FM antenn***

[ka7niq]

Ok, let me give you another option ?

Vertically stacked Small FM Yagi's ! http://www.anarc.org/wtfda/stagger.pdf

http://www.teeveesupply.com/product_pages/antennas/winegard_antennas.htm

Here is why.

Antenna gain is seldom a problem in FM reception, thanks to million watt transmitters.

The problem we encounter is noise, and adjacent channel interference.

There are 3 parameters one must consider in a Yagi or a Log Periodic array.

Gain, Front To Back Ratio, and bandwith.

Because the FM band is so wide, it is hard to get a single Yagi to cover the whole band, and keep its pattern clean.

Thats why you see so many Log Periodic antennas.

A Log Periodic will have multiple driven elements, where as a Yagi will have but one or two.

To make matters even more confusing, sometimes a Log Yag is used with a small Log Periodic driven array and Yagi directors and a Yagi type Reflector!

The best Yagi's are called FM high, and FM low.

That is, they are optimizzed for a particular part of the band.

It is very difficult , even with Computer modeling, to get a Yagi to have a clean pattern over the entire FM band!

The link I have provided is for a small 3 feet long, lightweight 4 Element Yagi.

It provided more or less constant gain over the entire FM band.

It does so by sacrificing some gain and front to back ratio for bandwith.

Remember, the definition of bandwidth here is the ability to have reduced, but constant gain over the entire FM band.

It must be noted that an FM only Yagi, cut for either the Hi or Low part of the FM band, will seriously outperform this antenna!

Let me know if you have some particular stations ONLY in mind that happen to only fall into either parts of the band!

If thats the case, I have a much better option, but that would mean pissing away performance on the other part of the band!

Now, let me tell you the neatest "trick" you can do to this 4 element antenna!

Buy TWO of them, and stack them vertically, pancake style, on the same mast!

Why ?

Because stacking them will not only increase gain, but much more importantly, it will cause a reduction in side lobe amplitude!

It is possible to get side lobe reduction with deep nulls of 40 db or so by close stacking!

Usually, about a 1/2 wavelength distance is best for an antenna this size, IF you seek to only increase foreward gain.

But, at spacings a little less then optimum, the side lobes go way down.

1/2 wavelength is only about 4.5 feet at 100 mhz !

So, if you get a 5 foot mast into your rotor, you will have enough mast to effect vertical stacking!

Remember, we dont have to go out to the full 1/2 wave stacking.

Anything from 3/8 to 1/2 wavelength will effect the side lobe amplitude reduction we seek.

Of course, you will need a phasing harness to connect the two antennas, and if you contact the antenna manufacturers engineering dept, they can supply one.

I know that Channel Master, Finco, Winegard, and others have them.

This should be a wonderful little antenna array that will provide a super quiet signal because of its high degree of side rejection.

Also, because it is vertically stacked, it has the ability to respond to a larger variety of wave angles, and will reduce fading under DX and Tropo conditions!

Of course, it will not outperform a Yagi cut for a particular part of the band, except on DX because of its larger aperature.

Maybe, just try one of these little guys first, and see if it does the job ?

Then, you can always stack later, if it dont ?

If you want a larger antenna, I reccommend a Log Periodic.

The more elements a Yagi has, the more high Q it becomes, and the narrower the frequency range that it will work in.

This little guy will cover the whole band, is small, light, and low Q.

Plus, its cheap too!

KA7NIQ

[ka7niq]

I WISH I had an AK 3!
Mine is an old AK 2.
Is it fairly easy to upgrade the AK 2 to AK 3 ?
I cant seem to find the Info ?
Nice Pix BTW

[Al Klappenberger]

To change the AK-2 to and AK-3:

*change the 140 uF cap across the woofer to 50 + 50 uFd (100 uf total).

*change the 4 mHy inductor across the squawker to 5 mHy,

*change the T5a autoformer to a T4a

I am not sure what the turns ratio is of these two transformers, but the Universal Transformer #3636 will replace either type.

