Joe is Back!

[JoeFM1]

LOL Good luck with that!!
Doesn't apply to federally regulated airwaves. Also CB operates in the 26-27mhz area. 49 mhz was the original FM band currently used for unlicensed wastelands of whatever, typically baby monitors, RC cars, and old school cordless phones.

FWIW CB was originally a Licensed service. KSC-2934 is stamped on one of my really old CB radios.

Remember, unlicensed operation is a privilege, not a right.

NT... I'm getting forgetfull in my old age. You're absolutely right. CBs are 26-27 not 49 MHz (I have an old 5 watt 5 channel CB that uses crystals, and the numbers are stamped right on them).

And you are right about the other aspect, too. Brings us full circle to the old argument that the federal government exceeds its constitutional authority by exercising jurisdiction over matters that don't cross state lines or affect interstate commerce. Its why some folks in Texas advocate this republic pulling out of the union.

The fact here is that I travelled to Washington and met with the FCC suits about how a certain person I can't name deprived the citizens of Houston of a valuable resource -- e.g., a portion of the spectrum allocated for two TV stations within the city. The FCC read correspondence and listened to recorded calls. Despite being sympathetic about evident wrondoing, they said the laws were written in such a way that they couldn't reinstate the surrendered licenses. Afterwards, we discussed and the "suits" encouraged unlicensed use of TV band white space. This was essentially the "bone" they threw to this old dog to get me to go away. And I ran with it...

And now while this old dog is gnawing on the bone, they have figuratively yanked it out of my mouth...

 

[JoeFM1]

Another Experimental Broadcast Tonight

Had a conversation with Washington today. Turns out there was a misunderstanding. The recently adopted rules aren't yet in effect. And in a nutshell I was told that for right now -- and until after the spectrum auction and repacking -- they don't care what I do with open whitespace, as long as I'm not transmitting porn or causing interference to a licensed broadcast.

JoeFM will conduct another experimental broadcast tonight. ATSC video/audio on digital TV Channel 6. Analog Audio on 87.85 MHz. (FCC says 87.9 is not "whitespace," but 87.8 is -- thus, this slight deviation in frequency keeps it legal, but shouldn't prevent digital tuners from locking onto the signal at 87.9 MNz). We shall see if it works...

I have secured the use of a downtown 43rd floor office with a north facing window. As mentioned in other posts, with low power transmissions height is far more important than power. I'm really curious about how well this will work -- e.g., having a building behind an antenna positioned against a large window. How much will the plate glass attenuate the signal? Will having a building behind the antenna concentrate the signal directionally to the north?

Anyway, unless I have technical problems, the broadcast should be up and running by 10 p.m. Reception reports appreciated.

 

[LibertyNT]

The Glass won't bother it a bit, but the metal construction will seriously attenuate the signal and get you some nasty reflected power.
But your coverage to the north if you're still running 4 watts will be fantastic.

I know 15 watts at about 30 feet will yield around 6 miles on flat land. So 4 watts at 430 feet should kick some ass.

Edit:
Looks like at 131 meters with 4 watts will put a 60 dbu to Collingsworth Street, possibly up to the loves on 45.
Maybe a 50 dbu signal at E Crosstimbers Street

 

[JoeFM1]

The Glass won't bother it a bit, but the metal construction will seriously attenuate the signal and get you some nasty reflected power.
But your coverage to the north if you're still running 4 watts will be fantastic.

I know 15 watts at about 30 feet will yield around 6 miles on flat land. So 4 watts at 430 feet should kick some ass.

Edit:
Looks like at 131 meters with 4 watts will put a 60 dbu to Collingsworth Street, possibly up to the loves on 45.
Maybe a 50 dbu signal at E Crosstimbers Street

Ran the device from 9 to 11 p.m. while driving around seeing the effect. First, despite the height, the range of the TV video signal (shown in black) was not good. Of course I'm using a mobile TV, so folks at home with rooftop antennas might do better.

The red depicts a good clear audio signal. The blue depicts a weaker but nonetheless listenable signal. I drove up 50, to Beltway, and back down 45. I heard it very faintly a couple of times on the Beltway, but too garbled to listen to.

Also drove a little ways out I-10, both east and west. The signal dropped off quickly after getting out of downtown, which proves the point that broadcasting from a window makes a highly directional signal.

 

[JoeFM1]

Testing again this afternoon with a different antenna. Stereo audio on 87.85 MHZ. Colored bars on channel 6.1

 

[frankberry]

Joe,

What FM transmitter are you using?

 

[JoeFM1]

Joe,

What FM transmitter are you using?

