[Lf] Mobile Antennas for Antenna Efficiency Msmts]

[Andre' Kesteloot]

Todd Butler wrote:

> Don wrote:
>
> > What kinds of antennas and receivers are you guys successfully using for
> > field strength measurements when checking antenna efficiency?
> > --
> >
> > Years ago as a kid with a ham licnese, I went to work several summers for a
> > guy named Walt Kean in Riverside outside of Chicago. He was a broadcast
> > consultant and I spent many nights checking field strength at the standard
> > measurement spots for AM station directional arrays. It was interesting to
> > watch patterns change over time due to new construction of buildings, water
> > tanks, etc. We used some very interesting measurement gear to do this job but
> > I'll be danged if I can recall who made it or what it was called.
>
> Having utilized that same process and similar equipment in Indiana,
> Connecticut, Wisconsin, Minnesota and Iowa as a broadcast engineer, I can
> report the readings are:
>
> taken at specific locations called "monitor points".....
>
> taken with a "field intensity meter" (normally battery powered), highly
> calibrated (until someone drops it), and very expensive -- manufactured by
> companies like Potomac Instruments in Maryland......
>
> two types of readings.....peaks or nulls.....peaks where the signals are
> directed toward, nulls where a minimum of signals are pointed to avoid (same or
> co-channel) interference.....
>
> the readings not only change due to construction/renewal -- but can (and do)
> change with the seasons, the amount of precipitation (soil moisture), and
> vegetation (trees with or without leaves as an example) growth between the
> source being read and the location.....time of day (or night) changes the
> readings as well....two reasons for this.....skywave propagation from other
> stations and power and/or pattern changes required by the Federal
> Communications Commission by the licensee.....
>
> Hope this helps your memories.....the worse readings I ever took were in a
> mosquito filled swamp (near the tower) at night with the humidity higher than
> the transmitted power in watts.....
>
> 73,      Todd      N0NCL      10 - 10  #66816
>
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