A Different Kind of Noise Problem

[RadioDaze]

My brother got a HP-1 last month, and now, to my jealous horror, I find that he's mounted a Diamond Discone high on his rooftop. I drool, being in a restrictive condo.

Reception is just fine. But he's in a wind-prone area, and the thing resonates at maybe a middle-C note that can be heard throughout the house. Seriously, sounds like a ghost up there.

Anyone else have/had this problem? Maybe a standing wave setting up in the elements? I thought maybe they could be bound together with something to dampen it. He thinks it's just not an industrial grade antenna so it dances around too much.

His frequencies of interest are VHF-air, fire ops at 150-160 MHz, and LA County Fire ops at ~470-ish.
I think he needs a nice dual- or tri-band solution. He's willing to throw money at the problem.

 

[GKolo]

The 300 foot tower at the dispatch center i worked at in Florida made a loud humming noise during hurricanes, I was neat to listen to.

 

[ridgescan]

My brother got a HP-1 last month, and now, to my jealous horror, I find that he's mounted a Diamond Discone high on his rooftop. I drool, being in a restrictive condo.

Reception is just fine. But he's in a wind-prone area, and the thing resonates at maybe a middle-C note that can be heard throughout the house. Seriously, sounds like a ghost up there.

Anyone else have/had this problem? Maybe a standing wave setting up in the elements? I thought maybe they could be bound together with something to dampen it. He thinks it's just not an industrial grade antenna so it dances around too much.

His frequencies of interest are VHF-air, fire ops at 150-160 MHz, and LA County Fire ops at ~470-ish.
I think he needs a nice dual- or tri-band solution. He's willing to throw money at the problem.

Oh yeah I got two up there singin their song which is about the same tone and pitch as an owl but steady, but I think it's cool-plus it keeps the crows away

 

[wyomingmedic]

I have a couple of things that may help. Being an an extremely windy area myself, I have had (and still do) some similar issues. Currently by large Rohn tower sings in the incessant wind.

Make sure with his antenna that the pipe it is mounted to is not OPEN at the top. The wind blowing across those things is the #1 reason for a low pitch noise. Usually the antennas themselves are too small to hum, so the pipe is the problem.

Also, if there is any kind of loading coil or anything, put apiece of heatshrink tubing over it (works on mobiles as well) and shrink it down. You can also add it to the tips of radials to changes how it resonates.

But my first bet is still the pipe

WM

 

[RadioDaze]

Make sure with his antenna that the pipe it is mounted to is not OPEN at the top. The wind blowing across those things is the #1 reason for a low pitch noise.

That sound exceptionally insightful. I will relay that to him.

Ridgescan, are YOUR pipes open, so to speak?

 

[ridgescan]

Yeah matter of fact they are-on the bottom where tha coax runs in to the connector. I tend to think the coax would kill any harmonic at the hole though-no? The pipe that the scanner discone is only a 1" condiut. The other one is now mounted on a RS 5' mast but this noise happened long before that went up.

 

[killmoles]

Another vote for the pipe here. You should hear the Northwest winds make a similar noise with the culverts across the street from me.

 

[neondesert]

Anyone else have/had this problem? Maybe a standing wave setting up in the elements? I thought maybe they could be bound together with something to dampen it. He thinks it's just not an industrial grade antenna so it dances around too much.

His frequencies of interest are VHF-air, fire ops at 150-160 MHz, and LA County Fire ops at ~470-ish.
I think he needs a nice dual- or tri-band solution. He's willing to throw money at the problem.

I think that wyomingmedic may be on the right track with the open pipe although my mast pipe is open and I haven't experienced middle-C.

I believe more study needs to take place with this unusual situation. I recommend he throw some money into the pipe and try a different antenna. In the meantime he can ship me the Diamond and I will perform extensive testing on it, which I estimate should take no longer than 8-10 years.

 

[ridgescan]

I thought it was that my Diamonds were so perfect that angels were up there singing their praise

 

[neondesert]

His frequencies of interest are VHF-air, fire ops at 150-160 MHz, and LA County Fire ops at ~470-ish.

Since Middle-C is at a frequency of 262Hz I would have to conclude his antenna needs serious tuning!

Now if he was trying to pick up his local church choir, that's a different story.

 

[majoco]

Me too. Discone made of ali tubing. Bungs on the outer ends but open inboard. Hummed and whistled a variety of notes. Unfortunately mounted on the end of the house righ over our bedroom. If the humming of the antenna didn't wake me up, then a nidge from a sharp elbow sure did!

Filled the tubes up with that aerosol foam stuff - absolutely dead now.

Incidentally, you should stop your antennas 'organ-piping' as it can eventually lead to metal fatigue and cracking at the fixed end.

Cheers - Martin ZL2MC

 

[madhatter66]

As someone else mentioned, you might try shrink tubing. I used shrink tubing on the radials of my 20-146 to stop is from making noise... Home depot has the stuff for a pretty decent price... Just the tube the end of each radial and shrink it down, if it needs more put one all the way up against the other end of the radial where it is threaded in... I ended up using like 8 on my 146...but it no longer whines in the wind... Cost me ~$2 Also used it on the antenna I have on my car to stop it from making noise as well because the loading coil made it whine something horrible... Used some shrink tube to dampen it down to where it won't whine until I hit about 110... :roll:

 

[AK9R]

The cone elements of the Diamond discone are aluminum tubing. The top end is filled with a plug, probably aluminum or zinc, so that the set screw has something to tighten down on. The bottom end is supposed to be protected with a plastic cap.

Are those caps in place? If not, maybe the wind is blowing across the open bottom of the tube setting up a resonance in the column of air in the tube.

If the caps are in place, maybe the tube needs to be filled. I wonder if you could pour something like the plastic used to dip tool handles down the tubes to fill them.

 

[jim202]

Antenna vibrating in the wind

The ham radio operators have had this same problem with their beam antennas for years. The simple
solution for the larger tubing was to add a piece of nylon rope to change the resonant frequency of the
tubing. On the smaller tubing of the discone antennas, as someone else has mentioned, you could
try to blow in some of the spray foam insulation inside the tubing.

If you really wanted to get creative, you could get some of the black nylon rope that is used for the
support of antennas and tie it around the bottom end of each element to keep them from vibrating.
This would in effect create a ring around the bottom end of each element. If you use a clove hitch
or something of that sort, it should hold and not slide off the end. Just bear in mind that this is only good
for about 4 years or so before the rope gets destroyed by the sun and weather.

 

[RadioDaze]

When my brother first put up the mast, it had only a weather station sensor, and the top of the mast was capped. No wind noise. Then he added the discone, but omitted the cap. Then the wind noise started. I heard the noise myself, and it seems to be of a low enough register to be the mast. Middle-C - who knows... it wasn't even an educated guess. But when he goes up to re-cap the mast, I'll have him check for open tubing ends. Maybe save the rope or heatshrink tricks in case it isn't resolved with the cap.

 

[vdubb16]

you know it never donned on me till i saw this post, i noticed a strange sound usually during late nights workin in the garage and has since stopped since the 20-176 turned into a lawn dart.