WKOX, WRCA, WUNR at full power
Wed Mar 18 09:00:43 EDT 2009
From: firstname.lastname@example.org (Dan.Strassberg)
Subject: WKOX, WRCA, WUNR at full power
This time there is no doubt that the three stations are operating at full power.
At night, none of these signals is impressive here at the southern end of Billerica (Pinehurst area, less than a mile from jct. Routes 62 and 3A; 15 miles northwest of downtown Boston and about 8 miles north of Dan's location in Arlington Heights).
WKOX-1200 is the best of the three.? Strength is similar to that of WWDJ-1150 and WMKI-1260 so that would put it around 1.6 mV/m (64 dBu) based on V-Soft night numbers for zipcode 01866 (P.O. half a mile from the house).? That is only about 4 dB better than the old Framingham night signal (given as 59.9 dBu).? The station is listenable though there is occasional background intrusion of CFGO Ottawa and a bit of WPHT-1210's IBOC hash.? Similar-strength 1150 has some French Canadian chatter behind and 1260 has the New Brunswick country station at times.? So none of those?64 dBu?guys is really a full quality night local like 680 at 115 dBu, 850 at 84 dBu, 590 at 80 dBu, or 1030 at 78 dBu.
WRCA-1330 is not as good as it was from Waltham.? The co-channel New Yorker gives it a lot of grief.? An average listener would not put up with that.
WUNR-1600 is the worst.? Unless a radio is pointed just the right way, I'm finding that WWRL from NYC often dominates.? This is poorer than when it was running 5 kW FROM THE SAME SITE !? On one of the weeknights around 8 p.m. I used to listen to an Irish show that was on WUNR.? If driving home from Boston via 93, 128, and Winn Street to 3A, the 1600 signal hung in quite well right up to the Winn Street / 3A junction in Burlington and was still OK - albeit with some NY intrusion - two miles farther north at my house.? With the present signal, I won't be able to enjoy the WUNR Irish show (assuming it's still on) until May or June when sunset is after 8 p.m.
As for consumer radios with AM signal-strength meters, I have a CC
Radio Plus. I got it about nine months ago when my Super Radio III
died. The CC Radio has a visual AM signal-strength display (bars at
the right side of the digital display). The bar display is not
reliable. In fact it is nearly as unreliable as the meter on the
decades-old Pioneer receiver in my living room stereo system. Dollar
for dollar, the Pioneer's AM section is probably the worst ever
manufactured. I'm sure that there must be communication receivers that
have reliable AM signal-strength displays, but put me down as a
skeptic about AM signal-strength displays on consumer products. If I
ever again think that I have found one, I will have to live with it
for a few weeks before I even begin to have faith in the readings
The WinRadio, Perseus, and RF Space SDR-IQ / SDR-14 DSP-based communications receivers have spectrum displays with signals shown quite accurately in dBm.? These are receivers which operate off a host computer.? A Google search will bring up all you need to know.
There are also standalone receivers (actually mostly modern ham transceivers with general coverage receivers) that accurately display dBm or Vrms input level as well as the more traditional "S-units".
The big problem is the antenna being used.? To get something that gives you reasonable accuracy, the antenna must have a relatively flat response (or at least a linear slope that can be calibrated) over the 530-1710 kHz frequency range.? The antenna should present a resistive 50 to 75 ohm broadband impedance to the receiver's RF input jack.? It should also be non-directional.
Active whip antennas such as the MFJ-1024 ("http://www.mfjenterprises.com/Product.php?productid=MFJ-1024") can be useful since the high impedance of the short vertical element is applied to a buffer amplifier to convert to 50 ohms out.? Over the AM broadcast band, sensitivity is a bit less at the bottom of the dial that at the top, but the gain plot is a relatively linear one (y=mx+b as you'd remember from school days) and, when compared to V-Soft's values for the same site, can have strength accuracy transferred to measured signals by a simple formula that can be plugged into an Excel spreadsheet or handheld calculator.
I have done tests here as well as at Menotomy Rocks Park (Arlington), Granite Pier (Rockport), and a couple of other sites with computed daytime groundwave measurements lining up pretty well with the V-Soft numbers.
One problem with active antennas is that they can be overloaded when operated close to transmitting sites.? I'm 3 miles from WRKO-680 and hearing them come out on 1360, 2040, etc. with various active antennas is not unusual.
The other thing is that you do have to perform these measurements outdoors a fair distance from buildings and powerlines.? Parking lots in commercial areas or backyards in residential area would typically be preferable to on-street measurement sites.? Not only can powerlines and structures weaken the signals and add noise, they can also distort the directionality of pick-up: weakening stations from some directions more than from others.
Even with a super-accurate FIM, the choice of an appropriate field site is necessary.? Indoor measurements are seldom an option, even at relatively benign wooden structures.? Pipes, power conduits, heating ducts, and the like will distort the pick-up pattern even if noise or overall attenuation aren't that bad.
For the same reason, direction-finding with a loop is seldom that accurate if done indoors.
Mark Connelly, WA1ION - Billerica, MA?
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