HFU HF Underground
Technical Topics => Equipment => Topic started by: [tRMZ] on May 30, 2018, 1347 UTC
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Hey guys I'm new I really like this website; I've been into radio for only bout 5 yrs and only SWL for 2 yrs.
I hear signal reports a lot. I own all sorts of radio equipment in storage...like an SWR meter (missing one gigantic coax). I'll set up SWR later probly for CB.
Anyway plz tell me how to read the •Grundig Satellit 750• signal meter?
You already know this but the top meter goes from 1--9 in black, then continues in green with +10...+20...to 60dB.
Bottom meter is read and goes from 0--5.
If, for example I receive a signal that hits '9' on top meter...is that "S9"? I see you guys reporting signal strength like that.
And does that meter show a SWR?
I hear: "you're 5/9 in Nova Scotia. You're 5/9 in Glasgow." Does this Grundig Signal Meter show me that ratio also? Or only signal strength?
Thnx again you guys are absolutely gr8
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I have yet to try a 750, but I've had the chance to try the 800 that a friend of mine asked me to resurrect from battery acid leakage on the motherboard. (And I was able to get everything, but FM going on that.) Anyway, I've found the 800's "S" meter to be close to the "S" meters in my Icom and Kenwood rigs. That dual display analog meter on the 750 is always a nice feature to have on any radio, desktop, or portable. Kind of a ballpark figure, but an S9 reading on older rigs with around a .25uV (Microvolt.), sensitivity would be a signal of around 30uV in strength. (A decent signal.) A +10 reading (S+10/9, ten over nine.), would be 10dB (Decibels.), over that S9 reading. And scaling up that meter would be the same, +20 on that meter would be +20dB over S9, and so on. As far as that 1 - 5 meter scaling? My $0.02 worth, it matches the 1 - 5 signal meter scaling that's on their lower priced and moderately priced radios receive meters. Since this is a receiver, there is no SWR (Standing Wave Ratio.), reading. That is only for transmitters and transceivers, so that's not what that is for. However, an antenna good low SWR reading on the transmit side can indeed compliment the receive side for better reception. I am kind of going off topic talking about SWR, but since you asked about it, I'll hit it. Generally, the radio transmission standard impedance is 50 Ohms. What an SWR meter tells you is how close, or how far, your antenna is from matching that. Anyway, I hope that this helps, and doesn't confuse you. (Anyone else want to add to this?)
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I don't know how linear the agc action is in your radio, nor do I know the sensitivity level for s9, so it's hard to say what it means in absolute measurements, but suppose the makers are smart enough to use some standard, and anymore all of these rigs are factory aligned by a computer so they should perform well and uniformly from unit to unit.
Until you can feed it a known signal level and note the response, the s meter is just a relative signal level meter, from one signal to the next, but don't let that stop you from reporting the signal level observed. You might also look into the sinpo code some guys use here.
Me I just look at the dB meter on the r390a to read the deebees or the s meter on the sdrs. A strong am local will put in about 80dB on the R390-A smeter, the same sig on hdsdr/rsp2 shows -37dB or S9 +40dB, however each rig is on a different antenna system.
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One point to consider is that the calibration of signal meters on many/most radios is dubious at best. Consider it useful for relative/comparison purposes when comparing signals on a given radio, but not much more than that. Certainly not for absolute values, unless you've verified them with a calibrated signal generator. And even relative readings can be dicey, with non linear response, and often not the official 6 dB per S unit. A quick googling will turn up many sites where the author has checked the S meters of well known and famous radios, showing how inaccurate they are.
An SDR has the potential to have an accurate S meter, if the software is correctly written ;D
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If the S-meter reads S9 on an incoming signal that means strength 9. You would give a signal report of "S9". Above S9, strength is expressed in decibels (dB).
A reading of +20 on the meter is +20 dB over S9, usually simply said "you are 20 over".
A "you are five-nine" signal report means readability 5, strength 9. Look up the RST signal reporting system for complete details on how to give a signal report.
Not sure what the bottom 0-5 scale is all about on the 750. My guess is that it is just a relative scale.
Neither upper nor lower scale has anything to do with SWR... a measurement of transmitter forward vs. reflected power that has nothing to do with a receiver.
A HF set with a properly calibrated S-meter would display S9 for a 50 microvolt (uV) input signal (assuming the receiver input impedance is 50 ohms). Each S-unit would represent
a signal level difference of 6 dB. That said, you probably won't find too many receivers that have a perfectly calibrated S-meter. For example, my experience with the 750 S-meter leads me to believe that it is quite a bit too generous in what it reads out for a given signal.
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If it's a high quality receiver/transceiver I pay attention to the S meter and how it sounds, then I extrapolate it to my portables. Otherwise I just go with a SIO estimate.
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There is another method of signal reporting that you may encounter known as SINPO (or sometimes just SIO)…
Strength, Interference, Noise, Propagation, Overall. Look it up for all the details.
You probably won't hear it on the air because Hams don't use it but you will find it in SWL literature.
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If it's a high quality receiver/transceiver I pay attention to the S meter and how it sounds, then I extrapolate it to my portables. Otherwise I just go with a SIO estimate.
I tend to use SIO most of the time, although I'll throw in an S meter reading under special occasions, like with extremely strong signals.
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yea I figured the measurements were not absolute, I know the meter is probly off a bit...the Grundig is cool but I obviously noticed it's not 100% accurate best receiver in the universe!
So yes my question was in general just how to read the meter. I kno that the calibrations and such...I know the radio itself could be off but I didn't have a clue how to read that meter.
First of all I need to be able to read the meter...then I can worry about its accuracy + calibration. :-) ...but all the info is gr8
Thnx to you all!