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Re: uBITX ... AGC or AVC?
Loris,
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Try something else.. Use a SBL-1 or similar. DBM. it is a BiDi device Connect one? RF port to signal INput and second to OUTput or other way. Feed a DC control voltage through a resistor to the IF port. Try with 1-10K. Vary the voltage and see the signal level change. The behavior is opposite of the varicap control voltage. We can use this for AGC and ALC in either direction. Raj At 28/10/2020, you wrote: On Wed, Oct 28, 2020 at 12:31 PM, Raj vu2zap wrote: |
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Re: ?BITX ... AGC or AVC?
Sorry guys,
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On the TX side it is R23/43 on RX side is R13/33. It worked as AGC for RX and ALC on TX. On RX I controlled the gain from received audio on TX was a DC gain control pot. I can't provide specific circuit details from here as I am holed up at the farm. All these experiments were done on a bitxv3 board. To experiment with this idea you will need to be knowledgeable on the subject and not for beginners. Raj At 28/10/2020, you wrote: Loris is right, Raj's R23 and R43 are both on the transmit side of the uBitx bidi amps. |
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The LED solutions always seemed too fussy for me - too component dependent so I took a different approach,? I recently built a new audio module for my not-a-biTx "Furlough 40" SSB transceiver which you can read about and see demonstrations of on the ? This circuit includes and audio AGC and relative strength signal sensor (S-Meter).? It would be fairly easy to adapt to the uBitx but I haven't done so.? I haven't done a post of the new audio module yet - but it will go something like this.....
The audio AGC works by sampling the audio output of the LM-386 audio amp (in parallel with the speaker jack) - and feeding it back through a simple diode/capacitor peak detector that drives a BS170 MOSFET which is used as a voltage controlled variable resistor that forms 1/2 of a voltage divider with the other half being the volume pot wiper.? The AGC level is controlled by a 10K trimmer at the output of the LM386.?? To adjust it I set the volume pot to about 50% and adjust the trimmer until both weak and strong signal sound good.? It attenuates the very strong signals sufficiently that I no longer jump out of my chair when they come on and I have plenty of volume control for weak signals.? Hint - use a multi-turn trimmer for finer adjustment.? Many thanks to uber-Elmer N6QW, Pete Juliano for this sub-circuit. The relative signal strength meter works by sampling the output of the audio pre-amp through an op-amp to another diode/capacitor peak detector.? The voltage on the cap is sampled by an Arduino analog input pin and a simple look up table conversion is used to translate sampled voltage into an "S level" on the display.? Attentive readers will recognize the signal strength sensor as the same one the Ian Lee KD8CEC proposed some time ago and is well documented on his blog. So my circuit should work just fine with the KD8CEC firmware if you decide to use it. Just plug the output of the sensor into Arduino pin A7 and you should be golden.? Similar to KD8CE, my sketch uses a look up table of sampled voltage to convert to "S levels". I calibrated it by adjusting the lookup table until the S display matched what I saw on my Kenwood transceiver for the same signal.? Not scientific, nor precise - but it matches my commercial rig and allow me to say "You are S9+20 OM, Fine Business, indeed."? No, it does not measure ?V at the antenna and convert it to a log scale - but it's output matches my commercial rig. And it makes a nice bouncy display to impress all of your friends and family. If you follow the reviews in QST you will know that event the "best" commercial rig S-meters vary a lot and don't do much better than this simple circuit, despite the IARU S-level specification. Have fun - and if anyone decides to build this please drop me a line.? Happy to share the s-meter code from my sketch if anyone is interested. 73, Dean KK4DAS |
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Re: Duh-oo
It appears that we are talking about two different circuits, causing even more confusion. Going back to making soup. {;-> Bob ¡ª KK5R
On Wednesday, October 28, 2020, 8:07:12 PM EDT, Curt via groups.io <wb8yyy@...> wrote:
Let's see you guys are making too much of this -- the meter operation was an after thought in the scheme of this AGC.? Certainly there is no log response in this circuit that an S-meter needs.? The function is this - the audio is sampled and amplified, fed to an ordinary silicon diode - and this drives a transistor with a dc bias in linear fashion (more or less) that feeds an LED.? The current through the LED is measured using an ammeter shunted with a small appropriate resistor (4.7 ohms for the meter that Sunil shipped).? That's it for the meter.? (possibly the brightness of this LED may be a better measure of signal strength than meter deflection perhaps).? I need to make a couple updates to the AGC schematic - but it is very similar to what VK3YE sketched out.? It works nice enough in this transceiver to suppress big signals.? I will caution that the behavior needs some tweaking to actual LED and LDR parts - but it works nicely.? 73 curt |
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Notice that I said that if "calibrated" that it would be accurate at one point, the point where it was calibrated. Therefore, you are right that: "you will never be able to calibrate it correctly over the entire range." HOWEVER, it would possibly be useful for the engine behind an AGC circuit. Also, who cares (I don't...) if a signal is S7, S9 or 40 over S9. I don't unless someone asks about his/her signal ¡ª which is rare. An AGC circuit would be more useful, anyway.? The label for the diagram, that it an S-Meter circuit, was the label from the Indonesian designers. I wonder if you paid notice to this. Bob ¡ª KK5R
On Wednesday, October 28, 2020, 6:56:51 PM EDT, IW4AJR Loris <lorisbollina@...> wrote:
Hello Bob
I do not agree with you, a VU-meter will never be able to give a reading that is responsive to ?V levels in the antenna, you will never be able to calibrate it correctly over the entire range of signals! if it suits you it will indicate signals from S6 or S7 upwards and in any case certainly not related to the signals in the antenna, I did it with an ILER-40 and I assure you that the withdrawal from the BF is only used to swing a needle on the indicator instrument. Not for nothing, all the rigs that are respected, take the signal in MF (directly proportional to the signal received in the antenna) and convert it in various ways.
