Re: Understanding Spurious Emissions
What about installing these ?as switchable bandpass filters at the wiper of RV1?
--
N5KBP
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Re: Harmonic performance - SSB vs CW
This page contains three simple filters that were used to augment the internal filters of the Softrocks RXTX which suffered similar harmonic issues.
I have built all three filters plus one with scaled values for 14 MHz. I just tested them and the 30 meter filter described brings 80, 60, 40, and 30 meters into compliance. My 20 meter version does the same.
So, in my case, a single external filter gives me four bands and a second gives me 20 meters.
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Re: rotary encoder without detents
A suitable one made by Bourns is available from Digi-Key. ?Their part# is PEC11R-4020F-S0012-ND and I've used these with my various uBITX radios since day 1. ?Not terribly expensive either, I believe less than $2, plus shipping. ? ?? www.digikey.com
Jim, W0EB
------ Original Message ------
Sent: 8/4/2018 2:32:08 PM
Subject: [BITX20] rotary encoder without detents
Can anyone give me a pointer on where I can purchase a replacement encoder for the Ubitx
Thanks
73
art - n2ajo
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rotary encoder without detents
Can anyone give me a pointer on where I can purchase a replacement encoder for the Ubitx
Thanks
73
art - n2ajo
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Re: New "ANTENNAS" group has been formed.
Yes, I keep trying to forget the yahoo mess.
There are a few there most I unsubed from.? The only ones there of interest is EMRFD, COSMACELF (1802 cpu), R2PRO.
There are a few other with high noise traffic and a few more than are moribund.
Allison
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Re: Harmonic performance - SSB vs CW
As a daughter board it would fully replace the back half and its a non-trivial
effort.
It could be done in? the same width but the depth would have to grow.
Ways to make it smaller would be careful choice of filters at the input
such as a mix of low pass and band pass with diode switching.? at the
output the existing filters with smaller relays (6 in all) would do and a
single TR relay.? DC switching can be fully done with transistors with
some of the pop reductions added (pulling the unpowered line to ground)
*The power amp you need a minimum of 4 stages but not 9 transistors.
*Mounting the finals to the underside so the can heatsink with insulators
to the case bottom or back cuts the needed space and would make for
better RF layout.? IRF510s are fine if employed correctly.?
*Dumping the paralleled devices saves space and cleans things up.
*Using balun cores can help with space.? The Q90 stage does not need
a FT37 size core when a BN43-2402 is more than large enough and likely
the thing device pre-driver a BN43-302 is more than enough.?
An example of small and packed.? That is a modified Kitsandparts 5W Class C amp
using IRF510s ( and heatsinks on the back) and a 2n3866 driver. It takes 10mw
and makes 10W flat from 3-10mhz and slow droop to 5.5W at 29mhz. Not a lot
of fancy hardware just a solid and dirt simple circuit.? The ruler is in inches.
Allison
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My latest build, using a? Context Engineering (Fry's Electronics) case.? It's a tight fit and not for the beginner.? I had to "mill out" (dremel) areas for the stand offs.? We also chopped (bandsaw actually) off the back? 1 3/4" of the case.? It's using the 3.2" Nextion display and also has a quiet (because it's 24 volts) fan to keep the finals cool. Final size is 3 x 6 x 6 1/2"..
Your mileage may vary,
Jim W0CHL
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Re: Harmonic performance - SSB vs CW
I realized this early when the uBITx first came out.? It was a very easy fix to simply decommission the filter networks on the uBITx, use an external filter network that accepts 4-bit binary band code (I wanted to use the uBITx on 160 and 6 meters anyway which can¡¯t be in its factory state, QRP filter network purchased off eBay), re-write the code to give a binary band output (with one extra digital output).? Done. Case closed. ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Warren Allgyer
Sent: Saturday, August 4, 2018 7:43 AM
To: [email protected]
Subject: Re: [BITX20] Harmonic performance - SSB vs CW ? No one is going to want to hear this but the design of the PA output filter is probably fatally flawed and it is likely due to board layout issues.
