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#1
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On Mon, 24 Mar 2008 04:32:39 -0700 (PDT), Artem
wrote: I've observed that, and I have observed it is not enough from your photo - if you still have self-oscillation. Your pictures do not reveal any choking of the RF Out cable. It's inside. Nearby BNC socket. Which defeats the choking. As for the diagonal arm for "ground." This is fine insofar as it being placed in the electrical middle of the antenna loop (a ground), but all this rat's nest of wiring throws the concept of balance out the window. I think that some disbalance should compensate differencial amplifier on transistors. That makes no sense whatever. another invitation to problems when a 9V battery would solve that too. Local power would discard the need for the ground Yes. But FETs draw more that 10ma each. That is trivial. However, you can bias for less because you don't need that much drain current. coming from the loop's perimeter, eliminate unnecessary AGC, reduce the complexity of choking, lower gain (it obviously has too much), and give you only one coax coming from the antenna. Cable length is not problem. I'm living in apartment. I can put antenna outside the window. But not on the roof. I can make power supply over coax cable. I can put Atmega8 (en example) to amplifier and add DACs for operate varicaps, AGC. I can add rectifier and filter for detect self-oscillation and automatics reduce AGC. But it's not necessary. Sounds like a lot of unnecessary complexity. The one thing you repeat is varicaps, but I don't see them. 73's Richard Clark, KB7QHC |
#2
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On Mar 24, 5:45 pm, Richard Clark wrote:
As for the diagonal arm for "ground." This is fine insofar as it being placed in the electrical middle of the antenna loop (a ground), but all this rat's nest of wiring throws the concept of balance out the window. I think that some disbalance should compensate differencial amplifier on transistors. That makes no sense whatever. Disbalance mean in-phase signal on gate 1 FETs. differencial will not amplify this signal. Sounds like a lot of unnecessary complexity. The one thing you repeat is varicaps, but I don't see them. I have. I just did now how them because this is trivial. |
#3
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On Mar 24, 4:59 pm, Artem wrote:
I just did now how them because this is trivial. I did not show varicaps because this is trivial. Sorry. |
#4
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On Mar 24, 4:59 pm, Artem wrote:
I just did now how them because this is trivial. I did not show varicaps because this is trivial. Sorry. |
#5
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On Mar 24, 4:59 pm, Artem wrote:
I just did now how them because this is trivial. I did not show varicaps because this is trivial. Sorry. |
#6
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On Mon, 24 Mar 2008 07:59:50 -0700 (PDT), Artem
wrote: I think that some disbalance should compensate differencial amplifier on transistors. That makes no sense whatever. Disbalance mean in-phase signal on gate 1 FETs. differencial will not amplify this signal. This is still a strain in language as you have done nothing to describe what the "compensation" is for. The circuit of your schematic is fully differential in a bridge configuration, so saying it will not amplify still makes no sense. To offer a deliberate imbalance to a balanced circuit gives rise to astability which is the first hallmark of oscillation - especially in an amplifier with too much gain, and too much current drain - or a lockdown. I get every impression that this bridge configuration arrived from some sense of "ground" that then drove the need for the cross piece to the midpoint of the loop. That point is "ground", but only as an electrical neutral to the loop. It carries no other "ground" distinction and you could have as easily built a single MOSFET amplifier rather than a bridge configuration. A split shield around the loop (or integrating it into the design) would have simplified AGC and control lines too. You tried to incorporate some of the split shield design into this when you enclosed the amplifier and made a socket connection, but you defeated the benefit of the choke at the same time with a zero net gain (the choke, as built, has no use). Sounds like a lot of unnecessary complexity. The one thing you repeat is varicaps, but I don't see them. I have. I just did now how them because this is trivial. They are not shown in your schematic. I don't see them in your photos. Making them operational is adding yet more lines, although I can see they would be necessary for your purposes. Providing the decoupled varicap bias into a balanced circuit is not trivial at all, and offers the prospects of returning to that self oscillation. There will be something like half a dozen components for that alone. HOWEVER, this is all beside the point unless your design breaks into oscillation again. You haven't informed us how you cured that since you announced you had solve all your problems. 73's Richard Clark, KB7QHC |
#7
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On Mar 24, 10:02 pm, Richard Clark wrote:
On Mon, 24 Mar 2008 07:59:50 -0700 (PDT), Artem wrote: I think that some disbalance should compensate differencial amplifier on transistors. That makes no sense whatever. Disbalance mean in-phase signal on gate 1 FETs. differencial will not amplify this signal. This is still a strain in language as you have done nothing to describe what the "compensation" is for. The circuit of your schematic is fully differential in a bridge configuration, so saying it will not amplify still makes no sense. To offer a deliberate It will not amplify signal in-phase signal. It's same like differential amplifier. I get every impression that this bridge configuration arrived from some sense of "ground" that then drove the need for the cross piece to the midpoint of the loop. That point is "ground", but only as an electrical neutral to the loop. It carries no other "ground" Yes. It's "Ground" only for bridge amplifier. distinction and you could have as easily built a single MOSFET amplifier rather than a bridge configuration. A split shield around It's more difficult for me. It's looks more simply for me to build fully symmetrical amplifier. the loop (or integrating it into the design) would have simplified AGC and control lines too. You tried to incorporate some of the split shield design into this when you enclosed the amplifier and made a socket connection, but you defeated the benefit of the choke at the same time with a zero net gain (the choke, as built, has no use). I have. Sounds like a lot of unnecessary complexity. The one thing you repeat is varicaps, but I don't see them. I have. I just did now how them because this is trivial. They are not shown in your schematic. I don't see them in your photos. Making them operational is adding yet more lines, although I can see they would be necessary for your purposes. http://img245.imageshack.us/my.php?image=d3du5.jpg |
#8
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On Mon, 24 Mar 2008 15:40:53 -0700 (PDT), Artem
wrote: This is still a strain in language as you have done nothing to describe what the "compensation" is for. The circuit of your schematic is fully differential in a bridge configuration, so saying it will not amplify still makes no sense. To offer a deliberate It will not amplify signal in-phase signal. It's same like differential amplifier. This still makes no sense. You have not described what you are "compensating" for, and differential amplifiers amplify without distinction to "in-phase" or "out-of-phase." If it did, you are not using the right topology because you are using operational amplifier terminology - the circuit is not an operational amplifier, even by discrete components. They are not shown in your schematic. I don't see them in your photos. Making them operational is adding yet more lines, although I can see they would be necessary for your purposes. http://img245.imageshack.us/my.php?image=d3du5.jpg Nice close-up. Choking of some of the lines seems OK, but not the coax. So, now where is the schematic of the biasing for these varicaps? If those two clear insulation lines are going to the loop, it is going to be hard to apply DC to a dead short - or does that black shroud cover more than the varicaps? 73's Richard Clark, KB7QHC |
#9
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On Mar 25, 9:33 pm, Richard Clark wrote:
On Mon, 24 Mar 2008 15:40:53 -0700 (PDT), Artem wrote: This is still a strain in language as you have done nothing to describe what the "compensation" is for. The circuit of your schematic is fully differential in a bridge configuration, so saying it will not amplify still makes no sense. To offer a deliberate It will not amplify signal in-phase signal. It's same like differential amplifier. This still makes no sense. You have not described what you are "compensating" for, and differential amplifiers amplify without distinction to "in-phase" or "out-of-phase." If it did, you are not using the right topology because you are using operational amplifier terminology - the circuit is not an operational amplifier, even by discrete components. They are not shown in your schematic. I don't see them in your photos. Making them operational is adding yet more lines, although I can see they would be necessary for your purposes. http://img245.imageshack.us/my.php?image=d3du5.jpg Nice close-up. Choking of some of the lines seems OK, but not the coax. http://img370.imageshack.us/my.php?image=d2eb0.jpg Could you find in this picture choke? So, now where is the schematic of the biasing for these varicaps? If those two clear insulation lines are going to the loop, It's lines from resonance loop to amplifier. it is going to be hard to apply DC to a dead short - or does that black shroud cover more than the varicaps? Now my Antenna in broken. I will fix my antenna mad make a web for schematics, software for calculation? etc. PS: Could anyone know, What I can receive in QRSS, 7 MHz in Europe on this http://www.radiointel.com/review-degende1103.htm receiver? |
#10
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On Tue, 25 Mar 2008 13:55:16 -0700 (PDT), Artem
wrote: Nice close-up. Choking of some of the lines seems OK, but not the coax. http://img370.imageshack.us/my.php?image=d2eb0.jpg Could you find in this picture choke? What material is used in the ferrite? So, now where is the schematic of the biasing for these varicaps? If those two clear insulation lines are going to the loop, It's lines from resonance loop to amplifier. Does this mean the varicaps are across the loop? If so: it is going to be hard to apply DC to a dead short - or does that black shroud cover more than the varicaps? Now my Antenna in broken. I will fix my antenna mad make a web for schematics, software for calculation? etc. You've done it by parts already, so, sure. 73's Richard Clark, KB7QHC |
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