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Re: #ubitx Power output on 40 / 80 m with high current levels
#ubitx
Alex - PA1FOX
Thanks John and Jerry for the supportive comments. Here are some replies:
Are you sure you are using SSB? And the amplifier class is really AB? Remember, SSB output is Pk-Pk, while AM is "100% modulation". I would be interested in seeing if there is any carrier output. This sudden current jump is suspicious of extra oscillation. Yes, I am using SSB but also can switch to CW. With no modulation in SSB there is no carrier. Well there is if you listen on a nearby receiver but it does not give any output on the power meter. Suppression seems ok. I think I was not clear in my explanation about the current. There is no sudden jump when the modulation sinus is increasing graduately. The gain seems quite linear and with the mic attached the voice sounds quite nice. During the building process I did encounter some spurious oscillations but managed to get rid of them by proper decoupling and repositioning of the toroids. The jump in current I meant was when switching from 40M to 80M. At 80M I get 5 watts RF with about 3A current. The rig in TX mode with no modulation runs about 0.75A so the IRF's are taking the remaining 2.25A at full modulation. Today I finished the second LPF and this gives more interesting information. Overall gain of the TX chain decreases dramatically when tuning from 80M to 17M (my current highest band with LPF). The following occurs: 80m: 5 watts 3A 40m: 5 watts 3A 30m: 1.1 watts 1.4A 20m: 0.2 watt 1.04A 30m: 0.25 watts 1.06A If I turn RV1 for more TX gain I can increase the power output on 20m to 8 watts at 2.6A On 30m I can get 8 watts at 2.5A after setting the right gain with RV1. Don't go above 3v or so on the IRF gate. Maybe even 2.5v. These are very touchy devices and hit a full on current condition with no warning...as you have already found out. Correct but these are not adjusted by RV1. I have built the 'original' uBitx version where RV1 is between two 2N3904's. in the block before the 2N2219's The optimal bias for the IRF's in my rig is around 2.8 volts. I can adjust both bias pots so that the second harmonic is minimized which is normal. IRF MOSFETS are notorious for being extremely variable. You are right that a different batch will give entirely different results. The use of #10 material for the toroid is very good, but I would increase the size to at least a T50, and probably would go to a T68 or even a T100 for high power levels. It doesn't take much to saturate a T37, and then the transformer is an entirely different one. Also, it might be prudent to look for a different form factor for the output transformer, one with a bit more shielding than a toroid. I know, they have a good reputation, but they are not perfect in a strong RF field. This is true when the T37-10 is saturated at high power. Changing the size should not have influence if I would hold the measurements in the say '1 watts' range. Note, I am not trying to pull maximum output power of the IRF's. I would be glad with 6 watts but with a good PA effciency. 2A overall rig current would give 1.25A for the IRF's At 12 volts this would be 16 watts power input and at 6 watts output for a class AB amplifier this would be nice. It does seem to do that at the higher bands. It's unlikely that the bidirectional amps have much to do with radiated power...provided the throughput is adequate. In the case of the BITX, that is roughly 10 dB. Know also that the IRF510 is not a very good device above 40m. Yes, they can be made to work well, but it takes a good impedance match and heat control to do so Well the overall gain of the TX chain is not the problem, it's frequency dependant. at 80m there is some 10dB more gain than at 20m. There is however a solution to that. I will use three LPF's (as opposed to two LPF's in the original schematic) and these are selected by two relays. The logic table for the two outputs from the arduino are: 00 : no relay activated, 80m and 40m LPF selected 01: relay 1 selected: 30, 20 and 17m LPF selected 10: relay 2 selected 15, 12 and 10m LPF selected (yet to finish) 11: not applicable I could use the relay1 activation line to increase the TX gain at some stage. Or use '00' to reduce a bias setting of one of the TX preamps. This way I could adjust the overall TX gain in three steps and compensate for the gain loss at higher frequencies. The thing that bothers me most currently is the high current at 80m and 40m. With 3A at 5 watts maximum a lot of power is used to heat up the sink. Not good when running portable (although handy to keep the hands warm in case of winter SOTA ...:) Jerry, I will try the 10 ohm resistors in series with the IRF gates. Have not tried that yet, thanks. And I will dig into the article from WA2EBY. More knowledge and theoretical background will help. I've built a lot of VHF amplifiers but not yet in the HF range which 'normally' should be simpeler. Unfortunately I don't have a spectrum analyzer (yet) but I ran some test with the frequency counter connected to an RF probe near the LPF coils. The counter always displayed the correct frequency. I did not hear strange things on my Icom rig when tuning over the bands as well. To be continued... 73, Alex PA1FOX
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Re: #ubitx uBITX keyer change
#ubitx
Gordon Gibby <ggibby@...>
I got my CW working pretty reasonably. I did all the changes below in John Pieper's suggestions. I also took out a write to the serial port that I thought might slow things down. I took out the 5 mSec delay. And I altered the "numbers" chosen as the dividing points between dot dash both straight key. By my calculations you can increase the both to a much higher number, like 240 or so, and that makes the straight key much more likely to work. The Key I was using was also pretty lousy and that may be the remaining problem.
