We seek to understand and document all radio transmissions, legal and otherwise, as part of the radio listening hobby. We do not encourage any radio operations contrary to regulations. Always consult with the appropriate authorities if you have questions concerning what is permissable in your locale.

Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - Kage

Pages: [1] 2 3 ... 5
1
Found this topic from 2015 on bandwidth but few replies and I never hear people discuss emphasis usage.

With mediumwave broadcasting it's almost necessary as listeners radios will have 75 microsecond de-emphasis built in, so the old standard NRSC mask 10db up near 10kHz with the sharp cut gets the job done like the big stations. Most audio processors will take care of this so no reason not to use it and I've noticed when not used the broadcast sounds muddy on AM radios able to pass the highs.

On shortwave I'm guessing there is no real need for it since standard audio bandwidth is out to 5kHz or so. What about some of you running higher bandwidth? I'd imagine most of the standard multi-band radios use de-emphasis on all the AM bands including shortwave since it's easier in circuit, and leave the FM broadcast section to do its own thing. Maybe some pre-emphasis on the shortwave transmission would help? Boosting up to 7.5dB at 5kHz and then brick walling it at that point to accommodate peoples average analog receivers using the mask on all AM bands internally?

Also wondering if anyone here has tried any practical bandwidth tests to see if lower/higher on both transmit/receive being equal made a difference in long distance listening?
I'd think that technically speaking lower bandwidths would conserve transmit power thus increase broadcast range slightly but the difference between 5kHz and 10kHz audio bandwidth is so small compared to something like FM upwards of 200kHz to AMs 10-20kHz occupied space that it probably doesn't matter so why not use higher fidelity audio on AM to make everyone happy from cheap radios to SDRs set wide open? We're talking pirating anyways, so no need to follow strict bandwidth rules unless the pirate band gets congested.

Just some caffeinated thoughts ;D

Edit: Discussion of SSB bandwidth welcome too! I'm so used to AM mode that I forgot this applies to SSB as well.

2
Does 34 count?  8)

Yeah I'm a bit over the age of your question but I am no 50 or 60. The local library was my best friend as a preteen/teen and though I always had a burning interest in pirate radio there were books like Pirate Radio Stations - Andrew Yoder, 200 Meters & Down - Clinton Desoto, and Underground Frequency Guide -  Donald W. Schimmel that threw me into obsession. Add in the ARRL/QRP Notebook books and an interest in electronic circuitry that grew from my earliest childhood memories of the wonder of electric lighting and my first transistor radio that put me to bed when I was probably 6 y/o or so.

Earliest memory I have that fascinated me with transmission was having two radios, probably not much older than when I got that first AM/FM radio and finding that if I tuned one nearby to a frequency near the one tuned in on the other it would blank out the static. This made me realize these radios weren't only listening, but also sending out a weak signal on their own (internal oscillator). It didn't take long being one of those kids that charred his hands by shoving things in the wall outlet and later tore apart all his brothers electronics to his dismay to figure out how those radios were working. Was probably only weeks later that I was poking wires around inside one from an audio amplifier output to see if I could modulate it, which I somehow managed to do and had neighborhood friends tune into by using a random wire connected somewhere near the oscillator/tuner variable capacitor as an antenna, and injected audio going God knows where into that radio.
Also had a lot of fun knocking out my mothers TV set from fun little escapades like that. Hopefully no aircraft comm. interference lol.

Years later as a teenager the bug hit me hard after toying with CB radios back in the late 90s when skip was otherworldly. At that point I was well accustomed to small RF electronics thanks to those Radio Shack springboard kits and the radio projects in the manuals. Soldering iron came next, breadboarding, Ramsey FM kits, and the rest is history.
Finally got on the air with some serious power and antenna height via 40' self erected tower in my 20s covering all of my town on FM and later the AM broadcast band which took another serious level of effort thanks to mediumwave antennas at such shortened lengths. Had some decent second or third hand equipment at that point and knew how to repair electronics so trash picked stereos and audio mixers and other gear could be had free with just some fixing. Like redhat I also managed to connect with the local station and get some basement equipment they were going to junk. Wish I still had some of that old Gates stuff.
Mics and music started coming to me as friends grew heavy interest in getting on the air with me so lots of equipment and broadcast material flooded in until things got a bit too big were we knew we were on the radar of the wrong people.
Now I mostly hang low but still tinker and run shows, just not to those extremes anymore and prefer using my knowledge to help others new to the hobby, hence the forum I run dedicated to the more technical aspects of the art.

