Antennacraft U8000 Hardware Hacks
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Forget NARODs on bowties, they dont work the same way.
For vhf-hi on bowties, just use about a 32" to 40" (connected) wide reflector. 28" to 32" better for channels near 13, 36" - 40" better for channels near 7. (Wider will also work, but not much point to going wider than 40". ) Continuous mesh is the easiest way to accomplish this.
Conversely, the wide reflector does nothing for vhf-hi gain on a GH.
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We experimented a bit with the idea of Narods with the cm4221 elements. Narods didn't seem to have much advantantage with the wisker antenna.
Could you run an aperture antenna on the back of the 8800? Would it serve simply as a reflector and/or connected to run with the 8800 elements? http://www.digitalhome.ca/forum/showpost.php?p=1126233&postcount=8
Hmmm! Here's a shot in the dark. Extend the upper and lower wisker with 5" legs similar to the GH element extensions and then add the narods above the extentions?
Could you run an aperture antenna on the back of the 8800? Would it serve simply as a reflector and/or connected to run with the 8800 elements? http://www.digitalhome.ca/forum/showpost.php?p=1126233&postcount=8
Hmmm! Here's a shot in the dark. Extend the upper and lower wisker with 5" legs similar to the GH element extensions and then add the narods above the extentions?
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Thinking out of the box again!
Could something like this work for Hi-VHF/UHF.?
Obviously the dimensions are not defined. This is just an example sketch of combining 4bay with gh tips and added narods.
note 1: I think the missing wisker spacing dimensions [@yellow arrows] were 3" and 5"
note 2: Crossover phase lines may not be required.
note 3: The balun feed point would be centered.
Could something like this work for Hi-VHF/UHF.?
Obviously the dimensions are not defined. This is just an example sketch of combining 4bay with gh tips and added narods.
note 1: I think the missing wisker spacing dimensions [@yellow arrows] were 3" and 5"
note 2: Crossover phase lines may not be required.
note 3: The balun feed point would be centered.
I didnt use those dimensions above, but used a reflector less CM4221a (the good one) model and added 5.125 inches for stubs like you did above, and a 28" NAROD .5 inches above/below the stubs.
Theres some potential there. The gain pattern is backwards up to channel 9 and then forwards up to channel 13. The good ole gain flipping syndrome, heh. The dip in uhf gain after channel 37 goes to near zero and doesnt really recover until well after channel 51. Symptoms similar when I was developing the GH with NARODs, but a lot more pronounced.
With a lot of tweaking, and maybe adding NAROD reflectors, it may be able to be as good as simply adding a 32" - 40" mesh reflector, but is there any point to it ? In a lot of cases, a piece of 32" X 32" mesh (or even chicken wire over existing reflectors) will cost less than 4 - 28" aluminum or copper rods, and less work.
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The crossover phase lines may not be suitable with the extra additions at the top and bottom. I tried an old 4221 with straight phase lines once and I didn't really notice a significant difference in performance. I still have that old 4221, but just the mast and wiskers, the reflector and the reflector mounts were used on some else. If anyone has any ideas, I am willing to butcher it for some performance testing.
Before I found this site, I did a bunch of research and came up with the U8000.
There is very little chatter about this antenna anywhere, so I figured I would float it here. I'm getting ready to hang it next week, so this is an academic exercise for a learning experience.
There is very little chatter about this antenna anywhere, so I figured I would float it here. I'm getting ready to hang it next week, so this is an academic exercise for a learning experience.
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I've been using that old CM4221 for spare parts, repairs etc.
I had two brand new CM 4bays in the shop until last week. Someone spotted them and made me an offer well above the 4221HD price. When we checked them out of the box, they were so old they had the RG59 twist on connectors in the sealed balun baggie and the balun itself was slightly different [no undercut or tapered ends] than the CM94444 baluns. They were probably hiding up there for 10 years or more. The same guy had me build him a SH for his cottage down on the lakefront in Port Maitland
I think there is some potential for VHF, so using the old 4221 for experiments would be well worth the sacrifice if we could break through the barriers.
I had two brand new CM 4bays in the shop until last week. Someone spotted them and made me an offer well above the 4221HD price. When we checked them out of the box, they were so old they had the RG59 twist on connectors in the sealed balun baggie and the balun itself was slightly different [no undercut or tapered ends] than the CM94444 baluns. They were probably hiding up there for 10 years or more. The same guy had me build him a SH for his cottage down on the lakefront in Port Maitland
I think there is some potential for VHF, so using the old 4221 for experiments would be well worth the sacrifice if we could break through the barriers.
I'm game.
I have hi-res photos of the entire (new) rig, and took a bunch of measurements (inches).
It is billed as a 14~69 UHF range, so it will be interesting to see how well it handles 9 and 10, 32.2 and 28.5 NM(db) respectively.
