Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Mon, 15 Apr 2002 10:23:41 -0500
The filtered sawtooth will always have the least delay. The filter can be a simple two or three pole low pass. The effect of the twin T is to make a narrow bandpass filter and its high Q in the feedb
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Tue, 16 Apr 2002 17:24:00 -0500
Scherrer Instruments on Manchester in St. Louis or a suburb, used to do meter movements. But the last time I wished a fix for a broken taut band movement, it proved years faster and cheaper to buy a
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Wed, 17 Apr 2002 10:24:11 -0500
Leaky transistor... A bipolar transistor is operated with one junction reversed biased (base to collector). If that junction is leaky, not super high resistance, the collector voltage will leak some
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Wed, 17 Apr 2002 10:24:07 -0500
Transistor tend to be fairly sensitive to heat. And most good oscillator circuits have large capacitors in shunt with the transistor so that changes in the transistor have minimal effect on the frequ
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Fri, 19 Apr 2002 15:56:48 -0500
I HAVE read the IEEE articles about the folded conical helix antenna. That has not convinced me that the skepticism expressed in the forum by others is unfounded. But I've kept quiet until now. 73, J
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Sat, 20 Apr 2002 11:53:43 -0500
Gary, your Corsair VFOs are mucked up. The bezel is held on by a spring sliding in a groove on the outer PTO shaft (which is the one that has the thread to drive the slug through the pistol). The kno
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Sat, 20 Apr 2002 12:17:56 -0500
You could be right. Still probably Gary needs to pull the bezel off and make sure it turns freely on the shaft and that it hasn't been glued in place when someone couldn't figure out the spring... 73
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Sat, 20 Apr 2002 21:53:01 -0500
That's a relatively cheap Japanese key of the 60s, ball bearing pivots. Its NOT a J-38. Not that a J-38 was ever a great key. I think I paid about $28 for a good E.F. Johnson "speed" key (conventiona
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Wed, 24 Apr 2002 08:54:09 -0500
When there's a transmitter in the area, there's only one GOOD circuit for connecting balanced to unbalanced audio. That's a shielded transformer. Any semiconductor circuit will have a tendency to act
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Mon, 29 Apr 2002 21:54:06 -0500
I see reports that the Corsair II is noisy. It just has lots of gain but the RF stage uses circuitry that should be very quiet. Practically quiet enough for VHF/UHF without a significant preamp. The
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Tue, 30 Apr 2002 08:19:55 -0500
Since the RF envelope and the audio envelope in SSB do not correspond, audio derived AGC tends to produce a smoother audio output. (Its analogous to audio clipping versus SSB RF clipping, where the f
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Sat, 02 Mar 2002 17:21:43 -0600
The Scout was planned for mobile where it would get more shock and vibration. Probably those that move the most need some care in soldering ALL the components solidly to the board. Then maybe the cas
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Sun, 03 Mar 2002 18:41:57 -0600
Better, use some hot air and freeze mist to identify the one bad capacitor watching out for temperature compensating capacitors that should move. Then fix the poor solder joints. The temperature comp
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Thu, 07 Mar 2002 11:11:17 -0600
Tom, I agree. And notice that all the NEC programs give antennas over ground 3 dB excess gain. They do this by presuming that the isotropic reference is located at coordinates 0,0,0 and half immersed
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Fri, 08 Mar 2002 09:04:25 -0600
I went by the library after ham club meeting last night and made a copy of the folded conical helix antenna. I've not digested it yet. My initial impression of the illustrations is that it tries to m
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Sun, 10 Mar 2002 20:44:30 -0600
Actually the K2 uses known good technology to achieve very good results. Complexity is not necessarily a sign of good technology, more a sign of technology for technology's sake. The other makers KNO
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Tue, 12 Mar 2002 02:45:49 -0600
www.mouser.com my printed catalog says 84 cents each for 1892 rated at 1000 hours life. Perhaps you might want to look at the 756. 2/3 the current, half the light, 15 times the life. $1.04 each. No m
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Tue, 12 Mar 2002 02:47:34 -0600
If a SWR bridge is going to mess up, its most likely at the highest frequency used. Also the closer you get to the cutoff frequency of a low pass filter, the more it will affect SWR. 73, Jerry, K0CQ
Author: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
Date: Tue, 12 Mar 2002 15:03:55 -0600
Icom has been doing that: bring out a new model with more features to kill the used market price for at least 22 years since they couldn't figure out how to fix the manufacturing problems in their IC