Mohu Leaf Omni-directional OTA Antenna

[roger1818]

Originally Posted by ADTech

Here's a pic of what's under the hood.

Thanks for the pic. I see one big issue with the design right away. The feed points for a 2-bay antenna should be half way between the two "bow ties." With this design there will be some phase interference. If they want to have the connector at the bottom, they should have put vias in the middle and run tracks on the back side to the connector.

[ADTech]

Antenna construction is a sandwich of the foil elements between a piece of black and a piece of white construction paper which was then run through a heavy-duty laminator. The balun was a surface mount ferrite core balun.

The speckles you observed are just byproducts from soaking the sandwich in hot soapy water to allow for the white paper to be removed. In other words, they're meaningless.

[ota_canuck]

Another thing that is puzzling is that it's being advertised as a VHF/UHF antenna, yet the design appears to be a basic UHF 2bay layout. Yes,. the feed point should be centered to be a balanced 2bay UHF antenna,.. but as we found with playing with the original Stealth Hawk designs,.. the offset in the feed point centering may influence some VHF improvements, but at a cost to some UHF performance.

From my previous posted MOHU specs:

• Antenna for Digital TV/HDTV Reception
• Frequency Range(MHz): VHF 170-230MHz UHF 470-860MHz
• Gain: 5dBi(max)

I fail to understand what is 'Digital' or 'HDTV' about this antenna.

It is designed to recieve well above the 700Mhz and it only has a 5dbi (max)gain.

My initial gut feeling is that the Stealth Hawk [SSH 289 element design] similarly made into a flat foil antenna may actually perform better as an all around VHF/UHF & multidirectional antenna with more raw gain.

[specialized]

Originally Posted by ADTech

Here's a pic of what's under the hood

Can we get the measurements for the foil? Thanks!

[mvashi]

Got the antenna yesterday and the best I could get was 3 Channels.
That was a very expensive experiment

[stampeder]

Please provide your TVFool report and much more info so that we can understand your findings. Right now we have nothing to compare your Mohu Leaf reception with.

[mvashi]

Here is report you wanted: http://www.tvfool.com/?option=com_wr...b1a85cafb41431

I managed to get 5.1,19.1 and 25. I think this one would be useful in a highrise building with clear line of sight to the transmitters

[meridish]

Hi mvashi,

Try installing it in Attic. I hope you will get better results there.

meridish

[educator_bhoy]

I am completely new to the OTA community and wanted to ask a question, I recently bought the Leaf Plus HDTV Indoor antenna, I set up with my tv which is an older model
http://reviews.cnet.com/flat-panel-t...-32443521.html

The problem is I am not getting that scan for channels screen, it just says channel not available when connected and the antenna is placed against a window, can anyone help?

[ota_canuck]

There is an existing thread to discuss the mohu and mohu plus.
http://www.digitalhome.ca/forum/show...=138226&page=3

The antenna has nothing to do with your TV's menus or the scan screen. You'd have to use the main menu to find the complete 'full scan' & 'air' options/etc... found in your Panasonic TC-32LX700 manual. [you could also find the manual for that TV model online]

[antennanovice]

ADTech,

It looks like the section with the balun got ripped away during dissasembly. Do you have any pictures you can post of the balun? Do you have any information on what type of matching it did / does?

In a UHF design, having less leads (inductance) between the antenna and the termination (balun) means a better match and better performance. A surface mount soldered on balun would give superior performance.

Also... the leaf plus claims to have a low noise amp directly at the antenna with built in matching. If they did this right, they could turn the antenna into a phased array and get pretty much any pattern they needed.

Do you have any information on the leaf plus?

I just ordered one to try out (not to take apart) I want to use it in my mom's room at the nursing home to get a channel that is on the other side of the building and through the other wing. Transmitter is only 5.3 miles out, but she is in a room on the opposite side of the building and the other wing (T shape) is also in the way of LOS.

http://www.tvfool.com/?option=com_wr...1349eb031f4cc9

A simple dipole antenna just gets enough signal to occasionally grab a frame, then pixelates and freezes. I am not sure I can get this reliably with an indoor antenna at all, but no choice, can't put up outdoor antenna, or anything big or bulky.

I am also using a UHF / VHF diplexer to combine the provided basic cable 2-32 with over the air UHF, so there is some signal loss involved with that to overcome. I am hoping an amplified antenna will also prevent any re-transmission issues in addition to the filters used in the diplexer. I am assuming the amplifier is a one way connection and will block or attenuate any leakage through the diplexer.

[majortom]

antennanovice,
I hope it works for you, just out of curiousity the channel ur having issues with at the nursing home, guessing it is the low power channel 43 (only ch at 5.3 mi)?

Take a look at the coverage map from rabbitears site for ch 43 and see if any of the "holes" from the irregular terrain happen to be near where the nursing home is. It likely won't account for nearby buildings, so on. Wonder if ur a little closer to one of them indoor coverage holes than the prediction says.
http://www.rabbitears.info/contour.p...=1340066&map=Y

I know it's not practical for the long run, but have you noticed if there is better signal qual from ch 43 if propping an antenna out a window somehow?
If it doesn't work out, a while ago I made a Stealth Hawk for my niece's 1st floor apartment. She placed it in a picture window, behind the curtains for best reception. Worked pretty good for her.

[antennanovice]

MajorTom

Interesting site.

I zoomed in to the satellite image to see the building she is in, and it is all green. there are a couple of orange areas just outside its perimeter, so not so sure how well map matches satellite image, but it is up on a hill so signal should be ok. Problem is that it is on the opposite side of the building and then through the other wing, or just skirting it if I am lucky. she is about halfway down on the south side of the east facing wing of a T shaped building that has a north and a south facing wing as well. The signal is at 329 degrees (North West) from her location. LOS is not possible, i need to find a reflection. She is on the hall side of a semi private room, not near the window. I was surprised I got any signal from the dipole (true omni directional, with vertical nulls).

[antennanovice]

Update: I swapped out some longer cables for shorter ones and found a loose sheild on the one going to the TV, then swapped the dipole for a Radio Shack single bowtie 300 ohm twin lead antenna, and a twin lead to coax balun (actually a UHF/VHF twin lead to coax combiner), then a short cable to the UHF coax in of a UHF/VHF combiner (double filtered UHF). I was able to find a spot on the wall where I get a 35% to 50% signal on 43.2 (at least with the door open to the room across the hall), and still get all the other local channels in range. Maybe I didn't need the amplified Mohu after all. I will still try it out since I already ordered it.

as for the stealth hawk... I looked at that. Has anyone tried it upside down? it looks like the longer VHF legs would be a nice deflector for the shorter UHF diamond and reduce the vertical portion of the pattern, remaining multi-directional, while providing better horizontal pattern against a ground plane. I haven't run it against 4nec2x yet, but I did play with some similar theoretical designs, and a top deflector and ground plane usually gave significant gain boost. Vertical lobes are useless unless you are trying to bounce off the ionosphere.

[ota_canuck]

antennanovice,

Everything you've said about the SH has already been done, modeled and tested to near death

This is the optimum SH design:
http://www.digitalhome.ca/forum/show...&postcount=289