Yes, I have observed this. If your frequency is adjusted to be within 10 Hz. of the channel carrier frequency this is supposed to be inaudible, however, it will manifest as a fading in and out of your signal. Nothing you can do about this except keep you carrier frequency within 10 Hz. and hope the “fading” is not as annoying as an a…[Read more]
Paul nailed it with his comments. You have to consider the antenna impedance when optimizing the transmitted power and the impedance of a 3 meter wire antenna is high and reactive.
I built a tube transmitter based on the KnightKit design and it compares equally in performance (except for DC input power) to my KK using the wire…[Read more]
Classically, the function of a choke coil connected from the antenna output of a transmitter to chassis ground is to prevent an electrical hazard in case the output coupling capacitor shorts and causes the B+ of the final to appear on the antenna. Its function is to shunt the DC voltage to ground while allowing the RF signal to pass and it is n…[Read more]
Can we please get back to the topic of the original post and help and encourage Pat to get on the air.
Griping about the power/field strength limits in various countries is not helping him.
Add something positive and useful.
Don’t get hung up about the impedance of the coax. For practical purposes in part 15 (in the US this means license free radio) considering the power levels involved this is not a controlling factor. I operate here using 75 ohm hard line for my VHF transmitter ham system and get a reliable 40 mile range with a 25 watt transmitter designed f…[Read more]
Some of you might recognize the lifted quote used in this thread title and may understand it better as you read on.
A few days ago my neighborhood lost power. The outage began at about 3:30 AM and lasted until 6 AM. I was viewing a streaming movie and had to shut down and to fend off boredom I turned on my battery powered portable AM radio. Th…[Read more]
radio8z replied to the topic 2 Transmitters 1.3 Mile Apart Is That To Close Together?? in the forum Transmitter Talk 4 months, 3 weeks ago
Regarding the proximity of the two transmitters, please consider operating them on different frequencies. This will eliminate problems of constructive/destructive interference and audio delays.
Operating two transmitters within radio range of each other on the same frequency will result in patterns of practically unknown RF performance,…[Read more]
My comments re AM “fidelity” were directed to the technology and for support I included measurements of my system. There is nothing inherently limiting the AM bandwidth other than legal restrictions. As I read Part 15 rules, there is no restriction on bandwidth of such transmissions.
Rich commented that the audio bandwidth may be l…[Read more]
Mark asked “Is the response of 20-17000 HZ the frequency response of the transmitter itself or what you are getting on the air?”
The audio response and THD were measured from the transmitter input to the receiver output. The BC-1004 receiver I use has an adjustable IF bandpass with steep skirts, and it was set to maximum IF BW for the test…[Read more]
Very interesting post and thanks for sharing your thoughts and experiences.
AM is still my preferred way to reach out, including to my most important, and probably only, listener…Me..
Your comment about AM ‘fidelity” deserves a bit of a contradicting response. My AM system has a measured audio bandwidth of 20 to 17000 Hz,, better than…[Read more]
radio8z replied to the topic Bad Language Reports from some Unlicensed Stations in the forum General Discussion 7 months, 3 weeks ago
Someone who I consider wise once told me “Freedom includes the ability to make an ass of yourself.” Perhaps those who broadcast “objectionable” content, by whatever definition, are excising this freedom.
If some clown wants to broadcast such material so be it but I do not assume any guilt by association because I am a license free…[Read more]
radio8z replied to the topic Bad Language Reports from some Unlicensed Stations in the forum General Discussion 7 months, 4 weeks ago
What’s going on here?
A post questioning the appropriateness (is that a word?) of some alleged Part15 stations’ broadcasts has devolved into examples of what some may deem inappropriate.
If you think it is inappropriate then the solution is simple…don’t play it on your station.
I don’t know how this thread promotes or helps us at all.
Way off topic question and advice for RadioJoe.
Did you ever solve your hum problem with your KnightKit broadcaster?
I did so for mine. The problem here was the signal was so strong that it was being modified by all the electronics throughout the house by means of these devices intercepting the RF and producing non-linear mixing with the 60…[Read more]
Thank you very much for report on your testing of various FM “car” transmitters.
Sorry, but I think it is not workable to promote range beyond a few hundred feet on the FM band since the regulations (15.239) technically and severely limit FM transmission range.
It is also necessary to consider the other requirements for 15.239 regarding purity…[Read more]
Thanks for the report and glad you had the chance to meet
I look forward to the day (not going to happen?) when the rest of us can run a 10 Watt transmitter and be “full quieting at three miles” with our signals .
Tim remarked “I’m perplexed by the comment about 25 minutes of advertising in an hour. I’ve never actually heard this anywhere, no matter how many complain about it.”
I am also perplexed but I measured this using a stop watch during the third hour of the Rush Limbaugh program aired on WTVN in Columbus, Ohio. I stopped the watch if any comm…[Read more]
Mark, you make a good point that they can still play commercials because some are listening, however, the linked article demonstrates that the broadcasters apparently perceive a problem with declining numbers of listeners.
I only spoke for myself in my previous post but I know my wife does not listen to broadcast radio, and neither do my sons…[Read more]
Thanks for the link which has content which I classify as wishful thinking. Interference has never stopped me from listening to programming which I wanted to hear. The reason I no longer listen to broadcast radio, neither AM nor FM, is that there is nothing I want to hear available and that I cannot stand 25 minutes per hour of commercials and s…[Read more]
Not knowing anything about this specific device I will make a general comment about spectrum analyzers applied to Part 15 devices.
For AM transmitters, an analyzer most likely will detect harmonics and spurs on the signal but, as Rich mentioned, the absolute amplitudes are not guaranteed to be accurate, but amplitudes relative to the carrier are…[Read more]
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