Re: [Elecraft] Question from a newbie noise blanker
There are two different types of night vision. Light amplification and thermal imaging. Since the power company used IR to find the problem, the devices used were likely thermal imaging devices. Light amplifiers must have some light to work, and I don't believe they pick up thermal emissions. Many consumer devices are light amplifiers. David Wilburn [EMAIL PROTECTED] K4DGW K2 #5982 Leigh L Klotz, Jr. wrote: Fred, Was this at night? Do you think consumer grade ones would work? Tnx es 73, Leigh/WA5ZNU On Mon, 12 Mar 2007 11:58 am, Fred Jensen wrote: Night vision goggles work quite well in some cases. I mentioned it to a friend in the Guard and the 1st Sgt at the local armory decided to have a short training session. The troops spotted the two perpetrator insulators within 2 mins just by looking around. PGE came out with their IR device in about a week, and it was fixed tFred K6DGW ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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] Re:EQP and Nets
On 12 Mar 2007 at 4:04, [EMAIL PROTECTED] wrote: Nice work, Kevin. This is about how many Q's I had in all of EQP this year :) I didn't get round to looking into EQP at all this year. The main reason is of course that those of us in the UK (and VE land) were participating in BERU (or the Commonwealth Contest). Nice bits of DX around and an excellent opportunity to get a few VK and ZL stations in the log. It also clashes with the AGCW QRP contest, another one I would have liked to have a look into but BERU was more interesting. As to the nets, these are at an inappropriate time for those of us over here and not at the best time for USA propagation. Maybe you should take note of these clashes in future years. 73 Dave G3YMC http://www.davesergeant.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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] Question from a newbie
I wonder if those that see no results from the KNB2 have forgotten to remove a jumper or something? I could not operate without the KNB2. I have line noise that runs 20 dB over s9 at my location on 80 meters (almost as bad on 60, 40, 30, and 20) without the KNB2. Operations of any kind would be impractical. My Drake 2b receiver can only pick up the strongest stations. Message: 7 Date: Sun, 11 Mar 2007 06:42:55 -0700 (PDT) From: Fred (FL) [EMAIL PROTECTED] Subject: RE: [Elecraft] Question from a newbie To: elecraft@mailman.qth.net Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=iso-8859-1 I built my K2 #54xx in May 06. Built the KNB2 Noise Blanker. Then found it never really seemed to work on any noise! One day, 4 cement trucks 2 large pickups sat like 30 feet from my shack - all running, all working. The KNB2 did nothing to remove any of that man-made noise. Also it doesn't work on any band noise - that I ever found. I even got a 2nd KNB2, from Elecraft - and it didn't work either? The K2 itself - after build - operated true to all specs, calibrations, alignments beautifully. I've since felt, the KNB2 is a design job left to be re-done, by some Elecraft designer, when they get around to it. The IC-7000's Noise Reduction and Noise Blanker circuitry - amazingly almost always reduces most band noises, real or imaginary, dramatically. Maybe in the K3? Fred N3CSY -- -bz- pardon my infinite ignorance. The set-of-things-I-do-not-know is infinite. 73 de N5BZ K2/100 # 5884 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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] EQP report
All, I haven't seen many reports back from the EQP. How did you do? I had #5670 operating park bench portable with a random wire in the trees. While doing a good job promoting amateur radio, I did not make any EQP QSOs! I was able to make several Qs with stns in the OKQP so I know I was getting out ok. Where was everyone? Back at the apartment, I managed to make one EQP contact with K5WA in TX but he was the only one I heard calling. I just have to say the internal ATU, battery, and DSP unit work great and add another dimension to an already awesome rig. 73, KA2P/4 P.S. I am at the controls of the Pentagon club station, K4AF using 20 CW from approximately 1600-1700z M-R. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] Question from a newbie
Hi Bob: I wonder if those that see no results from the KNB2 have forgotten to remove a jumper or something? I could not operate without the KNB2. I have line noise that runs 20 dB over s9 at my location on 80 meters (almost as bad on 60, 40, 30, and 20) without the KNB2. Operations of any kind would be impractical. Yesterday morning, I had some pretty horrendous line noise, which the KNB2 completely eliminated... then, in the afternoon I had what appeared to be the same noise (at least it SOUNDED the same to my ears), but the KNB2 couldn't do much at all. Same band, same RX settings, same antenna (and pointed in the same direction), same apparent direction of the noise, but something(!) had changed, to the point that the NB couldn't blank it adequately. Of course, the NB in my TS-950SD couldn't/didn't touch it either! But I agree that the KNB2, when it 'sees' an appropriate noise type, is WONDERFUL. 73, Tom N0SS ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] Question from a newbie noise blanker
with the FCC becoming more and more deaf to our pleas to fix broken powerlines and the like ; wouldn't it be great for somebody ( hello Larry LP Jack PAN) to make a NB widget hat was tunable width /depth and whatever parameters are needed...maybe using his PAN box to examine the junk ??? I know that the scopes on icoms can tell a bunch abt the pulse junk. AND the NB in the K2 still amazes me ... how well it does. bill At 07:17 AM 3/12/2007, Tom Hammond wrote: Hi Bob: ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] AGC Independent S-Meter?
