Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Mon, 21 Jul 2008 00:57:06 -0600
That's not necessarily true. The loaded Q depends on the impedance ratio. The higher the ratio, the higher the loaded Q. So for a large impedance ratio, there has to be a high loaded Q and large circ
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Mon, 21 Jul 2008 08:50:18 -0600
Unun is simply a transformer. Can't call it an unun balun. Probably made with two windings series connected like a 1:4 voltage balun but connected to the world differently. Where the 1:4 voltage balu
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 22 Jul 2008 09:08:52 -0600
EXACTLY the definition of just a transformer. Only the frequency range is different from the power transformer out on the power pole. Gives that 1:4 impedance ratio (1:2 voltage ratio) over a wide ra
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 22 Jul 2008 15:24:12 -0600
Yes. The match box always has the two differential capacitors across the tuned winding and they can't be small enough to work good at ten meters and be big enough for 80 meters. My ten meter tuners a
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 29 Jul 2008 17:40:08 -0600
If you park a shorted connector on each one, no static could build up. I've seen SO-239 flash over from static when not shorted. Raised me out of my chair the first time I heard that snap. A suitable
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 29 Jul 2008 18:04:54 -0600
Or shunt the feed with a shorted quarter wave of transmission line, probably coax. Bleeds all the DC. Costs more than 2 watt resistors though and makes the antenna single band. 73, Jerry, K0CQ
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 29 Jul 2008 18:24:30 -0600
But those impedances are 6:1, not 4:1. The DX-60 would load up practically anything including the open coax connector. It wasn't nearly as picky as modern SSB gear. I'm sure I have Heathkit catalogs
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Sun, 01 Jun 2008 09:49:32 -0600
Lots of classic RG specs have been abandoned by the military, either to reduce their number or to incorporate new designs and materials. I have an 80m inverted V fed with the miniature single shielde
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Sun, 01 Jun 2008 10:15:39 -0600
What abuse has the board suffered? Bad PC board manufacture? Is the board single sided, double sided, or multiple layer? Direct lightning hit? 24 volts DC to the 5 volt logic chips? Bad chip no longe
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Mon, 02 Jun 2008 12:41:06 -0600
I too have made that analysis, but I figure the slightly increased bandwidth is mostly due to the use of twinlead for the end sections giving a fatter conductor and so greater bandwidth. The two stub
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Mon, 02 Jun 2008 12:51:15 -0600
So get out the temperature controlled soldering iron and the good solder with an activated rosin flux and heat every solder joint on the whole board. And if that doesn't work get out the hot air gun
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 03 Jun 2008 12:45:17 -0600
I chose 120 feet, I think. My tuned circuit resonated at a higher frequency and the SWR was never 1:1. It was a circle, that when shifted through 5/16th wave (or 50' in real coax with Vp of 0.66) of
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 03 Jun 2008 12:48:17 -0600
Look at my other post. Plot those resulting values on a Smith chart and then transform them through a 5/16th wave length of 72 ohm coax and look at the result then. I assumed no losses when I compute
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 03 Jun 2008 12:51:17 -0600
A 100 watt light bulb can give nearly that bandwidth, but the impedance match is drive sensitive. Cross country HF contacts have been made even back in the AM days with a light bulb dummy load (not s
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Wed, 04 Jun 2008 10:58:21 -0600
And it has to carry significant current. If the resonant impedance is 100 ohms, 100 watts puts 100 volts RF across the capacitor. And with a reactance of 20 ohms that puts the current at 5 amps. Take
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Wed, 04 Jun 2008 11:02:10 -0600
Or that the receiver is responding to noise at frequencies other than the band of interest (wide band FM heard in a 2 KHz bandwidth sounds like noise) and the stubs of the bazooka are rejecting that
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Wed, 04 Jun 2008 11:08:35 -0600
When I did my antenna, I based it on 14 gauge wire and used calculator, table of dipole impedances, and Smith chart. The earliest Bazooka data I saw (about 1960) used RG-58 for the antenna and standa
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Wed, 04 Jun 2008 12:32:13 -0600
Except that any good receiver should already reject all the out of band noise. There could be some benefit there, though I've had great success with lumped element filters that survived the event bet