Re: When do you use fast AGC?
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Like Ron AC7AC , as a marine commercial op, I always used the RF
gain control (no AGC) when running traffic on ships, but this is a totally different situation for example, if you are in a CW contest when signals in a pile-up vary from barely audible to ear-shattering. Fast AGC is mandatory. Can't comment on SSB - rarely use it, and never in contests. Showing my bias - we have several IcoYaeWood radios in our Multi contest station, and they all have their advantages but the K2 has a bomb-proof receiver and does not de-sense the other radios with white noise, even when it's driving an amp to 500 watts ouput - no clicks, no spurs. Only disadvantages are that it looks too small to be that good, and it moves if you push the buttons too hard. Only crazy contesters would think like that. For casual operating, I would use fast AGC. The only time I need to turn the K2 AGC off is to use a noise bridge. 73, Ken ZL1AIH _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: Re: When do you use fast AGC?
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I guess I'm the oddball. I run CW on AGC slow 90% of the time. Turning off AGC disables the S-meter and watching the S-meter is part of my enjoyment of the hobby (there, I said it)! If the signal is coming over the north pole and is fluttering rapidly, I'll go to Fast AGC. Using fast AGC increases the background noise as the receiver recovers gain between the various CW elements. Running slow AGC holds the gain down (and therefore the background noise) between elements, letters and possibly words. I often use the RF gain but I leave the AGC on. I'll back off the RF gain so the S-meter deflects up only when the signal fades up to max. If the signal is fluctuating from S7 to S9, I'll back the RF gain down to where the meter stays around S8. This is basically the same as turning AGC off but the AGC is still there to handle unexpected strong signals. - Keith KD1E - - K2 5411 - _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: Re: When do you use fast AGC?
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Ha, ha!! Don't feel bad Keith. Watching an S-meter is definitely part of the
'shortwave mystique'. I knew I had "arrived" when in the 1950s I acquired an HRO-5 that featured a beautiful back-lit S-meter. That receiver required the AGC be turned off in CW mode because the BFO would trigger the AGC and desense the receiver, but I had tons of AM signals in the Ham bands and outside to watch the S-meter respond to. Shoot, the Hallicrafter's S-76 receiver featured an S-meter that must have been over 4" across, using up as much space on the front panel as the whole tuning dial. I think it's not been an issue for me with the K2 because I've never been able to look at a bargraph or even a computer image of a meter on a screen as a real "meter". They just don't provide the same feeling as the old "wiggly needle" d'Arsonval meters. Still, top o' the line receivers like the K2 feature I.F. AGC that is far more versatile than the receivers with those huge S-meters. And maybe the piddlin' little bargraph puts the real value of an "S" reading in perspective <G>. Ron AC7AC -----Original Message----- I guess I'm the oddball. I run CW on AGC slow 90% of the time. Turning off AGC disables the S-meter and watching the S-meter is part of my enjoyment of the hobby (there, I said it)! If the signal is coming over the north pole and is fluttering rapidly, I'll go to Fast AGC. Using fast AGC increases the background noise as the receiver recovers gain between the various CW elements. Running slow AGC holds the gain down (and therefore the background noise) between elements, letters and possibly words. I often use the RF gain but I leave the AGC on. I'll back off the RF gain so the S-meter deflects up only when the signal fades up to max. If the signal is fluctuating from S7 to S9, I'll back the RF gain down to where the meter stays around S8. This is basically the same as turning AGC off but the AGC is still there to handle unexpected strong signals. - Keith KD1E - - K2 5411 - _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: Re: When do you use fast AGC?
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-----Original Message----- Still, top o' the line receivers like the K2 feature I.F. AGC that is far more versatile than the receivers with those huge S-meters. And maybe the piddlin' little bargraph puts the real value of an "S" reading in perspective <G>. Ron AC7AC -------------------------- Yea, I have 2 rigs, the K2 and the TS-830s. I'm not sure which I like better but for now I've been on the 830 most of the time. After last night's QSOs in which I was just struggling to copy signals, I'm about ready to switch back to the K2 for a while. Bar-graph S-meters, yuck! I hear you about putting the real value of an "S" reading in perspective, but I still want to watch that meter move! I'm still wondering how hard it would be to hook that LDG meter up to the K2 to give me a real analog S-meter! One of the things I've noticed about the K2's AGC is that it doesn't seem to boost gain as high as my 830s. In other words, it will allow background noise to remain in the background. I need to spend some more time under the cans with both rigs to get a better long-term feel for them. - Keith KD1E - - K2 5411 - _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by zl1aih-2
I remember my old SX-96 that had an S-meter that totally dominated the front panel of the receiver. As I recall it went to S9+80 dB or something equally ridiculous. It was also incredibly generous so watching the needle fly back and forth could be very distracting!