What I was referring to is the common circuits used in most receivers of olden days. (Tube era) Most receivers depended on the AGC level for signal strength indication. At best a large approximation and some wishful thinking. Not only do 50 microvolt (if that's your standard) S-9 levels vary from band to band, but also at the high and low ends of the bands as well. I have dealt with Field strength meters where the S meter actually indicates microvolts per meter, and they go thru some rather careful procedures to make sure the receiver's gain is the same wherever the measurements are made. I've never used the H-P instruments that are popular on the 500 Khz experimental band at present. Anyway, the short of it is one can't depend on an S meter on a 'communications receiver' to really be accurate. No matter who makes the receiver generally. Unless it is some special purpose device especially made for measuring the input levels. One of the silliest ideas I have ever seen was when Bill Halligan's folks put that HUGE 4-1/2 S meter on the S-76 when they came out with it. I personally thought that they'd have done better if they had just jeft the loudspeaker there and offered an external S meter. The S-76 was a big improvement over the old S-40, but why that big meter? Also calibrated in microvolts by the way! 73, Sandy W5TVW - Original Message - From: Don Wilhelm [EMAIL PROTECTED] To: Sandy W5TVW [EMAIL PROTECTED]; [EMAIL PROTECTED]; elecraft@mailman.qth.net Sent: Sunday, March 11, 2007 11:41 PM Subject: RE: [Elecraft] AGC Independent S-Meter? Sandy, As far as I know, there is no direct relationship between the strength of a signal and receiver AGC. My AD8307 power meter can measure signal strengths directly off an antenna if called upon to do that, it goes down to -80 dBm (about S-8) with no other amplification. This is strictly a power meter, no AGC implied or implemented - the output is the base 10 logarithm of the input signal. All one must do is measure the strength of the received signal to drive an S-meter - but it must be calibrated if it is used as an absolute measurement device. Yes, the implementation in most receivers derive the AGC voltage from the same signal strength measurement circuits, so things get a bit mixed up, and often appear as a 'chicken and egg' situation. 73, Don W3FPR -Original Message- Circuitrywise, an AGC/AVC free S-meter is an oxymoron! Can't have one without the other. (snip) 73, Sandy W5TVW -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 268.18.8/718 - Release Date: 3/11/2007 9:27 AM -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 268.18.8/718 - Release Date: 3/11/2007 9:27 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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] K2-100 Xmit Problem
I'd appreciate suggestions that might help me isolate a problem that I believe to be in the KPA100. Receive is fine on all bands. My K2/100 has been working wonderfully for three years. Now, suddenly, a problem appears on both on low and high power settings on 160-10mtrs. K2 Display shows, high current (briefly), high swr and much below requested power even when feeding a 50 ohm dummy load. Basic K2 checks out OK on RX and TX on all bands with QRP top installed. The only section shown in the KPA100 schematic that would appear to alter the desired rf flow in both low and high power settings would be the SWR Bridge. No burned components visible so far. If the SWR section is a likely candidate, would it be correct to suspect first D16 and D17? Or could the T-R switch section be at fault based on some of the anomalous voltage readings present. Have completed voltage reading of D1-D14 and Q1-Q12 and U1-U7. Q4 and Q5 show lower than expected readings on TX. Other readings of note: D7 -20 volts Anode and +19 volts Cathode, and D8 20 volts Anode. Any suggestions for proceeding would be appreciated, 73, Jack, KT6JS ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] EQP report
40m conditions were not good here during the weekend except for European QSOs and only two EQP callers heard briefly on 40m from the States, none from Europe. A fair number of Stateside stations heard working the OK QP on 40m but only out to Arizona / Texas, nothing from the West Coast on either short or long path. A sick antenna did not help either. 73, Geoff GM4ESD - Original Message - From: Kirk Brown [EMAIL PROTECTED] To: elecraft@mailman.qth.net Sent: Monday, March 12, 2007 10:54 AM Subject: [Elecraft] EQP report All, I haven't seen many reports back from the EQP. How did you do? I had #5670 operating park bench portable with a random wire in the trees. While doing a good job promoting amateur radio, I did not make any EQP QSOs! snip ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] K2-100 Xmit Problem