The ATSC signal is generated with this device. http://www.provideoinstruments.com/...oax-wm-series-wall-mount-hd-rf-modulator.html

The analog signal is generated with a generic Made In China $10 FM transmitter. See post #2 in this thread for pics. The RF output of these devices are combined via a simple homemade capicitor/coil circuit. This is fed into a homemade 2 transistor 20 db amplifier (variable to adjust output power). The final stage is a larger transistor mounted on a fan cooled heat sink. The output is paases through a vintage Radio Shack SWR/power meter, 10 feet of LMR 400 coaz, to a homemade J-pole. The coax is coiled at the antenna as a choke.

Its beyond my know how to calculate the effective radiated ppwer based on height, antenna gain, etc. Im simply keeping the output at 4 watts on the meter.

What I dont understand is why the analog signal gets out well, but not the ATSC. Is there something I didnt grasp... Do you need a special type of amplifier for ATSC signals?

Last night I was using a dipole. Got a lot of reflected signal. Seems to be working better with a j pole but still alot of feedback.

 

[frankberry]

Joe,

Please stop the BS now.
You cannot combine FM and ATSC signals using "simple homemade capacitor/coil" circuits. The bandwidth of the L/C circuits are far too narrow to pass such wideband RF.
Your 87.85MHz signal cannot be received by a digital tuner which is tuned to 87.9MHz. Your signal would be 50kHz off-frequency.
The little FM transmitters from China are frequency-adjustable in 100kHz increments. They can't operate on 87.85MHz.

Further posts about this will be deleted.

 

[JoeFM1]

Joe,

Please stop the BS now.
You cannot combine FM and ATSC signals using "simple homemade capacitor/coil" circuits. The bandwidth of the L/C circuits are far too narrow to pass such wideband RF.
Your 87.85MHz signal cannot be received by a digital tuner which is tuned to 87.9MHz. Your signal would be 50kHz off-frequency.
The little FM transmitters from China are frequency-adjustable in 100kHz increments. They can't operate on 87.85MHz.

Further posts about this will be deleted.

Frank, I respect you and your knowledge as a broadcast engineer. However, human beings are smart. We have been inventing and innovating, pushing the limits of what can and can't be done for the entire time we have been on this planet.

Your last sentence brings us full circle, back to the issue of censorship. You say something can't be done, then say you will delete further posts -- effectively foreclosing all possibility of explanation or evidence, proof that something you say "can't" be is actually being done. I understand from a liability perspective how you don't want me naming broadcasters who violate the law and/or preachers who are false prophets. Here, however, I'm discussing a radio/TV topic in a thread that has had over 5,000 views, and where there is genuine interest into whether I can make this work.

I just got home and I'm dead tired. I received your email and will respond sometime tomorrow.

J

 

[LibertyNT]

Now Frank in Joe's defense, I find a lot of digital tuners are pretty forgiving on 50khz deviation. How do you think so many 87.75s get listened to. (granted some operate on 87.70)

Also while I personally haven't seen a china made FM transmitter capable of operating on split frequencies, doesn't mean they don't exist.

All that being said, You need more than a cheaply made combiner for those transmitters. Thats why theres a lot of reflected power, they are feeding into eachother which is killing your ATSC range. Not to mention digital on VHF-Lo isn't good to begin with.

 

[JoeFM1]

Now Frank in Joe's defense, I find a lot of digital tuners are pretty forgiving on 50khz deviation. How do you think so many 87.75s get listened to. (granted some operate on 87.70)

Also while I personally haven't seen a china made FM transmitter capable of operating on split frequencies, doesn't mean they don't exist.

All that being said, You need more than a cheaply made combiner for those transmitters. Thats why theres a lot of reflected power, they are feeding into each other which is killing your ATSC range. Not to mention digital on VHF-Lo isn't good to begin with.

The small transmitter has a tiny open air coil with wax on it. When I use a flat screwdriver to separate the windings, it throws the oscillator slightly off frequency.

I have an old Sangean ATS803a with .5 incremental tuning. It has a signal meter with five red LEDs. On 87.80 I hear my signal clearly, but none of the LEDs come on. On 87.85 all five light up. On 87.9, it flickers between two and three LEDs. So in theory, my signal could possibly be on 87.86 - 87.88 MHz. With the equipment I have to "play" with, I believe I have offset the frequency enough to be able to swear in Court that I was not broadcasting on 87.9.

As far as using the simple L/C combine of signals, it can be done; it just doesn't work very good. I get pixelation of the picture even when the TV is just 20 feet away from the transmitting antenna! (See pic)

In any event, this experiment is over and I'm disappointed with the results. Back to the drawing board.

 

[LibertyNT]

What you aughta do Joe is grab an old analog blonder tongue and run it on channel 6. That way you get 87.7 FM and feed some old school analog television. It'll get out farther than digital anyday.

And if you want seperate TV programming, run TV audio on SAP.

 

[JoeFM1]

What you aughta do Joe is grab an old analog blonder tongue and run it on channel 6. That way you get 87.7 FM and feed some old school analog television. It'll get out farther than digital anyday.

And if you want seperate TV programming, run TV audio on SAP.