Have you ever observed what the RSSI is out of some MF chips? (eg NE614) ... well, read the data sheet a bit and maybe you will understand what I mean by S-Meter that is useful for something!
Instead of working on various software and having two computers connect to each other and then saying that we did a DX, it would be better if we reviewed what it means is "learning and experimenting with wireless communications" and what data we exchange, don't you think?
Ciao de ?IW4AJR Loris
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You are right, Loris. If meter has a VU readings on meter face and calibrated as such, it would be accurate at one point on the meter ... per the calibration. The circuit was "borrowed" from the schematic of a radio produced in Indonesia ... and labeled as such. I put it out there for anyone who might want to play with it. Nothing more. Bob ¡ª KK5R
On Wednesday, October 28, 2020, 5:53:31 PM EDT, IW4AJR Loris <lorisbollina@...> wrote:
The circuit you show is not an S-meter, but a VU-meter, it is proportional to the quadratic law of the diodes used, quite similar to the logarithmic law of dBV (mostly referred to an impedance of a few hundred ¦¸) to l output from circuit BF, responding poorly to RF levels received in the antenna.
An S-meter is a substantially different circuit, it is proportional to precise RF levels (defined by the IARU as in the table below for the HF) at the antenna input and varies in steps of 6 dBm referred to the ?V levels on an impedance of 50¦¸.
If you want to see a needle that moves it's fine, if you want to give reports that make sense it's useless!
Regards, Loris IW4AJR.
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Right Arv ... Software is the way to go. Otherwise someone is being amazed by flashing lights and bird whistles. This is just one opinion, however. Bob ¡ª KK5R
On Wednesday, October 28, 2020, 3:12:56 PM EDT, Arv Evans <arvid.evans@...> wrote:
Bob and Jack Seems that if you are using that circuit and an ADC input in place of an analog? meter, you could use software to convert the ADC readings into VU meter,? S-meter, or anything else.? Might be a way to show Peak readings versus? Average, and even to calculate receiver input in Microvolts. Arv _._ On Wed, Oct 28, 2020 at 11:26 AM Bob Lunsford via <nocrud222=[email protected]> wrote:
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Re: Duh-oo
Everything is relative. One's S-meter reading depends on the receiver AND the antenna. One too many variables. A Volume Unit reading is based on voltage across a standard resister value. The VU reading may be more accurate but still has too many variables. Personally, I do not need an S-meter and unless someone asks me, I do not give a Signal Strength report. It means little to me when we are talking about readability. I can come up with a circuit that may warm someone's heart but my V6 does not need an S-meter. HOWEVER, the same circuit can be an operator for the AGC circuit. Old time operators used to pull the "cans" off the ears and put them over the temple to either adjust the audio level or keep excessive volume from waking them up. Been there, done that... Bob ¡ª KK5R
On Wednesday, October 28, 2020, 2:26:54 PM EDT, Jack, W8TEE via groups.io <jjpurdum@...> wrote:
My bad, it should have read: Again, I'm not an EE type, but if the metering is done off the volume control, is it really an? S meter or a VU meter??
On Wednesday, October 28, 2020, 1:26:27 PM EDT, Bob Lunsford via groups.io <nocrud222@...> wrote:
The signal off the volume control can be used as a signal source for either S-meter purposes OR a way to control an AGC circuit by causing attenuation for signals above a pre-set level. However, I learned with my G90 that there are times when the AGC should be shut off to provide maximum signal gain. Bob ¡ª KK5R
On Wednesday, October 28, 2020, 12:56:25 PM EDT, Jack, W8TEE via groups.io <jjpurdum@...> wrote:
Again, I'm not an EE type, but if the metering is done off the volume control, is it really an SWR meter or a VU meter?? Jack, W8TEE
On Wednesday, October 28, 2020, 12:49:45 PM EDT, Bob Lunsford via groups.io <nocrud222@...> wrote:
This again is offered to show an S-meter circuit borrowed from the transceiver circuit being sold from Indonesia. It is apparently attachable to the volume control and since it's in the receive system, it does not affect the transmit system. It can be "rubbered" here and there since the component values may be the best for this considering that they are what is available to the builders in Indonesia, the FET and transistor can work equally well when using substitutes. Attaching to the high end of the uBITX's volume control and making the 47K variable in the circuit below a set resistor for calibration purposes results in making this a usable circuit. The meter, of course, can be substituted with an LED barcode circuit OR merely provide a source signal for an on-screen display of received signal level. The circuit as shown is relatively simple, however. Bob ¡ª KKR
On Wednesday, October 28, 2020, 7:06:58 AM EDT, IW4AJR Loris <lorisbollina@...> wrote:
On the CCARC (Carroll County Amateur Radio Club, Inc.) website I found a very interesting article on automatic gain control that is worth reading!