Jack, Since the problem shows up on both low and high power, you are correct in believing the problem may be with the wattmeter, but do some preliminary chaecks first. The only other things that could be wrong are the Low Pass Filters (unlikely if it worked for 3 years) or the relays not operating. Both Hi Cur messages and High SWR indications may be the result of a non-operating relay. Switch to low power and check continuity between the J1 'RF IN' point and the center of the SO-239 - if that shows open, there is a relay or LPF problem to be found. Sometimes you can have receive through the path without full continuity - you just didn't notice the signal reduction - the continuity checks are quick and easy. Then check the voltage at U1 pin 1 - if the voltage is near 5 volts, then the relays should be getting control voltages to them. If there is not 5 volts, check the regulator. If the checks above indicate all is well, then yes the wattmeter is the most likely to blame. Other than the diodes in the wattmeter, U5 and U6 could be suspects as could Q10 and Q11. 73, Don W3FPR -Original Message- I'd appreciate suggestions that might help me isolate a problem that I believe to be in the KPA100. Receive is fine on all bands. My K2/100 has been working wonderfully for three years. Now, suddenly, a problem appears on both on low and high power settings on 160-10mtrs. K2 Display shows, high current (briefly), high swr and much below requested power even when feeding a 50 ohm dummy load. Basic K2 checks out OK on RX and TX on all bands with QRP top installed. The only section shown in the KPA100 schematic that would appear to alter the desired rf flow in both low and high power settings would be the SWR Bridge. No burned components visible so far. If the SWR section is a likely candidate, would it be correct to suspect first D16 and D17? Or could the T-R switch section be at fault based on some of the anomalous voltage readings present. Have completed voltage reading of D1-D14 and Q1-Q12 and U1-U7. Q4 and Q5 show lower than expected readings on TX. Other readings of note: D7 -20 volts Anode and +19 volts Cathode, and D8 20 volts Anode. Any suggestions for proceeding would be appreciated, 73, Jack, KT6JS ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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 -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 268.18.9/719 - Release Date: 3/12/2007 8:41 AM -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 268.18.9/719 - Release Date: 3/12/2007 8:41 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] Question from a newbie noise blanker
Perhaps something like the business end of an Evasive Noise Blanker? Jack's PAN box would be a great addition for hunting the rubbish. 73, Geoff GM4ESD - Original Message - From: Bill NY9H [EMAIL PROTECTED] To: Tom Hammond [EMAIL PROTECTED]; elecraft@mailman.qth.net Sent: Monday, March 12, 2007 1:38 PM Subject: Re: [Elecraft] Question from a newbie noise blanker with the FCC becoming more and more deaf to our pleas to fix broken powerlines and the like ; wouldn't it be great for somebody ( hello Larry LP Jack PAN) to make a NB widget hat was tunable width /depth and whatever parameters are needed...maybe using his PAN box to examine the junk ??? I know that the scopes on icoms can tell a bunch abt the pulse junk. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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] Another EQP Report
I just submitted my score summary to the scorekeeper. Only nine QSO's this year: four on 40m and five on 20m. Heard no EQP activity on 80m. Lots of competition from the OK QSO Party-- those guys are loud here in Missouri on 80 and 40m! W1SOC had an oustanding presence, and he was the only station I worked on two bands. I heard DK0SU and F8?, both QRP on 20m, but did not work either of them. Highlight of the contest was working Pete Hoover, W6ZH. One of these days I'll work Wayne and Eric. 73, Chuck NI0C K2 s/n 5853 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] Question from a newbie noise blanker
