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2018-07-13 Never Directly Connect RF Amp To Antenna!

Radio Frequency Receiver
on July 13th, 2018 by - No Comments

From FB group Building Transistor Radios, Jul 30

Hey, if you live in Central Florida, you really do need an optocoupler!

I got a Tennelec Memoryscan scanner on sale for a really cheap price back in the ’70s (the company quickly went out of business). I connected it to a VHF/UHF discone antenna on my roof. This had 3 elements only a few feet in diameter.

So a thunderstorm passed through and afterwards the VHF channels stopped working – UHF were ok.

Fortunately it came with a schematic. I immediately saw why. The VHF RF amp was directly connected to the antenna. No coil to give a DC path to ground. So I replaced the 2N3904 RF amp, and it started working again. So it’s a Big Mistake to connect a transistor, and especially a FET(!) to the antenna directly. Many good designs totally ignore this absolute no-no! And it happened to me with a tiny discone antenna. Imagine what happens with a hundred foot long wire!!

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2018-07-11 Communist Manifesto

Politics Rechargeable
on July 11th, 2018 by - No Comments

From FB group Orange Talk, July 13

Rebecca Joy
It’s still not spelled right. 😝 It’s not Columnist Manifesto.

The Communist Manifesto was only a few dozen pages long and at the time was considered the most influential document of the 19th century. The evil Commies were a totally different thing. The Communist Manifesto was written by idealists and its dogma was never fully implemented. There were upper, middle and lower classes in the Soviet Union and the so called proletariat never fully “owned” the state. The words on paper were not as shocking as the evil dictator Stalin who killed at least 25 million of his own people, many just for political reasons, because they were “counter-revolutionary”.

I was in Germany when the Soviets took over Czechoslovakia and scared the hell out of Europe and the rest of the world. Then the Commies threw in the towel and gave up and the Soviet Union broke up in 1990.

In 1960s, the Kiplinger Letter published an issue that said that the Soviets would become more capitalistic and the U.S. would become more socialistic. Half of their prediction came true with the breakup of the Soviet Union. And today the U.S. has become more socialistic as can be seen by becoming a welfare state.

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2018-07-09 Country Going To Hell In A Handbasket

Politics Uncategorized
on July 9th, 2018 by - No Comments

From FB group Orange Talk Jul 11

Rebecca Joy
You said “Bernie is a socialist” but there is no proof that he would change our government (he is a member of Congress!) to socialism.

HC, I assume you mean Hillary, is an experienced bureaucrat who has worked within the bureaucracy, and is not guilty of the fabricated claims the right wing extremists have reiterated ad nauseum.

The “bleeding heart liberals” you claim want coddling and “all the poor people” do not espouse any socialist agenda – they just see their world from a poverty viewpoint.

Meanwhile the poor person can’t afford to go to the doctor, for prenatal care for example (that’s why we have neonatal death rates equal to 3rd world countries). The poor wait until their health is so bad they have to go to the emergency room. There they get treatment that they can’t pay for, so the costs are paid by the taxpayers -that’s you and I. This is, plain and simple, socialized medicine. We are already living in a country where the most expensive part of a person’s life, healthcare, is socialized.

I’m not making any accusations, I’m just stating the way it is. And while you’re whining about whether your country is going to be taken over by socialists, you fail to see the reality that this country is already going to hell in a handbasket.

Wake up! 😬

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2018-07-08 Doomed To Repeat History?

Politics
on July 8th, 2018 by - No Comments

From FB group Orange Talk, Jul 11

Rebecca Joy
Has it ever occurred to you that you might be wrong about Dems being socialists?

When someone such as yourself tries to stereotype a group and categorize them into a pigeonhole, it becomes very unproductive to having an intelligent discussion about anything, especially politics.

You fail to take into account that about half the people in this nation are of one political party, and this does *not* mean that that half is evil by definition. We all want what we think is best for us and our nation, and belittling those because they don’t share your opinions doesn’t mean they are all Communists. Remember, Socialism is *not* Communism. I doubt you even know what Socialism is.

Apparently you are too young to have experienced the Communist threat to the Free world, which was what got us into the Vietnam conflict, the first war that we lost.

People who are young had better learn from history, or they are doomed to repeat it. 😱

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2018-07-06 PN2222A Vs. 2N2222A etc.

Uncategorized
on July 6th, 2018 by - No Comments

From FB group Building Transistor Radios

Stuart Bca
The TO-18 and plastic versions use the same chip and therefore the specifications are the same, except for power dissipation and temperature derating. Both of those depend on the case, and the same holds true for the MMBT2222A in the surface mount package.

The TO-18 metal case is connected to the collector, so the capacitance is higher, and that might make a difference at high frequencies. If you want the same transistor chip but higher power, you can use the 2N2219A.

The complementary PNP version is the 2N2907A.

