ChiwaukeeOTA's antenna modification thread - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 3Likes
Reply
 
Thread Tools
post #1 of 73 Old 04-13-2020, 05:13 PM - Thread Starter
Member
 
ChiwaukeeOTA's Avatar
 
Join Date: May 2016
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 2
ChiwaukeeOTA's antenna modification thread

Hi all,

I'm considered a newbie here, I am glad to be back. A lot has changed.
It's not about a reception issue at home, it's about a hobby project. Should it matter, here is my Rabbit Ears report:

https://www.rabbitears.info/searchma...study_id=80130

I'm hoping some of the great minds here can give me guidance on an antenna hack, my first, ever. I need design suggestions. I can and will alter what I made so far.

I always wanted to hack a 30-2476. Simply because they are economical and are a pretty darn good antenna right out of the box. Very light weight and 4 years later both of mine have survived windstorms and N.E. Illinois winters.

Newark has a 4 pack deal and along with another incentive I paid about $28.00 each. I bought the four.

This is just a "Hobby Project" and I want to try some light DXing. I am not competing with any of the DX'rs. Nothing serious.

I started my quest here on TVFool: http://forum.tvfool.com/showthread.php?t=16742

And, inspired by Len Mullen's attic 30-2475 hack which he had success with only by removing the front director and adding another front section from a donor antenna. I don't think he even changed director sizes.

https://freetvforme.wordpress.com/20...b2#comment-921


I did some measurements and the directors taper smaller and smaller to the front of the stock antennas. So, I have some front sections from the two donor 30-2476 antennas but the rear most directors in the new front sections will be wider than the front most directors on the two base antennas. I decide at least I could taper down the directors evenly by swapping them around as seen in red in my hand drawn diagram.

Oh, I forgot to mention. I'm making two and pairing them. I know, minor detail right?


I have a diagram:



Initial mock-up, not sure yet what to do with director spacing:



I could not find the correct Box Tubing anywhere, so I bought U channel that would fit inside (I turned the "U" upside down and then found U channel that fit the outside and put it underneath to support from the underside and... To not alter the director tabs, (Very important) :




Even with the inner and outer channels installed, still a lot of sag:



I corrected the sag with 3/16 galvanized cables, with turnbuckles. I mounted low on the mast so I could stand and work on the array at first for structural purposes. You will see why later! :



The first scan was highly disappointing:



I used my other single 30-2476 (unmodified) much higher on the mast to compare to. It is paired with a HDB91X using a RCA PREAMP1R.
Green is the single stock 30-2476, Blue is the double array :



More to come, improvement on the way, but I need help with director width and spacing, please!!

Attached Thumbnails
Click image for larger version

Name:	92824404_212110613419634_8363919278147108864_n.jpg
Views:	640
Size:	16.0 KB
ID:	2709746   Click image for larger version

Name:	20200403_170103.jpg
Views:	19
Size:	357.6 KB
ID:	2709748   Click image for larger version

Name:	20200403_190616.jpg
Views:	632
Size:	193.4 KB
ID:	2709750   Click image for larger version

Name:	20200408_135205-1024x768.jpg
Views:	636
Size:	226.6 KB
ID:	2709752   Click image for larger version

Name:	20200408_180232-768x1024.jpg
Views:	642
Size:	230.1 KB
ID:	2709754  

Click image for larger version

Name:	92818622_652904508612559_4158155880199618560_n.jpg
Views:	631
Size:	50.0 KB
ID:	2709756   Click image for larger version

Name:	1st scan of New 30-2476 pair extended .jpg
Views:	638
Size:	104.5 KB
ID:	2709760   Click image for larger version

Name:	2020-04-11 comparison of Signals. Blue is 30-2476 dual array Green is Milw point VHF UHF.jpg
Views:	627
Size:	74.8 KB
ID:	2709762  

Last edited by ChiwaukeeOTA; 04-15-2020 at 03:04 PM.
ChiwaukeeOTA is offline  
Sponsored Links
Advertisement
 
post #2 of 73 Old 04-13-2020, 05:45 PM - Thread Starter
Member
 
ChiwaukeeOTA's Avatar
 
Join Date: May 2016
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 2
Improvements...

