Wandel & Goltermann LEVEL METER SPM-30 ?? - Page 1
Forum section: electronics / rf-microwave

author: vinlove
author_rank: Frequent Contributor
timestamp: December 01, 2020, 04:38:02 pm
content: https://www.woutersenwouters.be/sold-products/235744/w%26g-spm-30-level-meterI just got this device, and it is a RF signal generator, but also can be used as a receiver I was told.I connected the RX antenna, and was trying to RX the LW and MW band with it.The signal level goes up on the meter on the local strong MW station frequencies, butcannot get the audio.Is the SPM-30 able to output normal analogue audio from the received signal?Or it is just for checking the signal strength only?There are what looks like audio outputs on the front, but cannot be certain because it isdrawn with signs, rather than written. I have connected cable into the output terminalsand connected to the external speakers, and even to Boombox LINE level amp. No joy, but just faint hum.And it is 1980s Made in Germany. I have downloaded the User Manual but it is 100% in raw German.Do you know about this device? or own one? Or if you can read German fluently, would you be able totell about the LW MW band reception?Thanks

author: vinlove
author_rank: Frequent Contributor
timestamp: December 01, 2020, 04:41:12 pm
content: Just saw this, but mine has no audio from the MW frequencies.The Meter goes up and down from the received signal.

author: srb1954
author_rank: Super Contributor
timestamp: December 02, 2020, 07:56:45 am
content: Quote from: vinlove on December 01, 2020, 04:38:02 pmThis instrument is primarily a level meter although it does have an optional a tracking signal generator. It was originally used for testing old analog telephone transmission systems so it is primarily intended for speech signal measurements rather than being a general purpose level measurement meter.It should be possible to receive AM broadcast stations on it if you attach an antenna to the input and attach an audio amp to the Demodulator O/P (three jacks in the upper left corner, possibly labelled Demod. Ausgang). You will need to select the demodulator mode on the switch below the jacks to demodulate the upper or lower sideband of the signal to get a demodulated output. It only works in single sideband mode. The bandwidth should be set to the maximum of 3400Hz (3 push-button switches in the approx centre of the panel, possibly labelled Rauschbandbreite) if you want to listen to speech. Listening to music won't be so great due to the limited bandwidth.My German labels mentioned above may not be completely accurate as I have transcribed them from my own W & G level meter (an earlier model than the SPM-30) which has both English and German labelling. For the rest of the labelling do a Google search for images of the SPM-30 as there are some showing English labelling.Also download the SPM-30_appendix.pdf file from the KO4BB manual site. This is a service document so it doesn't provide any user documentation but it is in English and includes a block diagram that may help you understand the operation of the unit. I haven't seen a full user manual in English but the operation of these units is fairly simple once you figure out what the front panel labels mean.A final and very important note - open it up and check if there are batteries inside. If there are remove them immediately and clean up any corrosion before it destroys the instrument. Wandel & Goltermann gear is the test equipment world's equivalent of Rolls-Royce and deserves careful preservation.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 02, 2020, 08:55:32 am
content: Great info and advice srb, thank you for that. Much appreciated.I tried connect my old boombox line input to the top left corner of the SMP30 output terminals, but failed to get audio output.Checked the AC voltage from the terminals, and there is AC output 2-3V.I will look at the internal battery in the set too, because I had impression that since it is a rechargeable battery in the set, they wouldn't leak out.But maybe I was wrong. I hate battery leaks, which destroyed many of my gadgets in the past.Usually the AA or AAA batteries are worst culprit for the destructive leaks in my experience.This SPM-30 is built like a tank, and feels the real professional instrument. Very rare too. No one seems to know about it, nor seen it in flesh.I don't want to ruin the set by the battery leak.My SPM-30 is also older and earlier model it looks. It is slightly different in that the 3x middle buttons for the bandwidth selector buttons in the youtube video, but mine has only 2x buttons.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 02, 2020, 09:04:59 am
content: And please explain more about the 3x demodulator jacks on the top left corner of the SPM30. How do you connect them to audio amp? Audio amp has 2 connections per 1x input + and -. Why does it have 3x jacks? Which one is + and which -?

author: srb1954
author_rank: Super Contributor
timestamp: December 02, 2020, 12:10:26 pm
content: Quote from: vinlove on December 02, 2020, 08:55:32 amIf it has batteries in it they will quite likely be Varta brand Nicad batteries which are notorious for leaking if they are left in equipment that hasn't been used for a long time. I have seen many pieces of test gear damaged beyond repair by these batteries.

author: srb1954
author_rank: Super Contributor
timestamp: December 02, 2020, 12:28:52 pm
content: Quote from: vinlove on December 02, 2020, 09:04:59 amThese connectors are an old type used in telephone exchanges. The 3 pins provide for connection to a shielded, balanced twisted pair cable although, in this instrument, this output circuit is an unbalanced one.Two of the pins should be labelled with a symbol showing a short line with a thicker bar across the end. Either can be used as the signal common and should be connected to the common of your amplifier. The desired output signal will be on the remaining pin of the three and should be connected to the line input of your boombox. This instrument is not powerful enough to directly drive a speaker and is monophonic so only needs to be connected to one channel of your boombox.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 02, 2020, 02:11:39 pm
content: Quote from: srb1954 on December 02, 2020, 12:10:26 pmHow do you open the casing for the batteries? This set is still operating normal, so hopefully the batteries had been already taken out by the previous owners. But I am not sure at this moment.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 02, 2020, 06:26:20 pm
content: Gawd, it was easy just opening the back panel. As guessed, the batteries had been taken out by the previous owners.The battery compartment is empty and clean.