HFU HF Underground
Technical Topics => Equipment => Topic started by: chanito on February 13, 2020, 0204 UTC
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Anyone have this gear? Comments? Thinking of putting one on to cover my property with lovely AM-ness.
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Looks a lot like the mosquito. I had to fix one for someone recently. Not much to it, commonly available parts, seems to do the job.
+-RH
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Waste of time, buy something decent.
From me!
;)
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Waste of time, buy something decent.
From me!
;)
Your transmitters are not legal for part 15 transmission in this country.
+-RH
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Who cares...
+ They transmit more than 10'!
Str.
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Under part 15 rules, AM coverage is up to a mile depending on the installation and so forth. The OP mentioned he was interested in covering his property only, not the county. Also keep in mind the US government recently enacted tougher legislation against AM and FM band pirates, with fines up to $2M. How they plan on enforcing that I don't know, but the point still stands.
+-RH
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Do part 15 transmitters need to be of an approved make or can you use any type providing it conforms?
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You are allowed to build your own equipment. If the commission comes out, they will measure your field strength to confirm it falls within the limits. They do have some arcane rules which are not real clear, probably to allow more latitude on the part of the inspector.
+-RH
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You are allowed to build your own equipment. If the commission comes out, they will measure your field strength to confirm it falls within the limits. They do have some arcane rules which are not real clear, probably to allow more latitude on the part of the inspector.
+-RH
Elsewhere there was a rather lengthy and amusing thread regarding the ground wire and whether it counts as part of the antenna. From a literal reading of the pertinent FCC regs, it does:
§ 15.219 Operation in the band 510-1705 kHz.
(a) The total input power to the final radio frequency stage (exclusive of filament or heater power) shall not exceed 100 milliwatts.
(b) The total length of the transmission line, antenna and ground lead (if used) shall not exceed 3 meters.
(c) All emissions below 510 kHz or above 1705 kHz shall be attenuated at least 20 dB below the level of the unmodulated carrier. Determination of compliance with the 20 dB attenuation specification may be based on measurements at the intentional radiator's antenna output terminal unless the intentional radiator uses a permanently attached antenna, in which case compliance shall be demonstrated by measuring the radiated emissions.
Yet the Talking House transmitter, which is certified as Part 15 compliant, has a ground connection via the DC power cord, which then connects to your house wiring. Which most certainly does radiate and effectively work as an antenna. In fact in one case the FCC brought this up during an inspection, the TH transmitter in question was in an apartment building and all the wiring was acting as an antenna. This is probably how some ops are able to get a mile range. The FCC itself mentions 200 ft as a typical range for Part 15. While this is not in the official rules, I suspect they use this as a rough guide, and if your range is significantly more, they will not be happy
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If I felt I could get away with it, I would put in a Stretchyman xmtr, hands down. Unfortunately, I can't take chances of retribution from local licensed stations who will invariably feel offended by the production quality of my station compared to theirs :-)
Got to stay with the 100mw and 9' antenna. I will probably take a whack at doing the SSTRAN antenna system and mount the xmtr on the pole to comply with Part 15.
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You can go the other option of AM Carrier-Current Coupling, like some college stations still do. Most ops tend to stay away from that method, since coupling to power lines tend to scare away folks. Some ops are running like 30W into the lines, while others are 5W, or less. I turned mine down to the TX's MIN of 200mW carrier, since more transformers have been installed on my road. Today, it doesn't matter if I run 10W, or 100mW, Carrier-Current, since the power transformers are a brickwall RF stop. And, I'm Neutral Injecting the James R. Cunningham way. https://sites.google.com/site/lowpowerradio/home/low-power-broadcasting-by-james-r-cunningham Still, some ops are getting out a few miles doing Carrier-Current, and it's totally Part #15 permissible still.
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It is interesting the TH is allowed to use a TH range extender connected via coax, supposedly legally.
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And, I wonder if the 3m rule applies to actual wire length or if a loaded coil with a radiator in excess of 3m of wire wound, but not in physical "length", would be in compliance.
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And, I wonder if the 3m rule applies to actual wire length or if a loaded coil with a radiator in excess of 3m of wire wound, but not in physical "length", would be in compliance.
Was thinking the same thing, you can put a lot of wire in a 3m space.
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And, I wonder if the 3m rule applies to actual wire length or if a loaded coil with a radiator in excess of 3m of wire wound, but not in physical "length", would be in compliance.
Was thinking the same thing, you can put a lot of wire in a 3m space.
Loading coils seem to be allowed, but you better make sure it's not really an antenna in disguise.
http://diymedia.net/old/stuff/lpamhandbook.pdf
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I got the Spitfire. With the provided 9' antenna wire it is piss poor. Not even good to 16 feet. POS. Won't go from 2nd fl to 1st fl in a house. Looking for an alternative.
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Does the provided antenna have a loading coil or is it just a wire with a connector on the end?