So, no more structural improvements this week. I didn't mention earlier over on TVFool, Tripelo has made some suggestions that I took to heart. He felt part of my issues were possibly due to a number of things, however all things checked out except for the ground reflections. So, I removed the original stock 30-2476 and replaced it with... the dual array. I fought with it half the day Saturday and the rain fell on me, but I got them moved. I hooked the array up to the VHF side of my RCA PREAMP1R. No time to adjust the guy wires. No wind predicted, good! Damn just in time for dark and rain to soak me.



So, I did a scan found that that no more powerful a signal, although the overall pattern had changed, more level. I did a couple more scans, documented, made some screenshots of my spectrum analyzer:



The next day, no rain and sunny skies and a bit better, stronger signal:



I did a comparative from the night before, the difference appears to be the rain:




So, I feel I'm no where where I want to be with this set-up. I downloaded some antenna modeling software, but it's too new for me, way above my pay grade! I can definitely and easily separate the two for individualized testing too...

Can some members offer suggestions?
Attached Thumbnails
Click image for larger version

Name:	20200411_193255-1024x768.jpg
Views:	623
Size:	169.3 KB
ID:	2709766   Click image for larger version

Name:	Dual 30-2476 moved up high single down low CROP.jpg
Views:	624
Size:	149.8 KB
ID:	2709768   Click image for larger version

Name:	Dual 30-2476 moved up high no rain compare to rain.jpg
Views:	626
Size:	81.4 KB
ID:	2709770   Click image for larger version

Name:	Dual 30-2476 moved up high no rain 2012-04-12.jpg
Views:	623
Size:	88.9 KB
ID:	2709772  

Last edited by ChiwaukeeOTA; 04-14-2020 at 10:27 AM.
ChiwaukeeOTA is offline  
post #3 of 73 Old 04-14-2020, 03:02 PM - Thread Starter
Member
 
ChiwaukeeOTA's Avatar
 
Join Date: May 2016
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 2
LNA-200 Vs. KT-200

LNA 200 VS. KT 200. After talking myself out of it several times, simply because I already had a "Low Noise" Winegard LN-200 and a couple of RCA preamps. I finally pulled the trigger and ordered a KT 200 directly through Kitz Technologies on Thursday. I talked with Jeff Kitz by phone and bit the bullet Thursday. Surprisingly, it arrived Monday morning! That was Amazon fast! It is a high-quality product.

It comes in a fairly thick and stout sheet metal aluminum case. Many will appreciate this because of the reflection of unwanted RF interference. In all fairness, the LNA 200 is about a year old and was just used minimally, I would say it's in good shape and I covered it with foil tape for RFI protection.



I hooked up my stock 30-2476. I tested VHF only today, it was very cold and windy on the roof:



Details for comparison of the two pre-amps, the LNA-200 is above the KT-200:




After some base line testing, I did a comparative spectrograph:



For fun, I looked at the UHF capabilities of the 30-2476. Most of those stations are actually watchable, even some coming from the rear of the antenna:
Green=LNA-200Blue=KT-250





Attached Thumbnails
Click image for larger version

Name:	93687099_1406123136261874_2256236605096329216_n.jpg
Views:	582
Size:	45.8 KB
ID:	2710080   Click image for larger version

Name:	93386284_1406123206261867_6089482092003983360_n.jpg
Views:	591
Size:	90.1 KB
ID:	2710082   Click image for larger version

Name:	93223423_1406123179595203_1789124916990181376_n.jpg
Views:	588
Size:	116.7 KB
ID:	2710084   Click image for larger version

Name:	93556064_1406123159595205_5344060813789364224_n.jpg
Views:	581
Size:	35.8 KB
ID:	2710086   Click image for larger version

Name:	93789919_1406123249595196_9099000186373406720_n.jpg
Views:	579
Size:	60.3 KB
ID:	2710088  

ChiwaukeeOTA is offline  
Sponsored Links
Advertisement
 
post #4 of 73 Old 04-14-2020, 03:10 PM
Super Moderator
 
DrDon's Avatar
 
Join Date: Mar 2002
Location: Metro Detroit, Tampa Bay
Posts: 17,727
Mentioned: 45 Post(s)
Tagged: 0 Thread(s)
Quoted: 2564 Post(s)
Liked: 5025
Threads merged. No point in starting a new one when the background information is in this one.

