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Re: Simple spur fix
I rolled the dice on a pair of filters and received Toyocom 45E1A9Fs which show up here as two pole filters at 1200 ohm termination impedance. If I parallel those will I bring that impedance down to 600 and should that be a goal? Should I try both in parallel? I do have a modest spectrum analyzer to take a look at the results with.
John KC9OJV |
Re: Simple spur fix
Warren,
>>1) 120 mVrms is far above the audio level that caused unacceptable IMD before the filter mod. IMD must be checked and the audio levels adjusted to make it acceptable. The problem is the balanced mod easily takes that but the gain after it means the 2nd mixer gets hit with a very high level.? With that the output of that mixer is high and that leads to the next mixer getting overloaded.? There is too much gain after the balanced mod.? This is why the balanced mod needs such a low input. Allison |
Re: uBitx Antenna
#ubitx-help
Gordon Gibby
¿ªÔÆÌåÓýNow that I know how to make one, I like doing that if I¡¯m going to do digital. ? Common mode and unbalanced currents wreck havoc with digital systems.But for the first 35 years that I was a ham, I didn¡¯t even know what they were. ? Somehow or another I made thousands of contacts and had a ton of ?fun.?
Here are some references that might help you with baluns (there are many good ones)?
Cheers,
Gordon kx4z
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Re: uBitx Antenna
#ubitx-help
Oh, thanks! I'm looking for an SWR-meter meanwhile. And about the balun ? Is it a "MUST HAVE" ?
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Re: uBitx Antenna
#ubitx-help
Gordon Gibby
¿ªÔÆÌåÓýGet an SWR meter. ? old CB types work fine. $15Most people use 50 ohm coax , but even 75 will work fine.?
Make a dipole, test the swr, adjust as necessary
That¡¯s how many of us started out over the years.
read, read, read, read, and learn, because there are lots of myths that float ?around. ?ARRL ?has good books.
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uBitX controller issues
I searched for this problem to no avail. So I am posting in case someone has an answer.
I bought a new uBitX, and installed it in the case from Amateurradiokits.in. Upon powering up the display shows: uBITX v4.3 LSB A: 7.149.950 If I turn the encoder to change frequency, the display shifts from 7.149.950 to 7.149.900. back and forth as I turn, either CW or CCW. If I push the encoder, the display shows Band Select > Turning the encoder does nothing Push encoder again and I get display showing Band Select: Turning the encoder now changes display between 7.349.900 and 7.149.900. If I power off, then back on, sometimes the frequencies shown in the display are a little bit different (some times when in band select, the display will change from 7.149.900 to 6.949.900, or similar). With an antenna attached I can hear signals from the speaker (noise, occasionally someone¡¯s transmission). So I know the receiver works. If I push the PTT the relays click. I assume transmitter works too. I thought I had a bad encoder, so I bought a new one from Digikey. Same results. Power supply is 13.27 volts. Power to raduino is 5 volts. Someone suggested pin 3 may be shorted to ground causing raduino problems, but I checked and not grounded. All wiring triple checked (or more). Any thoughts are appreciated. Thanks 73 Mark W3MSR |
Re: Simple spur fix
Gordon Gibby
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Re: Simple spur fix
Those messing with 45mhz filters might want to revisit the code of post:? ?/g/BITX20/message/44278
That post provides an easy an intuitive way to put your USB or LSB signal into a desired spot in the 45mhz passband. If there are two 45mhz filters involved, they should be matched. If that code is puzzling, then check out this post:??/g/BITX20/message/44515 Jerry |
Re: si5351 crosstalk
#radiuno
Miles Silk
On Sep 8, 2018 1:30 PM, "Gordon Gibby" <ggibby@...> wrote:
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Re: si5351 crosstalk
#radiuno
Gordon Gibby
¿ªÔÆÌåÓýUnfortunately in the uBitx design all three clocks are feeding impedance is a good bit lower than the maximum one suggested. ?These outputs are CMOS outputs, are they not?
So they have active device up and active ?device down, and the impedance is constantly changing as one device turns on and the other turns off. ?It¡¯s a digital system made out of analog parts.
So sure, running through a 50 ohm transmission line you would get some reflections, to a higher than 50 ohm load, but the line lengths ?so tiny fractions of a wavelength here that probably doesn¡¯t make that much difference. ??
I¡¯m not familiar with ground bounce, but because of these low impedance loadings, signals are getting coupled ?from one output to the other.
