691
The RF Workbench / Re: Cheap and easy PWM modulator for small AM transmitters
« on: February 26, 2018, 0812 UTC »
The aforementioned link would eliminate the need for a mod transformer, 24V boost onboard.
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Shortwave Pirate Radio In North America And Around The World, And Other Signals That Go Bump In The Night
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Always consult with the appropriate authorities if you have questions concerning what is permissable in your locale.
Build two identical tuned traps in different boxes to maximize isolation, each tuned to a different frequency of reject. You can probably tune them by ear with a receiver and tune for the deepest notch. When you couple the filters together, you may need to tweek the tuning of each filter slightly to account for coupling.
More info here.
http://www.qsl.net/kp4md/mwfilter.htm
https://www.dxing.com/tnotes/tnote06.pdf
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Speak for yourself. Someday I'll need a range outlet to power my solid state TX
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692
The RF Workbench / Cheap and easy PWM modulator for small AM transmitters
« on: February 26, 2018, 0434 UTC »
I've suspected this was possible before, but tried it today and verified my suspicions. Buy a TPA3116 amp board off ebay or amazon (about $12). Feed 24-28VDC into the amp board, apply audio, and take the L+ terminal to your RF amplifier.
Why it works;
These chips are PWM audio amplifiers. In order to produce symmetrical output, at rest the output of the amplifier is one half the supply voltage, minus a diode drop or two. Thus, with 25V of input, the output pins rest at around 12V. This is perfect for a small grenade/lulu/etc type AM transmitter. All the benefits of PWM with none of the hassle.
As a side benefit, the chip has built in thermal and over current protection.
Better yet, get this guy, as it has built in 12 to 24V boost so no need for 24V power source.
https://www.amazon.com/dp/B0767JLR84/ref=twister_B079QY7999?_encoding=UTF8&psc=1
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Why it works;
These chips are PWM audio amplifiers. In order to produce symmetrical output, at rest the output of the amplifier is one half the supply voltage, minus a diode drop or two. Thus, with 25V of input, the output pins rest at around 12V. This is perfect for a small grenade/lulu/etc type AM transmitter. All the benefits of PWM with none of the hassle.
As a side benefit, the chip has built in thermal and over current protection.
Better yet, get this guy, as it has built in 12 to 24V boost so no need for 24V power source.
https://www.amazon.com/dp/B0767JLR84/ref=twister_B079QY7999?_encoding=UTF8&psc=1
+-RH
693
Equipment / Re: oh masters of the RF circuit..have pity on my dual notch filter
« on: February 21, 2018, 2324 UTC »No, trying to notch out 700kHz and 800kHz in order to deal with the high power BCB stations near my house that are overloading my receiver. If possible i'd like to target those two frequencies as they bleed through the high pass filter I already have.
Perhaps I could either 1) make two filters and separate w/coax (which would give the resistance you pointed out), or 2) put a metal shield between the parallel trap and the series trap and connect them with coax (or maybe a 50 ohm resistor if i can brainstorm a way to do that inside the can).
Build two identical tuned traps in different boxes to maximize isolation, each tuned to a different frequency of reject. You can probably tune them by ear with a receiver and tune for the deepest notch. When you couple the filters together, you may need to tweek the tuning of each filter slightly to account for coupling.
More info here.
http://www.qsl.net/kp4md/mwfilter.htm
https://www.dxing.com/tnotes/tnote06.pdf
+-RH
694
Equipment / Re: oh masters of the RF circuit..have pity on my dual notch filter
« on: February 20, 2018, 0636 UTC »
Be sure the tuned networks are shielded from each other to prevent detuning. I would either use two 365pF AM radio plastic tuning caps for tuning, or use trimmers with parallel caps to get the value you need.
I would do two series tuned networks in parallel with some resistance between them to prevent detuning. I would need to muck around with it to get the response I need. A parallel tuned trap is going to act like a very narrow bandpass filter. If that's what you want.... I assume you want to pass everything but those two MW channels?
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I would do two series tuned networks in parallel with some resistance between them to prevent detuning. I would need to muck around with it to get the response I need. A parallel tuned trap is going to act like a very narrow bandpass filter. If that's what you want.... I assume you want to pass everything but those two MW channels?
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695
QSLs Received / Re: XFM eQSL
« on: February 18, 2018, 2219 UTC »
And with that, 2016/2017 is 'in the can.' We issued 181 QSL's for 9 shows in 2016, and 6 QSL's for one low power test in 2017. Thank You to all the listeners that makes this all worth while.
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696
General Radio Discussion / Re: TCS co-founder 'The Radical' lost to the rough seas of cancer
« on: February 16, 2018, 0350 UTC »
I almost missed this one too. Sorry to hear Poet 
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697
General Radio Discussion / Re: Longwave Pirates?
« on: February 16, 2018, 0113 UTC »
Electric fences anyone?
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698
General Radio Discussion / Re: Longwave Pirates?
« on: February 15, 2018, 1848 UTC »
There is an incentive for folks in Europe to do so; LW is a standard broadcast band and is in a lot of cars and stereo systems.
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699
General Radio Discussion / Re: Sony to Exit Shortwave Receiver Market
« on: February 13, 2018, 1852 UTC »
Look at the bright side; we live in the makers generation. There may come a day were, like once upon a time, we have to build our own radios.
...And its never been easier to do that.
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...And its never been easier to do that.
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700
QSLs Received / Re: Radio Powerplay eQSL email
« on: February 13, 2018, 0600 UTC »
Does anyone have a line on this movie? Might be fun to see, especially subbed.
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701
The RF Workbench / Re: 3kw pep solid state amp 1.8-54 mhz
« on: February 13, 2018, 0028 UTC »
Most likely the Kahn method with carrier leak.
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702
The RF Workbench / Re: A 1 Kw output broadband package
« on: February 12, 2018, 2149 UTC »
Yes, but who wants to do AM at 100 Mhz? I don't get the point of you posting all this amp pallet stuff. I can read NXP's LDMOS portfolio just as well as the next guy.
WHY DON'T YOU JUST BUILD SOMETHING FOR CHRIST'S SAKE.
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WHY DON'T YOU JUST BUILD SOMETHING FOR CHRIST'S SAKE.
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703
General Radio Discussion / Re: Get those long wave antennas ready
« on: February 12, 2018, 1934 UTC »
704
The RF Workbench / Re: A 1 Kw output broadband package
« on: February 12, 2018, 1901 UTC »
Buy something from broadcast concepts. Their stuff at least works, and its made here.
http://broadcastconcepts.com/MRF1K50h.html
Who wants FM anyway? I ran high power pirates for years on FM and the reward certainly wasn't worth the risk, and that was ten years ago. No one searches the FM band looking for something to listen to, not like the 80's anyway.
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http://broadcastconcepts.com/MRF1K50h.html
Who wants FM anyway? I ran high power pirates for years on FM and the reward certainly wasn't worth the risk, and that was ten years ago. No one searches the FM band looking for something to listen to, not like the 80's anyway.
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705
The RF Workbench / Re: 3kw pep solid state amp 1.8-54 mhz
« on: February 12, 2018, 1857 UTC »I don't think too many pirates would be interested in something that needs more than a (four words "Made in the USA") NEMA 5-15P to IEC C13 power cord.
Speak for yourself. Someday I'll need a range outlet to power my solid state TX
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