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Post by Deleted on Jul 24, 2017 15:07:10 GMT
Carl Steps Up to the Plate
DHR raises a valid question: "Carl's FM-30 also uses a 7.6 mHz crystal. It would be useful since he has an analyzer to see what he comes up with."
At Saturday night's meeting Jeff asked me to test my transmitters to find out what I'd discover.
I staunchly refused to do so based on the fact that I previously looked at each transmitter on the spectrum analyzer and found them 100% clean.
At that time the matter of the 7.6 MHz crystal hadn't entered the discussion, but now that it has I would be willing to re-test the Ramsey FM30b especially to see how it looks on the analyzer.
YES, I will do it and bring the results to this forum.
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Post by Druid Hills Radio on Jul 24, 2017 18:47:39 GMT
The main transmitter chip used is not the only thing determining how "clean" it is, there's also the quality of the low pass or band pass filter before the antenna. The better transmitters don't use those BH1415 or related chips. The Broadcastvision, Decade models with the exception of the CM 10, The Veronica most likely not as it's a higher quality level. They use totally different chips and more discrete components. From what I've seen even the CCrane does not use that chip. Mark FCC ID MCHCM-LT Here is the test data on the Decade. The conducted emissions scan on the phase and neutral side of the line does not indicate any emission at 7.6 or at 15.2 MHZ. (The scan range is from 150 KHZ to 30 MHZ) The radiated emissions test is clean also. So what I am asking is: Run your transmitter on battery power and see if this spur can be heard as opposed to AC power. I know that Carl's FM-30 can be operated from a battery. Also, while I don't disagree with the group's observations, but I am having a tough time wrapping my head around a 7.6 MHZ clock causing this problem.
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Post by Deleted on Jul 24, 2017 20:25:48 GMT
TEST RESULTS FROM CARL
This afternoon we set the Ramsey FM30b to 90.3 MHz, the same frequency used in Jeff's reports.
Power output is set at the legal Part 15 level, which was compared to 3 certified transmitters, all of which luckily agree with each other and are thus a fair guideline.
The spectrum analyzer is 15-feet away in a permanent position on a desk.
90.3 MHz showed 39 dB.
Next I looked at 105.5 Mhz, the frequency where Jeff reported receiving a strong spur. We do not have a local station on 105.5. There was no spur at all in our test.
Looked at 7.6 MHz in the shortwave band, the fundamental frequency of a crystal inside the transmitter. No signal observed.
Looked at 15.2 MHz on the shortwave band. No signal observed.
Looked at the 2nd harmonic of 90.3, 180.6 MHz, saw a bump measuring 15 dB, which is 24 dB below the main carrier, well within guidelines of 15.209.
No testing was done outside of Part 15 levels because I do not have verbal permission from the FCC to exceed the rules during testing.
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Post by Druid Hills Radio on Jul 24, 2017 20:33:52 GMT
TEST RESULTS FROM CARLThis afternoon we set the Ramsey FM30b to 90.3 MHz, the same frequency used in Jeff's reports. Power output is set at the legal Part 15 level, which was compared to 3 certified transmitters, all of which luckily agree with each other and are thus a fair guideline. The spectrum analyzer is 15-feet away in a permanent position on a desk. 90.3 MHz showed 39 dB. Next I looked at 105.5 Mhz, the frequency where Jeff reported receiving a strong spur. We do not have a local station on 105.5. There was no spur at all in our test. Looked at 7.6 MHz in the shortwave band, the fundamental frequency of a crystal inside the transmitter. No signal observed. Looked at 15.2 MHz on the shortwave band. No signal observed. Looked at the 2nd harmonic of 90.3, 180.6 MHz, saw a bump measuring 15 dB, which is 24 dB below the main carrier, well within guidelines of 15.209. No testing was done outside of Part 15 levels because I do not have verbal permission from the FCC to exceed the rules during testing. Thanks Carl. As I suspected, the plot thickens as they say, whoever they are.
