- January 7, 2019 at 3:45 pm #108587
Wasn’t someone at one time experimenting with part15 shortwave? How’s that work? How far can it go?
- January 7, 2019 at 5:54 pm #108591
We Made History At the Time
Several years ago a bunch of members designed a part 15 compliant shortwave transmitter that we named “The Big Talker”, especially designed for 15.360 MHz or was it 13.560 MHz (?)
Contributors included Radio8Z, PhilB, MICRO1700, Ermi Roos and probably other names I am forgetting.
The final design produced two designs, the mid-stage buffer having two possible circuits.
I had mine operating for a long time and the parts are now on the workbench waiting to be installed in a case.
If you are in a circuit-building mood I can link you to our diagrams.
- January 8, 2019 at 10:56 am #108594
Hmmm.. answered this last night at about 1am, little later noticed my comment wasn’t here so answered again about 2am… My comment is not here again!
AAaarrrg.. ok.. will try again…
Not ready to attempt to build anything yet, but curious how it sounded and how far the signal would travel. Did you do a show about it? Any recordings of the shortwave broadcast on the receiving end?
- January 8, 2019 at 11:09 am #108597
I definitely will re-link the Big Talker documentation because it includes a paper from PhilB (inventor of the AMT3000/5000 transmitters) explaining why at the allowed power level a vertical antenna would provide the best result and I think he also estimated the probable distance under normal conditions.
While visiting the Hobby Radio Super Center, click the Low Power Radio Resources and in the column under “Transmitters” scroll down until it says “Big Talker”. That’s where it will be after I re-link.
At the time I was running mine I had a dipole indoor 1/4-wave antenna but did not attempt to determine the range even though I looked around for a shortwave car radio but didn’t find one.
Now that we have two people experiencing submitted posts disappearing it is time for the website administrator to troubleshoot the problem.
- January 8, 2019 at 11:15 am #108598
How It Sounded
The Big Talker was Amplitude Modulated and sounded great!
- January 8, 2019 at 12:09 pm #108600
Oooooo… it was amplitude modulated? Cool! I want to be able to that. Where can I get an amplitude modulator from?
- January 8, 2019 at 12:11 pm #108601
All the requested links have been made.
Everything asked for is now provided.
The KDX web archives are a maze and labyrinth and I am lost in here and can’t find the exit.
- January 8, 2019 at 12:14 pm #108602
The question: “Where can I get an amplitude modulator from?”
A modulation section is built into the Big Talker Shortwave Transmitter.
It took weeks and maybe months to find a perfectly efficient modulation transformer but we spared nothing and deserve many rewards.
- January 16, 2019 at 3:44 pm #108829
This 1990 Monitoring Times issue relates to shortwave part 15 broadcasting -I think.. if that’s the same thing as “Medfer”.. Anyway, you can read/download the entire 4 page article (actually it’s the entire issue) from https://archive.org/details/MonitoringTimesMarch1990/page/n9?q=%22part+15%22
- January 16, 2019 at 4:50 pm #108830
Total posts : 443
This Can’t be true. 100mW with a 10 ft antenna can get 500 miles??
Only thing that’s true is the last statement about Canada…..no restriction on antenna length.
- January 16, 2019 at 6:59 pm #108834
Total posts : 240
Part 15 AM can skywave
There has been reports of legal part 15 installs going many miles out as some DXers has reported.
I’d really like to know about SW.
- January 17, 2019 at 9:56 am #108841
TheLegacy knows: “There has been reports of legal part 15 installs going many miles out as some DXers has reported.”
In all these years I have never heard those “reports”.
Can you link some of them?
- January 17, 2019 at 12:04 pm #108848
I don’t think Legacy was referring to the broadcast bands but in other frequencies like (as reported in the above article) broadcasting part 15 at 1619.5khz was receivable 500 miles away.
- January 17, 2019 at 12:10 pm #108849
Wait a minute… now I’m confused. That can’t be right, but it’s what it said.
Edit.. oh, sorry, that’s was exactly Marks point..
- January 17, 2019 at 12:21 pm #108851
“..Recently, the Federal Communications Commission updated their rules and regulations allowing the MedFERs (Medium Frequency Experimental Radio Stations) to operate from 510 to 1705 kHz. For the first time, experimenters can transmit in the nearly unused 1610 to 1705 kHz band where, almost nightly, signals can be heard from amazing distances. Until the FCC begins to authorize commercial broadcasters on these frequencies, it is a DX paradise that awaits your visit!…”
At the time (1990) the expanded band was still completely vacant, so the article makes more sense now.