I'm having problems with the "core.a" "unable to rename" problem.....that really slows me up....Even when "administrator." Any solution for this?
Now I need to figure out exactly which of the above changes made the most difference.
Also---in the photos on the Wire up of the uBitx he is connecting the resistor to the RING, not the tip. At least it looks that way to me. I think you want it connected to the TIP. I had to pull my plug out slightly to make things work, which clued
me into this.
Darndest thing --- I discovered a SHORTED patch cord of coax when connecting up to a dummy load. Never saw THAT before....
Gordon
From: BITX20@groups.io <BITX20@groups.io> on behalf of John Pieper <j.pieper@...>
Sent: Friday, December 29, 2017 2:29 PM To: BITX20@groups.io Subject: [BITX20] #ubitx uBITX keyer change I was disappointed by the performance of the built-in keyer code in the uBITX when using my paddle. In particular I was having a hard time getting the first code element of a character to come out, especially if it was a dit. It made the whole thing seem
clunky and basically unusable. Looking into the code I quickly spotted the likely cause. Near the beginning of
cwKeyer():
//if a paddle was used (not a straight key) we should extend the space to be a full dashThis is trying to enforce character spacing, but has the effect that between characters the paddle is only sampled once every two bit times, making it quite unresponsive. My opinion is, let the operator produce the correct character spacing, make the paddle as responsive as possible. I took out those two lines. I also took out the 5 ms delay below, right before the continue statement. Now the paddle is always being sampled at a high rate and the feeling is much smoother. This seems usable now. While I was in there I also took the opportunity to insert a 10 ms delay after the calls to startTx() and updateDisplay() (lines 120-121), but before the end of the conditional block. This gives the T/R changeover time to settle before the key goes down, so that an initial dit won't get cut off. Finally I redefined CW_TIMEOUT to be a multiple of cwSpeed, so that faster code speeds can have shorter timeouts. 600 ms was way too long for me. I used 7 times cwSpeed; maybe that can become a setting at some point. 73, John AD0RW
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Re: No TX
#ubitx
joe kallo <quietglow@...>
Just got home from work and checked: brown wire properly hooked up. I measure 13.5v to the heatsink w/o the key down and ~13v with it keyed.
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Re: No TX
#ubitx
Gordon Gibby <ggibby@...>
rats. wished it could have been something simple..... sorry.....
From: BITX20@groups.io <BITX20@groups.io> on behalf of joe kallo <quietglow@...>
Sent: Tuesday, January 2, 2018 6:10 PM To: BITX20@groups.io Subject: Re: [BITX20] No TX #ubitx Just got home from work and checked: brown wire properly hooked up. I measure 13.5v to the heatsink w/o the key down and ~13v with it keyed.
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Re: Tuner? Well Sure!
Mansueto Grech
Hi Gordon, Fantastic idea. I would be interested 73's Mans. 9H1GB
On 29 December 2017 at 16:05, K9HZ <bill@...> wrote:
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Re: No TX
#ubitx
joe kallo <quietglow@...>
Me too! I even turned up the bias pots a little. Didn't help. I also removed the radio from the box and set it up again with jumpers, also with no effect.
Raj I am not sure exactly what you mean re: putting the wire to c80. I see c80, but I am not sure what you're suggesting I try to do. Joe
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Re: No TX
#ubitx
Gordon Gibby <ggibby@...>
I thought he was trying to create a tiny "antenna" to allow you to listen with another receiver and ascertain which STAGES were ampplifying.....