Actually, a swept spectrum analyzer is a very difficult machine to use for tracking noise, unless the sweep is triggered with the power line zero crossing. If you look at a pulsed waveform from broadband noise with a spectrum analyzer in free run mode (the normal operating mode) you may see some noise spikes drifting around, perhaps moving to the left on the screen; perhaps moving to the right. In the worst case, where the law of perversity applies, the spectrum analyzer's sweep rate will be such that no spikes are seen. If the noise is power line generated and hence has a rep rate of 2X line frequency, then switching the SA to line synch mode will cause the spikes to stand still. The reason for these effects is that a the spectrum of the gap-discharge noise is a line spectrum. If you hook an oscilloscope to a broadband receiver (such as the output of a Z1 buffer amplifier on a K2's post-mixer stage) and if the interference is strong enough and the scope has enough gain (or an auxiliary broadband amplifier is employed) and you set the scope trigger to the power line, you can often see the RF pulse produced each multiple arc and ringing. (The arcs are extinguished every half-cycle in the ordinary case.) If one were to go about an effective noise blanker, I believe you could do much worse than building a new version of the old Collins approach -- a broadband receiver tuned to 30-35 MHz to detect noise and then a fast gate (with suitable delay for synchronization) to clip the received signal. The tunable subtraction units have, in my experience, highly variable effectiveness. I have one here and there are some noise sources that it will work with, but far more that it does not. My experience is that most power companies will fix problems, but they are often not well equipped or staffed to locate problems. The tools of the trade include a wide band receiver in a vehicle, a hand held AM receiver in the 200 MHz band with a built-in yagi, and an ultrasonic receiver with a parabolic dish. In the vehicle, drive around listening to the noise, and keep increasing the frequency as the higher the frequency, the shorter the distance over which it can be heard. If you are fortunate, this will localize it to a few poles (in really severe cases, you can hear the noise up to 600 or 800 MHz). Then, the hand held 200 MHz AM receiver and ultrasonic receiver are used to locate the specific pole or insulator. Like most things, it takes a bit of practice and experience, but the noise sources can be found. In my case, it took Dominion Resources 10 years to find and fix the problem that made it impossible for me to operate below 10 MHz, unless it rained. It turned out to be an arcing wavetrap on a 500 KV line, at a substation perhaps 5 miles from where I live. The 500 KV line runs about 800 feet in back of my antenna and Dominion's EMI techs kept looking for the problem on the transmission line near my house. After the main EMI boss retired, one of his former technicians was promoted and started the hunt from the beginning and zeroed in on the substation. Jack K8ZOA www.cliftonlaboratories.com Geoffrey Mackenzie-Kennedy wrote: Perhaps something like the business end of an Evasive Noise Blanker? Jack's PAN box would be a great addition for hunting the rubbish. 73, Geoff GM4ESD - Original Message - From: Bill NY9H [EMAIL PROTECTED] To: Tom Hammond [EMAIL PROTECTED]; elecraft@mailman.qth.net Sent: Monday, March 12, 2007 1:38 PM Subject: Re: [Elecraft] Question from a newbie noise blanker with the FCC becoming more and more deaf to our pleas to fix broken powerlines and the like ; wouldn't it be great for somebody ( hello Larry LP Jack PAN) to make a NB widget hat was tunable width /depth and whatever parameters are needed...maybe using his PAN box to examine the junk ??? I know that the scopes on icoms can tell a bunch abt the pulse junk. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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: [Elecraft] Question from a newbie noise blanker
Night vision goggles work quite well in some cases. I mentioned it to a friend in the Guard and the 1st Sgt at the local armory decided to have a short training session. The troops spotted the two perpetrator insulators within 2 mins just by looking around. PGE came out with their IR device in about a week, and it was fixed tFred K6DGW - Northern California Contest Club - CU in the 2007 CQP Oct 6-7 - www.cqp.orghe next day. YMMV ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] Question from a newbie noise blanker