RF will always fascinate me, and I will always be an avid SWLer and RF engineer. It's simply in my blood. Pirate radio is a life mission for many I believe. Just sucks for us 30 somethings or younger that we kind of missed the boat now that most of the younger generation are mostly listening to digital mediums, but the airwaves still need to be occupied in my opinion, especially now more than ever that commercial stations are killing listenership with their trash.

3
This reminds me of the story in the early 1990's EBN from Ernie Wilson, (Yeah, the ex-Panaxis Productions dude.). This story was about how a French TV station engineer noticed a minute more RF current drawn at the transmitter site right at the time a well watched soap opera aired, then after it would air, the minute current level dropped back down to where it was set. I thought that it was an interesting observation, but never heard anything about it since. You'd think that someone would have wanted to do the math more and figure out the TX RF current to the number of RX stations tuning in. Oh, wait... That might just put the Nielsen Ratings out of business.  So, never mind...

How would a receiver several miles away affect current draw in a transmitter?

Unless the engineer was reading the current of the power grid itself? I can see how a power company could notice a change in current draw if everyone in a city turned their TVs on at the same time. But in today's multichannel world, I don't think anything like that would work.
It's an old myth. I've heard that story eons ago and it's always told in a slightly different form. It is similar to the story of a guy who lived near a high powered AM radio station and setup some wire antenna outside to capture the field strength of the local station to light his attic at night only to get a knock on the door because the station engineer noticed the transmitter RF ammeter raised significantly causing tube failures or something as such.
They are fun tall tales :)

4
Here is more information about it and the overall internal layout and flowchart...
https://aa7ee.wordpress.com/2018/03/13/the-sw200-a-budget-am-broadcast-processor-for-lpam-and-hams-too/

I am actually building my own AM audio processor that is similar in layout but uses FET compressors instead of PWM compressors for simplicity and is loosely designed after the Dorrough DAP 310 from 1973 which is yet another popular 3 band compressor/clipper of its time (some say the first of its kind that started the loudness wars). Luckily the Dorrough schematics and manual are available online so it's not too hard to clone your own similar box if you have a lot of time and electronics skills. It's actually pretty simple under the hood, tons of op amps though. The SW200 looks to be similar while utilizing modern parts.

Software processors rival even the best analog processors except when it comes to the audible latency. I really love Stereo Tool and have an excellent AM preset I found a while back for it and tweaked. It gives *loud* punchy audio that is equal to the major market radio stations in my area and can really drive a modulator hot. The problem is that there is the need of a fast dedicated computer with a quality sound card and ASIO4ALL really needs to be running to make the latency the least noticeable. The OS needs to be stripped to bare bones so the computer can dedicate all its processing to the software and not other useless junk.
Even with the fastest computer I have it had delay that was enough to drive me crazy for live programming and really screws with my head if I listen to myself talk over the live feed.
Of course this can be fixed by only listening to the program feed output rather than the live OTA feed, but I like hearing the transmitted audio through my modulation monitor.

So in that respect I still prefer analog audio processors where suitable and if setup properly can still sound pretty damn good. If all you are broadcasting is prerecorded shows or only listening to the studio audio then digital processing is fine.
Comes down to personal preference but digital processing will give the edge, and possible listener fatigue if overused.

On a funny side note, I have heard of stations using their retired analog processors just for the studio talent since it's real-time and let them hear that "radio sound" in their headphones while using the new digital processor at the transmit end so to trick the DJs and not anger them with the delayed live processed audio ;D

5
Heard a station playing old music and some quick Christmas jingles tonight.
0224 - "Moonlight Serenade" by The Ray Eberle Orchestra.
The Sept. 11 memorial station occasionally fades up to dominate the frequency.