From: BITX20@groups.io <BITX20@groups.io> on behalf of joe kallo <quietglow@...>
Sent: Tuesday, January 2, 2018 6:53 PM To: BITX20@groups.io Subject: Re: [BITX20] No TX #ubitx Me too! I even turned up the bias pots a little. Didn't help. I also removed the radio from the box and set it up again with jumpers, also with no effect.
Raj I am not sure exactly what you mean re: putting the wire to c80. I see c80, but I am not sure what you're suggesting I try to do. Joe
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Re: #ubitx Power output on 40 / 80 m with high current levels
#ubitx
John Backo
Good job, Alex:
The more you explain, the more it looks like there is VHF oscillation occurring at the lower frequencies. Jerry's suggestion of adding 10 ohm resistors to the gates is designed to suppress oscillation. It seems to be the standard "repair" and almost always works... The observation of greater gain in the output chain of the uBITX with lower frequencies is also interesting. That would probably help to explain some of the overdrive you are experiencing. The fact that Farhan did not report it means that he either did not measure it or he did not drive his rig to the point where it became a problem. If you examine the W7ZOI paper, you will see that gain on the amplifier is adjustable with the proper choice of bias and feedback resistors. That may have to be done. I suspect, though, that your real problem is oscillation with transmit in the lower bands. There have been various methods derived to attack the problem. Yours is as good as any (maybe). Hi. The finding that power output decreases the higher one goes in frequency is perfectly consistent with these devices. That's a good sign that the basic design and operation is right...and that the layout for higher frequencies is good. The real problem seems to be oscillation and the overdrive from RV1 at lower frequencies. This is probably what is to be expected as the gain of the IRFxxx MOSFETS increases rather dramatically below 40m. Perhaps it might be simpler to provide a simple attenuator inline for driving these ranges. It would seem that your layout is too much for the lower bands and requires more gain suppression. Keep it up. You're doing good...Farhan? john AD5YE
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Re: #ubitx Power output on 40 / 80 m with high current levels
#ubitx
John Backo
Incidentally, it would be nice to see exactly how your particular layout
differs from that of hfsigs. Can you upload a picture or two? And I presume it is more through-the-hole and not smd parts. No? It may be that the choice of parts is more critical than first believed. john AD5YE
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Re: uBitx IRF510 to IRF510 physical measurement
Tom Christian
Bill, Thanks for the good idea (and John for your input too). I ordered the heatsink as opposed to my original idea of mounting to the metal case (isolated). Still waiting for the ubitx and the heatsink. I would be curious to know how it goes for you.
Tom AB7WT
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Re: BCI filter question.
K9HZ <bill@...>
You can build an excellent W3NQN BC filter for about $5.
toggle quoted messageShow quoted text
Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ
Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois
Owner – Operator Villa Grand Piton - J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com email: bill@...
On Jan 2, 2018, at 7:52 AM, KG5NII <kg5nii@...> wrote:
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Re: My µBITX in its new home
Sajid Rahum
Ordered same box as well. Thanks for great feedback.
what did you do for the speaker?
