Antenna reflector materials

[americannight]

I am considering building a better reflector for my 8 bay Antennacraft U8000 antenna. I have heard the reflectors on these antennas are somewhat sub-par. What are some recommendations for good material to use? I have heard that the fencing material with the rectangular shapes in it is good but all I can find in my area is a 100 foot role of that stuff at Home Despot. Just looking for a small piece of suitable material, about 3'x3' to craft the reflector out of. Curious what you antenna builders use out there.

 

[RF Steve]

I've been know to use aluminum brazing rods, for both reflectors and driven element construction. I have been able to find them locally with the welding supplies for between 60 and 90 cents in three foot lengths. I don't know how many rods come in a 1.75 pound package, but this is what I found on a quick internet search.
Amazon.com: Forney 46002 Bare Aluminum Brazing Rod, 1/8-Inch-by-36-Inch, 1.75-Pound: Home Improvement
Now someone can tell me why it's the wrong product to use antenna work.
25 foot rolls of 2 foot high rabbit fence shouldn't be to hard to find. Only the bottom 16 inches of the rabbit fencing I have right now are useful at UHF frequencies. The bottom 12 inches are 1 inch spacing, then 2 wires at 2 inch spacing. The top 2 wires are 4 inch spacing too wide for UHF frequencies. On the bottom 12 inches you could clip the wire to make it 2 inch spacing to reduce wind load, and it should have no noticeable difference in performance as a UHF reflector.
I look at antenna parts every time I visit a local hardware, or farm supply store. I've sometimes found useful antenna parts in the electric fencing department.
Steve

 

[RF Steve]

I just put one of my aluminum rods on a postage scale it looks like about 44 come in a tube if did my math correctly, and if the old scale is accurate. I think I can still buy 9 AWG aluminum wire in about 50 foot rolls at a local hardware store for about 30 cents a foot. Think clothes line department. I'll take a look at the Antennacraft antennas you are working with. The horizontal wire is the one that is of use as a reflector for horizontally polarized ATSC signals. I don't really know the optimum spacing between wires for a UHF reflector. 3 inches comes to mind. At 2 inches it should start to work as a solid reflector at UHF television frequencies.
Steve

 

[americannight]

Thanks for all the good info, Steve. One thing I could use some help understanding is how the overall size of the reflector can help. Is bigger better?

On my working attic antenna, even the sheet of tin foil acts as a sufficient reflector behind the U4000.

Should I be looking at a better antenna for the roof mount? I can spend 50 in materials building a reflector but, heck, a lot of 4 or 8 bay bow ties go for that!

 

[RF Steve]

Well you got me thinking, and searching. As a general rule in order for it to work as a reflector it needs to be wider than one half wave length for the lowest frequency of use. Without doing computer modeling it can be difficult to predict what effect adding a few wires is going to have. An interesting effect of reflectors being less then one half wave length can be seen in some UHF antennas when used to receive VHF signals the gain of the antenna on VHF frequencies is off the back side. The U-4000 is an example of this.
Antennacraft U-4000 - 9 Reflector Rods
I did take a look at this page, but I've not studied it much.
M4 (9.5x9) + Various Number of RRs - OPT
In most cases you well never see a significant change from a one dB increase in antenna gain.
Steve

 

[Fringe Reception]

Hardware cloth as used on screen doors, should be available at Hardware stores or Lumber Yards.

Jim

 

[americannight]

The info about the VHF signals is holding true here. I added a reflector using galvenized fencing material yesterday, 36 inches square. The individual squares in the material are 2 in tall by 4 inches wide. The effect made the antenna pull in my VHF 9 and 11 stations. Cool, now I no longer need the Y7-13 antenna and can scrap all the associated splitters and cables for that and run this antenna straight into my hdhomerun tuner. Bad news, still no UHF 48 (virtual 5) buy next I am going to try different spots on the roof as per Steves suggestion.

 

[americannight]

Moved the antenna to a different part of the roof today, same general area as where my attic antenna is located. Success! I am getting all the major networks now and also KONG TV channel 16 which my attic antenna would not receive. I did find that in this spot the U8000 will not pull in the VHF high band as it was doing when up on a higher section of the roof. Oh well, I am using the Y7-13 for that and it works fine. Thanks for all the help here.

 

[Fringe Reception]

americannight,

Have you tried to receive KVOS-12 (real 35) transmitting from the San Juan Islands? Its one of the better stations in our area.

Jim