Panoramic Spectrum Display - Cheap solutions survey

1. monitoring frequency usage.
   This is the case whenever you need to:
   • check at a glance a wide section of spectrum with low activity such the the entire 70cm ham band. Probability of intercept is function of the number of channels monitored in a timeframe whose size is that of an average communication. A spectral display shows a big number of channels at the same time, hence high probability.
   • check for traffic on correlated channels, like the up and downlink of repeaters or the channel hopping in trunk networks.
   • have a different perspective on wideband/spread spectrum signals that may not be noticed with a normal receiver. This may be the case of my friend's WIFI router whose performance degrades badly on the lower channels: I strongly suspect a TV-sender for this.
2. tuning of simple rf devices, such as filters for my receivers.

Some AOR receivers (SR2000, and the recently announced AR-Alpha) are now featuring the spectrum analysis feature. I didn't consider much this option on the basis of sheer prejudice. I'm under the (probably wrong) impression that the SR2000 may be an AR8600 and an SDU5600 put in the same box. If that is the case, I don't like much the idea in the same way I don't like a VCR (or DVD) and TV combo. Separate components can be upgraded separatley and better tuned to need/taste. Not to mention that in case of faults you loose two devices and not just one. List price for the SR2000 is around € 2300.

PRICE is the most important, but several other factors will influence choosing the right instrument for you, given a pretty wide range of options.
My requirements:

• real time spectrum display
  if you can drop this requirement there are several radio control programs that can plot spectrum activity. Testing and tuning of basic devices can therefore be achieved with a setup like:
• accuracy in measurements not very important
• direct tuning and demodulation of signals preferred, as opposed to using the scanner/receiver as a frontend and feeding the instrument from a I.F. socket. Only mid/high range receivers sport such connection and available bandwidth can be an issue, as it will represent the maximum portion of spectrum visible at any time
  

  AOR AR3000, AR5000	10 MHz
  AOR AR8600	4 MHz	requires modification to enable IF out in all modes
  Icom R7000, R7100, R8500	10 MHz
  Yaesu VR5000	150 kHz	limited use if you are looking at V/UHF AM/FM transmissions, where channels are mostly spaced at 12.5 kHz around here

  Probably other radios can be tapped accordingly, but this is beyond my skills

From various readings I understand that prices for such instruments is now much lower than in the past when sticking to basic requirements. Nevertheless they don't come cheap at all and I decided to focus mostly on second hand gear, as extensive searches on the internet draw this picture (feb-mar '06):
approximated prices taken from eBay and several surplus/used equipment stores

test equipment	second hand HP and Tektronix boat anchors	from € 900 € 600	field test
	new Far-East made equipment, Atten in first place	from € 500
oscilloscope adapters	Homemade, such as the "Poor man's spectrum analyzer"	€ 600 full options
	commercial	€ 500 used
personal computer adapters	test equipment, such as Velleman's	€ 400 new
	software defined radios	€ 900 for top notch
TV level meters	designed for testing and tuning of TV/sat aerials. Promax products quite common.	€ 250/300	field test
spectrum display monitors	purposedly designed units such as the AOR SDU5xxx.	€ 350

Up to date professional stuff is still on a different planet. Have a look at this old page for a taste.

Last update: 24Jul06