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Re: Harmonics and Relay Replacement
Gene,
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Here's a post from the old thread on the spur fix: ? ??/g/BITX20/message/60678 The entire thread is worth browsng. Raj found that replacing the toroids at L5 and L7 with 1210 surface mount inductors of 680nH improved the spurs. Note that he used a specific brand and part number of inductor, some of the others he tried did not work so well. He also swapped out L1,2,3,4 with surface mount inductors of the same type and saw some improvement there too. His post says to get four of 330nH for those, but I'd think it should be two of 330nH and two of 390nH. The spur fix is is still being developed.? Replacing those inductors may not cure it sufficiently to fully meet regulations,? especially if you drive the mike audio hard to get maximum power out of the transmitter. My guess is that at least some of the spurs are caused by coupling from the? inductors in the final power amp back into L5,L7 of the 45mhz IF. So these spurs a re not harmonically related to the output frequrency there is some addition/subtraction going on also due to the mixer at D1,D2. These spurs are only an issue for SSB transmissions, not CW transmissions. We also have trouble with harmonics on the uBitx, which are integer multiples of the transmit frequency. That is due to the use of relays at KT1, KT2, KT3 that did not provide enough RF isolation between internal elements, and also due to how the board was routed at those relays.? Just replacing the relays with Axicom relays seems? to solve this well enough.? These harmonics are an issue for both SSB and CW transmissions. You definitely want to do some sort of harmonic fix. Either replace the relays with Axicom, or add an appropriate external low pass filter for the band you are using into the antenna line. ? With or without mods, not a good idea to run a uBitx into a high powered linear amp? unless you have a spectrum analyzer handy to check for spurs and harmonics. At 10 Watts out or less,? it's not so much an issue. . On Thu, Nov 1, 2018 at 03:07 PM, Gene Nitschke wrote:
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Re: Harmonics and Relay Replacement
Gene Nitschke
¿ªÔÆÌåÓý
HI Raj,
Thanks for the info, I have the relays on order.
Should I also change L5/7 at the same time?? (Exactly what is the L5/7 Change?, Is it a value change or just convert to SMT?)
Gene N2IJF
From: [email protected] <[email protected]> on behalf of Raj vu2zap <rajendrakumargg@...>
Sent: Thursday, November 1, 2018 1:25 AM To: [email protected] Subject: Re: [BITX20] Harmonics and Relay Replacement ?
Hi Gene,
There is no final solution. So far my conclusions... the harmonics floating around the board is the cause of the spurs. Changing the L5/7 reduced the spurs but not the cause which is harmonics. Changing 3 relays KT1/2/3 reduces the harmonics dramatically specially on lower bands. Lower bands 40/80 can be driven higher without crossing the red line! Keep the drive/mic level at where you get 10W on 40M and you should be kosher without SMD coils on higher bands. If you over drive the uBitx on higher bands then you will be in the red! Some boards behave a bit different, relays are a good simple mod bet for now. Raj At 01-11-18, you wrote: Sorry to ask but I been offline for a few weeks and the subject seems to have died out (after reading past posts).? So is there a final solution for the spurs/harmonics for the V3 uBitX? |
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Re: my uBitx Power
Joe Puma
Okay on SSB without talking that was .80a
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I forgot to mention that my measurements was taking while pressing the CW key. Joe On Nov 1, 2018, at 3:13 PM, Clark Martin <kk6isp@...> wrote: |
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Re: Cursed?
David Berkompas
I really do appreciate all the help everyone is offering, really gives me hope that I can get this working.
As to the RF probe that Arv posted, I knew I had seen it before. It's part of the build process when you you build an Elecraft K2 (which I did a decade ago and sold). Again, my thanks to everyone, and especially Arv and Timothy. Dave - AI6K |
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Re: Cursed?
Timothy Fidler
Given that the problem is on audio Rx and the BFO mixer seems to work for? Tx I would try to lash up a known good high Z audio amp eg LM358 set at gain of 50 or so? with an earpiece and try moving forward to the speaker frm the mixer.? I have sent a PM re more radical surgery? at that first mixer if? the simple approach does not work. If there is no audio on the mixer output port then you have a half failed mixer (very strange concept)? or possibly a glitch that allows 12 Meg signal from the Si into the mixer on Tx but kills it on Rx.? I'd be suspecting a? bad trace, a? bad audio component or bad solder joint first - iMHO.?
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Re: my uBitx Power
I should have said you need to subtract the Tx idle current instead of the Rx idle current.
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Sent from an iPhone, don't ask whose. On Nov 1, 2018, at 12:13 PM, Clark Martin <kk6isp@...> wrote: |
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Re: my uBitx Power
You also need to subtract the Tx idle current. You can find this by keying up the mic with no audio input. This current is mainly the bias current in the finals but also the relays and some other things. The Tx idle current will vary with band.