Walking the fine line between jaw-dropping and a plain ol' yawn.
DrDon is offline  
post #5 of 73 Old 04-14-2020, 03:54 PM - Thread Starter
Member
 
ChiwaukeeOTA's Avatar
 
Join Date: May 2016
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 2
Quote:
Originally Posted by DrDon View Post
Threads merged. No point in starting a new one when the background information is in this one.
That's fine, but they are really two separate threads. One is about a pre-amp test on a stock 30-2476.

The other thread is about a antenna design on a Modified 30-2476. I didn't want to confuse the two.

The only thing in common is me
ChiwaukeeOTA is offline  
post #6 of 73 Old 04-14-2020, 04:37 PM
AVS Forum Special Member
 
keeper's Avatar
 
Join Date: Aug 2005
Posts: 1,822
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 658 Post(s)
Liked: 277
Quote:
Originally Posted by ChiwaukeeOTA View Post
That's fine, but they are really two separate threads. One is about a pre-amp test on a stock 30-2476.

The other thread is about a antenna design on a Modified 30-2476. I didn't want to confuse the two.

The only thing in common is me
This is great work. I have two of these antennas just laying in my garage. I use the old antenna craft antenna. I will be following these results closely.
keeper is online now  
post #7 of 73 Old 04-14-2020, 04:42 PM - Thread Starter
Member
 
ChiwaukeeOTA's Avatar
 
Join Date: May 2016
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 2
Thanks, for your interest!

Quote:
Originally Posted by keeper View Post
This is great work. I have two of these antennas just laying in my garage. I use the old antenna craft antenna. I will be following these results closely.
Thanks for responding! I am hoping to get some of you guys who know a lot about antenna and can help me with the director width and spacing!

Also boom spacing too. I can fabricate what I need. I want to make this modification work, but so far, I don't feel the modified antenna is any better than the original (stock) 30-2476.
ChiwaukeeOTA is offline  
post #8 of 73 Old 04-14-2020, 04:52 PM
AVS Forum Special Member
 
keeper's Avatar
 
Join Date: Aug 2005
Posts: 1,822
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 658 Post(s)
Liked: 277
Quote:
Originally Posted by ChiwaukeeOTA View Post
Thanks for responding! I am hoping to get some of you guys who know a lot about antenna and can help me with the director width and spacing!

Also boom spacing too. I can fabricate what I need. I want to make this modification work, but so far, I don't feel the modified antenna is any better than the original (stock) 30-2476.
I don’t know much about antennas but if you get help and great results then I will try to copy your plans. I also have the old CM7777 I believe vhf/uhf. I added the Kitztech and haven’t noticed much difference if any. I may need to compare those two preamps again because when I swopped them I believe the Kitztech improved the SnR
keeper is online now  
post #9 of 73 Old 04-14-2020, 04:54 PM
AVS Forum Special Member
 
Calaveras's Avatar
 
Join Date: Jan 2007
Location: Hereford, AZ
Posts: 6,290
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 1966 Post(s)
Liked: 486
Quote:
Originally Posted by ChiwaukeeOTA View Post
More to come, improvement on the way, but I need help with director width and spacing, please!!

You would need to model the antenna with 4 more directors to get the element lengths and spacing correct for max gain. It's unlikely that guessing as you did results in it working correctly. It could make things worse.

Also, 4 more elements are not going to make much difference. You need to double the number of elements to get 3 dB of gain. That means the antenna needs to have 20 elements. Four more elements will only give you about 1.5 dB if the lengths and spacing are correct.

How did you combine the two antennas? It's hard not to lose a large part of the 3 dB gain that two antennas can give if everything is perfect.

The KT-200 should improve the SNR over the LNA-200 by about 2 dB if you don't have any environmental noise problems, something that is common on high VHF.
Calaveras is offline  
post #10 of 73 Old 04-14-2020, 05:17 PM - Thread Starter
Member
 
ChiwaukeeOTA's Avatar
 
Join Date: May 2016
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 2
Director Spacing

Quote:
Originally Posted by Calaveras View Post
You would need to model the antenna with 4 more directors to get the element lengths and spacing correct for max gain. It's unlikely that guessing as you did results in it working correctly. It could make things worse.