- January 17, 2019 at 12:30 pm #108852
“..MedFERs had a relatively quiet band for a few years, apart from fishnet buoys and Latin American areobeacons. Now, however, the expanded AM broadcast band has largely filled up with its major users (commercial broadcasters), along with Travelers Information Service and Highway Advisory Radio transmitters…”
- January 17, 2019 at 1:23 pm #108854
Total posts : 443
Even if it was 1990, and 1600 to 1710 was vacant, could a part 15 signal operating with a 10 ft antenna and 100mW have enough power to get to the height needed for the skywave bounce and get the distance back to earth to be heard 500 miles away? Somehow I don’t think so. If it doesn’t make sense, is it really true?
It would have to get to the ionosphere and bounce back, minimum 60 miles to get to it and 60 miles back to earth. And that’s minimum distances.
- January 17, 2019 at 3:14 pm #108857
Damitt… my reply disappeared!.. glad I copied it!
I don’t know Mark, but really when you consider the whole world is consist of radio waves, regardless if it’s modulated with a signal or not.. even light is a radio wave, and if a frequency is not already saturated, but quiet, then why wouldn’t a tiny modulated signal manage to travel long distances?
It brings to mind another old article I read long ago which always stuck in my head, took me a few minutes to find it again, thought it was in QRZ, but it was actually in an issue of ’73 Magazine’ published in March 1975 on pages 81 thru 87 titled “The Mystery of Antenna Radiation – Is it still a mystery? It’s a semi long article, but here is a short story excerpted from it which is pretty interesting, that if I understand correctly essentially used a light bulb as an antenna to travel long distances with very low power:
“……Predictions can be made and results that have been achieved by this popular concept of wave formation have been for the most part quite satisfactory. The only thing is, I don’t believe a word of it! Many years ago, the Earth was considered to be the center of the solar system, or even further, the center of the universe. It certainly appeared to be,….
…An interesting incident occurred one evening last year to prove this point. Myself and a few other fellows were in QSO with VE3DMU in Ottawa, about 190 miles from Toronto, Band conditions that night were very good, and the further contacts were bouncing the S meter needle to 5 x 20/9,
We decided to try a few experiments with each other to see what would happen. In one experiment we reduced the audio modulation lower and lower, until it barely showed on the oscilloscope. The Ottawa station could still copy the signal, but reported a drop in audio. The same result occurred the other way — then VE3DMU in Ottawa did something else. He restored the audio to 100% modulation and reduced the rf to a bare minimum on his scope. Several of us tried the same thing and the results were the same — we were able to copy each other remarkably well on such low power*
Then the Ottawa station tried something that has had us talking ever since. He disconnected his antenna and loaded into a light bulb as a dummy load, Restoring the output to full power, he then modulated the signal. With each modulation the intensity of the light increased and decreased in brilliance.
He then asked in a joking manner, “Do you copy me now, Doc?” “Yes, I do, Gordy” was my response, and the S-meter showed 5×7! Everyone else in Toronto heard him too, and we held quite a QSO that night on a light bulb!
- January 17, 2019 at 3:32 pm #108858
I should mention that asterisk * after “low power” is not on the article, I guess I somehow accidentally hit it.
Mark said: “..It would have to get to the ionosphere and bounce back, minimum 60 miles to get to it and 60 miles back to earth. And that’s minimum distances…”
You should read the entire article as it’s rather interesting and the whole point of it is that he doesn’t believe the accepted theories of radio propagation are entirely correct and why he thinks so.
- January 17, 2019 at 4:07 pm #108860
A Story I heard Years Ago
In the early decades of analog TV a radio buddy told me he heard an anecdote about a clearly received TV signal from a station that had been off the air for 2-ywears!
Speculation was that the original signal traveled into space at the speed of light until it bounced off a solid body and reflected back to earth.
I agree that the present state of radio physics probably does not allow for possibilities that have yet to been discovered.
- January 17, 2019 at 4:19 pm #108862
Told yah.. a quick “Control A and C” before submitting eliminates a lot of aggravation.
Oh, your post changed while I was replying.. I guess the site doesn’t owe you $2,000 anymore.
- January 17, 2019 at 4:19 pm #108863
Notice to Admin
My first attempt to make the previous post disappeared and had to be re-done.
Then I saw Id misspelled the word “year” but the EDIT was already closed. What’s it set to, 1-minute? My request that EDIT be set to a reasonable time, such as 1-hour.
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