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Re: My uBitx Easy-Digi interface for under $20
All the signals coming out of a 9pin RS232 port on an old PC will flip between
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approximately -12v on mark, +12v on space, driven by inverting RS232 level buffers: ? ??https://en.wikipedia.org/wiki/MAX232 Your USB-to-5v-UART cable wont have those inverting RS232 buffers, and and may or may not power up into the same state as an old 16550 UART chip. If the USB-to-5v-UART cable consistently powers up into the wrong state, perhaps you can tell the software on the host to use the opposite polarity of RTS to key the rig. Jerry, KE7ER On Wed, Mar 20, 2019 at 01:20 PM, Joe Puma wrote:
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Re: QRP kit amplifiers
Laurence Oberman
OK, I started looking at what I need to yank out of the V4 board power
finals , mosfets etc to connect t the off board 10W amp. (I am happy to sacrifice it). I am going to start however with first removing, then doing a full SSB and CW capture of the spurs and harmonics. I am also working on a copper enclosure to separate RF from digital. I have capabilities for bending to make the shields and some old sheet metal lying around. My intention is enclose the main board in a shield, keep the 10W amp a ways away, at least about an inch, shield that too in its own enclosure. Ground them all to common ground and wont have the heatsinks anymore with rf voltage anyway. Only the Digital stuff will be exposed. Probably going to use a Arduino mega and add a second screen so wont have the Raduino. Worth a try, as the V5 is working fine and that one is destined for the Jack-Al board anyway. On Wed, Mar 20, 2019 at 5:36 PM Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
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Re: QRP kit amplifiers
Yes, got I got a QSX amp together and working.
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Tested it with a square wave from an si5351, but haven't done anything vaguely useful with it yet. Right now, trying to finish up a straw bale house. Liz wants the sunporch sealed up so she can start some tomatoes. Even though it's 62 degrees today, still a foot of snow in the fields. Jerry On Wed, Mar 20, 2019 at 12:47 PM, ajparent1/KB1GMX wrote: Build one yet? |
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Re: My uBitx Easy-Digi interface for under $20
Joe Puma
¿ªÔÆÌåÓýHi Dennis,I can¡¯t confirm what you heard but there is also another problem. When the usb serial is initialized on the computer it causes the RTS to go high. The mic will key, it has on mine, the opto-coupler powered up no problem. ?It does not stay low like a USB to Serial or a regular serial port until you use program that needs the serial port and then the RTS will go low. that¡¯s gonna be a problem. I use a transistor to flip the signal and pass 5v from the USB to power the octo-coupler . Both problems solved I guess.? I used the circuit on the right For my yaesu ft-840 I used this wiring.? Heres another good reference? Joe KD2NFC
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Re: Thank you Sunil!
Joe Puma
¿ªÔÆÌåÓýHi Oliver,Here is a link to the case, it's currently sold out. Hopefully Sunil stocks some more, it's such a nice case. Kinda feels like you're building a Heathkit (not that I would know) minus the tubes. ?:)
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Re: QRP kit amplifiers
Jerry,
The gain was measured using a 50 ohm class A brick amp (Qbit and minicircuits). There was not impedance translation though when adding a 1:4 balun it was higher. but barely 3db.? There is a lot of worry about something.? Build one yet? So driving it from a some imagined 50 ohm source is fine.? As far as any of the uBitx stages none are 50 ohms as there is no impedance control. In the mean time I have four operating and they are good.? The best predriver is a 2n5109 or 2n7000 and that get eh drive to about 2mW.? Image included. V5 is better.? Not great but better.? As to fully compliant I've not see one posting to prove that.? What I have see is "marginal pass".? ?That means tun up the gain (after all who would do that) or maybe bad swr and thing go downhill.? Allison? |
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Re: QRP kit amplifiers
Arv,
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True.? (The part about turning down the drive level). Should work fine. Need to adjust the gain when switching bands, but that should not be a big deal. This is primarily an SSB rig. CW is an afterthought with a wide IF filter and no QSK. Seems good enough that CW on one of the bands might require an extra LPF inline with the antenna to knock down a harmonic. Or could key the d3,d4 mixer instead of the d1,d2 mixer, any harmonics due to the square wave CLK1 will be?stripped out by the 45mhz crystal filter. Jerry On Wed, Mar 20, 2019 at 11:58 AM, Arv Evans wrote:
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Re: QRP kit amplifiers
Allison, not sure I follow.
