that there are both benefits and problems associated with
implementation.?
Arv
_._
On Tue, Aug 14, 2018 at 10:22 AM ajparent1/KB1GMX < kb1gmx@...> wrote: Jerry,
It referred to your post? #57037
Its the exercise of why DBMs look easy but make people unhappy.
Nowhere is ther e more than one conversion in that discussion or even a receiver.
its about what you get from mixers (some much worse than others) for two simple
signals.
Now to your topic:
>>>>Perhaps my vague suggestion of going back to a single conversion rig.
The thought being, if we are adding all these filters between the first mixer and the power amp,
could make them all bandpass and do away with the 45mhz IF.? <<<<
First be warned its long and goes round some covering a lot of ground for what and why.
Opening:
The problem with single conversion is the choice of IF.? Minima used 20Mhz and 15M was?
too close for simple low loss wide filters.??The Minima issues spawned HF1 which begat?
uBitx.? The underlying desire was?for low cost?continuous tuning from some low frequency?
to at least 30mhz.? ?That is its history and its important as it is why some paths and?
choices came to be.
Single conversion does work.? I have 14 radios that mange to do well on on or many
bands though 2m!.? A few are even multiband radios.
Those that come to mind are the Tempo-one (9mhz if) but 17M and 30M are near impossible.
WM20 has an 8mhz IF, which is too close to 40M to do that.
Two of my radios have nice commercial 8 pole filters at 7.8mhz which rule out 40M also too close.
The Atlas-210X a classic 80/40/20/15/10 radio uses a IF of 5.520mhz single conversion.
It might work on 30M (the 2if spur is 10.44mhz but can be trapped). All the other possible
bands are a go save for 60M (way to close to the IF to filter).
FYI the HW101 is dual conversion low IF at 3.395mhz and the second conversions is
hIghly pre-selected in the 8mhz range (tunable IF) to keep birdies down.? This was the
common technique for many radios and also KWM2, S51, HRO others many using
455khz filters in the last if.
There is a lot of history there for single and dual (even triple) conversion
and the key is those known to be great radios were big, well shielded and well?
filtered ( some with frightening mechanics to tune many stages).
At least two of the commercial radios I have Argo505 and the Triton have a 9mhz IF but are
from the 80/40/20/15/10 only era.? So bands like 17M are plagued with 2if (~18mhz) spurs,?
30M requires really good filters to keep 9mhz out of the air.? For those radios 60, 12M
are easy though.?
The only radio I have that has 500khz to 30mhz (+6M) tuning and a 9mhz HF First IF
is the Tentec Eagle first IF is 9mhz but the level of filtering is intense. You cannot tune
close to 9mhz without hearing negative effects.
So a single conversion can work but you have to jump a few hurdles.
IF it were easy everyone would have done it already.
If one is willing to dismiss with all that Phasing radios using digital IFs
are doable now with inexpensive processors and fairly simple RF to
base band conversion. That is other wise known as image rejecting
DC RX/TX where the image is the other sideband!
Allison
|
Warren's Spectrum Analyzer screenshot of 2W out on 15m shows the 23mhz spur to be 50dB down, which is fully compliant.? ?? ?? /g/BITX20/photo/65861/2?p=Name,,,20,1,0,0Of course, shouting into the mike to get a bit more power out will make it worse. And there is some worrying cruft below 15m, I have no idea where that's coming from. Jerry ============================================== So what is the problem again on 15m ? 73 Kees K5BCQ
|
Of course none of that helps the current uBITX owners but shows that in the last
4 years technology things hinted at then the current way.
And in there why it came to be this way.
Allison
|
Jerry,
It referred to your post? #57037
Its the exercise of why DBMs look easy but make people unhappy.
Nowhere is ther e more than one conversion in that discussion or even a receiver.
its about what you get from mixers (some much worse than others) for two simple
signals.
Now to your topic:
>>>>Perhaps my vague suggestion of going back to a single conversion rig.
The thought being, if we are adding all these filters between the first mixer and the power amp,
could make them all bandpass and do away with the 45mhz IF.? <<<<
First be warned its long and goes round some covering a lot of ground for what and why.
Opening:
The problem with single conversion is the choice of IF.? Minima used 20Mhz and 15M was?
too close for simple low loss wide filters.??The Minima issues spawned HF1 which begat?
uBitx.? The underlying desire was?for low cost?continuous tuning from some low frequency?
to at least 30mhz.? ?That is its history and its important as it is why some paths and?
choices came to be.
Single conversion does work.? I have 14 radios that mange to do well on on or many
bands though 2m!.? A few are even multiband radios.
Those that come to mind are the Tempo-one (9mhz if) but 17M and 30M are near impossible.
WM20 has an 8mhz IF, which is too close to 40M to do that.
Two of my radios have nice commercial 8 pole filters at 7.8mhz which rule out 40M also too close.
The Atlas-210X a classic 80/40/20/15/10 radio uses a IF of 5.520mhz single conversion.
It might work on 30M (the 2if spur is 10.44mhz but can be trapped). All the other possible
bands are a go save for 60M (way to close to the IF to filter).
FYI the HW101 is dual conversion low IF at 3.395mhz and the second conversions is
hIghly pre-selected in the 8mhz range (tunable IF) to keep birdies down.? This was the
common technique for many radios and also KWM2, S51, HRO others many using
455khz filters in the last if.
There is a lot of history there for single and dual (even triple) conversion
and the key is those known to be great radios were big, well shielded and well?
filtered ( some with frightening mechanics to tune many stages).
At least two of the commercial radios I have Argo505 and the Triton have a 9mhz IF but are
from the 80/40/20/15/10 only era.? So bands like 17M are plagued with 2if (~18mhz) spurs,?
30M requires really good filters to keep 9mhz out of the air.? For those radios 60, 12M
are easy though.?
The only radio I have that has 500khz to 30mhz (+6M) tuning and a 9mhz HF First IF
is the Tentec Eagle first IF is 9mhz but the level of filtering is intense. You cannot tune
close to 9mhz without hearing negative effects.
So a single conversion can work but you have to jump a few hurdles.
IF it were easy everyone would have done it already.
If one is willing to dismiss with all that Phasing radios using digital IFs
are doable now with inexpensive processors and fairly simple RF to
base band conversion. That is other wise known as image rejecting
DC RX/TX where the image is the other sideband!
Allison
|
Re: Does anyone have an AGC/Click kit to sell?
Sorry, the postage was $8.50, total cost was $11.50 -- Ion
VA3NOI
|
Nick VK4PP
Leonard
Ion Petroianu, VA3NOI