I have been puzzled how the high order harmonics of 80 meters, for example, could possibly survive a 7th order filter which should have well over 50 dB of attenuation at the 5th harmonic. So today I set out to test the results with a 9th order filter, figuring more is better. The harmonics remained. But in troubleshooting that installation the source of the issue was revealed.
In the attached screenshot the purple trace is the 80 meter CW output with the harmonics clearly far in excess of the green -43 dBc legal threshold. The blue trace is the output with L20 removed which disables the 80 meter filter and blocks RF output from the finals from reaching the output connector. (Don't worry..... the tests were carried out with the drive reduced so the output was only one half watt. And I have a bag of spare IRF510s on hand......). The harmonics remain! How can that be? Pic #2 shows the path 80 meter RF follows through all three switching relays in order to reach the filter. It is a very novel and inventive concept to use three relays to switch both ends of 4 filters. Most manufacturers would require 8 separate relays to do this job. And for a very good reason. In order for a filter to provide the required 50+ dB of attenuation, the filter itself must have 60 dB or more of input-to-output isolation. If it does not then the unwanted products simply bypass the filter and go directly to the output. That appears to be exactly what is happening in the filter complex of this unit. There is no easy fix for this. No amount of on board filtering and tweaking is going to improve harmonic suppression until the path around the filters is blocked. I suspect that path is via the relays themselves but board layout often is critical as well in such cases. My guess is the only solution would be either extensive external filtering or a carefully laid out daughter card to replace the existing filters and relays. WA8TOD -- ¡_. _._
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Re: Harmonic performance - SSB vs CW
Allison and Scott
Thinking old-school raises the question about using a broadband transformer to
raise the MOSFET output impedance up to around 5K and then use a Pi-network
as was done in ancient times to match almost anything.? Pre-aligning the Pi-net
on receive mode should allow sneaking up on desired power output without over-
stressing the MOSFETs.? Real problem might be in finding suitable variable
capacitors for the pi-network.? Younger hams probably have never experienced
the pain of an RF Burn.
Arv
_._
On Sat, Aug 4, 2018 at 12:39 PM Scott McDonald via Groups.Io <ka9p= [email protected]> wrote: There is a good example of such an old school preselector on the AA3SJ Progressive Receiver Page, I think originally designed by W3TS (?).
Pretty much exactly as Allison describes, 2 bands, total HF coverage.? I¡¯ve built a couple that I use for receiver front ends, and other than getting the matching toroids to track and finding a 2 gang tuning cap of 300 of/sec or greater, they are pretty quick and easy to build, especially when compare ty winding 10 bands of toroids.
Scott Ka9p On Aug 4, 2018, at 1:19 PM, ajparent1/KB1GMX < kb1gmx@...> wrote: >>>>Has anybody looked at making those multi-band filters into tunable BPF designs?
That would add some more knobs and possible operator errors but it is an?
interesting thought.<<<
Old school:
A pre-selector.? The form for tha tis a double tuned circuit with top coupling between
elements and link coupling to the adjacent 50 ohnm circuits.? ?It would require a
multi-gang capacitor as varicap diodes may be modulated by RF at that level
(testing required) and switching as you would need a few maybe two bands to
do 3-30mhz.? ?At most one knob as the Raduino can do the band select.
Its adjustment would be fairly uncritical as it would be in the RX path poor RX
set the pre-selector.??? However If a real cap is used a dual section of the 30-365
form is the minimum but would cover 3-30 in two bands with switched coils.?
Varicap diodes do not have that tuning range so 3 bands possibly 4 using switched coils.
I tried that for the RX with good result for some of the spurs and out of band signals.
since it was in place of the 30mhz filter it did have significantly less spur output
as it was bandpass.? I put it aside for a later day as it made for space issues in
the desired box.? ?That and suggesting it seemed a big complex mod for most.
Allison
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Re: Harmonic performance - SSB vs CW
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On Sat, Aug 4, 2018 at 12:22 PM ajparent1/KB1GMX < kb1gmx@...> wrote: Arv,
That was a narrow cut. ;)?
