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Old 2nd July 2017, 04:19 AM   #11
benb is offline benb  United States
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Quote:
Originally Posted by Tubelab_com View Post
...
Making a bunch of complete radio transceivers and selling them would also require type acceptance, which is a process generally not possible for most DIYers. Radio kits, bare PC boards and accessories fall into a grey zone.
I presume you mean thing like these, often used for (among other things) robot remote control and such. I've got a wireless thermometer that transmits for about one second every 30 seconds in the UHF range. I don't know what output power these things have, I presume they are a lot less than 100mW:
https://www.sparkfun.com/search/results?term=rf

Quote:
My 41 year career as an RF engineer and transmitter designer at Motorola ended 3 years ago, and the employment agreement preventing me from making RF stuff ended 2 years ago. Will I design and build a "Tubelab style" ham radio? It's on my list. I had a rather complete RF setup on my workbench at Motorola. I have been slowly buying dead RF test equipment cheap on Ebay and fixing it. My plan is to duplicate the setup that I had at work.

I haven't seen an RF forum dealing with advanced RF design, but I haven't really looked either.
I don't know much about RF design (learning more is an item on a long list of things I want to do), but obviously part of the problem with doing it is the exponential cost of test equipment for it.

After so many decades ago when my father tried to teach me Morse code, I finally got my amateur license five years ago. It was a ham cram to get people technicians licenses, and I passed the tech, general and extra tests all in one go. That was largely from having a career doing (non-RF) electronic design and embedded programming, as well as my father's influence of having been a ham.

I knew an RF designer at work a few years ago, it seemed what he mainly did was order parts from MiniCircuits and put them together with the fancy RF interconnects, though I'm sure he had a lot of experience from before those things were available (he talked about how much easier things were with the MiniCircuits things than in the old days), and a lot of knowledge about which components to buy and how to connect them.

The ARRL puts out a magazine named QEX (in addition to the standard QST magazine that all ARRL members receive) that only has articles on designing and building homebrew amateur equipment. I've found a couple copies at hamfests, it looks really interesting to me, I don't know how the articles would compare with your experience, but it looks like a good resource for anyone interested in RF design.
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Old 2nd July 2017, 05:31 AM   #12
Shhh its me is offline Shhh its me
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Originally Posted by Tubelab_com View Post
The OP is in Australia. I'm sure that firing up a 50 watt radio station is illegal there too, but I don't know how well such things are enforced.
.....
The operator was on the air for over 10 years. He started out with a 17 watt transmitter that covered about a 3 mile circle around his house.
.....
He got his equipment from a mail order outfit in Israel. There was a card that plugged into a PC, a box that sat on top of the PC, and the amplifier when he had it.
.....
The entire setup could be automated in the PC.
.....
Thats interesting recall of the past, and akin to my 'want and need'.
My past experience in the field was in the mid 70's as a ratbag on 27MHz band, so I have a basic recall of SWR etc..... interference... and somewhat 'misspent youth'.
None of us were 'legal' as such and some were using up to 100W linear amps in the rig.
A lot of the technical expertise for equipment repair, additional PPL Chanel's and output power mods was provided by sympathetic HAM operators who realised some of us would pursue careers in the field or join their ranks... and that we all weren't evil, punk, anarchistic ratbags out to cause mayhem.
There was always the myth of being raided by the 'powers that be', but this only ever happened when other pirates fought over territory. It's a bit difficult to hide a decent 1/4 or 1/2 wave ground plane stick in the air mounted on a home or car.

Crazy days indeed. Now...

I've had 'need' due to an ongoing 'problem' yet to be remedied, but this is forward planning to address the issue by "an means necessary" should other means fail. Think, 'neighbor from hell generating an equal opposite reaction'.

Automation fits the plan, start operation upon reaching an audible noise level threshold.