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Re: Simple spur fix
Warren,
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That IMD could be in the IF amps (Too much gain for 2n3904's at 45mhz?? Mixer overload?) or in the power amp.? If IMD gets worse when RV1 is cranked up, that would suggest it's in the PA. If it's in the 45mhz IF, the new filter will help but is too wide to clean up the immediately adjacent channels. Seems it should be straightforward to clean up this IMD on v5, but may take lots of small hacks to? clean up existing rigs.? Fortunately, at 5 or 10 watts out it seems to not be just too bothersome as I don't recall any reports of trouble in the forum.? But it should be fixed on v5, and v3,v4 should not be used with an external high powered linear. Jerry On Sat, Sep 8, 2018 at 09:30 AM, Warren Allgyer wrote: Before the mod the radio showed terrible IMD at any input level higher that about 25 mV and, at that level, the radio produced less than 2 watts. If it turns out the filter is a 'magic bullet' and the radio can actually sustain this level of input with acceptable IMD, then the input audio stages need more gain. |
Re: Simple spur fix
Hi all, good job.?
1.The output? of 45-2pole in C22 position needs transformer 50/600 and small C <10 pF- it will have close to flat responce. 2.As I wrote befor as main filter I used SMD: DSF753SDF 4POLE marked as D45015GQ +/-7.5 dB. I put it on board on the back side and used transformers 4t/10t in small binocular 2402. Best to all George. |
Re: Right-sided relay harmonic attempted fix for v3/4 ubitx
All three relays are de-energized during received, so contacts are as shown in the uBitx schematic
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with a path through the 10m filter. At the start of transmit, the following routine gets called (file ubitx_20.ino of the stock HFSignals firmware) Should be readable enough even if you've never seen C code before. Jerry ######################################### void setTXFilters(unsigned long freq){
?
? if (freq > 21000000L){? // the default filter is with 35 MHz cut-off
? ? digitalWrite(TX_LPF_A, 0);
? ? digitalWrite(TX_LPF_B, 0);
? ? digitalWrite(TX_LPF_C, 0);
? }
? else if (freq >= 14000000L){ //thrown the KT1 relay on, the 30 MHz LPF is bypassed and the 14-18 MHz LPF is allowd to go through
? ? digitalWrite(TX_LPF_A, 1);
? ? digitalWrite(TX_LPF_B, 0);
? ? digitalWrite(TX_LPF_C, 0);
? }
? else if (freq > 7000000L){
? ? digitalWrite(TX_LPF_A, 1);
? ? digitalWrite(TX_LPF_B, 1);
? ? digitalWrite(TX_LPF_C, 0);
? }
? else {
? ? digitalWrite(TX_LPF_A, 1);
? ? digitalWrite(TX_LPF_B, 1);
? ? digitalWrite(TX_LPF_C, 1);
? }
}
##################################
On Sat, Sep 8, 2018 at 09:33 AM, Brent Seres/ VE3CUS wrote:Just a question, and I apologize if it's been covered before. |
Re: Right-sided relay harmonic attempted fix for v3/4 ubitx
Just a question, and I apologize if it's been covered before.
Could someone tell me the LPF relay sequencing for the existing ubitx configuration? What relays are energized for what frequency ranges? I want to figure out the logic for building an off board LPF solution using a cleaner layout and switching (ie..1 relay path only per filter...or separate relays at the input and output of each filter....basically a more symetrical, conventional layout. Thanks for everyone's help Brent |
Re: Simple spur fix
Warren Allgyer
More data...... Comparison of CW power out with SSB power out using the added 45 MHz filter: Kees, I have no plan to change out the original filter at this point. It is pretty moot until we know what the IMD is. |
Re: si5351 crosstalk
#radiuno
Allison Thanks.? You may have just saved me from overloading some of a recent purchase of Si5351a devices. I too was under the impression that 50 ohms meant 50 ohms, instead of "use a 50 ohm line and a much higher termination".? That though does raise a question regarding 50 ohm line with significantly higher impedance termination at the extreme upper frequency limits?? Might this cause higher reflected signal on that 50 ohm line?? Maybe it doesn't matter? Arv _._ On Sat, Sep 8, 2018 at 10:03 AM RCBoatGuy via Groups.Io <ijnfan-HamRadio=[email protected]> wrote:
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Re: si5351 crosstalk
#radiuno
jim
Indeed THIS ....Explains why I'm seeing 0.6 volts (p-p) at R103? on the 45 Mhz mixer thingie
Jim
On Saturday, September 8, 2018, 9:03:33 AM PDT, RCBoatGuy via Groups.Io <ijnfan-HamRadio@...> wrote:
Allison,
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Re: si5351 crosstalk
#radiuno
Allison,
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