Al K.

[ka7niq]

Thanks Al !

i am pretty well sold on your wooden horns for the future, and perhaps your crossovers too.

I really MUST discipline myself, and sell off some stuff, hi hi!

I wass told that the quickest, cheapest way to improve my horns was to upgrade AK 2 to AK 3 ... Do you agree ?

Where might one find the parts from ?

I can source caps, but I am unfamiliar with Autoformers.

Are you aware of any detailed, step by step instructions w.part sources for this change ?

What will the net result of all this be ?

What is the change, if any in the sound ?

Wouldnt the less capacitance on the woofer allow it to play up higher, and further muddy up the sound ?

This "woody" resonant sound is my cheif complaint in my horns now that the TEAC digital amp has "tamed" the harshness and spittyness.

Or, is it the low end of the squaker that is the culprit, and one needs the woofer to play higher up to cover this coloration ?

[BEC]

Ka7niq,

I can help you with the autotransformers. I keep them in stock. I will attach a pic of an AK-3 I have built.

Bob Crites

[Al Klappenberger]

ka4niq,

I don't think there is major difference between the AK-2 and

AK-3. I suspect that the changes were more to correct a phasing

problem between the woofer and squawker at the crossover rather than to

allow the woofer to go higher. Rather than do a conversion to the AK-3

you would do better to simply build and all new AK-3 or buy one of the

new clone networks Bob offers. You might also build one of my

Universal replacement netwroks. The ultimate would be my "ES-Khorn"

extreme-slope netwrok combinations. I beieve that what you really need

is to get rid of the K400 squawker horn in favor of my Trachorn. I

think the network upgrade should be second on the list no matter which

netwrok you choose.

Al K.

[ka7niq]

Ok, then thats what i need to do.

I will contact you off the board.

TNX

Ka7niq

[jerseydevil]

Thanks.

[Al Klappenberger]

JerseyDevil,

Sorry we took so many diversions off of your subject! I hope your question got answered ok to spite all of it!

Al K.

[jerseydevil]

Not a problem. In fact I had studied a little for a Ham license way back when in the late 70's -80's.

[IB Slammin]

Outdoors is best - and on a rotor, with PROPER common bond grounding , although Audio Amateur did have some plans for an attic mounted antenna some years ago (...that as I recall, I never could quite figure out the plans!)

But hey, if the elements are sturdy enough, it could always double as a clothes drying rack! Or extra closet space!

But I gotta run, Tennessee is about to play Florida (boo! - damn I wish Spurrier was there to hate!), and as history is my source, UT always wins when they are the 200 point underdog and they always seem to find some novel trademarked way to lose when they are favored!!

But who cares, as the Smokies is/are the prettiest ('purtiest') place on earth!

Is there anyone who does NOT hate Spurrier?

Terry

[westcott]

What are the ramifications, if any of using an antenna for both video and fm audio?

Does the video quality degrade if you split the coax signal for fm audio and hd video?

I do not listen to fm radio very often so I have not tried to split the signal yet. I installed the antenna on the roof to get OTA reception of local stations and HD video. It was a unit from Radio Shack that was omnidirectional and I believe was given a purple rating. It is rather large and facing north\south. I made sure it was well grounded.

[ka7niq]

Well, Unfortunately many Video Hi Def antennas are UHF antennas, and FM is VHF.

However, If it is truly a VHF - UHF TV antenna, then it will work ok for FM.

This is because the FM band I believe lies between TV channels 7 - 8

Please be aware that when you split the signal, there will be some loss.

This loss may not be significant enough for visible degradation of your video signal.

But, you will have to try it and see ?

I would first split the signal using a splitter, and give both a try ?

If it works, leave it alone, and enjoy.

IF not, then take DJK's excellent advice and get a small masthead signal amplifier, and hook it before the splitter.

This will more then make up for the lost gain.