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Re: Si5351/A Utility Console
Bruce MacKinnon KC1FSZ
Hi:
I had a sweep feature on a different branch that I've merged in for general use. Documentation is updated as well. Basically, it's a simple way to sweep any of the clocks through a range, reading an analog pin at each step. I've used this feature in several testing scenarios, particularly when trying to characterize a crystal band-pass filter or LC low-pass filter. There's also a trigger output at the start of each sweep that could be used to hook up an oscilloscope to get one of those old-school phosphor traces of your device. Dim the lights, so cool looking ... The N2CQR blog included a write-up that I did when the feature was first created. This gives you an idea of how it might be used: http://soldersmoke.blogspot.com/2017/05/homebrew-peppermint-bitx-kc1fsz-goes.html The digital read at each step in the sweep would be a power level or something useful like that. Poor-man's Sweeperino I guess. But these methods yielded a fully working receiver, and I'm certainly no RF expert. 73s, Bruce KC1FSZ
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Re: Variable power control
Much of the rig power during receive is going to the Nano and display and si5351. Could cut that significantly with a 12 to 3.3v buck switcher (using 3.3v display and processor) if you could get it clean enough. Thanks, Jerry. This is one reason why I'm interested, as I'm moving to a Teensy 3.5, Si5351, and a true touch screen display. Jack, W8TEE
From: Jerry Gaffke via Groups.Io <jgaffke@...> To: BITX20@groups.io Sent: Tuesday, January 2, 2018 5:03 PM Subject: Re: [BITX20] Variable power control Yes, a switcher is much more efficient than a linear regulator, but amps of current getting switched at one mhz or so can create hash you hear in the receiver if not properly filtered and shielded. I can receive well using a desktop 12v brick meant for use with a monitor, it is also a switching power supply, so it may be possible to use that ebay buck converter. Another possibility is to normally power from 12dc, and enable a boost converter to generate 24v only when transitting. Many switcher chips have an enable pin, though I don't see an enable talked about on most of the board level products available on the web. Much of the rig power during receive is going to the Nano and display and si5351. Could cut that significantly with a 12 to 3.3v buck switcher (using 3.3v display and processor) if you could get it clean enough. Jerry, KE7ER On Tue, Jan 2, 2018 at 01:47 pm, Jack Purdum wrote:
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Re: No TX
#ubitx
That is fine Joe. Every board will not behave the same or even meters read the same.
toggle quoted messageShow quoted text
Check why there is no RF getting to the finals.
At 02-01-2018, you wrote:
Right, so the directions say to go to min and then turn one pot until the current is 100mA higher, then to do the same w the other. Thats what I did, but my starting min current was 50mA lower than the spec in the directions. I didn't think it was enough it make a difference, but now with it not working I'm wondering.
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Re: Tell me your favorite uBitx mods
I'm adding this to my development µBITX: Check on ebay #172488451918 Jack, W8TEE
From: David Arthur <mumrah@...> To: BITX20@groups.io Sent: Tuesday, January 2, 2018 5:03 PM Subject: Re: [BITX20] Tell me your favorite uBitx mods A mini usb "breakout" would be nice for uploading new Raduino sketches without opening up the box. Could double as a CAT control interface. On Tue, Jan 2, 2018 at 4:53 PM K9HZ <bill@...> wrote:
-- David K4DBZ Unofficial bitx chatroom: https://discord.gg/CrHvWFc
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Re: Variable power control
Maybe Jerry's idea of only boosting on TX would be the way to go in removing any hash. Jack, W8TEE
From: M Garza <mgarza896@...> To: BITX20@groups.io Sent: Tuesday, January 2, 2018 4:56 PM Subject: Re: [BITX20] Variable power control Jack, Nothing wrong with that. It should work fine, as long as it doesn't introduce any RF hash from the switching regulator. I would think that you could replace the variable that controls the voltage with a panel mounted one. Marco - KG5PRT On Tue, Jan 2, 2018 at 3:47 PM, Jack Purdum via Groups.Io <jjpurdum@...> wrote:
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Re: No TX
#ubitx
Joe,
toggle quoted messageShow quoted text
The bias current flow is not linear with bias pot. The current will suddenly increase. Put your PS on current limit to about 1A and then set the current. touch or temporarily solder a short wire to the component so that it will act as an antenna. Then you can pick up your low level TX signal on another receiver. Raj
At 03-01-2018, you wrote:
Me too! I even turned up the bias pots a little. Didn't help. I also removed the radio from the box and set it up again with jumpers, also with no effect.
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Re: Variable power control
John Backo
"I understand now that it's not a simple add of a potentiometer. Anyone done this yet?"
Jim, this is relatively simple for the BITX if one builds a linear power supply, and regulates it with a LM338 or other regulator capable of 5A output. make the regulator variable by adjusting the voltage input to the ground reference. Use about 24v for the top value and about 9v for the bottom. Just be aware that the lower one goes in regulated voltage, the less current is available. But 12v and above with 4-5A is easily possible. You can double these regulators with the proper configuration and so double the output. Or you can easily add a bypass transistor and increase the power available that way. See the datasheets for the details. I use a similar home-brew power supply for all my bench work. It works well. john AD5YE
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Re: No TX
#ubitx
Ashhar Farhan
can you hook an RF probe together? - f
On Wed, Jan 3, 2018 at 9:16 AM, Raj vu2zap <rajendrakumargg@...> wrote: Joe,
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