Also, 4 more elements are not going to make much difference. You need to double the number of elements to get 3 dB of gain. That means the antenna needs to have 20 elements. Four more elements will only give you about 1.5 dB if the lengths and spacing are correct.

How did you combine the two antennas? It's hard not to lose a large part of the 3 dB gain that two antennas can give if everything is perfect.

The KT-200 should improve the SNR over the LNA-200 by about 2 dB if you don't have any environmental noise problems, something that is common on high VHF.

Hello Calaveras,

Thanks for joining the thread.

So, making the antenna longer with more elements? No Problem! I still have the rear sections with reflectors, and directors. I could salvage parts from them. I'm curious on how to space the directors and width. Any advice there?

I had no choice than to guess on spacing. ..

Combining. I started with the Holland GHS 2PRO combiner but ended up using a Winegard CC-7870 for no particular reason. I think they both are parasites. Would like to know about phasing harnesses though..

I have not applied the Kitz Tech Amp - yet. I had consider buying more than one and pre-amping before the combiner, but I've heard different things about that. What's your view?

I have two of these, I can scavenge:

Attached Thumbnails
Click image for larger version

Name:	20200404_170257.jpg
Views:	569
Size:	209.8 KB
ID:	2710198  
ChiwaukeeOTA is offline  
post #11 of 73 Old 04-14-2020, 06:31 PM
AVS Forum Special Member
 
Calaveras's Avatar
 
Join Date: Jan 2007
Location: Hereford, AZ
Posts: 6,290
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 1966 Post(s)
Liked: 486
Quote:
Originally Posted by ChiwaukeeOTA View Post
Hello Calaveras,

Thanks for joining the thread.

So, making the antenna longer with more elements? No Problem! I still have the rear sections with reflectors, and directors. I could salvage parts from them. I'm curious on how to space the directors and width. Any advice there?

I had no choice than to guess on spacing. ..

Combining. I started with the Holland GHS 2PRO combiner but ended up using a Winegard CC-7870 for no particular reason. I think they both are parasites. Would like to know about phasing harnesses though..

I have not applied the Kitz Tech Amp - yet. I had consider buying more than one and pre-amping before the combiner, but I've heard different things about that. What's your view?

To do it right, the antenna needs to be modeled. Absent that, I have seen some long antennas where the director spacing and length remains the same after the first few directors. If you were to do that, all additional directors would be 21 3/4" long and the spacing would be 10 1/2". The final director would be the 20 3/4" original one with the same spacing. This is a guess is on my part. I'm pretty sure that making the additional directors longer again is not the right thing to do.

All those splitters used as combiners have at least 1/2 dB loss. There is a way to make a nearly lossless combiner. Use a 1/4 matching section. I've done this several times and it does work. The matching section is a 1/4 wave piece if coax whose impedance is the geometric mean of the two things you're trying to match. Two 75 ohm antennas in parallel is 37.5 ohms. The preamp (or feed line) is 75 ohms. The correct impedance for the matching section is very close to 50 ohms. If you use a piece of RG-58 or R-8 with solid polyethylene dielectric, the length is exactly 10". Attached is picture of a UHF version I made. The little box can be a 2 way splitter with the guts removed and replaced with wires. The matching section is very broadband and covers the entire high VHF band with very low loss. The length of the matching section includes connectors.

I had a pair of 12 element log periodics up for some years. Eventually though I ended up with a single 22 element log periodic on an 18' boom. Even though it is long, it's easier to deal with than phasing a pair of smaller antennas. It's the best high VHF antenna I ever used.

I also tried the idea of using two preamps on phased high VHF antennas. Sometimes it worked but sometimes there would be feedback between the two antennas and the oscillation would wipe out all the stations. Don't bother with it. Stick with one preamp.

The 22 element LPDA plus the KT-200 preamp is a very good combination and it's simpler than phasing antennas. See attached image.

