Re: Low IMD MMIC replacement for TIA
Warren,
You may want to check how Pete/N6QW? ? handled it a few years back
as he has done a bi directional iF radio using MMICs.
Myself I've used that part and a series resistor along with the on board choke worked very well
The value is such that you make the 12V source to a 75ma bias at 3.2V or about 120 ohms.
Allison
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Re: Harmonics and Relay Replacement
On Fri, Oct 19, 2018 at 09:05 PM, Donald wrote:
If the files are open to the public, I will quit this group.
he files are open and the wiki too.? Based on the statement you have to quit.? Sorry. You have hit on my annoyance with groups.io.? The search engine is terrible or worse. And everything scrolls by and get lost in the great pile that takes forever to hunt though. Now if someone would contribute to the wiki it may help you but that means someone has to do something.? I tried to start that but its been moribund since the work I did in September.
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Re: Harmonics and Relay Replacement
Joe Puma,
Yes and no.? Yes the mods were tested on my board but no its no longer
a rig as it was sliced to sections to test grounding issues.? So the board?
section is functional but not a rig.
The colored lines show the changes and wires to be places and there is descriptive text.
Myself I've reached the point of its a waste of my time and have built a far better radio
with my free time.
Allison
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Re: Harmonics and Relay Replacement
I would not be offended.
It was poorly worded, but should not be taken as a personal criticism.
There is a lot gong on here lately, and things are in considerable flux.
There is no consensus yet on the best and easiest way to resolve some of those issues,
When there is, we will have a short document posted somewhere describing recommended mods.
Until then this will be confusing for old and new forum members alike.
Jerry, KE7ER
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On Fri, Oct 19, 2018 at 09:05 PM, Donald wrote:
As a new member to this group I am offended. I have been reading posts, and reading posts, and reading posts. One problem is, to find the "good stuff", I have to read through posts like Arv's.
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Re: Harmonics and Relay Replacement
Hi,
Nobody is going to see a "messy" looking solution if we keep the cover on :)
73,
Bill KU8H
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On 10/19/2018 10:43 PM, ajparent1/KB1GMX wrote: Sascha,
The problem with yet another board is that there is no good way to
couple the grounds between them.
As to clean solutions, just what is that? You have a dirty board and
the only clean solution is fix the board
as everything else is simply trying to make it work...maybe.
Allison
--
bark less - wag more
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Re: Low IMD MMIC replacement for TIA
Detail omitted in the post:
Gain of the board is a bit over +22 dB which I believe is more than enough. I have left provision for an input attenuator on the board. It currently has a placeholder 0 ohm resistor which will be replaced by a pi attenuator for level setting and impedance matching once the prototype is tested on board.
WA8TOD
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Low IMD MMIC replacement for TIA
Once the harmonics and spur issues are put to bed, what will remain is unacceptable levels of intermodulation distortion produced by the Termination Insensitive Amplifiers used as bi-directional IF amps at both 45 and 12 MHz.
This is a prototype MMIC amplifier utilizing the ERA-3SM+ (80 cents each on eBay) mounted on an RF prototyping board ($2.50 each from SV1AFN) that is the proper size and form factor to replace both transmit TIAs. The MMIC/board measure flat response from 300 Hz to well over 200 MHz.
This test quantifies the IMD performance of the combo. The reference point on the SA is shifted +6 dB so that the readings reflect the power level that would be achieved with a single tone for convenience of interpretation.
Measurements were taken at Vcc of 3.3 volts and current draw was the recommended 35 ma.
The blue trace shows performance at 0 dBm out and is an acceptable -42 dBc (-36 dB minus 6 dB for a single tone carrier). Performance at - 10 dBm out, the level needed to drive the uBitx driver/PA chain, is an excellent -51 dBc (-45 dB minus 6 dB for a single tone carrier).
Yet to be determined is how to add the?LM1117-3.3 regulator to hold the Vcc at the required level.
?
WA8TOD
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AGC AND POP FIX KITS.FOR SALE.
Hi, ???? I have 1 agc kit by N6 DT and the 2 pop fix kits by K5 CBQ all with circuit diagrams and all componants..$15.00 plus post to your country the weight is 6 grammes and will be in a jiffy bag..paypal as gift please....contact me off site to wylyeguy2@... ? Dave G0AYD QTHR ??
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Re: Harmonics and Relay Replacement
Allison,
I haven¡¯t looked at the wiki in a week or two. Do you have pics of the rig with the mods you made, removing traces, rewiring, etc. I just saw the board with the parts removed.?
Joe
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On Oct 19, 2018, at 1:03 PM, ajparent1/KB1GMX < kb1gmx@...> wrote: On Thu, Oct 18, 2018 at 02:08 PM, RCBoatGuy wrote:
has anyone tried shielding the relays from the PCB using copper tape between the board and relays
Carl,
Yes back in early july.? Didn't help much at all maybe 2db at the high end of the band.
Look at the wiki pictures two of the longer lines have RF power on them and they all loop
back to KT1 and past all the others.? Not good.
