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Re: the cause for the spurs, found!
What is the expected level into the Tx bi-amp stage at 45MHz? I don¡¯t have a feel for this and can¡¯t check it as my uBITX is in pieces at present. If it's a relatively high level then the 45Mhz amp stage maybe into limiting. But, my testing on a proto build of these stages, shows that the bi-amp as it is, although fitted with a BFR106 in 1st stage, is indeed, severely limiting at levels above about -13dBm. ? Ie at -10dBm input level, 2nd harmonic is ~21dB down, 3rd is -22dB And at -13dbm input, 2nd harmonic is -33dB, 3rd is -32dB. Around a 10dB improvement in harmonics for a 3dB input level drop! ? This is probably the reason why fitting the extra filter mod works reasonably well, as it's actually just reducing the gain of these stages, as Allison has surmised before. If this is actually the case, then a simple ~3-4dB (or more?) pad at the input may be a solution although better would be to re-calc the Bi-amp stage for lower gain.? Currently the gain is about 18-19dB. Glenn?? -vk3pe |
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Re: Volume Pot
Joe,
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? I've been using these 10k pots with switches from Mouser.? They're out of stock right now until the end of Nov, though. Here's a candidate from digikey:?? This Alpha from Tayda is $0.59?? These are all 10K audio (logarithmic) taper with switches. Andy, KG5RKP On Wed, Oct 31, 2018 at 05:52 PM, Joe Puma wrote:
Does anyone have a link to a 10K pot I can use for volume control for the uBitx that has power switch. Oddly the one that came with the kit went bad on me. It just freaks out when I touch it and can go from just producing full volume to nothing at all or it just works. |
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Re: the cause for the spurs, found!
¿ªÔÆÌåÓýThe BFR106 parts will work pretty well, but I¡¯ve used the ERA/MAR/GALI series of MMIC successfully there too with just a little circuit modification.? Some tend to be very low noise factor. ? ? From: [email protected] [mailto:[email protected]] On Behalf Of Ashhar Farhan ? allison, let me try those out. thanks for the tip. ?i had 2n2222s so they went in. i remember you explaining why 2n2222 was better than 2n3904.? - f ? On Mon, 5 Nov 2018, 01:31 ajparent1/KB1GMX <kb1gmx@... wrote:
-- ¡_. _._ |
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Re: the cause for the spurs, found!
Gordon Gibby
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Re: the cause for the spurs, found!
allison, let me try those out. thanks for the tip. ?i had 2n2222s so they went in. i remember you explaining why 2n2222 was better than 2n3904.? - f On Mon, 5 Nov 2018, 01:31 ajparent1/KB1GMX <kb1gmx@... wrote: Farhan, |
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Re: PSK31 ghosts below my signal
On Sun, Nov 04, 2018 at 06:22:25AM -0800, Don - KM4UDX wrote:
Ideally you'd use a scope. The crud is close enough in to your suppressed carrier you'd be able to hear it on a SSB receiver by zero beating the carrier that is leaking. It appears you should hear it on both upper and lower sideband at about 500Hz. Your PSK31 signal is at 3581.140 which is 1.140 Khz above 3580 so you might also see a much weaker image at 3578.860 Khz of your PSK signal. If the ssb filter is properly set up you shouldn't see much at all at 3578.860 I can't tell if that's a trace of it on the left of your picture or not, if it is, it looks well down from the main signal. (As Allison has pointed out the carrier suppression could also be better. ) I'm surprised the filter isn't knocking down the 500Hz crud more than that, hence my query about alignment. If you can listen to the crud on an external receiver it may give you a clue as to what it is coming from. I'd also turn the sound card down to 0 at the computer and see if you are still getting that crud. It could be the sound card output amp clipping as well. Really a scope would help a lot here. :-( Yes there are guides in the wiki. It has been covered here. Personally, I wouldn't. -- - db@... db@... |
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Re: Si5351 correction question
¿ªÔÆÌåÓýForgot to state that that¡¯s 15 MHz WWV.? It¡¯s been about an hour and a half now ant the temp has stabilized at 96F (35.5C) with drift at 90 Hz.? Using WWV and WSJT-X is also a good way to visually zero beat for calibrating frequency.? The WWV carrier is obvious relative to the audio sidebands.? Tune to 14.999 USB and adjust tuning until WWV carrier aligns with 1000 Hz on WSJT-X waterfall display.? May have to program in smaller frequency steps like 5 Hz. Mike K5ESS ? From: [email protected] [mailto:[email protected]] On Behalf Of Jerry Gaffke via Groups.Io ? Assuming you're still at 14mhz, that's a 1e6 * 74hz/14mhz = 5.3ppm change over a 92F-79F = 13 degree F temp change. Here¡¯s the result of my uBitx start-up frequency drift test.? The thermocouple is not in direct contact with the crystal but is positioned next to in in between the Raduino main board and the LCD . Mike |
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Re: Si5351 correction question
Assuming you're still at 14mhz, that's a 1e6 * 74hz/14mhz = 5.3ppm change over a 92F-79F = 13 degree F temp change.
