question about SWR meters

How low of a frequency will a typical SWR meter register? When I key the mic without talking into it when trying to transmit in SSB, should there be any deflection on the swr meter?

Unfortunately there's no such thing as a "typical" SWR meter. The operating frequency of an SWR meter is determined by the frequency range of the bridge/directional coupler at its heart, which is dictated by it's architecture/implementation.

_Generally_ speaking, a meter using ferrite cores/transformers will operate a lower frequencies that one with waveguide couplers, although either architecture will function beyond its intended frequency range - albeit with degraded sensitivity/directivity. If you have a meter to hand, just try it! Terminate the output port with known loads* and compare the theoretical SWR with what the meter measures :)

* You could avoid the hassle of high power non-inductive resistors by perhaps trying simple combinations such as:
- 50 ohm dummy load
- 2 paralleled dummy loads (= 25 R)
- Short circuit
- Open circuit

You can build a SWR meter to cover any specific range of frequencies rather than a very wide band range

As I answered in your other thread on this subject .... no you wont seen anything on the meter till you talk, when using SSB mode

Dave

How low in frequency? SWR meter measures forward and backward powers, so if your frequency is so low that the length of transmission line is a small fraction of a wavelength, I guess there can not be a standing wave, and as such the SWR meter will stop working. Also, as mentioned, the SWR meter itself needs to have coupling down to the low RF frequencies also.

How low do you want to go? Do you need to keep it in circuit all the time, or can it be removed once the SWR has been measured? What is the application?

I see recently a circuit for a wide band SWR meter, which would go down to DC. The issue was that it had 3 dB of loss, so could not be left in all the time. It was some variation of a Wheatstone bridge, but I can't recall the details.

Some HP vector network analyzers go down to 1 Hz. I'm not sure how they work, but if you dig out the manuals from the Agilent web site, you might be able to work it out. One often sees "impedance meters" on eBay, which can measure a complex impedance. Once you know the impedance, you can work out the SWR quite easily.

Deborah

No, because the transmitter output power is zero without talking.