FM Tuner performance measurement guideline

[mikebeth]

Hello all,
Does anyone have information regarding the measurement parameters to be used in making Tuner performance measurements as per manufacturer spec's. Just for instance:

• For FM Tuner distortion @65dBf 1kHz mono, what level of FM peak deviation is specified?
• For FM stereo measurements what is the 19kHz pilot level? 10% ?
• For FM stereo distortion measurements is the MPX generator set to L=R, or is only the channel under measurement (L or R) modulated?
• What is the measurement bandwidth specification? 50-15kHz?

These are just a few of several questions that came up this morning while measuring an FM tuner I just aligned for comparison to the manufacturer spec sheet. Changing any of the above settings changed the levels measured.

These are the kind of details that I need to sort out to make tuner measurements for publication. A reference or link to a published guideline would be awesome and most appreciated. I have not found such a guideline on-line so far. Thanks, Mike

 

[rayma]

This has some info.
https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_application/application_notes/1ga43/1GA43_0E.pdf

 

[mikebeth]

This has some info.
https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_application/application_notes/1ga43/1GA43_0E.pdf

Thanks. I already scanned through that, but I will go through it again in case I missed something. Mike

 

[BrianL]

Many years ago, I remember seeing either an hp or Tektronix ap-note on FM tuner measurements. Unfortunately, I don't have it. Maybe google will help find it.

 

[rayma]

Thanks. I already scanned through that, but I will go through it again in case I missed something. Mike

Pretty sure the measurement bandwidth is 50Hz-15kHz.

You might want to ask here:
FMtuners@groups.io | Home
Tuner Information Center - Vintage Stereo Tuners
List of EIA standards - Wikipedia

 

[mikebeth]

Many years ago, I remember seeing either an hp or Tektronix ap-note on FM tuner measurements. Unfortunately, I don't have it. Maybe google will help find it.

Thanks. From your suggestion I found a manual for an HP 8920 that has information on making measurements which will be helpful.
I am hoping to find an official standard like IEEE xxx.xxx that lays out the rules of the road so to speak.

 

[mikebeth]

Pretty sure the measurement bandwidth is 50Hz-15kHz.

You might want to ask here:
FMtuners@groups.io | Home

Thanks. I'm making best guesses at settings right now, like the bandwidth spec. Did post at FMTuners and AudioKarma forums



Hoping to find an official standard so I can know what the manufacturers use (or should!) so our numbers are apples to apples. I can find what settings give me the best numbers with some trial and error, but that doesn't make my measurements "legal" so to speak!

 

[Bill_P]

http://w140.com/tekwiki/images/9/98/26AX-3582-3.pdf is an application note from Tektronix regarding FM broadcast measurements using a spectrum analyzer.

 

[mikebeth]

http://w140.com/tekwiki/images/9/98/26AX-3582-3.pdf is an application note from Tektronix regarding FM broadcast measurements using a spectrum analyzer.

Thanks Bill, I'll check it out. I think a relevant publication may be


ANSI/IEEE STD 185-1975: IEEE/IHF Standard Methods of Testing Frequency Modulation Broadcast Receivers


but not it's something I have ready access to.

 

[Bill_P]

You may be aware that the 185-1975 standard is inactive-withdrawn. IEEE will sell you a copy for $60 though. 185-1975 - IEEE/IHF Standard Methods of Testing Frequency Modulation Broadcast Receivers - IEEE Standard

There is a critique of the standard at Updating IEEE 185-1975. The author may be able to help you further on standardized testing.

 

[mikebeth]

You may be aware that the 185-1975 standard is inactive-withdrawn. IEEE will sell you a copy for $60 though. 185-1975 - IEEE/IHF Standard Methods of Testing Frequency Modulation Broadcast Receivers - IEEE Standard

Yes, I saw it was for sale and did not feel that as audio hobbyist/amateur I wanted to part with $60 for that info. Thanks

 

[BrianL]

Bill, that Tek ap-note is the one I was thinking of.

 

[mikebeth]

Thanks all for the info. Searching around I eventually found that the info I was looking for was in the old copies of the Pioneer Tuning Fork service guides I downloaded a long time ago.

 

[rayfutrell]

The Institute of High Fidelity used to publish test standards for amplifiers and the like but they went out of business years ago. I did a search on IHF standards but didn't find anything.

 

[mikebeth]

Thanks Ray,
Pretty sure the modulation level for distortion testing tuners is 100%. Now looking into why the measured THD varies so much with modulation level - a minimum of ~0.09% at about 50kHz FM going up to around 0.3% at 75kHz and 30kHz. Puzzling...

 

[stocktrader200]

I got a sx-780 and sx3700 playing to near cd quality on stations with no compression.
you need a strong 88 to 90 mhz station 96 ish and 107 mhz. then turn the trims until all have about the same sensitivity. This will get you real close to ideal.