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

[mrvanwinkles]

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

"KROSS 4 Bay Digital Outdoor Antenna"

Starting a *NEW* thread so we can investigate this inexpensive antenna on the FORUM.

I purchased one in July 2011 at a Factory Direct discount store in Kingston for less that $20.

It came disassembled in a small, easy to carry compact box.

It was a bit of a puzzle to assemble, but the instructions inside were good enough and I managed to assemble it fine with some basic tools (screwdriver).

We used it as an indoor antenna at work, mounted on a salvaged ventillation fan stand on a low table. I took the fan head off, fan must have died, someone threw it out, looked like a good mast and stand for the antenna so I salvaged it.

UHF performance seemed pretty good. It's 4 bay whisker antenna with reflector rods.

VHF - so so - not so great - Probably because the VHF part is only a 29 inch folded dipole. No reflector or directors for the folded dipole.

In the next posts, I'll post some information and details I have of the antenna.

Some measurements and sketches - hopefully someone would like to try and model it on computer - and we'll get an idea of performance. Maybe some suggestions for MODIFICATIONS (I've tried a few practical real life MODS myself on it - with some success).

[ Another member on the FORUM requested we start a THREAD on this antenna to start to investigate it - since I had purchased one and used it already, I though ... SURE ... I'll start a thread, and add my info ]

So here goes.

[mrvanwinkles]

Here's a picture of it I got off the internet somewhere and put in my Photo Album:

KROSS 4 Bay Digital Outdoor Antenna

model: GY-TVA 003

[mrvanwinkles]

Here's a scan of a hand sketch I made of the basic measurements of the antenna. A rough drawing of dimensions.

I will try to type some info, description, and measurements in the next post.

I hope this sketch and the measurements are reasonably viewable in this post.

KROSS 4 Bay Digital Outdoor Antenna

model: GY-TVA 003

Sketch / drawing with basic dimensions.

Dimensions in INCHES

[ota_canuck]

It does look interesting for VHF/UHF applications.
http://www.youtube.com/watch?v=9gUp7Uy_qEk
With your post the dimesions, it may be worth someone doing some nec modeling.

[ota_canuck]

Here's some manufacturer specs:

Kross 4 Bay Digital Outdoor Antenna (GY-TVA003)
Kross 4 Bay Digital Outdoor Antenna for reception of outdoor TV signals and compatible with analog and digital terrestrial signals. Has high impedance matching and strong reception giving the antenna high sensibility, for reception of clear picture in weak signal areas or frequencies. Works great in outdoors, attics, indoor, mobile homes, etc.

Product Features
Frequency range: VHF & UHF & FM (VHF:88~230MHz/UHF:470-862MHz)

Gain: 20dB

Maxium output power: 94 dBµV

Reception method: horizontal

Impedance: 75ohms

Connector: F Type
http://www.***********/en-CA/product.../10179935.aspx

I think the source and the gain claim makes this product immediately suspicious, but the design is definitely interesting.

[mrvanwinkles]

Basic Measurements and Description in Text form.

(hopefully you can refer to the drawing in previous post)

Overall Antenna height comes to 30" (reflector tube array)

Overall Reflector dimensions (horizontal AL tubes) come to 30" x 19"

The folded Dipole in the center makes the overall antenna width 29"
(since it is wider than than the reflector tubes)

Whiskers:
- made of 3/16" OD light AL tube
- 6 1/2" length x 5" tip spread
- 2 1/2" gap between pair points
- top pair and second pair separated by 6" (measured vertically between the points)
- four in top half and four in bottom half separated by 8" (see drawing)
- placed 3" in front of reflector rods

Folded Dipole in center:
- made of 5/16" OD light AL tube (a little larger OD than the whiskers)
- 29" overall length
- 2" width
- 1/2" feed gap in center where it connects
- it sits in the same plane as the 14 reflector rods (3" behind the whiskers)

Reflector Rods:
- Qty 14 total. 7 above / 7 below Folded Dipole - in same plane
- 5/16" OD light AL tube
- 19" long x 2" separation between
- 3" behind whiskers in same plane as the Folded Dipole

The Phasing lines connecting the Whiskers as sketched on the drawing:
- I would estimate they are probably close to 12 GA size AL wire.
- they cross over, as shown, to the very top and bottom whiskers.