On Nov 1, 2018, at 11:07 AM, Joe Puma <kd2nfc@...> wrote: Hey guys,Clark Martin KK6ISP Another Designated Engineer on the Information Super Railway. |
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Re: my uBitx Power
Hi Joe,
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You could separate the brown wire that feeds the Drains of the finals and measure just that current. It will probably not be substantially different from the way you did it - subtracting the receive current. The power you are measuring that way is the DC power *input* to your finals. In the olde dayes the TX power and the vacuum tube ratings were defined in terms of *input* power. That is always going to be higher than the RF output power. The difference will be accounted for by the efficiency. If the finals are 50 percent efficient (a reasonable possibility) and you calculated say 24 watts then your RF output power would be about 12 watts. One details that is good to know is the efficiency of your finals. You will need to measure the actual RF output power and calculate the DC input power as you already have done. Dived theout put power by the input power and get a decimal number less than 1. If that number is 0.5 then your efficiency is 50 percent. It could be less. Probably not much more. Some tube amps made greater than 75 percent! But you could not use them for SSB. If you know the efficency then you can calculate output power by measuring that DC input power and leave your fancy, expensive RF wattmeter in the case at home when you take your radio to Field Day. 73, Bill KU8H On 11/01/2018 02:07 PM, Joe Puma wrote:
Hey guys, --
bark less - wag more |
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Re: TDA2822 Replacement
¿ªÔÆÌåÓýThe population is likely to continue for at least another
generation. On 03/06/18 22:27, David Wilcox via
Groups.Io wrote:
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Re: Cursed?
Dave AI6K Having two uBITX boards that both do not receive well is interesting.? Normally one would be able to compare a working board with a non-working one.? Don't know what test equipment you might have available, but if just a VOM the RF can be traced from input to audio with just a home-built diode detector.? Audio can be traced with an external AF amp and speaker or a home-built AF amp (LM386...?). If you have an oscilloscope you can trace RF input all the way through the uBITX and audio out to the speaker.? Here we would be looking for presence or absence of a signal, not at the specific level at each stage.? Once you have established signal continuity you can then start looking at levels to optimize performance.? Advantage of the uBITX over other rigs is that the layout is fairly simple.? Just follow the signal paths on the schematic.? Arv? K7HKL _._ On Thu, Nov 1, 2018 at 11:49 AM David Berkompas <david.berkompas@...> wrote:
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my uBitx Power
Joe Puma
Hey guys,
I will probably have a watt meter in the coming weeks but I still haven¡¯t measured my power out on the uBitx. So with a dummy load hooked up I took some power measurements with my DMM. I am not sure if this is a good way to tell power output but here are some measurements. Voltage is 12.67 Radio idle and 12.45 while Tx¡¯ing. not sure which one matters most when calculating power or if the difference is negligible but I calculated wattage from the 12.45v band current watts 80 2.18 27.14 60 1.50 18.67 40 1.97 24.52 30 1.42 17.67 20 1.65 20.54 17 1.22 15.18 15 1.15 14.31 10 1.0 12.45 If I take into consideration the .33a for radio idle (4w) is my RF wattage 4w less then my measurements. |
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Re: Cursed?
Gordon Gibby
¿ªÔÆÌåÓýIt amazes me the problems people are having. ?I have only put one of these together, but I had absolutely no trouble. ?Used it for many WINLINK contacts. ? Before that I had a bid ex 40 which I also got to work on 80 m, and it worked fine also. ?But I remember the first rig I had as a novice, it took me six months to make it work. ?So perhaps the learning that is going on as people figure out what the problem is, which are similar to the learning that went on in my head as a high school student,
or actually useful in making better amateur radio operators out of these hams. ?
I¡¯m getting ready to help teach a general class coarse, and it has all these things about different stages in receivers and transmitters, and simple semi conductor circuits. ?Understanding the uBit ex is just slightly more complicated than what I will
be teaching the technicians going for their general class.
Gordon
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Re: Cursed?
David Berkompas
On my v4 boards, first one is latest CEC firmware (1.1), and 2nd board is stock firmware. They transmit just dandy, but useless if they can't hear anything. |
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Re: Ubitx5 ?
The question was "whether there would be a version 5 of uBITX".? Nothing to do with open or closed source for unrelated equipment from a different vendor. Arv _/_ On Thu, Nov 1, 2018 at 10:29 AM James Lynes <jmlynesjr@...> wrote:
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Re: Harmonics and Relay Replacement
The use of AXICOM relays for the LPF switching does appear to allow the uBITX to meet FCC requirements relative to harmonics based on what others have observed. The results variation relative to relay proximity to the board by as little as a "socket height" and the variation between boards is an indication of just how RF sensitive (conducted and radiated) this whole area is.?
We're still looking for a definite and measurable reason(s) for the differences and have come up with several effective solutions using a separate LPF section........ none are as inexpensive as replacing the relays. Will post pictures when done. 73 Kees K5BCQ? |
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Re: Cursed?
dear nsk, ? did you make the ubitx yourself? ?or bought? ?if bought , you had raduino, right? ?little more clarity please On Thu, Nov 1, 2018 at 8:50 PM Prathap Naidu <vu2pop@...> wrote:
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Leland Lannoye
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