I must admit my own limitations and the 'mail order' of equipment is the only practical start, but critical to effectiveness relates to the magical 'black art' of antenna design. The ideal configuration would be highly focused directional and efficient within a certain bandwidth [say 100 to 107MHz].
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Old 2nd July 2017, 03:22 PM   #13
Tubelab_com is offline Tubelab_com  United States
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None of us were 'legal' as such and some were using up to 100W linear amps in the rig.....Crazy days indeed.
Back when Smokey was chasing the Bandit all over the television screen I might have taken the tube from a scrap laser (a 4PR400, closely related to the 4-400) and operated it far beyond its ratings to push the wattmeter somewhere beyond 1200 watt. That thing ran about 3 KV and scared the bleep out of me, so I gave it away to a guy who would never use it.

Still I could barely talk to friend about 20 miles away who was running a Gates shortwave broadcasting transmitter on 11 meters. There were just too many "good buddies" on the air then and I had an interstate road in my backyard.

I found 3 old pictures from back then, 2 of me wiring up his Gates TX, and one of me holding up a fluorescent bulb near the antenna on his car....there was a Collins TX in the back seat.

Yes, I did go get my Tech license in the early 80's, which eventually became an Extra, and I experimented with EME (moonbounce) before the "powers that be" (City Code Enforcement) made my antennas go away.

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The ARRL puts out a magazine named QEX
We had them in out library at work. Even non hams would read them for current tech.

Quote:
MiniCircuits and put them together with the fancy RF interconnects
MiniCircuits did more to lower the barrier to entry for RF than anyone else. I used their stuff often at work for "one off" test fixtures, as did several other engineers.

Quote:
I don't know much about RF design (learning more is an item on a long list of things I want to do), but obviously part of the problem with doing it is the exponential cost of test equipment for it.
At least here in the US, the offshoring of almost all RF manufacturing and design has dumped lots of surplus test equipment on the market cheap. I have been getting HP Rf signal generators that sold new for over $20K for under $500 bucks. Most need repair, but I did 10 years in the cal lab at Motorola before becoming an engineer, so I can fix stuff.
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Old 2nd July 2017, 05:38 PM   #14
Gnobuddy is offline Gnobuddy  Canada
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Originally Posted by Tubelab_com View Post
...near the antenna on his car...
You neglected to mention that his car was no less than a '73 or '74 Plymouth Road Runner.

I had a '73 for a long time, with the 340 CID V8.

-Gnobuddy
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Old 2nd July 2017, 08:05 PM   #15
Tubelab_com is offline Tubelab_com  United States
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The 73 Road Runner had a rather anemic 318.......that's all his insurance company would let him have since he previously had a 71 Charger with a 440 for a total of 7 weeks before wrapping it around a power line pole sideways.

Note the 3 phase power supply schematic hanging from the top of the Gates HFL-3000. My task was to make it run from 240 volt single phase power without blacking out the warehouse complex.
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Last edited by Tubelab_com; 2nd July 2017 at 08:07 PM.
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Old 2nd July 2017, 08:43 PM   #16
DF96 is offline DF96  England
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Originally Posted by TheGimp
I disagree on the difficulty.
I'm not certain exactly what you are disagreeing with. Are you suggesting that people who don't know what they are doing can successfully build transmitters simply by following an ARRL handbook design? Such people would quickly find that handbook designs are not intended for them, but for those with the necessary skills and test equipment to debug their own build. This is not a criticism of ARRL designs, but RF is not like audio. Homebrew amateur radio is not the same as kit building.
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Old 2nd July 2017, 11:14 PM   #17
Tubelab_com is offline Tubelab_com  United States
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It is possible to build a working transmitter by following one of the construction articles in the old ham radio magazines, ARRL handbooks, and even old general electronics magazines EXACTLY as published. That is hard to do today since many of the old parts no longer exist.

The popularity of Japanese radios, the demise of Heathkit and other ham kit makers, and the difficulty in DIY building radio equipment led to a long dark age from about 1980 to about 2010. The ranks of amateur radio operators dwindled during that era, at least in the USA.

