KROSS model GY-TVA 003 (4 Bay whisker antenna)

[mrpeter105]

Originally Posted by balm

Would be interseting to see you K6sti yagi build if you have any pics...

I finally did it. I created an album and I posted some of its pics and comments in the original thread "Which VHF-Hi ONLY antenna or other solution?". This should be the url

http://www.digitalhome.ca/forum/show...&postcount=318

I hope that helps. Also if you check my album you'll see some of my other antenna pics such as my SBGH Gen1 builds. Not pretty but they work.

[mrpeter105]

Now that I figured out how to post pics I might as well do it here. The comment below the picture is pasted from my album.

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My KROSS GY-TVA003 with Philips SW2083W/17 preamp. I got the KROSS for $10 on sale. Grabbed it for my dad as I needed something that would survive outside. Obviously my SBGH builds are meant only for an attic environment.

Anyways, I didn't think that rf11 would be a problem with my SBGH but it was. I couldn't get it to decode even though there was some signal. So I tried the KROSS and it seems it has a much easier time picking up rf11. I get about 65% on the signal meter pretty consistently depending on where I put it. The spot where it is in the picture is a hotspot for rf11. I tried my SBGH there and it was able to decode rf11 but it was right at the cliff. The KROSS provides a nice extra margin with its folded dipole.

The yellow thing at the top is a plastic clamp that is hanging from some wire to the roof. It attaches to the front where the whisker elements are. I needed to do this because the pole that you see behind the antenna doesn't have a decent base to prevent the antenna from falling over.

Note the philips SW2083W/17 preamp. Got it for $20. I needed to use a radioshack fm trap with it. Without it rf11 would get down to 15 to 20 % on the signal meter. Adding it would bring the signal back up. If your gonna use one of these cheap preamps that is something you'll have factor in.

Note the chimney behind the KROSS. That points to Barrie. With the antenna where it is I get about 15% signal on the signal meter for CKVR rf10 with the KROSS. I think I even stuck it on the other side of the chimney and it didn't appear to dramatically make a difference. However with my K6STI yagi right between the chimney and the roof almost as high as I could get it I was getting around 45 to 55 % on the meter with 40 needed for decode. Also there would be some mild breakup every now and then.
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[mrvanwinkles]

300ohm, post #44

Originally Posted by 300ohm

Also, by closing the ends of a bowtie, making it a closed end bowtie, you effectively add about 1/2" of whisker length over an equivalent open whisker.

This can be quite useful - a good option - I think.

You may need more material for your bowties, to close them, but it adds strength and (effective) length - without increasing the overall space needed for actual longer whiskers.

So home made whiskers made of thinner material, say copper wire, would benefit from this. You could make your whiskers shorter, and joining the ends joins the whiskers and combines their strength - in a triangle shape.

So closing the ends of the bowtie could make the whisker/bowtie a little smaller - more compact for an indoor antenna.

Another thing that I am wondering about.

Whiskers - if I am correct - are a practical form of a Bi-Conical antenna.
And the bi-conical antenna - the cone shape was for making it more broadband - so it workes better over a larger frequency range.
(read that in an old theory book)

Bi-Conical = two 3 dimensional cones point to point - as an antenna.
(dipoles shaped as cones - getting wider as you move outwards from the center feedpoint)

And I have seen some manufactured bowties built like this:
(ignore the dots, they are just to space out the slash - the forum removes extra spaces)
__
\...\
/_ /


Where the closed part from tip to tip is bend in towards the center.

I wonder why that is.
Is that some performance optimization for the conical bow-tie shape?
Or was it just for looks?

Optimizing the bow-tie shape could give some improvements for all these sorts of antennas.

( What about tetrahedron bow-ties, or pyramidal bowties, or something similar - to approximate a 3-D cone ? )

[BOUVAL]

Where the closed part from tip to tip is bend in towards the center

Like this one:
That was to make sure not to pierce anyone's eye.

to approximate a 3-D cone ?

It's proven that the bowties we use do approximate cones.
.

[300ohm]

Where the closed part from tip to tip is bend in towards the center.

In my tests with innie and outie closed end bowties, it didnt make a difference gain wise. The innie bend does seem more structurally sound. Straight is fine too. Ill have to try out the lopsided whisker length variation like on the new DB2e and DB4e. Probably not a significant difference, except for aesthetics.

[mrvanwinkles]

Yes, the bowtie in the picture is what I had in mind / what I had seen before.

What about tetrahedron bow-ties, or pyramidal bowties, or something similar - to BETTER approximate a 3-D cone ?

I had also seen various bow-ties around that were cut out of metal sheet - a funny shape, but the outside angles at the tips were sort of bent forward.

Other ideas (to better approximate a cone).

Circular hoop at end with wire spokes coming to a point, forming the cone (ex. soldered in copper wire - you could vary the number of "spokes")

Alternately - Semi-circle pointing out towards the front with spokes towards the center (half a cone sliced lengthwise).

Funnel / cone shape made of a mesh.

Funnel / cone shape made of thin AL sheet?
(AL Auto body repair roll seen in Canadian Tire - and a couple AL rivets)

Large "CAN" (ex gallon Ketchup can / paint can) - cut some wedges out of the sides to form cone shape.
(cut can in half lengthwise, then cut wedges from sides - two half cones )

Aluminum foil over a constuction paper/cardboard cone.
(as both a practical experiment or possibly for an indoor antenna).
(arts and crafts project)

More sturdy - AL foil or thin AL sheet over a flexible plastic sheet cone.
(flexible plastic sheet cut from a container of some sort - formed and secured in a cone shape).