I'd love to know what music. I was just running a test broadcast with mostly Christmas music then went into a Devo escapade because I drank. Real curious if this rig is getting out on 1710kHz, long work in progress. Running 25 watts but the antenna needs far more work. I will probably run this all christmas on and off until it's perfected. http://darkliferadio.proboards.com/thread/1018/class-series-modulated-transmitter-build

6
Shortwave Pirate / Re: UNID 6950 USB 0157 UTC 17 June 2018
« on: June 17, 2018, 1501 UTC »
Listened into this last night but was too tired to grab my tablet computer to decode the SSTV, glad others here uploaded them!
Neat show, Kraftwerk fan myself so was nice to hear their music for the first time on shortwave :D
Signal was decent for the storms in the midwest, SINPO 55354

7
10/11 meters / What is with 11m lately?
« on: May 24, 2018, 1157 UTC »
Anyone else notice that even though we are on the low end of the 11 year cycle the CB band is picking up big at times I never recall? Yet lower frequencies are completely dead. It seems 10+MHz is doing swell but anything lower is worse than ever! I tuned in 80m last night and heard two hams and that was it, yet at the same time I heard hundreds of people on CB 11m.
Right now as I post this, 6:55AM EST I am hearing skip from all over, that's not normal. Even at night lately and last night I heard people talking skip into the moon hours.
What is up with the sun? I thought when we are on the cycle low we are working local only but I am hearing stuff that reminds me of years ago when the solar cycle was high.
What gives? Am I going nuts?
Meanwhile I can't even tune in coast to coast am at night, how will I sleep w/o george snoory telling me bedtime stories?

8
Huh? / Re: The definitive end-fed dipole discussion.
« on: February 28, 2018, 2220 UTC »
Where do I install the tophat and monocle to focus the beam width toward the hemorrosphere layer? 

9
10/11 meters / Re: 27025 AM CB Superbowl Ch.6 1925 UTC 29 DEC 2017
« on: December 31, 2017, 0956 UTC »
Yeah there seems to be a lot of skip right before noon on 11 meters in the last few days. Guessing it's some sporadic E activity given the low solar flux. Kind of nice to work some skip when the band is so damn dead the rest of the time besides the local weirdos and truckers.
Using my homemade EFHW mounted 30' up which has the same performance as an Antron/Solarcon A99, I get activity across all 40 channels when skip comes in. At the peaks I switch to the freeband frequencies and those can become quite clogged too. Helps to have an actual CB and antenna designed for the band, but ch. 6 is always a reliable indicator to see if the band (including 12 and 10m) is opening up.
Oddly I have yet to hear anyone on 10m besides some CW. CB 11m on the other hand lights up like a Christmas tree.

10
Was listening while they played Smash Mouth and STP. Was too tired to listen further but signal was good here in WI with slight fading. Nice clear modulation.

11
Huh? / Re: The Penguin Brief
« on: May 03, 2017, 1832 UTC »
Linux for life! :-*

12
The RF Workbench / Re: Stretchyman Pirate Radio Video
« on: May 01, 2017, 1617 UTC »
Incredible work 8)
Makes my perfboard homebrew look like crap lol. One of these days I will get around to making my own PCBs for projects.

13
Equipment / Re: very interesting transceiver
« on: February 18, 2017, 0318 UTC »
Windows 10? I'll stick to my penguin based SDR thank you.

14
Shortwave Broadcast / Re: Brother Stair on WBCQ, 9330 kHz
« on: February 03, 2017, 1231 UTC »
What isn't Brother Scare on these days?

15
The RF Workbench / Re: Help with an FM Jammer
« on: December 24, 2016, 1831 UTC »
Alternatively, you could modulate the oscillator with a sawtooth waveform which would be more annoying to the 'victim'.
Sawtooth through a varactor diode as half the tuning LC circuit to sweep frequencies around the range you desire, nasty thought :P
That is definitely one way to piss off some people.

redhat is right though, you should use either a zener diode and resistor to regulate voltage going into it or even something as simple as a three leg 5v regulator like a 7805 so that the free running oscillator doesn't drift around.
It's funny because as simple as this circuit looks, this is the one place where engineers start pulling hair because LC oscillators are the most finicky part of a far more complex RF circuit.
Want to get real nasty I recommend a push pull oscillator at half the frequency which runs in anti-phase to get up to the frequency you want to block. Far more stable and will create enough blackout at the frequency if you want to get in some trouble.

In all practicality though wouldn't it be easier to use an FM MP3 player transmitter set to the channel you hate and want to block? Add a piece of wire on the circuit for an external aerial and you're set. Run some fart noises into the audio input to annoy further, and remain somewhat legal doing so.

Pages: [1] 2 3 ... 5