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bitx40 on 80
hi
i am still waiting for the delivery of my bitx40 but while waiting i am pondering i have 40 and 20 using my trio ft520 and dipoles. but i do not have enough room for an 80 m dipole so i have built a qrp atu and erected an end fed long wire for 80. there is no way to reduce the 200w from the trio to use a qrp atu so the answer is the bitx40. 200 wats would be like a pan galactic gargle blaster to my atu !! but i need to hack the bitx40 for 80 nd6t has published a hack for 60 m which involves adding parallel caps to c2, c4, c6 and across l7 so i modeled the bpf and lpf using aade program with 560 pf across c2,c4,c6 and 390 across l7 and the plots look good for 80 m . the sketch also has to be hacked but that is not a problem as i am a retired computer programmer. What do people think about the? thoughts of an idle fellow. 73 de terry gm4dso |
Re: si5351 crosstalk
#radiuno
Vince Vielhaber
I've always used an ADA-4789 for DDS buffering. 50 ohm in and out, single supply and good to 2.5 GHz.
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Vince - K8ZW. On 09/12/2018 10:40 AM, Jerry Gaffke via Groups.Io wrote:
I suspect it is more critical that we have sufficient drive into the --
Michigan VHF Corp. |
Re: Searching for IMD
Warren Allgyer
Reasonable people can disagree. At -12 dB IMD distortion products become audible within the signal itself.?
IMD is one component of the Total Harmonic Distortion spec that we see for our audio equipment. Generally it is accepted that 3% THD is the maximum acceptable for any of the components in the consumer electronics world. In the professional world we want to be below 1%. Above that and the distortion becomes noticeable to the consumer ear.? 3% THD corresponds to -30 dB IMD. 12% IMD is nearly 100 times that amount.? There is is nothing illegal about putting distorted audio in the air. But I would not do it.? WA8TOD |
Re: uBitx Antenna
#ubitx-help
Lawrence Macionski
Daniel-
I've been studying and building antenna's for 52 years.. Here's some things I've concluded: With regard to uBITX (under 300 watts) operation: #1. The guy that tells you, you need a balun for a dipole, Usually is the guy that is selling them. They can be made for $5 or less. Markup is huge. #2. You need no better than RG-8X coax... Unless: ?????? A. Your coax run is over 75 feet? and used to 148Mhz. (27ft per dB loss -under 3dB which is 1/2 power) negligible loss. ?????? B. Your coax run is? 150 feet or less? under 30Mhz. (63ft per dB @28.4Mhz- under 3dB or less on lower bands) negligible loss. ?????? C. You are not running over 650 watts (approximate) #3. There is no "secret sauce" when? buying a manufactured antenna. ?????? A. One manufacture makes antenna's in colors and that is their #1 selling point. ?????? B. Virtually none come assembled, so you have to put them together anyhow and tune them. ?????? C. Markup on materials is 4-10x, so you get a "kit of parts" they put together for you. (and pay for the "secret Sauce" #4. If you can't afford Antenna books, your local public library will get you any Antenna Book with an Library of Congress number. ????? A. My antenna books stacked on the floor are Knee high.. 20+ years ago I paid $52 for John Krause's Antenna Theory. ????? B. Authors such as Lew McCoy, John Krause, R.L Cibek, Joe Carr, anything sold by ARRL are authoritative. This is a start, there are others. #5. Regarding coax in #1... Reference QST October 2017 page 72. #6. Remember? 3dB loss can be measured with instruments but never detected by ear. #7. An antenna constructed with sound engineering plans will get you on the air.? Having the test equipment/ tuners is optional (OCD frankly) #8. Watch them bash my sound advice.. Yet some will also agree with me. |
Re: I find This Shorted Circuit on Raduino, here the pics..plz Help?
#ubitx-help
Hello Armin nice to see you!
Ok thank you! I have a little bit wondering about that and the voltmeter test between both pins says that they are shorted circuit..? but then it should be ok when yours look the same. Have you a picture or vor video from your ubitx and its case with wiring up? I would happy to look at yours. In an other post i was wrote a large answer text to you but then windows was shutdown to update.. but after this all was delete all i wrote.. it was incredible how bad is this day at all today... But i write you again next few ours again in the other post from me...? Till then bye.. |
Re: Searching for IMD
Warren did us a service by showing that IMD on the uBitx is worse than it should be On Wed, Sep 12, 2018 at 08:59 AM, iz oos wrote:
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Re: si5351 crosstalk
#radiuno
On Wed, Sep 12, 2018 at 07:40 AM, Jerry Gaffke wrote:
Could also add a resistor from mixer port to ground to bring source impedance there down,Hi Jerry, The simple voltage divider you suggest in the linked message could provide a simple solution. No reason that the drive to the mixers needs to be set with a pad, as the Si5351 is not a lab frequency generator. Buffers may still be a good idea, but the divider may get close to the goal. Tom, wb6b |
Re: Simple spur fix
Warren Allgyer
Published on the IMD thread but wanted to include here for continuity: ? Here is what I did. I did not try with a second transformer because the results were good enough. After the IMD measurements I would be even more concerned about adding a second transformer because the Q22 emitter follower is operating at an impedance of about 400 ohms and, as such, is one of the major contributors to the IMD issue. Adding a low impedance transformer to this source is likely to make that problem worse. But I have not tested it so I cannot be sure. |
Re: Searching for IMD
Warren Allgyer
Joel
Here is what I did. I did not try with a second transformer because the results were good enough. After the IMD measurements I would be even more concerned about adding a second transformer because the Q22 emitter follower is operating at an impedance of about 400 ohms and, as such, is one of the major contributors to the IMD issue. Adding a low impedance transformer to this source is likely to make that problem worse. But I have not tested it so I cannot be sure. WA8TOD |
Re: Ubitx evolving fixes updated to wiki?