Without many frills Carol makes us understand that an AGC (automatic gain control) on the IF of the uBITX, due to the nature of the amps used (bidirectional), is very complex to make at this level of the circuit ...
therefore ? ...
Much better and less invasive to act directly on the volume control, implementing a simple but effective automatic volume control (AVC)!
Think man ... think ...
A little less software and a little more electronic experimentation and, with much less effort, very complex problems can be solved!
Think man ... think !
Greetings to all, Loris IW4AJR
-- Jack, W8TEE -- Jack, W8TEE |
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Jack, W8TEE
Agree. Jack, W8TEE
On Wednesday, October 28, 2020, 3:12:56 PM EDT, Arv Evans <arvid.evans@...> wrote:
Bob and Jack Seems that if you are using that circuit and an ADC input in place of an analog? meter, you could use software to convert the ADC readings into VU meter,? S-meter, or anything else.? Might be a way to show Peak readings versus? Average, and even to calculate receiver input in Microvolts. Arv _._ On Wed, Oct 28, 2020 at 11:26 AM Bob Lunsford via <nocrud222=[email protected]> wrote:
--
Jack, W8TEE |
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Bob and Jack Seems that if you are using that circuit and an ADC input in place of an analog? meter, you could use software to convert the ADC readings into VU meter,? S-meter, or anything else.? Might be a way to show Peak readings versus? Average, and even to calculate receiver input in Microvolts. Arv _._ On Wed, Oct 28, 2020 at 11:26 AM Bob Lunsford via <nocrud222=[email protected]> wrote:
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Duh-oo
Jack, W8TEE
My bad, it should have read: Again, I'm not an EE type, but if the metering is done off the volume control, is it really an? S meter or a VU meter??
On Wednesday, October 28, 2020, 1:26:27 PM EDT, Bob Lunsford via groups.io <nocrud222@...> wrote:
The signal off the volume control can be used as a signal source for either S-meter purposes OR a way to control an AGC circuit by causing attenuation for signals above a pre-set level. However, I learned with my G90 that there are times when the AGC should be shut off to provide maximum signal gain. Bob ¡ª KK5R
On Wednesday, October 28, 2020, 12:56:25 PM EDT, Jack, W8TEE via groups.io <jjpurdum@...> wrote:
Again, I'm not an EE type, but if the metering is done off the volume control, is it really an SWR meter or a VU meter?? Jack, W8TEE
On Wednesday, October 28, 2020, 12:49:45 PM EDT, Bob Lunsford via groups.io <nocrud222@...> wrote:
This again is offered to show an S-meter circuit borrowed from the transceiver circuit being sold from Indonesia. It is apparently attachable to the volume control and since it's in the receive system, it does not affect the transmit system. It can be "rubbered" here and there since the component values may be the best for this considering that they are what is available to the builders in Indonesia, the FET and transistor can work equally well when using substitutes. Attaching to the high end of the uBITX's volume control and making the 47K variable in the circuit below a set resistor for calibration purposes results in making this a usable circuit. The meter, of course, can be substituted with an LED barcode circuit OR merely provide a source signal for an on-screen display of received signal level. The circuit as shown is relatively simple, however. Bob ¡ª KKR
On Wednesday, October 28, 2020, 7:06:58 AM EDT, IW4AJR Loris <lorisbollina@...> wrote:
On the CCARC (Carroll County Amateur Radio Club, Inc.) website I found a very interesting article on automatic gain control that is worth reading!
Without many frills Carol makes us understand that an AGC (automatic gain control) on the IF of the uBITX, due to the nature of the amps used (bidirectional), is very complex to make at this level of the circuit ...
therefore ? ...
Much better and less invasive to act directly on the volume control, implementing a simple but effective automatic volume control (AVC)!
Think man ... think ...
A little less software and a little more electronic experimentation and, with much less effort, very complex problems can be solved!
Think man ... think !
Greetings to all, Loris IW4AJR
-- Jack, W8TEE -- Jack, W8TEE |
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Re: No output power on
#v3
The only "pop and smoke" experience I ever had was when I bought a Swan 350 at a hamfest that was a "Sure, it's working!" radio so when I plugged it in at home, it sounded like a shotgun shell going off. The power supply caps had to be replaced. Nothing like a PnS experience to add to one's bank of experience. Bob ¡ª KK5R
On Wednesday, October 28, 2020, 1:31:29 PM EDT, _Dave_ AD0B <davesters@...> wrote:
Hi Evan, The comment was not directed at you but as information for the poster of the statement.? I don't think that I can a recall a single instance where a pop and smoke left my equipment working. -- 73 Dave |
Raj vu2zap
Bob Lunsford