Fred Jensen wrote: Night vision goggles work quite well in some cases. I mentioned it to a friend in the Guard and the 1st Sgt at the local armory decided to have a short training session. The troops spotted the two perpetrator insulators within 2 mins just by looking around. PGE came out with their IR device in about a week, and it was fixed tFred K6DGW - Northern California Contest Club - CU in the 2007 CQP Oct 6-7 - www.cqp.orghe next day. YMMV Yes, I can see how that would help. Jack ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] Question from a newbie noise blanker
Fred, Was this at night? Do you think consumer grade ones would work? Tnx es 73, Leigh/WA5ZNU On Mon, 12 Mar 2007 11:58 am, Fred Jensen wrote: Night vision goggles work quite well in some cases. I mentioned it to a friend in the Guard and the 1st Sgt at the local armory decided to have a short training session. The troops spotted the two perpetrator insulators within 2 mins just by looking around. PGE came out with their IR device in about a week, and it was fixed tFred K6DGW ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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] Appalachian Trail Tuesday Afternoon
Hello, Going to be working close to the Appalachian trail on Tuesday, so I plan on going to work early. I will be on the AT north of Strausstown, PA south of Rte 183. I should be on the air by 19:00 UTC. K1 @ 5 watts and a vertical. 15, 20, 30 40m. I will start out on 15 meters and call CQ for 10 minutes, if I don't hear anyone I will go to 20m. I will be around the QRP Freq. I will be there until 21:00 UTC but if the bands are in good shape and I am making QSO's I will stay until 22:00 UTC. 72 and Thanks, Ron Polityka WB3AAL www.wb3aal.com www.n3epa.org/ K1 - SN 01011 K2 - SN 01392 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] AGC Independent S-Meter?
Sandy - You wrote: Circuitry wise, an AGC/AVC free S-meter is an oxymoron! Can't have one without the other. Well, I have late 1950s Hammarlund HQ170 whose S-meter works just fine with the AGC/AVC turned on or off. As far as I have been able to ascertain, the S-meter functions identically with or without the AGC/ AVC turned on. It was designed to do so. The QST review at the time commented on this feature. So it is possible to build a receiver with an S-meter that functions with the AGC on or off. It was done nearly 50 years ago. I am not sure why receiver designers have not incorporated this useful feature into more modern rigs. Now I am not a fan of AGC, in fact I think the most useful feature of a receiver with AGC is the ability to turn it off. :^)= - Dr. Megacycle KK6MC/5 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] Question from a newbie noise blanker
Understood. I had been pondering a trigger derived from the noise receiver's output pulses but with memory and variable delay added to freeze the display, and allow one or several output noise pulses to be displayed. Jack Smith wrote: Actually, a swept spectrum analyzer is a very difficult machine to use for tracking noise, unless the sweep is triggered with the power line zero crossing. snip If one were to go about an effective noise blanker, I believe you could do much worse than building a new version of the old Collins approach -- a broadband receiver tuned to 30-35 MHz to detect noise and then a fast gate (with suitable delay for synchronization) to clip the received signal. I agree and use a version. The old Collins system was first used in mobile installations I believe with the KWM-1, but the approach has undergone many changes over the years. Possibly the most significant changes that have evolved for HF use is to reduce the bandwidth of the noise receiver, and tune the noise receiver to a clear frequency close to the system's working frequency to get a more accurate sample of incoming noise. This mutation of the system has become known as the Evasive Noise Blanker, and in Amateur use the noise receiver is tuned to a clear frequency close to but outside of the band in use. From using this type of blanker system for many years I find that a noise receiver tuning range of 25 kHz above each operating band is satisfactory. I opted to avoid using a noise gate in the main receiver's signal chain in the interests of dynamic range, but use the noise pulses to inhibit a fast flip-flop which provides the H-Mode signal mixer with it 50% duty cycle LO squarewave injection, thus having the noise pulses switch injection. This type of blanker will not respond to legitimate in-band signals, a problem sometimes found during contests when using a blanker which samples in-band noise. 73, Geoff GM4ESD ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] AGC Independent S-Meter?