I would just get the lowest gain one they have, it will be the least expensive too.

If you have too much gain, you can easily freak your AGC circuitry out, and cause unexpected problem that can drive you nuts!

The splitter will only cause a 3 db loss, so if you get say a 10 db amplifier, you will still be 7 db ahead of the game.

You also might think about an increase in height.

At VHF, even an increase of only 5 feet can open up a whole new world of FM stations to you.

Us Ham Radio operators have a "rule" for antenna's.

If it didnt blow down within a year, it wasn't big or high enough, LOL

Chris

[ka7niq]

You wrote """Is there anyone who does NOT hate Spurrier?"""

I HATE Steve Spurrier !

He is one arrogant SOB.

I am glad he left Florida, and was glad to see him fail at Washington too.

I would gladly give a year of my life to cold cock his arrogant jaw just one time.

The Tennessee coach Fulmer, is a class act, as is our new Florida coach Urban Meyer.

Bobby Bowden, Joe Paterno, class acts too!

[westcott]

It is both uhf and vhf and is placed on the roof of my two story home. It is a new neighborhood with few adult trees and any obstructions for miles. I am pulling in about 16 stations for TV which is far more than I expected.

I will run down to RShack and pick up a splitter and let you know what the fm sounds like, number of stations, and video\sound quality.

Raising the antenna will have to wait until I am finished with the family room\home theater. I have more than enough work on my plate before the furniture and drapes come.

Thank you for your quick response.

[ka7niq]

Great Idea!

Be SURE and allow some extra cable for when you increase antenna height ?

I bet just a splitter will make you adequate for Tv AND FM too.

But, be honest, if you are having ANY TV reception problems, then just go get an amp from the git go.
If not, just split and enjoy!

[pauln]

If you only listen to a single FM station, a simple dipole can be cut to length for just that frequency.

Paul AD5FT

[JSharp]

If you only listen to a single FM station, a simple dipole can be cut to length for just that frequency.

Paul AD5FT

And those simple wires will work surprisingly well if they're outside and

have a little height, along with being oriented correctly...

--

Jim - KE9JR

[ka7niq]

Right You are!

I have had unbelievable results simply cutting a dipole for the center of FM Band, and pulling it up to the top of a tree!

Its SO easy to get a wire in a tree!

A fishing pole works great.

I use at lease 20 lb test line, with just a 1 or two OZ sinker attached.

Throw the sinker over the top part of the tree.

Then, go find the sinker, and tie some poly rope to it.

important to use Poly rope, it holds up way better!

Simply go back to the fishing pole, and reel the line with the rope attached to it back over the tree/

Once you have the rope in hand, simply tie it to the dipole, walk back to other side of tree, and pull dipole up.

Experience has taught that it dont really matter how the diploe is oriented, horizontal or vertical.

Just get that puppy up as high as possible.

of course, also tie a rope to bottom of dipole, to finally secure it in place.

Once dipole is up, tie one end of rope off real good.

Then grab the rope hanging off bottom end of dipole, and tie to something, being sure to leave some slack.

It dont matter how it looks, and it can be vertically oriented, if you wish.

In theory, Vertical will P/U more noise, but that high up, it really dont matter.

Your height will place you well above most man made noise sources.

Plus, vertical dipoles are omnidirectional too!

If you have to tie it at a 45 degree angle, it will favor the direction it is pointed in, so if it slopes to the south, it will favor that direction.

And, if you tie it to another tree, and its purely horizontal, it wilkl have nulls off the ends.

I really dont like to go horizontal, because that requires another tree, and when the wind blows, it can easily rip the antenna in half!

I had a vertical dipole up at 115 feet in a backyard tree in Seattle.

It was amazing!

Portland, Oregon and Vancouver Stations were full quieting!

In FM, Height makes might!

Plus, up at those heights, the signals received are much cleaner, and you can hear the difference.

This is how it's done KA7NIQ Style.

YMMV