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Post by station8 on Jul 24, 2017 20:51:23 GMT
Howdy All: My results are at the initiative/new radio revolution site. Under FM transmitter interference issues the-initiative.boards.net/You will be surprised Station 8
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Post by station8 on Jul 27, 2017 13:11:42 GMT
Howdy All: Carl this is on your test report please!
Questions for you please!
I notice some information was missing out of the test report!
TRANSMITTER SETUP:
1) Was test done in a one level or 2 story home?
2) Antenna used on Ramsey FM 30b ? (Example 1/4 wave ). A) length of antenna? B) Antenna in a vertical or horizontal position? C) How high was the transmitter off the floor?
SPECTRUM ANALYZER:
1) Brand and model number of spectrum analyzer?
2) Antenna used on the spectrum analyzer? ( example 1/4 wave ). A) Length of antenna? B) Antenna in a vertical or horzontial position? C) How high was the spectrum analyzer was off the floor?
Just a reminder you could of used the test sheet that I made that's On the alpb web site.
Thank you
Station 8
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Post by thelegacy on Jul 27, 2017 16:41:18 GMT
Testing is far from over here at The New Radio Revolution. If we get active members willing to pay dues $5-10/Mo we would be able to test more TX's to see what we get. Here is our exact link so you don't have to search. This is in our Open Forum so No Elite Access is needed. In Fact we have LOTS of info that DOES NOT require Elite Access to get. What should be Public Knowledge in this hobby STAYS Public knowledge here at The New Radio Revolution. the-initiative.boards.net/thread/132/ramsey-100b-fm-txEnjoy!
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Post by Deleted on Jul 27, 2017 18:38:18 GMT
Interference is Our Job
Jeff Station8 wants Carl to work harder: "I notice some information was missing out of the test report!"
TRANSMITTER SETUP: 1) Was test done in a one level or 2 story home? One level. 2) Antenna used on Ramsey FM 30b ? Telescoping antenna that came with it. A) length of antenna? 28-inches B) Antenna in a vertical or horizontal position? Vertical C) How high was the transmitter off the floor? 30-inches.
SPECTRUM ANALYZER: 1) Brand and model number of spectrum analyzer? ATTEN AT5005 2) Antenna used on the spectrum analyzer? Telescoping which came with it. A) Length of antenna? 13-inches maximized B) Antenna in a vertical or horizontal position? Vertical C) How high was the spectrum analyzer was off the floor? 30-inches
Jeff reminds us: "Just a reminder you could of used the test sheet that I made that's On the alpb web site."
Yes, that is an excellent test sheet but I cannot find it amidst the thousands of threads.
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Post by station8 on Jul 27, 2017 20:21:21 GMT
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Post by Deleted on Jul 27, 2017 20:51:06 GMT
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Post by Boomer on Jul 28, 2017 6:13:46 GMT
More to think about
Spectraman, with his spectrum analyzer, checks out Chinese FM broadcast transmitters.
I already knew that there were issues with the DSP that he talks about, the main focus of the video.
Apparently the original was a concept transmitter from a few years ago, digital generation of the multiplex signal and RF control functions, with the promise of getting rid of analog imperfections in the sound that the analog chips have, except it generates a noisy RF spectrum around the carrier.
The designer even noted the spectrum problems in his documentation, but that didn't stop the chipset from making it into many transmitter designs. The audio is crystal clear, separation best-of, but in most areas, don't amplify it.
In any case, it does show that different exciter chips do affect the noise, when I had thought that all analog chips after the BA1404 were about the same in spurious content, Spectraman believes they're not.
Boomer
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Post by thelegacy on Jul 28, 2017 15:37:09 GMT
Thanks for that video. I found that a while ago and lost it and thanks to you I have it again. What is most interesting is that the 1414K chip is better than the 1415F chip on the spectrum analyzer.
