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Transmission line efficiency - Does heat on the coax connector mean its not efficient?

dietermoreno

Dec 30, 2012
238
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Dec 30, 2012
Messages
238
Hello. I have returned after I successfully built the Ramsey FM transmitter after ordering the missing parts.

I daisy chained 3 Trisonic TV amps from the transmitter 75 ohm coax output to a rabbit ears antenna that has a really thin cable that doesn't look like a standard RG-6 75 ohm coax cable.

I am able to hear my broadcasts all around my house upstairs and downstairs. Also, when I take my battery powered boombox and walk outside down the street I am able to hear my broadcast until it fades out near the street corner about 40 yards away from my front door.

If I don't use the amps and the external antenna I'm not really able to hear it at all past a few feet.

I noticed interestingly that using only the included whip antenna: it works better when the sun is up. The moment the sun set at about 9PM I heard a static fade coming on for 30 seconds after it was getting more and more distorted and staticy for the past 15 minutes, and then when I couldn't see sun light anymore I only heard static. It appears that the low FM band (87.7-91.9 MHZ) that I'm broadcasting on is more noisy at night than in the day time like AM radio. I changed the battery and still only static. Then the static got quiet as soon as I connected to the amps and external antenna, and then I retuned to adjust for frequency drift until I heard the music.

I haven't had to adjust for frequency drift in the past hour to be able to hear it at all, but the audio quality does appear to be slowly decreasing right now from frequency drift so its time to retune it again now.

Unfortunately, when I turned it off and disconnected the rabbit ears from the amplifiers, I noticed that the connector for the rabbit ears cable was hot.

Doesn't heat mean inefficiency?

That heat has to come from somewhere, so that means that the heat is RF energy that isn't passing out of the antenna and is stuck at the connector?

Would upgrading to a rabbit ears antenna that has a connector for a standard RG 6 cable reduce the heat at the connector and increase my broadcast range?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
Who knows?

You're using input preamplifiers to amplify the output.

You're chaining three of them (which is probably pointless).

You're illegally transmitting.

I doubt the heat comes from wasted RF.

The mind boggles (as usual)
 

JMW

Jan 30, 2012
90
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Jan 30, 2012
Messages
90
You sir are the reason there are so many stupid laws and rules. I would be very happy to notify the local TV stations in your area of your activity(s). They could then sue you for millions of dollars for copyright infringement and we might be blessed with never, ever hearing from you again. Maybe just maybe there is a FCC person on this thread.
 

Gryd3

Jun 25, 2014
4,098
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Jun 25, 2014
Messages
4,098
LMAO. I needed a good laugh.
Then I noticed the quotes in the signature and did a quick forum search.

dietermoreno.. you sound to be very dangerous with electronics.

Please please please do some reading on the basics of electronics to understand what you are doing.
Daisy chaining amplifiers are a horrible idea regardless of use, and broadcasting at such a range as to interfere or project your signal into personal or commercial areas is illegal. There are specific radio spectrum designated for hobby use, and even then you are limited to the transmission power for such use.
The fact that the wires you are using are getting warm/hot proves to me you know just enough to be dangerous. You could easily cause harm to your person or property, or worse, someone else's.

I'm up for a good hack as much as the next guy, but it should always be done in a safe controlled manner.

Do you know what causes heat in wires? Wires have an internal resistance, as you increase the amount of current through said wire, the power dissipated in the wire increases.
If you attempt to put too much current through a wire, it has the potential to get red hot, burning the insulation off, and catching adjacent items on fire. (I know as I used a cheap 'hack' to cut Styrofoam with a red hot length of 24 gauge wire. I did not light anything on fire, as I knew what I was getting into)
 
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