I have an old Cadco CATV modulator. The same one shown in this ebay listing. http://www.ebay.com/itm/Cadco-Agile...bd0e2f&pid=100338&rk=1&rkt=30&sd=140966305582

And while all modern HDTVs will upon a rescan "find" analog TV signals, the image is so poor that nobody would want to watch it. Its also very hard to find computer video cards with a composite video or S-video output to feed into the modulator. The old XP Compac I had with composite video out died on me months back.

 

[ContinuousWave]

Now Frank in Joe's defense, I find a lot of digital tuners are pretty forgiving on 50khz deviation. How do you think so many 87.75s get listened to. (granted some operate on 87.70)

Also while I personally haven't seen a china made FM transmitter capable of operating on split frequencies, doesn't mean they don't exist.

All that being said, You need more than a cheaply made combiner for those transmitters. Thats why theres a lot of reflected power, they are feeding into eachother which is killing your ATSC range. Not to mention digital on VHF-Lo isn't good to begin with.

This is BS....a FrankenFM on 87.75 is distorted on 87.7....I know...I HAVE listened to several and one was illegally on 87.70 and it sucked because they were running in excess of 75k deviation...more like 120!....Liberty, sorry but Frank and I are REAL broadcast engineers...and have decades of experience...I am not a EE but was a EE student in college and have impressed MSEEs like Gary of mswdtv.con who WAS on the ATSC committee that developed DTV...Go figure

As to censorship, read the terms of service...Frank is 110% within his right to delete and ban anyone....anyone who signs up here has agreed to those terms...don't like em?? Go somewhere else....

Frank, delete away.....LOL

 

[LibertyNT]

Woah CW didn't mean to step on any toes! Was just giving out benifit of doubt! I engineer myself and know the limitations.
FrankenFMs are hit and miss on what recievers will actually put up with it. I have a few that do tolerate it, although it becomes very obvious when the signal gets weak and the tuner starts clamping down.

Edit: I messed up on deviation, should've said off set.

 

[JoeFM1]

This is BS....a FrankenFM on 87.75 is distorted on 87.7....I know...I HAVE listened to several and one was illegally on 87.70 and it sucked because they were running in excess of 75k deviation...more like 120!

CW, you wouldn't be referring to Mustang 87.7 in Lafayette, LA? (See pic)

I haven't heard KXKW-LP in awhile, but last year their 3 kW signal was booming into Houston every time tropo from the east kicked in. Sound wasn't bad at all, but it wasn't in stereo.

 

[JoeFM1]

I engineer myself and know the limitations.

Liberty, as an engineer, maybe you can offer an opinion that will save this non engineer tinkerer some time. As explained earlier, right now I'm doing something another engineer said can't be done -- e.g., combining ATSC with analog to feed a single amplifier. It works, but not very well. The analog signal gives acceptable coverage, but the ATSC signal pixelates even in the same room and covers less than a mile. What would happen if instead of trying to combine them, I kept the signals totally separate? Different amplifiers, different antennas. Perhaps position the ATSC antenna vertical, and the analog horizontal?

 

[LibertyNT]

Theres a few reasons why this won't work. The amp is too narrow and too dirty to pass ATSC. The analog can and will splatter into the ATSC signal enough to cause problems. You cannot have two antennas pumping out that close of frequency that close to eachother, they will feed into eachother without some heavy duty filtering.
The only way to make this work is have the FM carrier dead center on 87.9, and have a duplexer built to combine these signals.

But you're pretty much trying to have a station on 92.1, 92.3, AND 92.5

I really think you're biggest problem right now is trying to run digital on VHF-Low. Theres a damn good reason broadcasters abandoned this band when they could.

 

[JoeFM1]

Theres a few reasons why this won't work. The amp is too narrow and too dirty to pass ATSC. The analog can and will splatter into the ATSC signal enough to cause problems. You cannot have two antennas pumping out that close of frequency that close to eachother, they will feed into eachother without some heavy duty filtering.
The only way to make this work is have the FM carrier dead center on 87.9, and have a duplexer built to combine these signals.

But you're pretty much trying to have a station on 92.1, 92.3, AND 92.5

I really think you're biggest problem right now is trying to run digital on VHF-Low. Theres a damn good reason broadcasters abandoned this band when they could.

Yeah, and the problem here is that the FCC says I can't legally center the carrier on 87.9, which isn't "whitespace." 87.89, however, is whitespace, and if I had the ability to tune my modulation that precise it is where I would've been.

In a Private Message, another user suggested I adjust the ATSC modulator to another channel, and set the virtual channel so that 6.1 shows on the end user's screen. That'd work... never thought of that.

 

[frankberry]

Actually, 87.89 IS on the 87.9 channel. An FM channel is + and - 100kHz wide. 87.8 to 88.0 fall within the 87.9 FM channel.
You're splitting hairs. You have made you intent very clear. You want to operate on a forbidden frequency.