Dr Megacycle wrote: Well, I have late 1950s Hammarlund HQ170 whose S-meter works just fine with the AGC/AVC turned on or off. As far as I have been able to ascertain, the S-meter functions identically with or without the AGC/ AVC turned on. It was designed to do so. - The HQ170 S-meter rectifies the AVC signal separately in one diode section of a 6BV8 (that's a tube, folks! G), but it will not provide the same readings with the AVC turned off! In fact, in the HQ170 manual says, ...the 'S' meter circuit is connected to the separate AVC diode section of V8 (6BV8) and gives an indication of all types of signals in all positions of the AVC, however the 'S' meter calibration is valid ONLY WITH AVC POSITIONS SLOW, MEDIUM OR FAST and not in OFF position, although it will indicate and may be usable in MANUAL position. (Page 9 of the HQ-170 Communications Receiver Instructions and Service Information manual. The emphasis is in the manual text.) Let's take a look at how an S-meter works, starting with some background. It all started long ago with the superheterodyne invented by Col. Armstrong. That allowed a lot of amplification in a receiver that was easy to tune and without the howls and squeals that, even today, are used to signify one is tuning in an old time receiver! That basic superhetrodyne format is still the standard today in almost all receivers, including those in the Elecraft rigs. With the amplification the superhetrodyne provided came a nuisance: when listening to a weak station, if a strong station came on frequency it'd blast your ears! For CW signals the solution was easy. One added a hard limiter to the audio channel. If a really strong signal was encountered without warning, it was clipped of at some preset maximum volume (below the threshold of pain, hopefully). Most operators used the limiter at all times in case a huge signal came on frequency. The problem with a hard limiter is that is clips off the signal - turns a sine wave into an almost-square wave. The fact that the end result sounded like a buzz-saw was of no consequence. The current interest in soft, pure, sine wave tones when listening to CW is a recent pursuit that has many old timers chuckling. Everyone listened to CW signals that sounded a lot harsher than the sidetone from the stock K2 and it was (and still is) music to their ears. But phone transmissions were a whole different story. Distorting voice (or music) with a hard limiter was a serious problem. A means to prevent blasting listeners out of their chairs without distorting the audio was needed. Automatic Gain Control (AGC) a.k.a Automatic Volume Control (AVC) was the answer. AVC (or AGC) automatically controls the gain of some of the stages of RF amplification in the receiver to turn down the signal and avoid overload and blasting. It works like this. Phone signals were Amplitude Modulated (AM). That is, they consist of a steady carrier with sidebands containing the audio modulation. Two rectifiers are used in the receiver. One recovers the audio from the sidebands and the other, the AGC detector, produces a d-c voltage proportional to the strength of the carrier. The d-c voltage it produces is used to control the amplification of the stages in the receiver ahead of the detector. The stronger the signal, the more voltage produced, the more voltage produced, the more the amplification of the stages ahead of the detector are turned down. That produced a much-reduced change in loudness in the speaker or phones when tuning from a weak to a loud signal. The AGC circuit quickly became standard in virtually every superhet used to receive AM phone signals, from the console radio in the living room of the 1920's and 30's to the car radio of the 1940's to today's radios. A huge range of signals could be received with only nominal changes in volume - something easily controlled with the audio gain control. At some point some smart guy (or gal) realized that the AVC voltage changes in proportion to the strength of the incoming signal. That's the whole idea of the AVC! The stronger the signal, the greater the voltage! If we measure that voltage, we can show on a meter the relative strengths of various signals. The S-Meter was born! But AGC or AVC was only useful for AM phone reception. For CW reception we needed a beat-frequency-oscillator (BFO). The BFO is almost on the same frequency as the signal at the detector in order to produce the audio beat frequency we hear. The BFO is a huge, locally-generated signal, compared to the CW signal. It was impossible to keep the BFO out of the AVC detector. The relatively huge BFO signal made the AVC system react as if it was tuned into a very strong signal at all times, and so the AVC turned the receiver gain to minimum and kept it there. So, for decades, superhetrodyne communications receivers had a switch to turn the AVC off for CW reception and we continued to use the manual RF gain
Re: [Elecraft] AGC Independent S-Meter?
For CW signals the solution was easy. One added a hard limiter to the audio channel. If a really strong signal was encountered without warning, it was clipped of at some preset maximum volume (below the threshold of pain, hopefully). Most operators used the limiter at all times in case a huge signal came on frequency. Ron AC7AC I wonder if it is possible to adjust the AGC on the K2 to only work on strong signals, to act as a hearing protection limiter only, with little action on all other signals. I understand this would work for CW only rigs. I like to use my K2 with AGC off, but value whats left of my hearing. Was that why old time commercial operators wore headphones forward of their ears? Be hard to do with modern cushion phones. Rick Dettinger K7MW ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
