Station Monitoring Equipment

An amateur radio license allows a lot of latitude for the holder to experiment and build his own equipment. The point of the testing is to try to ensure that the license holders are capable of understanding the equipment that they operate and ensuring that any signals transmitted met FCC requirements, which in general mirror international requirements/agreements since those signal can potentially reach, and interfere with services anywhere in the world.

For many amateur radio operators this is not that much of a problem, since the hobby has moved from building your own station from basic components, or re-purposed ex-military or commercial equipment, to simply using "black boxes" - radios specifically built for amateur radio with compliance built-in to the design. That is ok. Amateur radio is a broad hobby. For some people the interest is in the deasign and construction of the equipment, for others, simply in using it to communicate, and everything in between.

However, part of the rules requires that you be equipped for, and capable of ensuring that your transmissions are within the prescribed bands, that any spurious emissions are below specific limits, that the signal is clean, and not interfering with others. There are no specified methods for doing this. It is entirely up to the operator.

This describes the equipment that I use. Others will have other ideas.

LP-500

The LP-500 from Telepost (there is a version with a larger screen, the LP-700) is a very useful piece of equipment, it serves multiple functions: It does more. For the full details look it up on the Telepost website. This is probably enough in itself to satisfy most station monitoring needs.

Siglent SVA1015X

Over the past few years, equipment that used to cost several tens of thousands of dollars has now become much cheaper. One example is wide-band spectrum analyzers. This one covers from 10kHz to 1.5GHz. This also has a vector analyzer function which is enabled by buying a key to unlock it. In its initial version I would probably have said that it wasn't worth the price that they set, but in newer firmware updates it is more useful.

Signal Sampler

One of the problems with having a 1kW signal is that you can't feed it directly into the input of the spectrum analyzer without blowing it up. You really want to check the signal after passing through the amplifier, because not only can this amplify any spurious emissions from the transmitter to a level where they become a problem, but it can add its own if it is not correctly adjusted.

What is needed is something to fit in-line with the antenna feeder which will take a small sample of the signal. Small enough that you can safely apply it to the spectrum analyzer input.

I built this. It works very well for the purpose. The plot on the left is testing the insertion loss using the VNA functionality of the SAV1025X. It is a quite flat response from 1 to 175MHz. Which is quite adequate for my purposes.
Click on the image for a full-size version.

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