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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Sat 01, 2018 8:11 pm 
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Erich Loepke wrote:
I see the Part 15 pharisees are coming out again. Why would it be illegal to buy or own a transmitter that either doesn't get turned on or is transmitting to the immediate vicinity allowed by regulations even if the power level is above some imaginary threshold not even stipulated in the law? Why the insistence on field strength readings when for all practical purposes a 200 foot range using a sensitive radio demonstrates compliance? I haven't yet seen anyone posting here who was intending to do pirate radio, yet the Part 15 pharisees continue beating the same old drum as if being 10% over the power or field strength limit is the same as a pirate station running 100W. 10% over the limit just MIGHT get attention, and probably no more than being told to lower the signal level and that's it. This black-and-white thinking is getting tiresome, IMHO. I'm not condoning illegal operation, but come on.


Because the law is the law and states the requirements to ensure compliance and also lists requirements such devices have to be built to in order to be legal to own and operate.

I remember a time when illegal transmitters weren't allowed to even be discussed here. Suppose that's still the rule though.


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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Sat 01, 2018 9:10 pm 
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Tube Radio wrote:
Because the law is the law and states the requirements to ensure compliance and also lists requirements such devices have to be built to in order to be legal to own and operate.

I remember a time when illegal transmitters weren't allowed to even be discussed here. Suppose that's still the rule though.


What specifically makes a particular transmitter "illegal"? Seems to be whatever certain members here think it is, and usually with no further explanation.

All I see in the regulations is that an uncertified device can't be offered for sale, nothing about buying, owning, or building a particular device beyond a vague statement about "good engineering practice". Unless you can show me chapter and verse where there is a prohibition on OWNING an uncertified or otherwise "illegal" transmitting device. I don't think there is one.

The only technical requirements have to do with field strength, spurious emissions, and frequency bands which do not allow unlicensed operation, nothing about power level, antenna design, or anything else (except for exceptions like 15.219 which is an alternative to field strength rules).

Absent any proof that shows that merely owning a particular device is against the rules I am sticking to my interpretation.

I'm going to repeat myself here, but I am not in any way suggesting or condoning operation outside of the Part 15 rules.

I just get tired of the same old "That transmitter is illegal" crap that some post after merely looking at a schematic of a proposed design, no measurements given that confirm or deny this except for the designer/builder saying they only got 100' or less range out of it which is most likely well within Part 15 limits.


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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Sat 01, 2018 10:28 pm 
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For a part 15 AM transmitter if the final draws more than 100mW it it illegal to operate even if the signal only transmits one foot.


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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Sat 01, 2018 10:43 pm 
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For the nitpickers, I wonder if a BCB or SW band regen radio connected to a longwire outdoor antenna is legal since we know they can radiate a signal and the antenna is way oversized for part 15. :)


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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Sat 01, 2018 11:02 pm 
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Tube Radio wrote:
For a part 15 AM transmitter if the final draws more than 100mW it it illegal to operate even if the signal only transmits one foot.


Under 15.219 rules, yes. But with a one foot range it's well within 15.209 field strength limits and perfectly OK. There is a serious misconception that 15.219 rules apply in all cases for AM band transmitters; 15.219 rules are only an alternative to the field strength limits under 15.209 that show compliance by a voltage/current (and therefore power) and antenna/ground length measurement in lieu of field strength measurement that is easier to do with normal test equipment. For all practical purposes a range of about 200' on a sensitive radio demonstrates a field strength within limits.


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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Sun 02, 2018 12:41 am 
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Doesn't that still make it illegal if it violates one part of the rules unless the operator has a field strength meter and can verify it is within limits?


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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Sun 02, 2018 12:52 am 
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Tube Radio wrote:
Doesn't that still make it illegal if it violates one part of the rules unless the operator has a field strength meter and can verify it is within limits?

Time to find the ignore button. :?

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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Sun 02, 2018 1:36 am 
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Geez you guys; news flash...Nobody in the real world gives a damn WHAT the electric measurements inside the transmitter are.

The only practical situation to consider is that you don't interfere with licensed commercial broadcasting -to include operating a pirate station that can be received beyond your property- so that they -the commercial broadcasters who pay the government for the privilege to broadcast- don't lodge a complaint against you with the FCC. Those are the only ones the FCC is gonna pay attention to anyway.

And if your signal IS heard all over town, the only recourse the feds will require is to diminish it to within the confines of your property, or shut you down entirely. Do you REALLY think they are gonna come out with equipment to measure the output wattage? Their car radio picking it up half a mile away is all they need.

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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Sun 02, 2018 3:07 am 
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What do you think? Is it time to put a ribbon on this and move on?


