Digital Communications and Frequency Hopping

A Spectrum Analyzer would be my choice for observing the output of a frequency hopping transmitter. Some models can be purchased for as little as several thousand dollars. A Tracking Generator is a useful option in that it can be used to sweep transmission cables as well as TX's and RXs. I am not aware of any online training. Spread Spectrum is not rocket science and a primer found at the library should be adequate. Hope this helps.

A spectrum analyzer (with peak hold) will allow you to view the hop set, but the original post wanted to see the hop sequence. You won't get that from a garden variety spectrum analyzer.

If one wants to know the hop sequence, check the manual.

The implication of that response is that there is only one, or only a small set of, preprogrammed and publicly available hop sequence(s). I'm not an expert on this, but it would seem useful to have any possible hop sequence available via some sort of programming. Might be useful to keep a communication link private. Or to allow multiple communication links operating in the same frequency band.

Most quality SS modems have the capability of selecting any number of hopping sequences. This is important when there are multiple modems at a hub that are communicating with an array of satellite (remote) modems. A unique hopping sequence is required for each link as this will prevent collisions. A sync trigger is generated by one of the modems that is configured as the master. This sync trigger is daisy-chained to each of the slave modems at the hub and that will keep the hopping sequences synchronized. Most SS modems also have the capacity to delete any particular hop or hops that were found to contain interference as determined by the use of a spectrum analyzer.

I forgot to mention: For SS installation and testing, a wattmeter with a Peak Hold function is necessary. Also, you might consider a Bit Error Rate Tester if you are dealing with digital communications. And, don't forget to throw in a few dummy loads.

Yes, we are dealing with Digital communications in the 2.8 Ghz rannge. We have no manuals or know the freq. hop of the unit and we are trying to figure it out. What dummy loads would we need?

If you would furnish the manufacturer and model of the device, I will see what I can find out. As far as dummy loads are concerned, they are good to have around when running up a transmitter without an antenna. It would be advisable to inset an attenuator between the transmitter and any test equipment connected to it so that the full power of the transmitter is not applied to the test equipment. The best setup would be to use a tee-adapter. One leg of the adapter is connected to the transmitter output, the second leg is connected to a dummy load, and the third leg is connected to the input of an attenuator. The output of the attenuator is then connected to the test equipment. Hope this helps.

There is another form of SS. It is referred to as Direct Sequence. This type of transmitter spreads its signal across nearly the entire band allocated by the IEEE 802.11 standard. In order to operate a hub utilizing multiple modems, a TDMA (time division multiple access) operation needs to be implemented. This will allow the multiple modems at the hub to time-share the 802.11 spectrum. So, when selecting a direct sequence modem, it is important to look for this option.