According to this video the 7 Watt TX I took back was inferior to that of the YF-15B or the YF 7 Watt version. IF we ever got more power we'd have to outlaw certain chips from being installed inside those hobby broadcasting Transmitters. I'd like to have known this guy cuz if we could have him join our group and have members pay dues we could have him test transmitters.
I noticed his spectrum analyzer went from 9Khz to 1.5 Ghz This means he could have even tested some AM Transmitters in which I think are very dirty spectrum wise. I'll also have to see if he has any more videos to watch.
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Post by Boomer on Jul 28, 2017 18:30:54 GMT
It seems AM struggles to get enough bandwidth, where FM is too wide, circuit-wise.
On AM, using the regulation 3 meter antenna, you have some kind of loading coil that's 'high-Q', meaning narrow band, and selective. Most .1 watt transmitters just connect the final stage right to the coil without any intervening filtering, it's simply not needed with the selectivity of the coil and 3 m antenna combination.
So, harmonics are gone on AM, and there can be synthesizer products, though the oscillator operates at 10.24 mhz, far above the AM band. You can get small amounts of phase noise near the carrier, and the 10 khz reference frequency sneaks through on the air, but usually you have to be right near the transmitter to hear any of that, an area where RF is measured in volts.
FM has such a wide band in use, and circuits have to be wide band to cover 20 mhz+. Now the reference oscillators are below the band, and low frequency, so they or their harmonics can sneak through, like is possibly happening with 7.6 mhz or other reference frequencies. On top of that, you have multiplex stereo that generates still more frequencies, and uncontrolled, that could cause spurs and mixing products.
Designers have to step in and make a really good multi-purpose chip that takes care of these problems, and design a killer circuit for everyone to use. I'm convinced they can do it, analog, and these days especially DSP, since that's the way things are going.
I think I see what the transmitter companies are doing, they find someone's innovative concept in a presentation or school thesis, and if it seems to work, and the chips are out there, so they seize on it. Companies make nicely designed PC boards, double sided beauties, but the circuit is half baked for one reason or another, and yet people are relying on this stuff for radio stations in their communities around the world.
Boomer
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Post by Deleted on Jul 28, 2017 19:00:30 GMT
Money Handling
TheLegacy moves closer to big time operation: "If we get active members willing to pay dues $5-10/Mo we would be able to test more TX's"
When the dues start rolling in I will handle all the book keeping and banking so you guys can concentrate on the technical side. I will be happy to do this.
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Post by thelegacy on Jul 28, 2017 23:39:44 GMT
Here's how it works for my radio station. Listeners donate to my station via PayPal. When I get the money for a piece of equipment that I need I simply go on eBay Amazon or whoever accepts PayPal. I buy the equipment that I need. For example if I need an antenna I would go to PayPal check my money and find an antenna that I want. For example a ground plane for instance. It cost $45
I then purchase that antenna through PayPal since PayPal keeps track of all the money that comes in.
Since Station 8 is doing all the testing he could for example set up a PayPal account. All you need to do is have a donation link on your website in which PayPal shows you how to do it. The website has to accept copy and paste HTML code. Copy and paste the HTML code to your website and Wala you have a way for people to pay dues for this project.
Say station 8 and I want to test a transmitter for example one of the Decades or we could test one of those variable transmitters 0 to 15 watt. Or even that new Rolls transmitter could be tested for harmonics and spur's. The group will choose a transmitter to test and then we simply wait until enough money is in PayPal. When the money is there you simply go on eBay Amazon or 108 megahertz wherever you need to go to get that transmitter. And simply order it and wait for it to arrive and then test it.
People do like my station however it takes a while to get around $100. But when I do get around that that's when I can get some equipment. It's worked for me very well so far and it's how I've gotten what I've gotten for my station so far and I'm disabled.
Where there is a will there is a way. And if you don't like the transmitter after the tests somebody will. Or even if you do like the transmitter and can't afford it there's always somebody out there willing to buy it.
I'm actually looking to get some equipment right now and I almost have the money for it. So like I said if you guys are really interested in starting a group like that it can be done.
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