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I believe that when efficiently driving the 200 ohm QSX amp through a 1:4 transformer from a 50 ohm source, the QSX amp has a power gain of around 26 dB. But driving the QSX amp directly (with some parallel resistance so the driver sees 50 ohms), the voltage to the QSX gates will be reduced by half, and power by a factor of 4, which is 6dB. Perhaps you assume we let the source just go ahead and drive the QSX amp at 200 ohms or so, forget about the 50 ohms thing.? Which may be fair enough, depending on what we drive it with. I agree that if the QSX Amp is used, the uBitx driver and final stages should be disabled. All that power so near the IF amps is likely causing some of the spurs.? The v5 uBitx is very close to fully compliant with FCC specs on all bands. Few in the forum will bother with the complication of switchable bandpass filters in front of the PA, and I'm OK with that on a QRP rig. If going to 100W or more (or if having higher standards than the FCC) then spurs, harmonics,?IMD, residual carrier, opposite sideband, and transmit pops should all be addressed. Perhaps best off just moving to a different rig, unless in it for the challenge. Jerry, KE7ER On Wed, Mar 20, 2019 at 10:50 AM, ajparent1/KB1GMX wrote:
You are wrong.? ?The voltage gain is still the same and the 26 DB is power gain. |
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Re: QRP kit amplifiers
I'm probably wrong...that is a chronic situation...but might it be possible to turn down the drive level on SSB until the signal is cleaner if driving an outboard amplifier? Arv _._ On Wed, Mar 20, 2019 at 11:50 AM ajparent1/KB1GMX <kb1gmx@...> wrote: Repost to fix editing lag. |
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Re: My uBitx Easy-Digi interface for under $20
Hi Joe,
I originally considered using a TTL adapter but opted for?a FTDI cable as the author cautioned against using a cheap TTL adaptor stating: "they do not put out high enough voltage for the opto coupler on the Easy Digi" I see several US suppliers of TTL adapters at reasonable prices on eBay. I would like to eliminate the bulky cable and this seems like a great solution. I take it that you had no problem with "not enough voltage". I plan to put the module inside the uBitx case with just one or two cables to the PC. I like your idea of using an internal usb hub. Additionally, could you provide a quick sketch of how you connected the 6 pins? Kind Regards, 73, Dennis W7DRW |
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Re: My measurements for L5/L7 & Relay Mods
On Wed, Mar 20, 2019 at 03:26 AM, Raj vu2zap wrote:
Not much, it seems to be wires that stand up like a vertical. If you keep a screw driverThat is the issue I've referred to many times in the past the board layout has ground loop? and isolation issue.? Ground is not ground, least not an effective one.?? I also found back then replacing all the Bidi amp mixer coils with those using FB43-2402? (small as in .25" two hole cores) had a positive effect on that as well.? For all the same reasons. When you look at the board the bidi amps eat about 1/4th the board area so grounding around them has to be good and effective. When I built the proto of ubitx back 2014 I used packaged mixers and laid the IF section in a straight line dead bug format on Cu-clad and never saw those issues.? I did then suggest band pass filters before the power amp then based on testing. Allison |
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Re: QRP kit amplifiers
Laurence Oberman
I should add:
RF is wizardry, now the new mm Wave is witchcraft, however even digital at high frequencies is RF as folks have found it. Nevertheless, my day job is a Principal software maintenance engineer at Red Hat where mostl all I worry about are Linux kernels Storage hardware and data structures with 1's and 0's. I have it easy to you Allison On Wed, Mar 20, 2019 at 2:26 PM Laurence Oberman via Groups.Io <oberman.l@...> wrote:
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Re: QRP kit amplifiers
Laurence Oberman
Great insight,
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I want to state once again, while some have bemoaned the Ubitx, I have never and I fully appreciate everybody's efforts, I watched you spend a huge amount of time on it and we all benefited from it. So again to Ashar, to you!!(ajparent) to Jerry, Curt, Jack and too many others too mention (you all know who you are), while it may seem like the moans from some, I need all of you to know its appreciated by all of us here. So Thank You!!! Kindly Laurence Oberman KB1HKO (a digital guy who wishes he had stayed in analog :)) On Wed, Mar 20, 2019 at 2:19 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
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Re: QRP kit amplifiers
Laurence,