Doug,W6JD -------------- Original message -------------- From: "Darwin, Keith" <[hidden email]> > > > -----Original Message----- > > Still, top o' the line receivers like the K2 feature I.F. AGC that is > far more versatile than the receivers with those huge S-meters. And > maybe the piddlin' little bargraph puts the real value of an "S" reading > in perspective . > > Ron AC7AC > -------------------------- > > > Yea, I have 2 rigs, the K2 and the TS-830s. I'm not sure which I like > better but for now I've been on the 830 most of the time. After last > night's QSOs in which I was just struggling to copy signals, I'm about > ready to switch back to the K2 for a while. > > Bar-graph S-meters, yuck! I hear you about putting the real value of an > "S" reading in perspective, but I still want to watch that meter move! > > I'm still wondering how hard it would be to hook that LDG meter up to > the K2 to give me a real analog S-meter! > > One of the things I've noticed about the K2's AGC is that it doesn't > seem to boost gain as high as my 830s. In other words, it will allow > background noise to remain in the background. I need to spend some more > time under the cans with both rigs to get a better long-term feel for > them. > > - Keith KD1E - > - K2 5411 - > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Darwin, Keith
Many [very many :-) ] years ago as a coastal marine op, we *always* ran
the AF gain wide open and used the RF gain only. As I remember it, the main reason was that with the RF gain up full, there often wasn't enough BFO injection on strong signals in the receivers of that era. It ran up the S-meter of course, but in commercial practice, a QSA reply did not require an S-meter anyway. We also wore the cans forward of our ears to protect somewhat against very strong unexpected signals. Electro-magnetic cans with the steel diaphragm could emit some raucous sounds when overdriven. I wonder sometimes what those now-expired OT's who banged the 16-yr old kid around would think if they could try out my K2? FWIW, I run my K2 on fast-AGC on CW which is essentially all the time. Fred K6DGW _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
When S-Meters are Useful (WAS: When do you use fast AGC?)
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In reply to this post by Darwin, Keith
Keith KD1E wrote:
I'm still wondering how hard it would be to hook that LDG meter up to the K2 to give me a real analog S-meter! One of the things I've noticed about the K2's AGC is that it doesn't seem to boost gain as high as my 830s. In other words, it will allow background noise to remain in the background. I need to spend some more time under the cans with both rigs to get a better long-term feel for them. ---------------------------------- The K2, like many modern receivers, has very limited "RF gain control" range compared to receivers of years ago that had multiple I.F and R.F amplifier stages active on all bands. In the K2, the only stage controlled by the AGC or the RF gain control is the I.F. amplifier. Like many modern receivers, the K2's front end or "RF" gain is manually controlled by switching a preamp or an attenuator in or out. That gives you another 24 dB control over the total gain, but that's not controlled by either the RF gain control or the AGC. The K2 uses an MC1350 I.C. It has a maximum gain control range of perhaps 60 dB. Now, in rigs like the K2 with their excellent dynamic range that's enough when it's coupled with manual control of the front end gain but, as you noticed, it's not enough to silence the receiver when it's turned all the way down, particularly if you have the preamplifier switched on. I agree with your lusting for a real meter on the K2! I've considered doing exactly that many times. It should be straightforward to do. The MC1350 uses an analog d-c voltage to control its gain. The voltage runs, typically, from +5 to +7 vdc to vary the gain of the MC1350 over its range. That voltage is applied to pin 5 of the I.C. There are times when an S-meter with good resolution is handy for more than just having fun watching it jump around. Comparative signal reports, for example. But it takes a meter than can be read with some accuracy. An S-meter, even if it's not calibrated to any particular standard, coupled with a step attenuator like the Elecraft AT1 at the receiver antenna input can provide very useful checks. When the other station makes a change, you note the change in the "S-meter" reading, then switch attenuation in or out to bring the meter reading back to the original level. Then you know the exact effect of the change in decibels. Once you know the difference in dB the signal has changed, it's easy to equate that to the change in "apparent power". For example, if a change raises the level of a signal such that you have to switch in 4 dB on the AT1 to bring the S-meter back to the same reading, you know that the change had the same effect as if the other station had raised his transmitter power 2.5 times, say from 5 to 12.5 watts or from 100 to 250 watts. That procedure works equally well for helping someone else understand the effects of change at their station or for doing A/B comparisons of two antennas at your own station while listening to signals on the air. Recognizing that a lot of folks don't like poking at calculators, the AT1 manual even includes a look-up table where you simple find the dB of attenuation changed and next to it is the value to either multiply or divide the original value by to see the change in watts, volts or amperes. A suitable interface using a simple op-amp circuit to prevent loading the AGC line in the K2, coupled with an adjustable offset to zero the meter with the maximum gain voltage applied to the MC1350 should drive