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Thread: B&K 2050 signal generator help for s-meter adjustment can it be used?

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  1. #1
    Join Date
    Mar 2010
    Location
    Boston ,MA
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    16

    Default B&K 2050 signal generator help for s-meter adjustment can it be used?

    Hello can anyone tell me if i can use a B&K 2050 signal generator to adjust an s meter on a radio. the standard is I think is 50 microvolts over an s9 but this generator puts out way too much power. I would think i need to find an attenuator but they are expencive , any advice in how i can use this equpiment for s-unit calibration.
    Thanks.

  2. #2
    Join Date
    Feb 2004
    Location
    Bakersfield, CA
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    4,592

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    This is going to be an interesting item to try. At the moment the S-meter has a better calibration on it then the B&K 2050 has. The only thought I have is to find another measuring unit to setup for the level you want. This could be another receiver that has a known good S-meter or you could have an oscilloscope with a definite level adjusted on the display and then use an attenuator that would specifically lower to the 50 uv level you desire. Now for that the oscilloscope has to be properly calibrated and the leakage around the attenuator has to be minimized. An attenuator need not be expensive you can build one if you know the attenuation in db you need to get to your 50uv level. The biggest problem is going to be getting rid of the signal leaking from the generator and this can be a lot. If you could put the signal generator on a 100 foot length of coax and put the generator 100 feet away that might work. The problems you're going to encounter are going to be numerous. The 2050 may not be overly stable, the output from the generator isn't constant and the constant walking back and forth is going to get old very fast.
    The best thing to do is find someone that has a good working HP8640 or something along those lines. Getting an S-meter to read constant from one band to the next is quite a chore. It can be done though.
    There are sites on the net that have attenuation caculators that can make the task of building one much easier. This site has online calculators for just about any type of attenuator you could possibly need or want. It's at; http://www.microwaves101.com/encyclo...attenuator.cfm.
    The variable that is unknown is the actual impedance of the output on the 2050 but that can be taken care of with a coupling resistance. I don't think you would need to do that though.
    There may be other thoughts on this from some of the fine folks that have already tried this. Hang in there.
    Hope this helps
    73
    Gary

  3. #3
    Join Date
    Mar 2010
    Location
    Boston ,MA
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    16

    Default

    Thanks for the reply i know this has leakage i have done some testing with it and it seems to be un worth the time to try to get it to work properly. I have seen this unit by elecraft. http://www.elecraft.com/XG3/xg3.htm

    Maybe this is a better way to go. Any thoughts on this little unit?

  4. #4
    Join Date
    Jan 2008
    Location
    St. Mary's County Md since 2000
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    7,483

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    There is NO standard for S-meter calibration. Some influential manufacturers adopt 50 uV per S unit back in the 50's but that never caught on as an industry standard. Each manufacturer has made their choices of how an S meter should work.

    If the S meter on any given radio can be calibrated, that procedure should be outlined in the Service Manual. You need to refer to the manual which will state the procedure, equipment required and the standards for the meter.

    There should be no assumptions or guess work involved. b.
    Bos Ebal Nolom! "South African Cows on a mountain in the West Bank!"

  5. #5

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    Actually, 50-microvolts for an S-9 reading was established by the RMA (forerunner of the EIA) back in the 1930s. Most of the amateur radio manufacturers did basically have this standard for many years including Collins, National, Hallicrafters, etc. Some people think that the Collins standard was 100-microvolts. However, Collins used a 6 dB "matching pad" between the signal generator and the receiver which resulted in 50-microvolts being applied to the radio. This was because most of the older signal generators did not have a fixed 50-ohm output and required a matching pad to achieve this impedance.

    These days, anything goes! A while back several of the Japanese transceiver manufacturers got into a "war" stating that "their" radios were "more sensitive" than the next manufacturer. However, all that they did was to decrease the signal strength to produce an S-9 reading. Then, they went even farther and made the "dB over 9" reading requiring a whole lot less signal strength.

    With the standard of 50-microvolts = S-9, it takes 500-microvolts for a "20 over", 5,000-microvolts for a "40 over", and a whopping 50,000-microvolts for a "60 over". I have measured a lot of "modern" units that produce an S-9 at under 10-microvolts and a "40 over" reading at about 100-microvolts.

    Basically, it is not what the "S" meter reads that is important. It is the signal to noise ratio of the signal that really matters. If the noise level is running S-9 and the signal is not much better, the signal is difficult to copy. However, if the noise level is low a signal that is not even moving the "S" meter may be perfect copy.

    Glen, K9STH

  6. #6
    Join Date
    Feb 2004
    Location
    Bakersfield, CA
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    4,592

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    In a research type of experiments having a known quantity helps determine what is or is not happening. In the simplest sense it is SNR that drives amateur radio communications but if you want real results you need real data. Knowing what the signals are doing in an exact manner can lead to further findings that are helpful or maybe a waste of time. It can be just a relative thing with no reference sort of like what we do now or we can start collecting data that might have some meaning to some research going on somewhere. There are however a number of other variables that can influence the data but that data would be mathematically in ratio to what everybody else would be reading.
    Now the S-meter on my rig is very difficult to get anything over S-9 and you would have to be parked right by my antenna to get a "60 over". Both my rig made by the same manufacturer read pretty much the same and they are completely different units. Maybe someone did pay attention to the old standards after all.
    The Elecraft hand held unit is a good one for general purpose applications and you could use it to set a S-meter. Mostly it was intended to be used in the field like when you go to someones home to buy that hot receiver from his personal collection that is in mint condition. You can now take this XG3 with you find out the facts. That reminds me, I said if I ever had the funds to get one I would. Well I've just bought a TS-590S, a VS35M and an ALS-600 and haven't bought the XG3. I'm going to fix that right after I finish this posting.
    73
    Gary

  7. #7

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    WB:

    Off the air signal strengths here are pretty much the same. All of my "S" meters are calibrated using the 50-microvolts for S-9 and are pretty accurate in the "dB over" readings. I do have above average antennas.

    There are 2 or 3 operators that are active that live within less than a mile from my house, the closest being 5-blocks away. Those stations occasionally peak about a "40 over" although they usually are higher than "20 over" but not reaching the "40 over" reading. The station 5-blocks away has a Heath SB-200 linear but, because he lives in the 2-square block area that actually has CC&Rs (the rest of the neighborhood has none), he is "antenna challenged".

    Way too many operators these days are used to getting at least an "S-9 report and usually considerably higher. A "20 over", a "40 over", and even an occasional "60 over" report is often heard on the bands. Most of those stations are not even making an S-9 at my location and a number of those giving the inflated reports are in this area. Since a number of the stations that are used to getting the inflated "S" meter readings actually get pretty insulted when they do not receive at least an S-9, I generally don't even think of telling them what they are actually reading on my "S" meter. I generally resort to the cerebral method of reporting which was in use for decades before "S" meters became a standard feature on receivers. That is, if I am not having any problems I give them an "S-9".

    Now on VHF and UHF "weak signal" contacts most operators are used to very low "S" meter readings. It is not unusual to hear an "S-0" report where the received station is not even moving the "S" meter yet is perfect copy because the signal is clear of the noise.

    Glen, K9STH

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