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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Sun 02, 2018 5:14 am 
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All I know is that while you guys were bickering, the AM transmitters sold out. :lol:

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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Sun 02, 2018 5:54 am 
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hi all. All parts of the part15 regs do not apply to any one device. Part 15.219 is one way you can comply with the rules. You can also comply with part 15.209 and be running a 10 watt transmitter into an attenuator as long as your radiated signal complies with part 15.209. And if you are running a carrier current transmitter as long as you comply with part 15.221 you may run up to 50 watts however in a home setup you would have to attenuate it heavily but it is legal as long as you comply with the rule that applies to what you are doing.
Just under part 15.219 you can end up with signal strengths all over the place just depending on the efficiency of the final all other values unchanged. As I stated before on another thread the part 15.219 rule was put there to make it easy to comply with part 15.209 as until recently most transmitters we use were not very efficient. And lets not leave out part 15.23 that talks about homebrew transmitters. It talks about good engineering practices and for inventors and experimenters they have reasonable lattitude which does not mean run 10 watts on am into an antenna to see what happens.


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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Sun 02, 2018 6:02 am 
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Exactly. There's so many variables.

If a complaint is lodged all the fcc will use is a field strength meter and if you're in violation that's it.

Now most of us do not have a field strength meter so we use the 100mW part as that ensures compliance when the specified antenna length is used.

That said most if not all of us are going to pick a quiet spot on the dial anyways so a little bit over won't much interfere with anything.

And most of us have receivers more sensitive than what the average joe has so when we pick a quiet spot it is indeed quiet even at night.


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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Mon 03, 2018 4:21 am 
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I have been running a Part 15 station in my house for 14 years, using an LPB transmitter and leaky coax antenna. It is legal, and can only be received in the house, and for a short distance into the yard; I doubt that the neighbors can even receive it.

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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Mon 03, 2018 6:18 am 
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The AM kit is the same one I built recently. viewtopic.php?f=12&t=344806
I'm pretty happy with it, after a simple circuit mod suggested by Dare4444.

As to hum issues, I'm powering it with a 12v auto jump pack. Haven't found a wall wart it likes yet, but I haven't really investigated AC power very much since the jump pack's battery works fine. I am using the close by main AC panel as transmitter ground and the house ground rod is right outside.
-Ed


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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Mon 03, 2018 1:39 pm 
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12V smps laptop type power adapters will eliminate the 60 Hz noise. Or you could use a 19V laptop adapter and bring the voltage down with a 7812 voltage regulator. Generic laptop adapters are available on ebay for around $7.


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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Mon 03, 2018 3:24 pm 
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If you can get to the rectifier bypass it with small value capacitors which may reduce or eliminate the hum.

Also you could try a 1:1 audio transformer on the input which isolates the transmitter ground from the audio input ground as I've found that the audio cable and source can increase the hum as with the audio source grounded to the transmitter circuit ground, the audio cable and source then becomes part of the ground circuit.

Also I've found some radios hum less if the transmitter is ungrounded.

Since doing the audio transformer modification to my transmitter I've had way less hum issues.


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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Mon 03, 2018 6:43 pm 
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Grounding my transmitter did reduce the hum greatly, and also increased the signal.

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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Mon 03, 2018 9:22 pm 
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I wonder what the power output of that PLL AM kit is. If it's the full 100mw it might be usable as a part 15 broadcast transmitter.

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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Sep Thu 13, 2018 2:01 am 
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Tim Tress wrote:
Grounding my transmitter did reduce the hum greatly, and also increased the signal.


I have found grounding through a .01 cap helps reduce hum sometimes, but not without it.

Why?


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 Post subject: Re: eBay transmitter kits - wow!
PostPosted: Nov Fri 09, 2018 1:57 pm 
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Ed in SoDak wrote:
The AM kit is the same one I built recently. http://antiqueradios.com/forums/viewtop ... 2&t=344806
I'm pretty happy with it, after a simple circuit mod suggested by Dare4444.

As to hum issues, I'm powering it with a 12v auto jump pack. Haven't found a wall wart it likes yet, but I haven't really investigated AC power very much since the jump pack's battery works fine. I am using the close by main AC panel as transmitter ground and the house ground rod is right outside.
-Ed



I bought and assembled one of the AM kits and am using a Linksys 12V wall wart and have a hum-free transmission on 1200KHz. No grounding or modifications required on mine. The only adjustment required was the potentiometer on the AM board. I am receiving a clean signal on my Zenith 12-S-265 at 30-40 feet with about eight feet of wire. I was feeding a signal from LAOldies on my computer. Now I'm on a quest for an appropriate housing to contain the unit. If I can't find a decent clear plastic box with correct dimensions, I will construct one.

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