just about any meter movement you can think of One of these days I'll get around to it. In the meantime, I'll continue to do it the "hard way" and carefully adjust the K2 so I'm certain it is not overloaded, turn the AGC OFF so the audio output accurately follows any change in signal level, and monitor the audio output at the headphone or speaker jack. But that loses all the "pizzazz" of the big S-meter! Ron AC7AC -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Darwin, Keith Sent: Monday, October 16, 2006 12:13 PM To: [hidden email] Subject: RE: [Elecraft] Re: When do you use fast AGC? -----Original Message----- Still, top o' the line receivers like the K2 feature I.F. AGC that is far more versatile than the receivers with those huge S-meters. And maybe the piddlin' little bargraph puts the real value of an "S" reading in perspective <G>. Ron AC7AC -------------------------- Yea, I have 2 rigs, the K2 and the TS-830s. I'm not sure which I like better but for now I've been on the 830 most of the time. After last night's QSOs in which I was just struggling to copy signals, I'm about ready to switch back to the K2 for a while. Bar-graph S-meters, yuck! I hear you about putting the real value of an "S" reading in perspective, but I still want to watch that meter move! I'm still wondering how hard it would be to hook that LDG meter up to the K2 to give me a real analog S-meter! One of the things I've noticed about the K2's AGC is that it doesn't seem to boost gain as high as my 830s. In other words, it will allow background noise to remain in the background. I need to spend some more time under the cans with both rigs to get a better long-term feel for them. - Keith KD1E - - K2 5411 - _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: When S-Meters are Useful (WAS: When do you use fast AGC?)
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Ron and all,
For anyone contemplating connecting an analog S-meter to the K2, A better connection point for the takeoff AGC voltage is Control Board U2 pin 1. That point should have a voltage relating to the signal strength whereas the AGC input into the MC1350 is a current based rather than voltage - the only difference between the two points is a resistor (R4), but still using U2 pin 1 will not have potentila adverse effects on the normal K2 AGC operation. I don't know what the voltage swing relative to S-meter readings are (that calculation is currently done inside the firmware), but those interested can experiment a bit. An op amp or two should be able to scale whatever AGC voltage is developed at U2 pin 1 to whatever your meter wants. 73, Don W3FPR > -----Original Message----- > ... snip > The K2 uses an MC1350 I.C. It has a maximum gain control range of > perhaps 60 > dB. Now, in rigs like the K2 with their excellent dynamic range that's > enough when it's coupled with manual control of the front end gain but, as > you noticed, it's not enough to silence the receiver when it's turned all > the way down, particularly if you have the preamplifier switched on. > > I agree with your lusting for a real meter on the K2! I've > considered doing > exactly that many times. It should be straightforward to do. The > MC1350 uses > an analog d-c voltage to control its gain. The voltage runs, > typically, from > +5 to +7 vdc to vary the gain of the MC1350 over its range. That > voltage is > applied to pin 5 of the I.C. > ... snip > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: When S-Meters are Useful (WAS: When do you use fast AGC?)
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Don, W3FPR wrote:
For anyone contemplating connecting an analog S-meter to the K2, A better connection point for the takeoff AGC voltage is Control Board U2 pin 1. That point should have a voltage relating to the signal strength whereas the AGC input into the MC1350 is a current based rather than voltage - the only difference between the two points is a resistor (R4), but still using U2 pin 1 will not have potentila adverse effects on the normal K2 AGC operation. -------------------------- Quite right. It's been several years since I last used that I.C. in a receiver I.F. design. While Motorola specifies a control voltage range 5 VDC to almost 7 VDC, they specify that the voltage must be applied to the pin through a recommended 5.6K resistor. Elecraft used a 5.1k resistor for that purpose, R4. So the metering circuit should be connected to the output of U2A rather than directly to the MC1350. Getting back to Keith's original comments, that receiver I designed - a single-conversion superhet using the MC1350 for an I.F. - was where much of my attitude toward AGC systems was probably created. I was playing with a variety of AGC systems including some "hang" AGC circuits, but the range of AGC gain control using a single MC1350 wasn't great enough to keep me happy. I was playing around with using PIN diodes controlled by the AGC to switch in fixed attenuators in the front end for greater range. One day, while I was sitting there looking at the schematic for an AGC system whose complexity rivaled the rest of the receiver, it occurred to me that I was doing all of that only to make an S-meter needle wiggle about! I think Wayne came up with an excellent design that balances complexity with effectiveness. That's the difference between one who tinkers and an engineer <G>. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Ron D'Eau Claire-2
All,
Is there any way to get the LDG Electronics FT Meter (S, Watt, VDC, ALC, SWR) to work directly with the K2? That would look good mounted in an EC2 box along with a powered speaker and other accessories. 73, Henry - K4TMC _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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