Sibilance=multipath?

Patrice B

AK Subscriber
Subscriber
Hello there,

This week, I've finally replaced my old little own-made Yagi :2 elements, 300 ohms wire for the main element and metal rod for the director. All of this on a wood frame on the rooftop. The bad weather had made damages to it.

So, I bought a little Yagi 3 elements and replaced the old one.

But now, I find that when the presenters talks, there's a lot of sibilance, particularly the female DJ's, exhibiting as a "ssssss" or "fffffff" in each channel (the presenters are in mono centered obviously).

The new antenna as more gain but was oriented the same way.

Signal is strong and clear on music and don't exhibit the phenomenon, the stereo light doesn't flicker at all.

Could it be associated to multipath and the new antenna having more gain? Yesterday, I climbed on the rooftop trying to orient the Yagi differently without sucess.

Maybe I didn't noticed it before with the old antenna and all of this isn't related at all. BTW, this problem is more prone to occur on my two Fisher's tube tuners (FM-200-B and 101R with addon mutiplexer). My Scott LT-110, also tube, seems less prone to this.

Or, is it normal for presenters to show a little more sibilance than recorded music?

Thanks,

Patrice

**I've just heard the news reader (also a women) and there was no right and left "sssss" or "fffff". Maybe the DJ's in the studio have bad mic habits or the mic is flawed...
**Deemphasis and compression related maybe???
 
Last edited:
I try different stations. If there on all stations pick the strongest and use a wire dipole and see if you get it. Really doesn't sound like Multipath.
 
No, not @ all. What are you using for an antenna?

A Yagi 3 elements.

I try different stations. If there on all stations pick the strongest and use a wire dipole and see if you get it. Really doesn't sound like Multipath.

Worst on a particular station but I climbed again today and turned the antenna maybe 10 degrees. Like I've said before, only some women DJ's.

As for a dipole, I tried it when we moved here first and it was a no go... Even a Beambox and different inside antennas. It's like a blockhaus here for fm signal.

BTW, background is completely black and meters and eye tubes are at their highest level.

Thanks to you all,

Patrice
 
Ah, and most of the stations I'm listening have their transmitters on the same spot: a little mountain about 5 miles away.
But, being in a city, there's a lof of buildings and obstacles between us and the transmitter obviously. A couple of TV dishes also on the same rooftop.
 
Sibilance would be on both channels. Multipath is the signal carrier channel & sub channel arriving @ slightly different times. Sorry to hear that Montreal is an FM desert.
 
Sibilance would be on both channels. Multipath is the signal carrier channel & sub channel arriving @ slightly different times. Sorry to hear that Montreal is an FM desert.

Not a desert per se: two or three good stations but they are hard to receive correctly in my location. In our first apartment, a simple dipole pinned on the wall was enough for good reception.
 
Conclusion: I was in the car today (don't know why I hadn't thought about it before) and selected the specific station while being in the parking and guess what? Same sibilance when DJ's are talking so I assume I should live with it...
 
I've formerly said that the signal was clean but upon analysis, it is not the case. There is sometimes distortion in addition to sibilance...

Well, the weird thing is there is a 25000 watts station transmitting on the same tower (CBC Radio2, 93.5 mHz) without distortion or artifacts...

The culprit station (100.7 mHz, CBC french) is 100 000 watts, same tower but there's something definitely wrong. A small audio of silence here: https://1drv.ms/u/s!AsCftN_jdRMFqkkFH8vEr3Bo6TOR
As you can hear, there's a wind effect easily heard on silent passage. What do you think?

Today, I managed to rebuild a small yagi 2 elements on a woodframe and put it in the backyard and at least, there wasn't any sibilance nor distortion. Wind effect was present with less intensity however...
 
Last edited:
Success: the rebuilt little own-made yagi is on the rooftop again with the right orientation and problem is almost solved.

Felix aka Catman provided me the plan a few years ago.I used simple 300 ohms cable for the driven element and metal coat hanger as director. A 75 ohms to 300 ohms balun and that's it. Fortunately, the bigger yagi cost me just 25 canadian bucks so it is not a great loss.

A little pumping sound (wind) remains but you have to know it's there to notice. Only on the Fisher FM-200B and the 101R. The Scott LT-110 seems immune to this... I'll have to investigate on this, it's like "fffttt" --- "ffffttt" - "fttttt" happening regularly. I've already noticed it in our old apartment with a simple dipole (the FM-200B).
 

Attachments

  • 2 Element FM receive yagi design..JPG
    2 Element FM receive yagi design..JPG
    60.8 KB · Views: 4
Last edited:
Talking to myself but it could help someone in the future:

Knowing the exact coordinates of the station ( http://radio-locator.com/info/CBF-FM ), I used a little iPhone app called "Commander Compass Lite" and entered those coordinates as a new location. Then, I climbed on the roof ( again ... ), reinstalled the Yagi 3 elements and aimed it precisely at the direction given by the compass.

I realized that at first (one week ago), it was maybe 20 to 30 degrees off and the little own-made Yagi installed yesterday was off by 10 degrees. Let me tell you that it was cold there ( -10 celsius ) but it finally rewarded me with a lot more clean stations and my preferred one is now distortion free. :banana: The iPhone however doesn't like cold temps as the compass had gone crazy after an hour outside but fortunately, the antenna was already positioned. I verified again with the same app on my iPad to be sure.

However, there's a really weak pumping sound remaining in the left channel (almost inaudible compared to yesterday with the DIY Yagi). I suspect that the MPX section in the FM-200B could maybe benefit from an alignment.

Thanks for listening...

Patrice
 
Back
Top Bottom