We seek to understand and document all radio transmissions, legal and otherwise, as part of the radio listening hobby. We do not encourage any radio operations contrary to regulations. Always consult with the appropriate authorities if you have questions concerning what is permissible in your locale.

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Messages - redhat

Pages: [1] 2 3 4 5 6 7 8 9 ... 106
1
All of the companies on that list are large manufacturers located overseas.  No doubt Kyocera or Abracon can make you an SMD crystal, but you'll have to order 100,000 units.

Domestically, you can try Bomar.  If its a common part, they can job shop it overseas and have them made in small quantities.  In this day though, better to look at other options than crystals.
http://bomarcrystal.com/

+-RH

2
The RF Workbench / Re: 15-Watt SHORTWAVE BROADCAST TRANSMITTER
« on: December 30, 2023, 2239 UTC »
FWIW, the top of all pages reads...

"We seek to understand and document all radio transmissions, legal and otherwise, as part of the radio listening hobby. We do not encourage any radio operations contrary to regulations. Always consult with the appropriate authorities if you have questions concerning what is permissable in your locale."

Chris just doesn't want to deal with the legal liability of allowing commercial traffic of questionable goods on his site.  He pays the bills, that's his right to do so.

You also have proven over the years to be rather obtuse and abrasive when confronted with concerns about your commercial activities, and that leaves a bad taste in peoples mouths.

+-RH

3
They have listings all over ebay as well.

+-RH

4
SDR - Software Defined Radio / A theory on Kiwi TDoA ambiguity
« on: September 06, 2023, 1639 UTC »
I was thinking about this last night over dinner.  I think the reason the TDoA function on Kiwi's doesn't work all that well is pretty simply;  There are no two Kiwi's with identical antennas, and more importantly, antenna cable lengths.  A few nanoseconds here and there can cause pretty severe distance errors.

If we had a network of Kiwi's with all the same antennas and cable lengths, I bet the results would be more predictable.

Thoughts?

+-RH

5
Huh? / Re: FCC Advances FM HD Power Proposal? Oh boy...
« on: August 11, 2023, 1856 UTC »
The proposal would not raise the current HD power ceiling, which is -10dBc, or 10% digital ERP relative to analog ERP, but instead allow the use of asymmetric sideband power on a non-experimental basis.  They are beating a dead horse at this point.

+-RH

6
The Gates 1KW class AM transmitters mostly used triode tubes, 833A's which are stubborn as a mule on higher frequencies.  Later rigs from other vendors (ITA, RCA, CCA, et al) used tetrodes, which were easier to drive, and didn't require neutralization.  These transmitters would be better candidates for HF service.

+-RH

7
Actually, TV ERP's went down with the conversion to digital.  What used to be a 3-4MW ERP UHF is now about 1MW.  There is one caveat; analog TV power was measured in PEP essentially (sync tip power) whereas DTV is measured in average power.  When factoring in the crest factor of the DTV waveform, ERP's are still about 2x what they once were.  The power limits are dependent on frequency range, as the equivalent service contour on a UHF TV station requires more power than VHF low and VHF high.  People used to put up with the noise in the picture to watch TV.  I remember sitting on the floor of my grandparent's farm in the midwest and watching snowy TV from far away, because there was nothing else.  Digital of course has the cliff effect.  The SNR required for the receiver to decode the datastream is much higher than what we would tolerate in the analog days.

+-RH

8
General Radio Discussion / Re: AM STEREO
« on: June 26, 2023, 1857 UTC »
Decoding C-QUAM as QAM eliminates much of the platform motion with a bump in low frequency distortion caused by intermodulation.  There were hacks to the older C-QUAM demodulator chips where you could disable cosine correction and force the chip into QAM mode.  In software this should be easy to do, and when the Kiwi folks added CQUAM demodulation, I advised them to add a QAM mode to get around the platform motion issue.  I'm not sure that this was done, however.

On HF, ISB would likely be a better choice.  You still would have phasing effects, but the complete channel reversal and wobble under fading conditions would go away.  I chose C-QUAM initially because of receiver support.  At the time, there were no software decoders available for ISB, and to date the only one I'm aware of is onboard the Kiwi.

+-RH

9
The RF Workbench / Re: Oscilloscope recommendation?
« on: June 17, 2023, 1629 UTC »
I have two Rigols.  The later ones are software limited, but can be hacked :)

+-RH

10
In the chance any of you folks ever hear a pirate claiming to be using "Kahn" or "Kahn-Hazeltine" AM-stereo, switch the Kiwi to SAS mode. I have yet to hear a pirate doing Kahn.

As with C-QUAM, there is a pilot tone with the kahn system as well, at 15Hz, Magnavox was 5 Hz.  This would be another tell-tale of stereo transmission.

11
If their intention was to mandate HD reception, they wouldn't have the exemption for all-digital reception.  As most laws, it is vague and confusing for a reason.

+-RH

12
There is an exemption that does not include all-digital AM, but implies hybrid mode must be supported.  This sounds to me like HD AM demodulation is not required.  Thus, as long as conventional AM is supported, the vehicle meets the requirements of the act.

+-RH

13
Nevermind FEMA has dumped untold millions into hardening transmission facilities in the fleet of EAS PEP AM stations....

I'm sure the government wouldn't want to see that money wasted..oh wait.

https://rbr.com/homeland-security-installing-transmitters-nationwide/

+-RH

14
My main processor these days is Stereo Tool running on a Raspberry Pi 4.  The declipper is mandatory with newer music.  I think with the options I bought for AM with advance dynamics and declipping, it was about $200.  Telos licensed the declipping algorithm from Hans, the developer of Stereo Tool.  They call it 'undo'

+-RH

15
Amateur Radio / Re: HAM Official Documentary 2022? SWL'ing rip.
« on: April 30, 2023, 1718 UTC »
I keep seeing it show up in my YT recommends....yawn.

+-RH

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