|Joined:||Mon, Jun 24th 2013, 14:48||Roles:||N/A||Moderates:||N/A|
|A shortened dipole that will get by CCRs||Jul 2nd 2013, 14:58||2||1,498||on 2/8/13|
|Keeping Oscillators Straight||Jun 28th 2013, 20:04||1||1,759||on 28/6/13|
|A shortened dipole that will get by CCRs||Joanie||on 2/7/13|
|I live in a condo complex, and while people have been putting up satellite dishes without BOD approval (mandated by the CCRs) I am having problems getting permission to put up anything, and to be specific, I have not been able to find any kind of an HF HT out there. I want to work SSB and CW on 20m, QRP to 10 watts and am considering a center loaded, shortened dipole about 12feet in length, but it will be too visible because of the loading coils.
I have found several designs, online that seem like they would be fairly nice, but as this is only going to be about 3m off the ground, I think I need the best possible radiation efficiency as we unfortunately have really good ground conductivity where I'm at. We also have a very noisy set of transmission lines within about 75 feet of my station location.
I know this is doable as where I lived previously, I was able to work QRP into Australia, EnZed, South America and South Africa on 15m using a full dipole mounted at eave level. I was renting back then and my landlord allowed me to set up several antennas including a Cushcraft R4 and a Ringo Ranger for 2m. It does so help to have a landlord that is a HAM!
Thanks in advance,
|Keeping Oscillators Straight||Joanie||on 28/6/13|
|I do not know if this is an original idea or not, but it is one that has been really useful for me over the years. I have been tutoring basic electronics theory and circuits, with the related math, on a Junior College level for the last 8 years. One of the things that a lot of my students have had a lot of trouble keeping track of is: "What are the main attributes of the three primary types of oscillators?” Over time, I have come up with a strategy that makes this easy. As this is also a question that often times comes up in element 4 exams, as well, I feel that this might be a good way to help aspiring Extra Class candidates remember the differences as well.
Having said that, the three most common types of oscillators used in Amateur Radio are the Colpitts, Hartley and Pierce oscillators. There is an easy key here that can help students remember the essential characteristics between the three types of oscillators, based upon the first letter of each type: Consider:
Colpitts : C = Capacitor/Capacitance: A Colpitts oscillator is controlled by a capacitive divider network.
Hartley: H = Henry, the unit of inductance. A Hartley oscillator uses a tapped inductor to control the frequency of the oscillator.
Pierce: P=Piezoelectric. A Pierce oscillator uses a crystal to control the frequency of the oscillator.
I have found out that those I mentor find this as easy as 3.14159 as a way to memorize the fundamental way in which the three types of oscillators differ from each other on a basic level.