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=a362c0be0f9d73
The above is my TVFool link for a 20 foot elevation. It will be mounted to my unused chimney. Fool says I have to have a 40 foot elevation for all LOS, but that isn't going to happen for me.
I have hi-res photos of the entire (new) rig, and took a bunch of measurements (inches).
It is billed as a 14~69 UHF range, so it will be interesting to see how well it handles 9 and 10, 32.2 and 28.5 NM(db) respectively.
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=a362c0be0f9d73
The above is my TVFool link for a 20 foot elevation. It will be mounted to my unused chimney. Fool says I have to have a 40 foot elevation for all LOS, but that isn't going to happen for me.
OK, what barriers ? The only thing I can think of is a clover leave pattern, but we have some other designs for that.
I forgot to mention (Im sure mclapp would have) that sticking those same four 28" rods behind each of the whiskers on a 4 bay would essentially accomplish the same thing, ie about a 5 to 7 dbi net gain on vhf-hi.
Do I honestly think I could get more than, say a db more on vhf hi from a 4 bay ? ? No way. And its been tried, the bowtie dates back to 1896. It would have to take a more radical design that that. I like radical break thru's, and in my gut there are still tons of them out there, but in this case, there probably isnt enough wire there.
Before putting it up, post detailed, I mean very detailed, including pictures, dimensions of it and we'll model it for you. AFAIK, there is no detailed NEC model of the Antennacraft U8000.
The phasing line and the cross over phasing lines are going to give modelers the most trouble, so thats where the super detail needs to come in. Maybe pictures of all the phasing line with marked dimensions on masking tape would be the ticket.
Im pretty familiar with Antenna Craft antennas, (still owned by the Tandy Corp I think) and for the money they are a pretty good deal. The quality of the plastic pieces is not as good as the Channel Masters or Winegards, but acceptable. The aluminum parts, while maybe thinner than CM or Wine, should still last hundreds of years, heh. The best thing to do with them, due to packaging, and this could apply to all shipped antennas, is to bend the parts back to spec, and reinforce anything you think looks weak.
For example, if you can move a reflector rod, use a punch and hammer to tighten the rivet.
We have been out of town the last week, but I managed to get the U8000 on a chimney mast yesterday. This was just in time for my wife's favorite dancing show.
TVFool Data
I'm surprised / shocked at the VHF channels seen by the U8000. I get a 50~85% signal strength reading on channels 3~13. The design is for channels 14~69.
TVFool Data
I'm surprised / shocked at the VHF channels seen by the U8000. I get a 50~85% signal strength reading on channels 3~13. The design is for channels 14~69.
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358 Posts
Look at the real channel column for the channels the stations are actually broadcasting on. You do have two high-VHF channels - KVIE on RF 9 and KXTV on RF 10. The other network stations broadcast on UHF.
Hacking the U8000
I've seen the CM4228HD get hacked for signal improvement, but is there anything about the U8000 that could be improved? I'm thinking about tying the reflector rods together (The U8000 is basically two U4000s next to each other).
The feedline system looks pretty elegant so I don't know if there's any legitimate reason for separating them. Since its a pretty obscure antenna for some reason I don't see it talked about much in comparison to the 4228/4221 series.
The whiskers are also a tad short but replacing them would require a lot of work. The U8000 already gets excellent reception but I could always use some more!
Any info or tips would be appreciated
I've seen the CM4228HD get hacked for signal improvement, but is there anything about the U8000 that could be improved? I'm thinking about tying the reflector rods together (The U8000 is basically two U4000s next to each other).
The feedline system looks pretty elegant so I don't know if there's any legitimate reason for separating them. Since its a pretty obscure antenna for some reason I don't see it talked about much in comparison to the 4228/4221 series.
The whiskers are also a tad short but replacing them would require a lot of work. The U8000 already gets excellent reception but I could always use some more!
Any info or tips would be appreciated
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452 Posts
get out yourr measuring tape and post all measurements of your antenna
then you can model and others can model along with you to see what can be improved upon. get yourself a copy of 4NEC2 model program, you can draw up you anteena and model test for improve ments
then you can model and others can model along with you to see what can be improved upon. get yourself a copy of 4NEC2 model program, you can draw up you anteena and model test for improve ments
AntennaCraft U8000 questions
To conform with rules here is TvFool report http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d8d17ea504085e9
Anyways I have just ordered a U8000 from the source and through my time meandering around this forum and others, have found very little real information about it. I was wondering about what information someone might need once received for someone to model it.
Just figured since it is on the recommended antenna list, some hard numbers may do it some good.
To conform with rules here is TvFool report http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d8d17ea504085e9
Anyways I have just ordered a U8000 from the source and through my time meandering around this forum and others, have found very little real information about it. I was wondering about what information someone might need once received for someone to model it.
Just figured since it is on the recommended antenna list, some hard numbers may do it some good.
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