Score again!!!!

Hello kc8gpd.

I am guessing that a nems clarke 120E F.I.M. is a measurement instrument, but I cannot guess what it measures.

I also guess that having one is very important for part 15 AM work, but I am not sure.

Those are two questions without question marks.

am broadcast field intensity monitor calibrated for measuring am f/s from 525-1600khz used in pro broadcast stations for proofing arrays used in part 15 for part 15.209 measurements

Oh, hey, that's something we all need. How much for a new one? Could we get a group rate?

potomac fim-21 close to 10k new

I remember once having $10k. It went for a down-payment on a house. Then it was gone.

So, $400 is a REAL good deal. Luck has smiled at you.

If I could just get to the Denver area you would be #1 in my Roll-a-dex.

All I have is carrier current, but you have a Potomac FIM 21.

Put a picture of it as soon as you can.

no potomac is the latest and greatest solid state. i'm getting a nems clarke. old tube meter from 60's or 70's but in the shape it's in 400 is a good deal

The history of your tube meter from the 70s must be interesting. What was it used for and did it belong to a radio station.... where has it been all this time....

From what I understand, Potomac was the last owner of Nems Clarke, but they have not supported these instruments for years. Will you be able to get a certified calibration for your 120E?

Thing is, will the Nems Clarke 120E detect AM using the quasi-peak detection method called for in 15.219??

I'm not sure that it does.

RFB

uses average.

i'll never be able to afford the 3k+ price tag on a used calibrated FIM that does quasi peak.

i personally find it very ridiculous that used commercial service monitors from the 70's on back still command over 3k+ as well on the used market.

i'm actually giving up on the meter. can't seem to locate anyone who calibrates them.

i'll just have to pay someone to come check my field strengths for carrier current.

i just want to set up my station right. i want them to come here (which they will) and go away happy everything was setup right.

The field strength limits of 15.209 and 15.221 are so low that an FIM is not ordinarily capable of measuring them because of the normally very high atmospheric background noise in urban areas. An LPB application note available on this website recommends bringing the measurement distance closer, from 30 m to 15 m (or to half the radianlength for 15.221), doing the measurement in the near field instead of the far field. The information on the LPB application note is not technically correct, but the FCC may have bought it anyway, since LPB had installed and verified some leaky coax systens, like along a highway leading to Disney World.

Using the LPB application note as a reference may allow 15.219 and 15.221 measurements to be made, because the FCC must have accepted the LPB results in the past. The LPB method underestimates the true field strength, giving you an advantage.

And the cost of renting an FIM? A lot. You may need to have a buddy who owns one.

do potomac 21/22/41's do cispr quasi peak? how is the fcc able to make compliance measurements?