Recently in Crackpot Category

MASERs and Why We Don't See Them

| No TrackBacks
Over the past few months, I've given thought as to why we don't see large scale development of MASERs. MASERs, which are like LASERs but generate radio frequency (RF) waves instead of light waves. Both light waves and radio frequency waves are electromagnetic waves. We have high power, coherent lasers used for cutting steel. However, we do not at the present time have high-power MASERs. Initially, I assumed this was because it would be the topic of strictly militaristic endeavors. And while that is true, the body of evidence shows that MASERs didn't develop into high-power variants because of different reasons -- there was no need. Beyond generating a stable frequency reference through cesium or hydrogen emission, there was no need seen in generating a high-power single frequency radio emission. I believe this may be due to the fact that radio waves are seldom coherent, and therefore may have been difficult to excite in a precisely controlled manner. So my conclusion is that the hydrogen and cesium MASERs do exactly what their name implies. The technology is mature. Unfortunately, the lack of a high-power derivative limits the offensive use of the technology, as well as use in communications. And we've gone on to use MASER-like technology to excite hydrogen atoms with magnetic fields -- we call them "MRI", or Magnetic Resonance Imaging.

Twist-Shift Keying or Primative PSK?

| No TrackBacks
Published, 2009-02-08 @ 21:08:58:

http://maxmcarter.com/twistmod/index.html or Twist-Shift Keying, documents an idea to modulate RF around the axis of the antenna ('boresight') instead of modulating the phase, amplitude, or frequency of the antenna.

I am at present formulating a response to this.

My current feelings are that this is a slow, imprecise version of phase shift keying, wherein the signal is phased at +90 or -90 degrees. This is a confusing idea to consider. According to documentation provided by the author, the transmitted signal is either left-hand circularly polarized, or right-hand circularly polarized. From the perspective of the discriminator, this should mean that the signal is approaching or receding, however one also has to think about the fact or concept that the antenna itself may force the signal to simply not appear at all.

I think that for the purposes of considering this signal or modulation method, it may be easier for the reader to work within the confines of linear polarization. Linear polarization is typically defined as either vertical or horizontal polarization, however one may also implement 45-degree and 135-degree polarization by implementing a dipole rotated to that particular alignment. Again, in simplifying mental math, vertical and horizontal polarization need only be considered because of the theoretical infinite loss caused by a linear polarization mismatch.

Moving further along the above idea, one may interpret that when a signal appears on the vertical plane, said signal is absent from the horizontal plane. This, in effect, makes the polarization modulation a crude form of a binary modulation, not unlike a form of Orthogonal frequency division multiplexing.  In the theoretical world, it is possible to determine four states from the two polarizations and the state of the transmitter for each polarization.  Realistically, this may approach the impossible as polarization may be affected by antenna location and/or nearby reflectors. In a long-distance implementation terrain, atmospheric, and ionospheric effects may render the signal completely unusable without some form of a transmitted reference or a guide signal or encoding. It is the opinion of this author that switching to circular polarization would not rid the signal of polarization modification.


The nice part of this supposed modulation method is that the receiver antenna orientation does not affect the capabilities of the receiver so long as the antenna area of sensitivity is pointed at the transmitter. The receiver is only required to differentiate between the two polarities of circular polarization.

Possible? Yes.
Implementable? Yes.
Practical? No.
A use for two Syntor X transcievers? Yes, better than holding down the dumpster. =)

Update: Now that I've had to opportunity to learn a bit more, I realize why this approach is novel but also useless. Previously, we have not modulated a signal based on polarity because polarity may be altered by the physical terrain the signal travels over and through. On HF, Faraday rotation may occur which causes a signal transmitted with a vertical polarization to be reflected in a different linear polarization, such as one at an arbitrary angle anywhere from zero to ninety degrees. For example, vertical polarization that has been shifted ninety degrees is horizontal polarization. Any shift from 90 to 180 degrees is indistinguishable from a shift of zero to ninety degrees without additional polarization information.  This shift may be resolved using interferometry and a second receiving antenna a fixed distance from the first.

The biggest practical reason I can see for not using Quadrature Polarity Modulation (QPM) is that it is often necessary to cross-polarize an antenna to minimize the effects of an interfering signal. Furthermore, using horizontal polarization for long-distance linking allows the reflections from the terrain to cancel each other out, resulting in less multipath interference at the receiving antenna.

I am certain the QPM was discovered at some point in the infancy of radio. I believe there are a number of factors which contributed to abandonment of this form of modulation.

2013-07-25: Edit and update

The fiber optic industry has, in fact, already done this:

http://blog.catonic.us/kirby/2011%20IEEE%20CTW_Peter%20J.%20Winzer_keynote%20slides.pdf

and did QPSK over it.

About this Archive

This page is an archive of recent entries in the Crackpot category.

Commercial Radio is the previous category.

Hacker is the next category.

Find recent content on the main index or look in the archives to find all content.