It would be the 1M band based on blade length. It was a
narrowband effort using a .9mm blade.
Its my signal slicer...? !groan!
Allison
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Re: Harmonic performance - SSB vs CW
There is a good example of such an old school preselector on the AA3SJ Progressive Receiver Page, I think originally designed by W3TS (?).
Pretty much exactly as Allison describes, 2 bands, total HF coverage. ?I¡¯ve built a couple that I use for receiver front ends, and other than getting the matching toroids to track and finding a 2 gang tuning cap of 300 of/sec or greater, they are pretty quick and easy to build, especially when compare ty winding 10 bands of toroids.
toggle quoted message
Show quoted text
On Aug 4, 2018, at 1:19 PM, ajparent1/KB1GMX < kb1gmx@...> wrote: >>>>Has anybody looked at making those multi-band filters into tunable BPF designs?
That would add some more knobs and possible operator errors but it is an?
interesting thought.<<<
Old school:
A pre-selector.? The form for tha tis a double tuned circuit with top coupling between
elements and link coupling to the adjacent 50 ohnm circuits.? ?It would require a
multi-gang capacitor as varicap diodes may be modulated by RF at that level
(testing required) and switching as you would need a few maybe two bands to
do 3-30mhz.? ?At most one knob as the Raduino can do the band select.
Its adjustment would be fairly uncritical as it would be in the RX path poor RX
set the pre-selector.??? However If a real cap is used a dual section of the 30-365
form is the minimum but would cover 3-30 in two bands with switched coils.?
Varicap diodes do not have that tuning range so 3 bands possibly 4 using switched coils.
I tried that for the RX with good result for some of the spurs and out of band signals.
since it was in place of the 30mhz filter it did have significantly less spur output
as it was bandpass.? I put it aside for a later day as it made for space issues in
the desired box.? ?That and suggesting it seemed a big complex mod for most.
Allison
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Re: Harmonic performance - SSB vs CW
Arv,
That was a narrow cut. ;)?
It would be the 1M band based on blade length. It was a
narrowband effort using a .9mm blade.
Its my signal slicer...? !groan!
Allison
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Re: Harmonic performance - SSB vs CW
>>>>Has anybody looked at making those multi-band filters into tunable BPF designs?
That would add some more knobs and possible operator errors but it is an?
interesting thought.<<<
Old school:
A pre-selector.? The form for tha tis a double tuned circuit with top coupling between
elements and link coupling to the adjacent 50 ohnm circuits.? ?It would require a
multi-gang capacitor as varicap diodes may be modulated by RF at that level
(testing required) and switching as you would need a few maybe two bands to
do 3-30mhz.? ?At most one knob as the Raduino can do the band select.
Its adjustment would be fairly uncritical as it would be in the RX path poor RX
set the pre-selector.??? However If a real cap is used a dual section of the 30-365
form is the minimum but would cover 3-30 in two bands with switched coils.?
Varicap diodes do not have that tuning range so 3 bands possibly 4 using switched coils.
I tried that for the RX with good result for some of the spurs and out of band signals.
since it was in place of the 30mhz filter it did have significantly less spur output
as it was bandpass.? I put it aside for a later day as it made for space issues in
the desired box.? ?That and suggesting it seemed a big complex mod for most.
Allison
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Re: Harmonic performance - SSB vs CW
Allison
Attempts at humor rarely work well on-line, but I have to ask...
"What band is your band saw designed for?"!? 8-)
Arv
_._
On Sat, Aug 4, 2018 at 12:02 PM ajparent1/KB1GMX < kb1gmx@...> wrote: Arv,
All the way to the 30mhz filter.? The first step is inset a set of band pass filters.
Basic scheme is make the board linear layout as you want the input as far
as possible from the output with a mix of low pass and band pass filters at
the input and low pass filters at the output.? Revised amp chain would be in
general form similar with better devices (from the Q90 spot to the drivers)
and revised transformers.? ?Two sided but plenty of top and bottom ground
plane well stitched with vias to improve the ground and limit ground loops.?