In my experience, once you have a good antenna like the 30-2476 up in the air, it is very hard to get much improvement. Twice the antenna can approach 3 dB and 4 times the antenna can approach 6 dB. 10 dB improvement is a fantasy.
Attached Thumbnails
Click image for larger version

Name:	2wayCombiner.jpg
Views:	70
Size:	168.4 KB
ID:	2710222   Click image for larger version

Name:	Antennas20150304-1.jpg
Views:	71
Size:	246.8 KB
ID:	2710224  

Last edited by Calaveras; 04-14-2020 at 06:43 PM.
Calaveras is offline  
post #12 of 73 Old 04-14-2020, 08:29 PM
AVS Forum Special Member
 
dr1394's Avatar
 
Join Date: May 2002
Location: Mizar 5
Posts: 3,525
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 225 Post(s)
Liked: 172
This is just a sidebar. Big multi-element reflectors like you see on the 30-2476 go way back to 1976 and this technical note on Yagi design from the National Institute of Standards and Technology..


https://tf.nist.gov/general/pdf/451.pdf


After computer modeling became available, it was shown that these multi-element reflectors don't do much of anything except increase the wind load of the antenna.

HD MPEG-2 Test Patterns http://www.w6rz.net
dr1394 is offline  
post #13 of 73 Old 04-15-2020, 08:16 AM - Thread Starter
Member
 
ChiwaukeeOTA's Avatar
 
Join Date: May 2016
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 2
Reflectors useless?

Quote:
Originally Posted by dr1394 View Post
This is just a sidebar. Big multi-element reflectors like you see on the 30-2476 go way back to 1976 and this technical note on Yagi design from the National Institute of Standards and Technology..


https://tf.nist.gov/general/pdf/451.pdf


After computer modeling became available, it was shown that these multi-element reflectors don't do much of anything except increase the wind load of the antenna.

Hello Dr. ,

Thanks for joining the thread. Wow, that's quite the document! It will take several reads to understand it (for me).

I see a lot about director spacing etc...

Maybe I should bite the bullet and try to learn the modeling software?

So basically the reflector does nothing? Does it help to remove it?

Since this antenna was (probably) designed and built in China, maybe they didn't get the message?

I may do some testing with the reflector removed, but right now I need to figure out the directors.
keeper likes this.

Last edited by DrDon; 04-15-2020 at 08:44 AM. Reason: Unnecessary formatting removed
ChiwaukeeOTA is offline  
post #14 of 73 Old 04-15-2020, 09:17 AM - Thread Starter
Member
 
ChiwaukeeOTA's Avatar
 
Join Date: May 2016
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 2
Quote:
Originally Posted by Calaveras View Post
To do it right, the antenna needs to be modeled. Absent that, I have seen some long antennas where the director spacing and length remains the same after the first few directors. If you were to do that, all additional directors would be 21 3/4" long and the spacing would be 10 1/2". The final director would be the 20 3/4" original one with the same spacing. This is a guess is on my part. I'm pretty sure that making the additional directors longer again is not the right thing to do.

All those splitters used as combiners have at least 1/2 dB loss. There is a way to make a nearly lossless combiner. Use a 1/4 matching section. I've done this several times and it does work. The matching section is a 1/4 wave piece if coax whose impedance is the geometric mean of the two things you're trying to match. Two 75 ohm antennas in parallel is 37.5 ohms. The preamp (or feed line) is 75 ohms. The correct impedance for the matching section is very close to 50 ohms. If you use a piece of RG-58 or R-8 with solid polyethylene dielectric, the length is exactly 10". Attached is picture of a UHF version I made. The little box can be a 2 way splitter with the guts removed and replaced with wires. The matching section is very broadband and covers the entire high VHF band with very low loss. The length of the matching section includes connectors.

I had a pair of 12 element log periodics up for some years. Eventually though I ended up with a single 22 element log periodic on an 18' boom. Even though it is long, it's easier to deal with than phasing a pair of smaller antennas. It's the best high VHF antenna I ever used.

I also tried the idea of using two preamps on phased high VHF antennas. Sometimes it worked but sometimes there would be feedback between the two antennas and the oscillation would wipe out all the stations. Don't bother with it. Stick with one preamp.

The 22 element LPDA plus the KT-200 preamp is a very good combination and it's simpler than phasing antennas. See attached image.

In my experience, once you have a good antenna like the 30-2476 up in the air, it is very hard to get much improvement. Twice the antenna can approach 3 dB and 4 times the antenna can approach 6 dB. 10 dB improvement is a fantasy.
Hi Calaveras!

