Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sun, 21 Nov 2010 21:22:07 -0600
The bottom like down below (and on the bottom of all posts) tells you how to accomplish going to the daily batch. ONLY you and the administrator can do that, none of the rest of the list participants
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Mon, 22 Nov 2010 22:28:43 -0600
The failing in vintage Astron supplies is that the emitter resistors have too little voltage drop to force decent sharing so the transistor with the highest current gain gets most of the load. When i
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Tue, 23 Nov 2010 05:16:12 -0600
Most linear supplies come with lousy efficiency, partly from the need for that voltage drop to achieve decent current sharing. Except for my shack supply that uses MOSFETs for regulation. They share
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Wed, 24 Nov 2010 10:10:44 -0600
When you KNOW you have a low impedance antenna at low frequency you can improve life for the tuner by adding a transformer. Not a balun, a conventional ferrite cored transformer. There have been such
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Wed, 24 Nov 2010 13:43:12 -0600
That coil does two jobs. The 3/4 wave vertical has nearly as nice a feed impedance as a quarter wave, resistive and not far from 50 ohms. And many of us have used a 40 meter vertical on 15 meters, th
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Wed, 24 Nov 2010 18:48:22 -0600
High swr seen by the exciter points to the cathode circuit tuning. It may need to be adjusted if there are two input circuits for 80 and 75. Typically the Q of that cathode tuned circuit is very low
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Thu, 25 Nov 2010 10:50:31 -0600
According to the downloaded manual, the ONLY thing that changes between 75 and 80 meters is the value of the fixed capacitor at the loading point in the output Pi-L network. The coil taps and the inp
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Thu, 25 Nov 2010 13:01:13 -0600
There is more than one way to look at it. The antenna shorter than quarter wave is capacitive. The antenna longer than quarter wave and shorter than half wave is inductive so a series capacitor bring
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Thu, 25 Nov 2010 13:06:46 -0600
The manual I have shows individual input circuits called low pass filters on the input low pass filter board. 81223. There is no more output filter after the PI-L. There is one per band from 160 thro
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 26 Nov 2010 09:37:13 -0600
On 11/26/2010 7:17 AM, kf6e@mail.com wrote: The problem was that I had a random wire antenna in my attic and wanted to use it on several bands. The impedance was low on one band and quite high on oth
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 26 Nov 2010 09:51:20 -0600
In the Titan, and I've not looked at the Centurion, schematic on 40, 80 and 160 the load capacitor has a large shunt fixed capacitor so the variable is a small part of that capacitance so it has only
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 26 Nov 2010 11:36:54 -0600
And the lower phase noise of the analog oscillator compared to a synthesizer without adding the complexity of the Omni V and VI with the synthesizer at VHF and divided down to 5 MHz. Some rigs came w
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 26 Nov 2010 12:18:06 -0600
That's the way I see it. Taking out C 18, 300 pf fixed requires adding that back with the variable loading capacitor. The cap labels are to the left of the part. And with the variable having only 500
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 26 Nov 2010 18:14:08 -0600
DDS may have their place but a transceiver VFO may not be one of them for the present state of the art. They can display low phase noise but over a broad background spectrum of coherent closely space
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 27 Nov 2010 11:25:30 -0600
Low or no output on a band or bands can be dirty switch contacts. 10, 12, and 15 haven't had much use in the past few year. It might be a quarter drop of deoxit on each contact with some vigorous swi
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 27 Nov 2010 18:18:42 -0600
Question is does it receive on those bands? The LO is as critical to receive as to transmit and its the same LO. Loosing two bands on transmit is indicative more of a low pass filter problem where th
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 27 Nov 2010 18:18:51 -0600
Actually according to the 564 manual and the schematics in it, the low pass filters are switched with relays. The band pass filters (used for both transmit and receive) are diode switched and unique
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 27 Nov 2010 18:20:19 -0600
The same bandpass filters are used for receive and for transmit. But unless there's a reason for multiple failures (like lightning) they are individual for each band. 73, Jerry, K0CQ Thanks again, Wa
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 27 Nov 2010 18:22:18 -0600
K6 and K7 switch 20 meters, K2 and K3 switch 10/12. 73, Jerry, K0CQ He didn't say how much to repair but I'd bet by the time you pay to ship it to TT, tech labor, parts, and return shipping, you'll h
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 27 Nov 2010 20:46:46 -0600
One of tentecs other lines is cases. Maybe they have one they will sell in single lots. 73, Jerry, K0CQ On 11/27/2010 8:12 PM, Ron Notarius W3WN wrote: I've been collecting parts for a few months now