Allison
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Re: Harmonics and Relay Replacement
As a new member to this group I am offended. I have been reading
posts, and reading posts, and reading posts. One problem is, to
find the "good stuff", I have to read through posts like Arv's.
If the files are open to the public, I will quit this group.
Donald West, KB5PWL
On 10/19/2018 4:45 PM, Arv Evans wrote:
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Problem,
and solutions are not that simple.? Allison has added comments
to the Wiki that
describe
both problems and solutions.? Kees has made a daughter board
available for the
relays
and LPF components.?
Overdriving
the audio apparently is a big contributer to some problems.?
Stage gain
arrangement
is another potential issue.? Board layout and component
placement has
been
identified as problematic.? There are ways to operate the
uBITX that mostly keep
it
within reasonable limits, but some apparently want to exceed
those parameters.
Unfortunately
those who have recently joined the group may not have followed
the process
that
has led up to present state of things.?
Arv
_._
On Fri, Oct 19, 2018 at 3:12 PM Sascha Bohnet |
DL5SMB via Groups.Io <saschabohnet= [email protected]>
wrote:
I would
really like to try out Allisons solution with the complete
rearrangement of the filters. However I am a big fan of
"clean" solutions,
and all this wiring, cutting etc. looks really sloppy to me.
And I would really hate it, if it did not work out as it
should and then i would have completly ruined my board.
Is maybe anyone good at pcb designing?
Then we could make a daughterboard, desolder the whole filter
part on the main board and put everything on the daughterboard
on top.
Maybe the placing of all the parts could remain the same on
the additional board and only the traces would need some
rearranging.
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I have built one of these variable band width filters!
Michael, I remembered that I changed C25/26/27 from 100pf to 82pf
for larger IF band width. You could try 75 or 68pf for even wider IF.
Raj
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At 20/10/2018, you wrote: Maybe no help, but here's a filter mod I've been playing with on the ubitx
Jim
On Friday, October 19, 2018, 6:49:31 PM PDT, Michael Trager <mtrager1@...> wrote:
The BITX40 I am building receives somewhat OK but the transmitters audio is terrible with distortion and/ narrow bandwidth.
I think I may have 1 or 2 bad 12.0 MHz crystals when I inject a signal thru the filter and look at the various nodes. I see
the strongest peak at around 11.997830 MHz.
The bandpass is only around 1,700 Hz at best (11.998800 to 11.997100)!
The crystals are from MEC and the letters / numbers on them are: 12.000 G
MEC AH6L1
Does anyone know of a suitable replacement in the USA for them?? Any special characteristics?
Thank you,
Michael
n2zdb
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What I did was remove C102 and put a little higher value trimmer into C103 (which is not fitter)
then adjust the carrier frequency and see if you make it sound better. Worked for me!
Raj
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At 20/10/2018, you wrote: The BITX40 I am building receives somewhat OK but the transmitters audio is terrible with distortion and/ narrow bandwidth.
I think I may have 1 or 2 bad 12.0 MHz crystals when I inject a signal thru the filter and look at the various nodes. I see
the strongest peak at around 11.997830 MHz.
The bandpass is only around 1,700 Hz at best (11.998800 to 11.997100)!
The crystals are from MEC and the letters / numbers on them are: 12.000 G
MEC AH6L1
Does anyone know of a suitable replacement in the USA for them?? Any special characteristics?
Thank you,
Michael
n2zdb
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Maybe no help, but here's a filter mod I've been playing with on the ubitx
Jim
On Friday, October 19, 2018, 6:49:31 PM PDT, Michael Trager <mtrager1@...> wrote:
The BITX40 I am building receives somewhat OK but the transmitters audio is terrible with distortion and/ narrow bandwidth.
I think I may have 1 or 2 bad 12.0 MHz crystals when I inject a signal thru the filter and look at the various nodes. I see
the strongest peak at around 11.997830 MHz.
The bandpass is only around? 1,700 Hz at best (11.998800 to 11.997100)!
The crystals are from MEC and the letters / numbers on them are:?? 12.000 G
?????????????????????????????????????????????????????????????????????????????????????????????????????????? MEC? AH6L1
Does anyone know of a suitable replacement in the USA for them?? Any special characteristics?
Thank you,
Michael
n2zdb
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Re: Harmonics and Relay Replacement
Sascha,
The problem with yet another board is that there is no good way to couple the grounds between them.
As to clean solutions, just what is that?? You have a dirty board and the only clean solution is fix the board
as everything else is simply trying to make it work...maybe.
Allison
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On Fri, Oct 19, 2018 at 06:49 PM, Michael Trager wrote:
Any special characteristics?
yes, they have to be matched within 100Hz of the others.? ? 12mhz crystals are easy to find
and buy but matching is up the you.? To get say 4 matched I often buy ten and test.
However if the filter is narrower than expected you might try different value loading capacitors.
for example if 100pf are used try 91 pf for all of them.??