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So 5.3/13 = 0.41 ppm frequency shift per degree F change in temperature. Considerably less than the worst case 1.0 ppm per degree F spec of the randomly chosen crystal datasheet I found. Seems about right. Could get worse if you give time for the change in temperature to fully soak into the crystal. Jerry On Sun, Nov 4, 2018 at 12:42 PM, K5ESS wrote:
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Re: Si5351 correction question
¿ªÔÆÌåÓýHere¡¯s the result of my uBitx start-up frequency drift test.? The thermocouple is not in direct contact with the crystal but is positioned next to in in between the Raduino main board and the LCD . Mike K5ESS ? From: [email protected] [mailto:[email protected]] On Behalf Of K5ESS
Sent: Sunday, November 4, 2018 12:59 PM To: [email protected] Subject: Re: [BITX20] Si5351 correction question ? Jerry, I was wrong in how much drift I was seeing.? The 200 Hz was the approximate amount my frequency calibration? was off.? Stand by for an update on drift with temperature measurements included. Mike K5ESS ? From: [email protected] [mailto:[email protected]] On Behalf Of Jerry Gaffke via Groups.Io ? Here's a randomly chosen datasheet for a 25mhz crystal out of Mouser: Hi Jerry. Makes me wonder how much of a temperature change is involved here. This may be on target. |
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Re: Si5351 correction question
¿ªÔÆÌåÓýJerry, I was wrong in how much drift I was seeing.? The 200 Hz was the approximate amount my frequency calibration? was off.? Stand by for an update on drift with temperature measurements included. Mike K5ESS ? From: [email protected] [mailto:[email protected]] On Behalf Of Jerry Gaffke via Groups.Io ? Here's a randomly chosen datasheet for a 25mhz crystal out of Mouser: Hi Jerry. Makes me wonder how much of a temperature change is involved here. This may be on target. |
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Re: Si5351 correction question
Here's a randomly chosen datasheet for a 25mhz crystal out of Mouser:
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? ??https://www.mouser.com/datasheet/2/96/008-0308-0-1160929.pdf On page 3, it say the "Frequency Stability Tolerance" is +/- 50ppm over an operating temperature range of -20C to +70C. That's 50ppm/(20+70) = 0.555 ppm per degree C, or 0.555*9/5 = 1.0 ppm per degree F. (I'm assuming frequency vs temperature is a linear relationship, should be close to correct.) Mark was seeing his correction factor change by 1170 ppb, or 1.170ppm. Using this crystal, we might see such a frequency shift when the temperature changes by just over 1 degree Fahrenheit. Mike said he saw 200hz of drift during warm-up while operating at 14mhz. That's? ?1e6 * 200/14000000 = 14.3 ppm. This particular crystal from Mouser could shift that much if the temperature inside the rig changed by 14 degrees Fahrenheit (or 8 Centigrade). Other (cheaper?) crystals can be worse in this respect. How the crystal oscillator circuit inside the si5351 responds to temperature is also a factor, this could add or subtract from that crystal frequency shift. Anyways, use a TCXO controlled si5351 board if worried about stability. Lots of the TCXO's available are digitally controlled and make adjustments in discrete jumps of several hz, you want a good old fashoned analog TCXO for radio stuff. A cheap solution might be to attach a temperature sensor out near the crystal and si5351. The processor reads the temperature sensor and adjusts how it programs the si5351 accordingly. The si5351 allows those adjustments to be made in increments of around 0.01ppm, or 0.14 hz at 20m. Some of the other SiLabs parts (si5338, si5341, si570, ...) allow these increments to be at least an order of magnitude smaller, to where there would be no perceivable jump.? Jerry, KE7ER On Sun, Nov 4, 2018 at 09:05 AM, Mark Pilant wrote:
Hi Jerry. |
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Re: New file uploaded to [email protected]
Check your power and make sure it is 12V and min 3A. Nextion LCD consumes more than stock LCD, therefore you may need to increase your power a bit.
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Re: Si5351 correction question
Hi Jerry.
Makes me wonder how much of a temperature change is involved here.This may be on target. I did a little more testing this morning and a different correction number was needed to get the correct frequency. Actually between the two from yesterday. Two temperature factors may come into play. First, my "shop" is in the basement and we had a fairly cool night. Second, everything had been powered off overnight, so it was all from a cold start. I just wanted to close the loop on this one. 73 - Mark N1VQW |
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Re: the cause for the spurs, found!
dennis, we keep rolling every confirmed change into the next version. - f On Sun, 4 Nov 2018, 09:49 Dennis Yancey <Kd4epg@... wrote: Will any of these mods be incorporated into uBitx v4 or even a new version soon? |
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Re: PSK31 ghosts below my signal
Gordon Gibby
¿ªÔÆÌåÓýGo find some carrier (or a CW signal) , set your radio on upper side band. and make sure that you can hear the carrier when you are below it in frequency, and NOT when you cross over and go above it. ? ?If both side bands sound the same loudness you have a problem in alignment.
You ought to be able to hear it loudly on one side and not at all or very softly on the other. ? That will tell you right quick how well your BFO is set.?
Think about it for a minute.?
Then set your radio for lower sideband and repeat the experiment; the result should be reversed.?
Gordon
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