+-RH
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Does the provided antenna have a loading coil or is it just a wire with a connector on the end?
+-RH
9' wire with RCA connector.
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That's why it sucks. You need to build a tuned antenna for something that short. Something like this...
(https://i.pinimg.com/originals/b9/5b/db/b95bdbb86177d995471b79644918000b.jpg)
To add insult to injury, anything in you house that radiates will get into the powerline, and cause apparent hum in your signal. Its actually RF getting into all the rectifiers in every switching supply in the house and through nonlinear mixing, superimposing 120Hz on the signal and re-radiating it. The transmit antenna should really be outside if you want to be able to listen to it.
+-RH
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The Talking House transmitter actually has a built in antenna tuner. You can hear the motor adjust the ferrite core as it tunes when you change frequency. A bit complicated, but certainly the best way to squeeze out every foot of range from a legal Part 15 transmitter installation.
I have a Talking House transmitter for sale BTW if anyone is interested. Almost new in box except for me taking it out a few times to play with it :)
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I got it cookin' now. It's running with internal ATU OFF, into a 9:1 balun and a respectable piece of wire length. Now to condense that wire down to a "load".
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The Talking House transmitter actually has a built in antenna tuner. You can hear the motor adjust the ferrite core as it tunes when you change frequency. A bit complicated, but certainly the best way to squeeze out every foot of range from a legal Part 15 transmitter installation.
I have a Talking House transmitter for sale BTW if anyone is interested. Almost new in box except for me taking it out a few times to play with it :)
I would really like to know how the TH & Range Extender setup works. Is it really a signal directly from the TH to the Extender tuner section? OR a low level signal that is then amplified by the Extender? OR, is it just audio and power down the coax with a bias tee on the Extender and a transmitter integrated there.
How did TH get FCC certification using a variable coax length?
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As I remember, the amplifier and matching network are out at the antenna. The coax merely brings a low level RF signal from the indoor unit to the outside amplifier. So rather than put everything in one box, they split it into two.
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Outdoor unit:
http://talkinghouse.com/range-extender-2.5.htm
https://www.hobbybroadcaster.net/reviews/iss-range-extender-2.5-talking-house-iam-radio.php
The antenna tuner in the outside unit looks a lot like that used in the inside unit (https://images.app.goo.gl/BMwyMH8ZS4LTTBT99).
I don’t know if they actually put the final amplifier outside or not.
Note the patent links on this page. They provide an explanation of how it works.
http://www.prc68.com/I/TalkingHouseTransmitter.html
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How did TH get FCC certification using a variable coax length?
I am not sure how they got the basic unit certified, since the ground connection turns the ground wiring in your entire building effectively into part of the antenna.
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Property coverage achieved. Sounds pretty good driving it with a cheap Chinese mini PC running RadioDJ, into a Behringer Composer Pro-XL.
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I got stereotool to run on a pi4 and a hifiberry card last weekend. Uses 1/3 the dc of my current processor, sounds good too 😊
+-RH
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Think I'll try StereoTool to see if it is better than the spartan integrated processing in RadioDJ. I'm only using the AGC control there and passing the peak limiting to the Behringer.
An aside...
Why do we want to transmit AM to our yard and home?
Well, for me, it's something odd. I have a veritable plethora of 70's music of all genres. A lot comes from the inevitable Time/Life series. In fact, I have a "TL" format on RadioDJ for this AM station. All Time/Life, all the time. Why???
All of this music, for me, was listened to via AM radio. During the majority of the 70's I was in an area that wasn't served by any listenable FM station, so everything was AM Top 40 from local and at night, distant stations. I have a certain affinity for the sound of AM radio. That's it. Carole King or Jethro Tull hit music sounds weird in pristine, clear, digital audio. I know it from AM. And I like it that way.
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All of this music, for me, was listened to via AM radio. During the majority of the 70's I was in an area that wasn't served by any listenable FM station, so everything was AM Top 40 from local and at night, distant stations. I have a certain affinity for the sound of AM radio. That's it. Carole King or Jethro Tull hit music sounds weird in pristine, clear, digital audio. I know it from AM. And I like it that way.
I recall hearing The Doors "Riders On The Storm" on a MW pirate out of NYC just above the broadcast band (1620 ish) back in the 80s, with static and fading. It's a memorable sound.
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Swapped Behringer out for a Aphex 320A Compellor. Much better.
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All of this music, for me, was listened to via AM radio. During the majority of the 70's I was in an area that wasn't served by any listenable FM station, so everything was AM Top 40 from local and at night, distant stations. I have a certain affinity for the sound of AM radio. That's it. Carole King or Jethro Tull hit music sounds weird in pristine, clear, digital audio. I know it from AM. And I like it that way.
There is a certain sound to AM too. Even if you listen to the highest quality through a modulation monitor it still has a different quality to it than FM because of the methods used for broadcast processing.
