HP 400EL AC voltmeter

[carlos2007]

Hello all,

 Recently I am in the process of  making alignments in some HF receivers, Panasonic RF-2200, Drake R4B and SPR4, need to have the IF, mixers, premixers preamps and other RF parts been calibrated.

 I have already purchased a TinySA signal generator and a Sanwa multimeter in order to start but I have realizad that I had hidden in a cupboard and old HP 400EL AC voltmeter and I have some doubts in how to use it.

VTVM is across voice coil in order to read the maximum output in the scale. Could I place the HP in the same configuration? Is it more accurate than the analog multimeter?  One think that bother me is that I do not understand the range switch and display.

Only works to 10Mhz or may it be used to 30 Mhz (shortwave bands)

Any help and advice is greatly wellcome I am a bit lost about this device.
Thanks in advance.

[wn1fju]

Meters like the HP400 series are particularly useful when trying to adjust things to peak a signal level.  Much easier to see the peak than on a digital multimeter.  Whether the HP400 is more accurate than your Sanwa, the answer is probably yes.  Typically, HP analog meter accuracies are in the 1-2% range (of full scale).

The meter is easy to use.  Just set the range switch until you get a reading.  The bottom scale is for the "3" ranges (0.3, 3, etc) and the middle scale is for the "1" ranges (0.1, 1, 10, etc.).  The top scale is a decibel reading and is referenced to 600 ohms.  In other words, about 0.773 volts through a 600 ohm load will give you a 0 dBm.  You can pretty much ignore the top dBm scale if you like.  The meter has a 10 Mohm input impedance and should be able to measure things without loading the circuit down.

These meters don't have overlapping scales.  By that I mean you will find there is only one range where you will get a valid reading.  The other ranges will either move the needle all the way to the right or to the left.

This is an average responding meter, not a "true RMS" meter.  In other words, for any signal input more complicated than a sine wave, the readings may be incorrect.  But again, if you are using the meter to make adjustments while peaking a signal, it is fine.