Cross two conducting sheets, cut wedges, in an X pattern (full cone approximation) or a T pattern (half cone approximation)

" The Funnelator Bow-Tie Antenna "

[300ohm]

I had also seen various bow-ties around that were cut out of metal sheet - a funny shape, but the outside angles at the tips were sort of bent forward.

Yeah, mostly used with corner reflectors.

Aluminum foil over a constuction paper/cardboard cone.
(as both a practical experiment or possibly for an indoor antenna).
(arts and crafts project)

I think you can get styrofoam cones at most craft stores, which would be even better.

[ota_canuck]

The objective is to lengthen the wisker material lengths to 8 1/2" ?

edit: just watched the assembly video again. It may be much easier to just make new wiskers using some #9 galv. wire.

Then just add a 3rd dimension to include the added 2" length and then the KROSS GY-TVA003 spacing layout can remain as is.

Going 3D would also have an effect on beamwidth and overall gain. Hopefully positive!

Note: the faint grey lines in the 'front view' show where the 3D bends would be.

[mrvanwinkles]

Originally Posted by ota_canuck

The objective is to lengthen the wisker material lengths to 8 1/2" ?

Yes. And that is a great idea, excellent suggestion for the KROSS antenna.

Make new whiskers and bend them forward in a manner to both increase their effective length and increase the spacing to the reflector rods.

ASIDE:
But ... based on earlier good suggestions to "close the bowties" - the thread seems also to have evolved into a discussion about possible investigation of other bow-tie designs or shapes. Even 3-D shapes.

Might have some possibilities - not sure.

Maybe the discussion of "Other possible bow-tie shapes or designs - even 3D shapes" should go into a NEW separate thread.

Maybe in Area 51.

Originally Posted by ota_canuck

Going 3D would also have an effect on beamwidth and overall gain. Hopefully positive!

Ya(!) - But not sure ... might warrant some research / investigation.

[ota_canuck]

Originally Posted by mrvanwinkles

Yes. And that is a great idea, excellent suggestion for the KROSS antenna.

Ya(!) - But not sure ... might warrant some research / investigation.

We've already crossed that line:

Here are some benchmark 3D SSH II antenna builds:
http://www.digitalhome.ca/forum/show...&postcount=209
http://www.digitalhome.ca/forum/show...&postcount=124

Make new whiskers and bend them forward in a manner to both increase their effective length and increase the spacing to the reflector rods.

No! Not just bent forward,.. but, bent into 3D form so that the KROSS GY-TVA003 spacing layout does not change at all!
Even though the wire length is increased from 6 1/2" length to 8 1/2" , the new 3D shaped wiskers will fit within the same 6 1/2" spacing..

Maybe this sketch will help:

[mrvanwinkles]

Sort of, but not exactly.

I'm suggesting cone shaped 3-D whiskers - or a variation of that.

And how that might be implemented simply and practically.

And if it is even worth the trouble to try.

(going to sleep now - to have some spaced out dreams about all this.
I am, after all, mrvanwinkles - time for a nap . )

[mrvanwinkles]

Originally Posted by ota_canuck

No! Not just bent forward,.. but, bent into 3D form so that the KROSS GY-TVA003 spacing layout does not change at all!

Yes, sorry, I understood the idea/the drawing, it was getting late and maybe what I wrote in reply was not exactly correct.

So YES (!) - The bent whiskers still fit in the same 6.5 inch length / space.

But parts of the whiskers are bent forward - and that increases the separation from the reflector plane, in some places along the whisker's length.

This may be a good thing - because another one of the "problems" mentioned with the KROSS antenna for North American UHF band - was the short 3 inch separation from the reflector plane/rods is "too small".

I think MCLAPP's M4's typically specify 4.5 inch distance to reflector.

So - your idea likely has other possible advantages.

Your idea and drawing made me think about:
(top view of whisker, ignore dots)

------------------------------------ Reflector rods.

___
.....\
......\
.......\____________________ Whisker - bent forward to increase distance to reflector rods.


( a bend forward to increase distance from reflector to something more than KROSS's 3 inches - closer to the 4.5 inches found optimal in the MCLAPP threads)

[ when we bounce ideas back and forth like this - new ideas come up. collaboration increases creativity ]

[mrvanwinkles]

Here's what I mean by [3D] cone shaped whiskers.

Biconical antenna:

http://en.wikipedia.org/wiki/Biconical_antenna

biconical = two cones

I started to search and research this subject more on the internet now.

Some other web articles recommend "semi-spherical ends" outwards - help extend the cone "electrically" longer. (theory describes an infinitely long cone - so it may be advantageous to do this - similar as "closing the ends of the whiskers" - mentioned earlier - or giving the closed end an angled bend outwards - or a rounded semi-circle bend outwards)

So the biconical type antenna could be fashioned from wire in a sort of 3D cage - for outdoor antennas. (reduced wind load).

Or - for indoor or attic antennas - you could make real cones from AL thin sheet. And somehow, semi-spherical end pieces. (wind loading not being a factor)


( > < ) <--- suggesting closed whiskers like this

[300ohm]

[Homer Simpson] Mmmmm, Ice cream cones, arrrrrggghhh. [/Homer Simpson]

[ota_canuck]

I believe that those biconical designs that you've linked to may have characteristics of their own that would require completely redesigning the reflectors/spacings/phasing, etc...

Simply closing the wiskers at the open ends may help extend the effective wisker length, and removing those plastic covers and relocating those phase lines inside the wisker's 'V' connection points may help to extend the effective wire lengths.

Extending wiskers or changing spacings by any amount beyond the current KROSS GY-TVA003 real-estate will most likely require redesigning pretty much all aspects of the antenna.