That big and loud sound coming from either rack processing or StereoTool, once setup properly gives a punch that you just don't hear on FM and sometimes even further removed from the actual music source. Musicians hate this because their music doesn't sound the same on radio but to the listener it can be enjoyable because of the exact same reason.
Then there is the fact that some of the early rock music was actually mixed down in the studio with AM radio listeners in mind, so not only did they aim for HIFI listeners they also aimed for a sound that would suit peoples car and kitchen radios of the time.
I like to keep it simple and use an AGC to three band audio downward-expander/compressor into a mix of limiting and clipping. Finally with proper audio bandwidth brickwalling and compensation it can sound exactly like the big market stations of the 70s and 80s pushing maximum modulation or even into the positive with asymmetrical clipping for that huge sound.
Of course I like all of this to be analog and rolled my own gear to do so, but modern software replacements can achieve the same, or better. I find it best to not over complicate it and keep the audio path cleaner so not be fatiguing but loud enough to punch through the static and noise. Anything more than this might give you that giant market sound but it becomes overkill with a dozen pieces of gear or plugins running.
With mediumwave all your investment of time and money is going to be in audio and antenna anyway. Transmitters for the MW band are so cheap to design and even those Part 15 transmitters can get a huge improvement out of the two being their best.
Besides all of that, there is nothing wrong with enjoying nostalgic sounds. Get the most out of the medium and have the most fun with it!
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I got stereotool to run on a pi4 and a hifiberry card last weekend. Uses 1/3 the dc of my current processor, sounds good too 😊
+-RH
Hello Redhat. How is pi4/HifiBerry with Stereo Tool working? Do you monitor it with a display? Can you change settings or adjust levels. I know once set up it may not be necessary. How is the latency performance?
I think that is a nice application. I have been looking at the pi4/HifiBerry board also.
Although I could run Stereo Tool on a notebook also (low power compared to a large PC). I like the fact it is on a another dedicated device because of CPU usage and not on the main station PC.
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The end plan is to replace the current intel based machine running ST with the pi. It would be neat to have a pop-out touch screen for changing parameters and such. Latency is about 1/4 second, which isn't bad considering the small amount of onboard processing power. I've tried lowering it to 100mS or so and it wasn't real happy. Good thermal management is a must, and even with the fancy case, CPU temp runs about 25 degrees C over ambient. That is not much of a problem now, but might be when its outside in a rack and the ambient is pushing 40C.
+-RH
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If Stereo Tool or another app with the same features is designed with the code to run on DSP chips directly you could get very close to (if not) zero latency. Not that latency is that important in a broadcast setup. 1/4 second is not that bad. Maybe someone will write a touch display code. Let us know how this project works out for you.
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I was told that with ASIO drivers under windows it can be reduced to 20mS. That said, bass distortion cancellation is reduced. Long waveforms take time to process. Even the delay in a modern optimod or omnia is on the order of a second or two. The industry has given up on low latency processing for all things but talent processing, mainly because no one monitors off air anymore. Thanks HD Radio...
+-RH
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I was told that with ASIO drivers under windows it can be reduced to 20mS. That said, bass distortion cancellation is reduced. Long waveforms take time to process. Even the delay in a modern optimod or omnia is on the order of a second or two. The industry has given up on low latency processing for all things but talent processing, mainly because no one monitors off air anymore. Thanks HD Radio...
+-RH
I don't think this is correct.
It's well under a second on any machines I use.
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22ms or less depending on mode for the Optimod 8700i.
Optimod 8600Si can go as high as 270ms for the MX presets.
25ms or less for the Optimod PC 1101e I use for ham radio. I can monitor my audio in headphones no problem.
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FWIW, I have had very little contact with the newer boxes, and most of what I've heard is second hand or from sales reps. The point being is that few folks are monitoring off air these days and latency is less of a priority. Add to that in the typical airchain the processor is only one source of latency. Often the STL path is far from instantaneous, and most of the newer AOIP routing systems have some delay as well. 30-50mS seems the be the break point where it becomes hard to use in a live situation, and by the time you approach 100mS I can't use off air monitoring. The effect is weird, you start to stutter!
Running HD? 8 seconds minimum coding and buffering delay for most HD systems. I believe DRM has similar delay, perhaps less.
Anyway, sorry to derail the topic. Perhaps we could pick this up somewhere else.
+-RH
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I based a station based around the early surf rock innovator, guitar player, Dick Dale. I do an "id" and the coyotes started howlng. I go into "Hava Nagila", they're going wild, into "Miserlou, and in two car loads of teenagers come barging in. I was very tempted to show them what a couple of loads of buck and ball would do their radiators, but I think they'd figured out by then that an armed older guy in sticks with a backpack meant he was placing meth labs.
I wish I had an aircheck of a mid's 90's one two liter bottle meth lab going off. They sounded just like the mines John Wayne miraculously managed to dodge as both a Marine and as a Green Beret