It why I gave up last year with it.? For the time and effort I had invested it could (and did) build something clean from the ground up. V5 fixes a few issues but some cases yes, some no, most at least somewhat better. The power amp issues are as they were last year and no improvements applied. Everything any one would ant to know about that is in the wiki. Everyone wants a single pill fix.? There are three areas that need to be fixes, band pass into the TX, the whole TX and output switching was a bandaid to keep the board the same size and form factor.? IT goes to prove that compared to a monoband radio? multiband has a far greater set of challenges and shortcuts will extract pain. Allison |
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Re: QRP kit amplifiers
Laurence Oberman
Hello Allison
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I was focused on the CW issue I had shared before with the example at 20m After a cabling/mic socket issue had crept in I had not tested SSB but I can now. What I am getting from all of this though is that you feel none of this now worthwhile to try. If you recall. I was going to chase the 20m spur I saw saying maybe its a fault on my board, but then others said they have seen it too and you confirmed what it was the heating issue. Anyway, its awesome to have you on this list and I am sure you get frustrated by all our crazy suggestions so I am thankful for your time. Sincerely Laurence On Wed, Mar 20, 2019 at 1:54 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
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Re: QRP kit amplifiers
Laurence Oberman,
The QRPL 10w amp is not your usual tail end linear amp its a two stage driver and linear. Many of the high end LDmosfet pallet amps (not the cheap Epay crap) are single stage using current generation with gains in the 20-24db region and 2W for many is still too much. So the only amps that behave like that are you run on the mill Ham linear design to take the power of 100W radio or maybe the more specialized ones for FT817 class radios.? Most all either use tubes, older bipolar designs, or if mosfets with input attenuators to tolerate that. Allison |
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Re: QRP kit amplifiers
Laurence Oberman
10:43am???#66868??
Using my Spec An at 2w on the V4 I dont see the heating or the spurs
on CW, hence why I was interested in trying it. Based on what I said many times in the last year.... CW had no spur issue only harmonic issues. SSB has serious spur issues.
And generally V3 and V4 had no (none) significant changes in the RF generation and it was only an attempt to fix pop/click and the audio amp chip issue. Allison |
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Re: QRP kit amplifiers
Repost to fix editing lag.
Jerry, You are wrong.? ?The voltage gain is still the same and the 26 DB is power gain. Going from 50 ohms to 200 will not cost 6db as the amp still still see voltage? (uses mosfets) and 4:1 is not as bad as it seems. However the attenuator to get to 25-30 Mw of drive is half the battle as the? ubitx amp set to 2W at 80m would barely make a few milliwatts at 10M. All the problems identified nearly a year ago would remain and you would? be wasting power. The best possible case is remove the finals, the drivers, and even the predrivers. Build a real predriver using the 2n3866 or 5109 in a wideband amp format.? Replace Q90 with a decent device or dial its gain to about 10. from RV1? feed the RF to the off board? predriver and QRPl amp to off board LPF and TR switching.? ?I would make the TR switching and LPF an off board addition as well to try and eliminate? the board level issues.? Since it would be needed at that point to add an input BPF before the external predriver and really clean up the mess.? Why? the QRPL amp has useful gain to beyond 70mhz so if you feed it crap (harmonics and spurs) it will do its very best to amplify it. I'd expect that to be a bit better but still not a full and complete cure for many of? the issues.? Its also untested.? I can hear the moaning now for I need a kit for that, it won't fit in my box, does that mean I need new software for the LPF and BPF filter boards?? ?? Allison |
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Re: QRP kit amplifiers
Laurence Oberman
Using my Spec An at 2w on the V4 I dont see the heating or the spurs
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on CW, hence why I was interested in trying it. Its an easy test now, as I can cap the Ubitx at 1W, use a 10Db attenuator and go into Hans's / Allisons Amp and into the Spec Ann again via the coupled minicircuits output like before. That way I can characterize it with the amp in circuit On Wed, Mar 20, 2019 at 1:23 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
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Re: QRP kit amplifiers
Laurence Oberman
Hi Jerry
Yes, I had in mind a 10db , I also have a 20db to use On Wed, Mar 20, 2019 at 1:18 PM Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
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