If you look at nodes you may get bad results as the act of probing the test point loads the
filter with some amount of capacitance and alters its behavior.? Even a 10x probe varied from
about 9-13PF depending on who made it and what length cable.? That is more than enough
to disturb the filter behavior.
Allison
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The BITX40 I am building receives somewhat OK but the transmitters audio is terrible with distortion and/ narrow bandwidth.
I think I may have 1 or 2 bad 12.0 MHz crystals when I inject a signal thru the filter and look at the various nodes. I see
the strongest peak at around 11.997830 MHz.
The bandpass is only around? 1,700 Hz at best (11.998800 to 11.997100)!
The crystals are from MEC and the letters / numbers on them are:?? 12.000 G
?????????????????????????????????????????????????????????????????????????????????????????????????????????? MEC? AH6L1
Does anyone know of a suitable replacement in the USA for them?? Any special characteristics?
Thank you,
Michael
n2zdb
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Re: Harmonics and Relay Replacement
I would really like to try out Allisons solution with the complete rearrangement of the filters. However I am a big fan of "clean" solutions,
and all this wiring, cutting etc. looks really sloppy to me.
And I would really hate it, if it did not work out as it should and then i would have completly ruined my board.
Ah Sascha, Looks aren't everything eh?? You would be happier with the supermodel that has an awful personality? The work need not look bad at all -- it's all up to how you do it and it gives one the chance to show their construction skills beyond the paint-by-numbers stage.? In the end it can be an accomplishment to be proud of! And I'm not sure if the off-board solution works the same as Allison's plan?? Hers also reduces the number of relays engaged and that need switching so CW and PTT operation would be smoother. 73, Mark. PS:? Only read Crime and Punishment from Dostoevsky -- really dramatic and emotional.? Always thought the TV detective Colombo was modeled after the police detective in that book.? And Quiet Flows the Don was a very good read also.?
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Re: Harmonics and Relay Replacement
Ahh so Kees has made a board. Is there a link to it? Are they for sale?
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On Oct 19, 2018, at 5:45 PM, Arv Evans < arvid.evans@...> wrote: Problem, and solutions are not that simple.? Allison has added comments to the Wiki that describe both problems and solutions.? Kees has made a daughter board available for the
relays and LPF components.?
Overdriving the audio apparently is a big contributer to some problems.? Stage gain
arrangement is another potential issue.? Board layout and component placement has
been identified as problematic.? There are ways to operate the uBITX that mostly keep
it within reasonable limits, but some apparently want to exceed those parameters.
Unfortunately those who have recently joined the group may not have followed the process
that has led up to present state of things.?
Arv _._
On Fri, Oct 19, 2018 at 3:12 PM Sascha Bohnet | DL5SMB via Groups.Io <saschabohnet= [email protected]> wrote: I would really like to try out Allisons solution with the complete rearrangement of the filters. However I am a big fan of "clean" solutions,
and all this wiring, cutting etc. looks really sloppy to me.
And I would really hate it, if it did not work out as it should and then i would have completly ruined my board.
Is maybe anyone good at pcb designing?
Then we could make a daughterboard, desolder the whole filter part on the main board and put everything on the daughterboard on top.
Maybe the placing of all the parts could remain the same on the additional board and only the traces would need some rearranging.
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Re: Harmonics and Relay Replacement
I¡¯m surprised someone hasn¡¯t fabricated a board that the relays and coils can be moved to and the board can be mounted on top of the ubitx with standoff¡¯s and then wired up to Ubitx.?
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On Oct 19, 2018, at 5:17 PM, Gordon Gibby < ggibby@...> wrote:
?Well.......you can do all that, and I'm sure that Allison's solutions would work quite well!? ??
however, that is an AWFUL LOT of work, which is why I came up with a pcb daughterboard to just add right hand side relays and move just a FEW traces to wires heading outbound.? ?This had a very salutory effect, in almost every case dramatically reducing
the harmonics.? ?
It is possible that there are other intermediate steps that might also solve the problem.? ?But Allison has already put a HUGE amount of effort into this and I doubt she is going to do any more ---- her suggestions for the current board would solve many
of its probems;, and her contirubtions to a different company's power amplifier have provided a road map to a better power amplifier solution.? ??
So there are likely now several solutions that work and you can just take your pick of how much work you wish to do in order to improve things.? ?
Cheers,
gordon
I would really like to try out Allisons solution with the complete rearrangement of the filters. However I am a big fan of "clean" solutions,
and all this wiring, cutting etc. looks really sloppy to me.
And I would really hate it, if it did not work out as it should and then i would have completly ruined my board.
Is maybe anyone good at pcb designing?
Then we could make a daughterboard, desolder the whole filter part on the main board and put everything on the daughterboard on top.
Maybe the placing of all the parts could remain the same on the additional board and only the traces would need some rearranging.
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Re: Harmonics and Relay Replacement
...and having read it, have you watched it (Frank Herbert's)? and follow-on Children Of (also a trilogy)? Well worthwhile!? Lord Of The Rings did that to me, too: sit down, read it, get up. 40 hours or more straight: Total immersion!
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Raj vu2zap