#ubitx
#ubitx-help
开云体育Jeff et al:
There are multiple proposed fixes for the multitude of issues. For example, for the harmonics on CW I have redesigned the filters so that the existing artwork can be used. Others have added external filter boards. Both work. The spur issue is still a works in progress. My suggestion to anyone that is not skilled enough to do the design and testing themselves is to wait. Enjoy your uBitx and in a few months clear solutions should arise, and HFSignals will probably make the appropriate modifications. Then you can decide if you want to tackle the upgrade yourself or get another uBitx with all the fixes. Howard On 9/12/2018 11:23 AM, Jeff Omundson wrote: I have been following the work everyone is putting in to solve the various issues with the ubitx.? The threads addressing the harmonic and spur issues are getting really long and trying to get a handle on it can be tough, especially for those of us who are not seasoned electronic wizards.? Is there enough consensus on working solutions so that we could write something up for each problem on the wiki?? It seems like solutions are still evolving, so may be this would need to be updated over time.? It sounds like the spur issue might have a fix at this point.? For the harmonic issue,? I know some people propose building separate boards.? I think another solution was to cut traces to the existing filters and re-wire them.? I don't know if I am the only one grappling a bit with understanding the best course of action.??
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Re: Searching for IMD
Indeed it shows some mess on the SSB mode. It is not a K3. I am curious how the MFJ SSB hf transceivers, like the 9420 which have a powerful average power, behave on this respect (IMD). And also how ham transceivers behave with external speech boxes. Il 12/set/2018 17:37, "Gordon Gibby" <ggibby@...> ha scritto:
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Re: Right-sided relay harmonic attempted fix for v3/4 ubitx
Gordon Gibby
开云体育All of the recent orders of 25 boards have now been mailed. If I do this again I’ll be a little smarter, and list them as order of one, or order of ?pair of 2; ?I was able to find enough dollar bills to help out the people who bought more than one with
a bit of a refund, but that was a pain.
I improved the inside paper to have a repeat of some of the important information, links, etc
I’ll mark them on eBay as shipped soon. ?I got to see the special stamp as mentioned by Kees I think
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Re: si5351 crosstalk
#radiuno
Putting them on the Raduino would allow an easy way to upgrade a current radio.
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Though the additional signal and ground currents across the Raduino-to-uBitx connector? might give more trouble than having the buffers on the main board. If we had coax and SMA connectors between the two boards then buffers on the Raduino should be fine, but that's significant trouble and expense for a uBitx. So to answer your question:? I don't know. To which I will add the weasel words:? Depends on how it gets implemented. Warren just reported that the? mixer at D1,D2 was adding 5 dB to the IMD problem, a buffer on clk2 might help some there.? But IF amp non-linearities were? most of the IMD problem.? ? Makes sense that the D1,D2 mixer would have more trouble than D3,D4 since the signal is bigger there after the second BiDi amp.? As I recall, Allison found buffers on the clocks helped reduce the residual carrier when transmitting, though some of the residual carrier was due to placement and routing. So adding buffers to the clocks may help somewhat, but is no panacea. As Allison has said, fixing these problems completely will require changes throughout the radio. Perhaps buffers on the clocks, plus BiDi amp transistors with higher Ft? Leave any additional power amp stage (for flat power out) and dealing with layout issues for v5. Jerry, KE7ER On Wed, Sep 12, 2018 at 07:52 AM, Kees T wrote: Would you suggest mounting those three 74LVC1G04GW parts on the Raduino board, close to the Si5351? ? |
Re: Ubitx evolving fixes updated to wiki?
#ubitx
#ubitx-help
Gordon Gibby
开云体育Jeff,I don’t know quite how to do what you are asking and I’m not sure who is appropriate to do so? ? For the little simple ?right hand side external relay board that I came up with, I have now shipped out 30 boards... so I think it’s beyond proposing.
I think there are loads of ways to fix that issue, depending on the exact requirements of the user.?
1. ?Fixed external filters, changed manually (no software change)
2. ?Replace the right-hand side of the relays with a daughter board as I did. (no software change in the way I implemented it)
3. ?Replace all the relays & filters ?with an external daughter board (May or may not require software change). Hey or may not use the existing components, might use all new components
4. ?There was even a commercially available multiple relay system that could be pressed into service.?
Hope that helps
Gordon
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Re: Ubitx evolving fixes updated to wiki?
#ubitx
#ubitx-help
开云体育I agree. ? David A Posthuma, WD8PUO 1 (616) 283-7703 ? From: [email protected] <[email protected]> On Behalf Of Jeff Omundson ? I have been following the work everyone is putting in to solve the various issues with the ubitx.? The threads addressing the harmonic and spur issues are getting really long and trying to get a handle on it can be tough, especially for those of us who are not seasoned electronic wizards.? Is there enough consensus on working solutions so that we could write something up for each problem on the wiki?? It seems like solutions are still evolving, so may be this would need to be updated over time.? It sounds like the spur issue might have a fix at this point.? For the harmonic issue,? I know some people propose building separate boards.? I think another solution was to cut traces to the existing filters and re-wire them.? I don't know if I am the only one grappling a bit with understanding the best course of action.?? |
Re: Searching for IMD
Gordon Gibby
开云体育Possibly the gain ?of the transistors at 45 MHz is insufficient, and thus there is much less effective negative feedback. ?Better transistors might allow the negative feedback to reduce the IMD. ??
Cheers,
Gordon
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Re: I find This Shorted Circuit on Raduino, here the pics..plz Help?
#ubitx-help
Hi Fabian,
As Jerry already pointed out, please don't worry about this. I have a V3 board and the connection looks like yours. Armin |
Re: Searching for IMD
Gordon Gibby
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