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| | |-+  Audio comparison of using a filter to improve reception.
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Author Topic: Audio comparison of using a filter to improve reception.  (Read 3852 times)
Squawk 7700
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« on: August 07, 2010, 09:21:50 PM »

Hello fellow feeders and listeners,

Attached is an audio file which shows the effectiveness of using a filter such as the HPN-30118 to reduce interference from FM broadcasters which can cause a loss of sensitivity in most scanners.
http://www.scannermaster.com/HPN_30118_Combined_Notch_Filter_p/24-531024.htm

I will leave the squelch open on my Uniden BC785D for this demonstration.

We hear Qantas 73 "heavy" checking in with San Francisco tower (120.500 MHz) for a landing clearance.

The white noise you hear immediately following is where the tower is giving the landing clearance. You can hear the Qantas acknowledging the landing clearance for 28 Right. Notice we didn't even hear the tower at all? Just noise. undecided

I inserted a sequence of DTMF tones to mark the audio recording for "without filter" and "with filter".
It's like night and day. You can now hear the tower transmissions including aircraft on the ground with the filter in place.

Hope this audio example can be useful?

73's

Ken (N6GOH) smiley
« Last Edit: August 08, 2010, 12:06:00 AM by Squawk 7700 » Logged

Feeder:
KHWD Ground/Tower
KOAK Del/Gnd/Twr
KSFO NORCAL App Rwy 28L/R
KSFO Tower/Ground
NORCAL Approach (KOAK)
NORCAL Departure (KSFO/KOAK)
KSJC NORCAL Approach #2
ZOA Oakland Center (35/40/41)

RJTT App/Dep
RJTT Tokyo Control
RJTT Twr/TCA
Fryy
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« Reply #1 on: August 08, 2010, 02:14:00 AM »

would this also make a difference on the UHF band? I like to scan VHF and UHF for both civil and military listening.
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silagi
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« Reply #2 on: August 08, 2010, 07:42:29 PM »

Is your monitoring site near an FM transmitter?  I have never had problems with the FM stuff bleeding onto the aircraft band.  That is amazing how it cleans it up though.
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Dngnkeeper
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« Reply #3 on: August 08, 2010, 10:01:27 PM »

silagi its not things bleeding through (as seen on the attached file) so much as it is things overwhelming the front end of your receiver and causing reduced sensitivity. This is particularly important when you use a wide freq antenna. Whether it is from commercial FM broadcasts or some other source it can greatly effect the way your receiver works.

At my location I have a tower that is about a half mile away that has all kinds of thing on it. While the transmitters are on frequencies above the aircraft bands they effect just about everything that I try to receive including 802.11 wireless data.

A good filter that filters out the unwanted RF from your front end of your receiver will help your reception.  While the one listed is for commercial FM and freqs above 30mhz you might want to check out your local RF environment and select the filter that gets rid of the unwanted parts of the spectrum, above or below your intended freq, in your neighborhood. There are filters that are specific to the aircraft bands, and only allow those frequencies, that works wonders. You might be surprised at what a difference it makes.

Rick
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silagi
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« Reply #4 on: August 08, 2010, 11:33:12 PM »

Interesting.   The only really major transmitter site I have near my house is Oakland Center which is about a mile down the street.  grin  Too bad my location does not allow me to pick up all Oakland Center frequencies loud and clear.   Darn remote transmitters!  I have never really have had a problem on any of the frequencies bands where I am now even with using a roof top antenna about 25 ft up.    Might be worth a try to get one of those filters that only allows in the aircraft frequencies. 
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Squawk 7700
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« Reply #5 on: August 12, 2010, 09:36:23 AM »

would this also make a difference on the UHF band? I like to scan VHF and UHF for both civil and military listening.
Yes, I just did a test with the BC785D and a J-Pole antenna cut to the UHF Military band with this UHF Filter http://www.scannermaster.com/Jim_HPF_0706A_UHF_Military_Airband_Filter_p/36-531262.htm and it does improve the overall noise floor. Noise test on 310.800 MHz S-Meter 4-5 with NO Filter and 0-1 WITH Filter. Improves reception slightly. Signal strength meter only increased by 1 S unit with a signal present.

Is your monitoring site near an FM transmitter?  I have never had problems with the FM stuff bleeding onto the aircraft band.  That is amazing how it cleans it up though.

I'm line of sight to both San Francisco Airport and Mt. San Bruno. Mt. San Bruno is home to some FM transmitters and TV stations.    

KSFO Tower in relation to Mt San Bruno
(photo attached)
« Last Edit: August 12, 2010, 10:04:56 PM by Squawk 7700 » Logged

Feeder:
KHWD Ground/Tower
KOAK Del/Gnd/Twr
KSFO NORCAL App Rwy 28L/R
KSFO Tower/Ground
NORCAL Approach (KOAK)
NORCAL Departure (KSFO/KOAK)
KSJC NORCAL Approach #2
ZOA Oakland Center (35/40/41)

RJTT App/Dep
RJTT Tokyo Control
RJTT Twr/TCA
theman280
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« Reply #6 on: August 13, 2010, 03:26:22 PM »

gotta say very impressive ....
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neondesert
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« Reply #7 on: August 20, 2010, 12:14:48 AM »

Hello fellow feeders and listeners,

Attached is an audio file which shows the effectiveness of using a filter such as the HPN-30118 to reduce interference from FM broadcasters which can cause a loss of sensitivity in most scanners.
http://www.scannermaster.com/HPN_30118_Combined_Notch_Filter_p/24-531024.htm

I will leave the squelch open on my Uniden BC785D for this demonstration.

We hear Qantas 73 "heavy" checking in with San Francisco tower (120.500 MHz) for a landing clearance.

The white noise you hear immediately following is where the tower is giving the landing clearance. You can hear the Qantas acknowledging the landing clearance for 28 Right. Notice we didn't even hear the tower at all? Just noise. undecided

I inserted a sequence of DTMF tones to mark the audio recording for "without filter" and "with filter".
It's like night and day. You can now hear the tower transmissions including aircraft on the ground with the filter in place.

Hope this audio example can be useful?

73's

Ken (N6GOH) smiley

Hi Ken,

Thanks for putting up the audio comparison on the HPN-30118 notch filter.  I live in Las Vegas about 6 miles from McCarran, 10 miles from North Las Vegas and 10 miles from Henderson Executive airport.  I'm using a Uniden Bct15x and when trying to listen to the air band I noticed a number of radio stations mixing in with the transmissions from the Tower at KLAS at times making it almost unreadable. With KVGT and KHND I was unable to hear any traffic from the tower or ground.

That is until I purchased the HPN-30118 from ScannerMaster!  Unbelievable is all I can say.  I am now able to hear tower, and ground traffic from KLAS and KHND at almost full quieting. KVGT has improved significantly as well.  smiley  

Also, the service from ScannerMaster was excellent.  I placed the order late in the day on a Sunday and received the unit via priority mail on Wednesday morning.  cool

Thanks again for the recommendation!
« Last Edit: August 20, 2010, 10:44:04 AM by neondesert » Logged

Larry
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