Hopefully this gives enough basic information for modelling.

[mrvanwinkles]

Yes, thanks

info from the BACK of the box:
[ my comments in square brackets ]

KROSS

4 Bay Digital Outdoor Antenna

HD Antenna
Model GY-TVA 003
Special Features:

Frequency Range:
VHF & UHF & FM
(VHF 88~230MHZ/UHF 470~862MHZ)
GAIN: 20dB
Maximum output power: 94dBuV
Reception Method: horizontal
Impeadance: 75ohms
Connector: F type

- For reception of outdoor TV signals, compatible with analog and digital terrestrial signals, reception frequency:
VHF: 88-230 MHz (channels 4-12)
[? strange - say ch 4-12. what about ch 2,3,13 ?]
UHF: 470~862 MHz (channels 21~69)
[ what about ch 14-20 ? ]

- Has high impedance matching and strong reception giving the antenna high sensibility, for reception of clear picture in week [sp weak] signals are or weak signals frequency. Use SMT technology for better stability, to ensure the quality of reception within the valid frequency range.

- Reflector structure uses plane radiation function, which can effectively restrain the refraction which causes "ghosts" due to mountains or high buildings, and these multi-way signals refracted from mountains or high buildings pass through the complex elements to effectively receive the signals coming form different directions to obtain higher gain.

- Professional structure design makes antenna structure firm and easy to install. Signal output uses F connector for better sheilding performance. Foldable structure makes packing volume small and saves freight cost.

[ I personally thought it could use some re-inforcing for outdoor use, and also to keep the plastic spine straight - it tended to curve a little after assembly. Yes - it comes packed in a pretty small box considering. Box size only approx. 3x7x20 inches with a convenient little plastic carry handle ]

- Works great in outdoor, attics, indoor, mobile homes etc.

MADE IN CHINA

[mrvanwinkles]

ota_canuck,

cool ... thanks. The you tube link you provided.

Someone has actually put up an instructional video on how to assemble it ! ?

I started watching the first part of it, then stopped to do some more posts.

I'll watch more of it now.

[mrvanwinkles]

What might be a mystery with this antenna is the black box in the center where the Folded dipole and the Phase lines from the Whiskers connect.

ie where the signals from the two different parts of the antenna are fed in and (combined?) somehow.

Where the F-connector is, and where you connect your coax wire to go to the receiver / the TV.

What's in there exactly and how does it perform?

Is it just a simple coupler / combiner? Or a UVSJ ? UHF / VHF joiner ?

Note: This antenna is NOT amplified. There is no power going to the antenna.

[ota_canuck]

Because the VHF element is built within the UHF wisker elements, I don't think a UHF / VHF joiner would do much to separate the VHF vs UHF signals or combine the VHF vs UHF signals. These Kross antennas sell retail $10-$20, so I doubt that there is any high tech phasing joiner in that box except for just a 75ohm balun.

I saw a DIY antenna on youtube that was based on a similar basic design using the wisker/dipole layout.
http://www.youtube.com/watch?v=-IN-O...eature=related

[mrvanwinkles]

With this picture I'm attempting to show a representation of the ANTENNA STAND I improvised from a salvaged ventillation fan stand.

Someone threw out the fan with stand. Broken FAN not working I guess. Took the FAN head off, kept the stand, and used it like a self standing MAST to mount the KROSS antenna and use it indoors - on floor or table.

Then, (home made YAGI shown) trying to show the attempt to improve VHF performance of the KROSS antenna by adding a longer YAGI reflector behind the folded dipole - and a couple directors in front. (attempt to improve ch 13 reception indoors on the KROSS antenna)

So I built a boom with wood trim, drilled it, painted black, added a longer yagi reflector behind the folded dipole at an appropriate distance, and a couple directors in front.