That has changed in recent times. The popularity of low cost simple SDR radios, and several internet published designs, particularly the Soft Rock and its variations have led a comeback in DIY radio equipment. Most of this however is aimed at the HF frequency bands (1.6 to 30 Mhz) and low power levels (under 20 watts). There is a 100 watt PA board and parts kit for the Soft Rock though. A few years ago it was stated that there are now more licensed hams in the USA that ever.

Can the average DIYer design and build his own ham set and verify that it meets legal requirements? I doubt it. Can the average audiophile design and build his own HiFi system and verify that it meets the design goals? I doubt that as well, but I will state that the probability of success is higher.
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Old 3rd July 2017, 06:36 AM   #18
PRR is offline PRR  United States
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> OP is in Australia. ... I don't know how well such things are enforced.

They find, seize, and fine. Reported seizures as small as 40 Watts.

"While ACMA inspectors are travelling around, they normally have a spectrum analyser running in the vehicle."

"Penalties for these offences can result in fines of up to $270,000 or up to two years imprisonment."

More unlicensed broadcasting stations shut down | ACMA
FM radio pirate prosecuted | ACMA
Illegal transmissions from Christmas Island stopped | ACMA
More unlicensed broadcasting stations shut down | ACMA

https://en.wikipedia.org/wiki/Pirate_radio_in_Australia

2011: August–November. 105.7 MHz ... closed by the Australian Communications and Media Authority consequently having equipment seized.
2011: 25 September-5 October. ... Australian Communications and Media Authority reported that it shut down an unlicensed AM radio station operating on 1485 kHz
2016: February 29. Dan Morris's West Wollongong home was raided by the ACMA... fined Morris a total of $3,000 and ordered the transmitter be forfeited.
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Old 3rd July 2017, 06:56 AM   #19
darklife is offline darklife  United States
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DIY transmitters are perfectly legal if you stay within power limits. It's not real hard to build a simple 100mw (input power to final RF amplifier, not radiated) AM broadcast band transmitter. Lots of those old phono transmitters of yesteryears used very simple designs to do just that to send it to your radios around the house.
Also there are leaky cable transmitters you can build that the FCC allows up to 50 watts of power into the power lines, which collages used back in the day without license requirements. Just had to connect the radios to the same power in the building to pick it up, or near by.

With FM broadcast band you are restricted to around 10mw of power, but it's more strict because it's field strength regulation, not necessarily power output since high gain antennas can be made for the band, but general rule is around 5-10mw power and you're safe from the FCC.

Most of these simple micro transmitters are incredibly easy to build really, just a simple tuned oscillator and modulator stage. Can be made far more complex with PLL oscillators, digital tuning readouts, audio limiting and pre-emphasis filtering, stereo multiplexing, etc.. to get broadcast quality sound.

If you want to cover a small trailer park or drive through theater you can easily do it with either AM or FM this way. With AM you can get far more distance, up to 1/4 mile legally usually. FM it's possible too if the listener uses a car stereo or sensitive house tuner.

Not condoning illegal activity but really anything transistorized with only a powered oscillator stage that is modulated is likely to fall within the Part 15 FCC rules and will be legal. Even a bit more power than field strength measurements will probably fall unnoticed.
Pirate radio is a whole other ballpark and suited to a much different forum obviously, and most pirates these days stick to shortwave on the 6850-6955kHz band. FM pirates are a dime a dozen in large towns and in some places like Florida can get cops at your door, not just the FCC.

Last edited by darklife; 3rd July 2017 at 07:00 AM.
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Old 3rd July 2017, 11:44 AM   #20
DF96 is offline DF96  England
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Quote:
Originally Posted by Tubelab_com
It is possible to build a working transmitter by following one of the construction articles in the old ham radio magazines, ARRL handbooks, and even old general electronics magazines EXACTLY as published.
Not quite true. Practical Wireless was famous in the UK for publishing designs which a certain author had not properly debugged. I'm sure the ARRL does better than that, but unless many prototypes have been built and component tolerance carefully tracked you can never be sure that an exact copy will work first time.
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