Re: Your DSP radio readings on/±20kHz strongest midday signals (incl. nulls)?

James McWain

Stephen, Just forget all of your number..listen to your radio!   James

From: Stephen
To: ultralightdx@...
Sent: Tue, November 2, 2010 4:36:12 PM
Subject: [ultralightdx] Your DSP radio readings on/±20kHz strongest midday signals (incl. nulls)?



1110      43,00 | 30,00 | 20,00
1130-KSDO 72,25 | 43,25 | 19,00
1150      45,00 | 34,00 | 19,00
1170-KCBQ 77,25 | 54,25 | 15,00
1190      43,00 | 29,00 | 15,00

First is when facing the transmitter, second is when rotating for a null (radio is still horizontal) and third is when tilting for maximum null.  In my case, I have two strong stations 40 kHz apart, both basically north of me.  The strongest one, 50kW 1170-KCBQ, is 9.3 miles away, heading 7°, and the runner-up, 10kW 1130-KSDO, is 6.3 miles away, heading 350°.  The difference in heading, and the fact that the tilt null is extremely narrow, accounts for why the 1110 tilt reading is higher than the 1130 reading, which was higher than that of 1170 - KCBQ's signal was upwards of 50-something dBu IIRC (I didn't take a note of it though) when 1130 was tilt-nulled.
On 1110, KDIS is faintly audible, but doesn't come anywhere near pushing through the 0dB barrier.  On 1190, I can barely make out KXMX, but I think KTLK is too far under the desense on 1150 to be heard.

Now... how do your DSP radios behave?  I'd like to know the readings on the strongest station, and the readings +/-20kHz.  (If your radio has selectable bandwidths, set it to 3kHz to level the playing field.)  If there are audible stations on those frequencies, either post only the one that doesn't have any audible station (unless the SNR is 0dB), or post the +/-15kHz readings, unless it's an IBOC station.  Also, like I posted, I'd like to see the numbers when the strong station is nulled.  (You don't have to do the tilt null, unless you want to.)  If your strongest station is such that you're getting 49,00 or 50,00 readings, then post over what range of frequencies you get those readings.  For example, at my grandma's house in San Gabriel I get somewhere around 85-90dBu if not more on 23kW 1300-KAZN and 50kW 1430-KMRB, both of which are diplexing from 1/3 mile away and visible from her front yard.  There, I get 50,00 readings from about 1200-1550 and 49,00 from about 960-1710.

Is my PL-380 and the G8 (which is going back to Radio-Shack tomorrow, although I may buy another one later as I didn't get to finish some comparisons I wanted to do) the only radios that show high RSSI levels on channels around strong signals?  I'm hoping to see some data, and compare to my own PL-380.  I especially would like to know if the PL-606 lives up to spec.  The manual states >60dB selectivity in 3kHz BW when tuned +/-9kHz.  If that's true, should I expect a 75dBu station to be reading 15dBu at +/- 9+ kHz, or a 90dBu station to be reading 30dBu at 9kHz (and lower when tuned farther off at a rate of 9.5dB/kHz, calculated by assuming the BW is +/-3dB, and dividing the dB difference (60-3=57) by the frequency difference (9-3=6) - 57/6 = 9.5)?

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