The black boom feeds right through the center of the Kross antenna folded dipole in the center and mounts to the FAN STAND with a U-bolt - just below where the KROSS ant U-bolt grabs. Then the yagi improvised elements slide through the boom in place.

Ya it helped. Esp adding the longer reflector rod behind the folded dipole.

CH 13 / CTV Ottawa improved with the MOD when it was still ANALOG. Got it clearer.

But no luck after ch 13 / CTV Ottawa converted to digital - even with VHF improvement / MOD attempt. Could not get CTV 13 in digital indoors at that location - after digital conversion.

No way no how ch 13 in digital indoors there.

So if anyone computer models this Kross antenna ...

An idea is to model a VHF reflector rod - behind the folded dipole of some appropriate size, length and distance - and see - there should be a corresponding improvement in the VHF performance of the KROSS antenna.

Adding directors in front - I only noticed a very very small change if at all.

[300ohm]

Because the VHF element is built within the UHF wisker elements, I don't think a UHF / VHF joiner would do much to separate the VHF vs UHF signals or combine the VHF vs UHF signals. These Kross antennas sell retail $10-$20, so I doubt that there is any high tech phasing joiner in that box except for just a 75ohm balun.

Because of the 29" folded dipole as part of the reflector, it doesnt need ANY connection at all to get vhf-hi, all 4 bays will do that. They probably should have used 3 of the 29" folded dipoles for max vhf-hi gain. I think it would have been cheaper for them to just use 29" wide mesh and be done with it.

The 6 1/2" whiskers are used because its designed for 862 mhz, which used to be our old channel 79 way back when. Thats where its max gain of about 14 dBi is going to be. At channel 51, expect about 11 dBi, and at channel 14 maybe 6 dBi, heh.

I would be curious to know its gain at 88 mhz. Probably about the same as rabbit ears maximum.

In summary, its designed for use in other parts of the world, not the US or Canada.

[balm]

The 6 1/2" whiskers are used because its designed for 862 mhz, which used to be our old channel 79 way back when. Thats where its max gain of about 14 dBi is going to be. At channel 51, expect about 11 dBi, and at channel 14 maybe 6 dBi, heh.

I was afraid of that...is it worth modeling then...

BTW, nice improvs mrvanwinkles

[ota_canuck]

I agree! That factory product right out of the box is not worth modeling, however the design concept is worth remodeling into a design to comply with today's DTV VHF-hi/UHF spectrum.

Example: Re-design for a DIY project with 8" UHF wiskers with a 29" VHF dipole and a much wider reflector. As 300ohn said, that dipole may just be a reflector, or maybe it could be a driven VHF element. I suppose the dipole needs to be modeled both ways to be certain.

[300ohm]

Re-design for a DIY project with 8" UHF wiskers

But then youre still stuck with the 6" bay spacing and the 3" reflector to whisker distance, both sized for good ole channel 79 (last used in the US and Canada in 1982, and looks like used in France until two days ago).

To make a 4 bay bowtie peak right before channel 51, you need around a 9.5" whisker over 9" bay spacing, around 4.5" reflector to whisker distance, like on mclapps M4. Im not sure how hard it would be to modify the Kross for that sizing.
By the looks of it, you got a good $20 worth of parts. 22+ ft of either 1/4" or 3/8" aluminum tubing, a 29" aluminum folded dipole, plus standoffs and other bars. You could make a high gain vhf-hi yagi antenna with 7 colinear directors from those for minimal extra cost. And still have the standoffs and the bars to make a M4 with 29"+ mesh reflector, if you could add another 1 or 1 1/2" to the standoffs. Edit: after watching the install video, I think you can by using strips of plastic decking.

Thats where its max gain of about 14 dBi is going to be.

Actually, because of the way gain scales at higher frequencies, it may get 15 dBi near channel 79. But no way near 20 dBi. (unless you use the Red Chinese dBi scale, then its anything the politburo says it is, heh)

UHF: 470~862 MHz (channels 21~69)
[ what about ch 14-20 ? ]

In some countries, channel 21 starts at 470mhz and they use 8 mhz wide channels instead of our 6 mhz wide channels.