Remember any plastic cased transistor that is labeled 2N2222A is not the Real Thing. The original, true 2N2222A came in the TO-18 metal package, and is registered with JEDEC, that’s why it starts with 2N. Any other plastic transistor does not meet the JEDEC specifications. The 2N2222A transistors in the plastic package came with the middle lead bent out from the others. This was so the plastic cased 2N2222A could be plugged into the triangle shapes hole patterns of the metal cased 2N2222As. Their pinouts were the opposite of the 2N2222A plastic transistors.

All of this meddling with the numbers of the original metal can transistors has led to much confusion and wasted a lot of time. They should have never used 2N for plastic cases, they should have used PN or MPS2222A that most legitimate manufacturers used. But ask the average hobbyist and he can’t tell you any of this confusing information.

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2018-06-28 Bootstrapped For High Z Input

Electronic Design Functional blocks Transistors
on June 28th, 2018 by - No Comments

From FB group Building Transistor Radios

For those who don’t want to or can’t use a JFET for high input impedance, you can use a regular transistor or two and bootstrapping to get a 10 Megohm high input impedance amplifier. This is from “Common Collector Amplifiers”, Electronics Now, Oct. 1993,
found at americanradiohistory.com.
For RFs, all capacitors can be 0.1 uF.

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2018-06-24 Stick But No Carrot – Spend $25 Billion to Make Jobs, Not A Wall

Politics
on June 25th, 2018 by - No Comments

From FB group Orange Talk

Chris Leist
You misunderstood. I didn’t say give money to Mexico. I said spend it in Mexico, like spend the money to get US manufacturers to move business from Asia to south of the border. The money could not be spent here because the wages would be much higher, and other businesses would complain about competition.

Right now, Boss Tweet is using all stick and no carrot. If there was some incentive for Mexicans to not leave the country, then $25 billion would not have to be spent building the wall. After the wall has been built, there will still be illegals (11 million) and drugs from Mexico here in the US.

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2018-06-24 Antennas Loopstick Vs Spider Web

AM Band Radio Frequency Radio, Television entertainment Receiver
on June 24th, 2018 by - No Comments

From FB group Building Transistor Radios

Jim Glover
You asked about performance. There are factors unrelated to either type that affect the performance, one being the type of wire used. If Litz wire is used it has lower losses, and therefore higher Q than solid wire. Same holds true for silver plated wire at HFs. The area of the coil determines the amount of signal captured, but at AM broadcast frequencies the limitation is background noise, so capturing more signal also captures more noise.

The best antenna, no matter what type, is higher off the ground and away from man made noise. Outside is better – there is some signal loss inside bldgs.

Also you can reduce the number of turns in the loop and use more capacitance. But variable capacitors can be excessively large. So the air variable in older sets is a compromise, and the polystyrene variables in small radios are even lower capacitance, and demand more inductance to tune the AM band.

So all your designs face some compromises that will be made. It’s up to the designer which compromise will be made. And for most designs it’s compromises that give small size.

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2018-06-23 Chapman Ave, Santiago Canyon College

Other Off Topic Politics
on June 23rd, 2018 by - No Comments

From FB group Orange Talk regarding accidents at Chapman and Jamboree

I stood on the balcony of the B bldg at Santiago Canyon College and watched the traffic going right through the middle of what is now D bldg, and saw bikers on their Harleys going 50 around the right hand turn lane from Chapman on to Santiago Canyon Road. That was before 1988, when they rerouted the roads to the way it is today. So high speed is nothing new at that point.

Back then, all those houses now south of the roads was the big empty piece of land that was where the college was originally supposed to be. It was the place where Handy Creek ran when there was enough rain, which seldom happened. The traffic was a small fraction of what it is now.

The college district had a study done and it foresaw a big growth in the number of people in that would be in the area, so they chose that land out in the boonies to build the college. Now there are tens of thousands of people there and the traffic is dozens of times higher.

It’s just a long way away from there to ‘down the road apiece’ and people want to get to their destinations ASAP. Speed kills, as they say. Back then there were accidents, but nowhere near the number we see today.

They monitor the speeds of traffic, and if they put up lower speed limit signs, people ignore them. Then the motorcycle cops ticket speeders and locals get pissed off and make a stink, and someone higher up pulls out the ‘fountain pen’ and gets the signs changed back again.

Until the next time the statistics show there’s a problem and the cycle repeats. 😕

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2018-06-22 Telco Craftspeople

Datacomm Telecom Telephone
on June 22nd, 2018 by - No Comments

From FB group Bell Telephone…

As a customer and the point man who interfaced with the Telco, I have nothing but good to say about all the fine craftspeople I dealt with during my 33 years with the college district. I only wish I could have spoken as highly of other contractors I had to deal with. 👍👍👍 👏👏👏

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