I took a band saw to mine and basically the rear half is everything TX and
TR switching and the front half is the IF audio and Raduino.? ?I abandoned
the rear half too many issues and too few ways for lack of room to improve it.?
Allison
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Re: Harmonic performance - SSB vs CW
Allison
I was afraid of that.? This daughter board idea is getting larger and larger.
Arv
_._
On Sat, Aug 4, 2018 at 11:51 AM ajparent1/KB1GMX < kb1gmx@...> wrote: Arv,
All the way to the 30mhz filter.? The first step is inset a set of band pass filters.
Allison
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Re: Harmonic performance - SSB vs CW
Arv,
All the way to the 30mhz filter.? The first step is inset a set of band pass filters.
Basic scheme is make the board linear layout as you want the input as far
as possible from the output with a mix of low pass and band pass filters at
the input and low pass filters at the output.? Revised amp chain would be in
general form similar with better devices (from the Q90 spot to the drivers)
and revised transformers.? ?Two sided but plenty of top and bottom ground
plane well stitched with vias to improve the ground and limit ground loops.?
I took a band saw to mine and basically the rear half is everything TX and
TR switching and the front half is the IF audio and Raduino.? ?I abandoned
the rear half too many issues and too few ways for lack of room to improve it.?
Allison
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Re: Harmonic performance - SSB vs CW
Has anybody looked at making those multi-band filters into tunable BPF designs?
That would add some more knobs and possible operator errors but it is an
interesting thought.
Arv
_._
On Sat, Aug 4, 2018 at 8:40 AM Jerry Gaffke via Groups.Io <jgaffke= [email protected]> wrote: This is primarily an SSB transceiver, and harmonic suppression seems adequate in
that mode on the stock rig.? Best and easiest fix is probably to either not use CW mode,
or do a minor hack to move the CW mixer injection an earlier mixer so the 45mhz
filter takes out the harmonics?as previously stated.
?
The uBitx relay arrangement is not that uncommon, though would be better
to double the relay count and use separate relays for input and output.
Board layout is important.? This guy definitely knows what he is doing:
? ??
Another solution might be to get an outboard set of filters such as the WA2EBY fllter board:
? ??
LPF's such as seen on the uBitx are usually adequate for use with class C amps
on CW transmitters (which are dealing with high power square waves).??
However the uBitx gets by with as few LPF's as possible by covering multiple
bands with each filter.? The corner frequency of the LPF may be a bit high to?
fully suppress the harmonics of the lowest band of that set.
Jerry, KE7ER
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Re: Harmonic performance - SSB vs CW
Alison
Assuming we could build a daughter board that replaced the RF PA section, how far
back in the TX path would we have to tap in to drive this board with a relatively clean
signal?
Arv
_._
On Sat, Aug 4, 2018 at 8:22 AM ajparent1/KB1GMX < kb1gmx@...> wrote: Arv,
For bitx20 (or 40) a monoband radio traps and Caur filters are a good solution.
For a multi band radio its a spot solution that is likely to case troubles on other bands.
The fundamental issue was inadequate to non existent filtering for the TX path
before the TX.
Allison
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Re: Harmonic performance - SSB vs CW
Warren
I will leave the forklift upgrade to Farhan and his elves in India.? Maybe there
will be a MK-II version of the uBITX someday?
I was wondering about the LC traps as a mod for existing uBITX boards.? Also
might be possible to move the whole RF PA section off to a daughter-board so
it could utilize the existing uBITX and have a new PA section with all your
suggestions.
Arv
_._
On Sat, Aug 4, 2018 at 8:11 AM Warren Allgyer < allgyer@...> wrote: I am not sure Arv. The real solution here is like a "fork lift" upgrade, replacing everything after T11 in the transmit chain. If I were doing a redesign I would use the same four filters, add five more relays, and decode the three lines to get four lines each driving the pair of relays bracketing the desired filter.
?
I would also use latching relays and move the TR switching to the PA side of the filter bank to allow the filters to be utilized on receive as well.
?
All relatively easy to do...... just takes time and money. And motivation.......
WA8TOD
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Jim Sheldon
MadRadioModder