Well, all of your points are well taken. And, thanks for showing interest.

Since I am committed to this project and have some time on my hands, I'd like to see it through.

My new list of questions, if you can answer at your leisure :

1) If I make the 2 way combiner out of RG 58, am I making a long enough RG-6 cable between the two antennas, carefully stripping back the insulation and soldering the 10" section of RG 8 to the exact center point? And just find a way to enclose them...

Or, take and old combiner , gut it, making two seperate equal length sections of RG-6 with extra core sticking out, and coming through the ports joining them inside and soldering them to a similarly skinned 10" section of RG-58?

Could a "T" connector work? Probably not I'm thinking.. Forget that.

2) Since guessing isn't a good way to space the directors, who can model the design? I am computer literate but is there a somewhat easy modeling software to use?

3) What do you think about the previous post where modeling suggests a reflector is a waste? I think I see your VHFs don't use them?

Last edited by ChiwaukeeOTA; 04-15-2020 at 09:57 AM.
ChiwaukeeOTA is offline  
post #15 of 73 Old 04-15-2020, 09:51 AM
AVS Forum Special Member
 
Calaveras's Avatar
 
Join Date: Jan 2007
Location: Hereford, AZ
Posts: 6,290
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 1966 Post(s)
Liked: 486
Quote:
Originally Posted by ChiwaukeeOTA View Post
[SIZE="3"]Hi Calaveras!

Well, all of your points are well taken. And, thanks for showing interest.

Since I am committed to this project and have some time on my hands, I'd like to see it through.

My new list of questions, if you can answer at your leisure :

1) If I make the 2 way combiner out of RG 58, am I making a long enough RG-6 cable between the two antennas, carefully stripping back the insulation and soldering the 10" section of RG 8 to the exact center point? And just find a way to enclose them...

Or, take and old combiner , gut it, making two seperate equal length sections of RG-6 with extra core sticking out, and coming through the ports joining them inside and soldering them to a similarly skinned 10" section of RG-58?

Could a "T" connector work? Probably not I'm thinking.. Forget that.

2) Since guessing isn't a good way to space the directors, who can model the design? I am computer literate but is there a somewhat easy modeling software to use?

3) What do you think about the previous post where modeling suggests a reflector is a waste? I think I see your VHFs don't use them?

I think you could use a T connector. The advantage of gutting a 2 way combiner is that you can replace the common port F connector with a BNC connector. Then you can put a BNC connector on the RG-58. Whatever you do, you want to make sure the total length of the matching section is 10", not 10" of cable plus connector lengths.

holl_ands who is active here has done a lot of modeling. I don't know if he's done this though. Find one of his posts to find the link to his modeling web pages. I don't know who does modeling for hire.

I agree that the multi-reflector yagis don't do anything. My understanding is that this design became popular in Europe and if it came from Europe and looks cool it must be better, right? My long boom UHF LPDA (37 elements on a 9' boom) was modeled with around 40 dB FB ratio. That's really beyond what you'll actually get in the real world.

Last edited by Calaveras; 04-15-2020 at 10:05 AM.
Calaveras is offline  
post #16 of 73 Old 04-15-2020, 10:05 AM
AVS Forum Special Member
 
Calaveras's Avatar
 
Join Date: Jan 2007
Location: Hereford, AZ
Posts: 6,290
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 1966 Post(s)
Liked: 486
Quote:
Originally Posted by ChiwaukeeOTA View Post
Maybe I should bite the bullet and try to learn the modeling software?
I'm not trying to discourage you, but it's not something you'll do in a few days. There's a reason there are so few people doing modeling.


Quote:
Originally Posted by ChiwaukeeOTA View Post
So basically the reflector does nothing? Does it help to remove it?
The multi element reflector works, it just doesn't work better than a single element. Don't just arbitrarily remove it.


Quote:
Originally Posted by ChiwaukeeOTA View Post
Since this antenna was (probably) designed and built in China, maybe they didn't get the message?
It's all about marketing. If you have a choice between a plain old flat yagi and a yagi with a cool 4 element reflector for a little more money, which will you buy?


Quote:
Originally Posted by ChiwaukeeOTA View Post
I may do some testing with the reflector removed, but right now I need to figure out the directors.
If you remove the reflector, you'll need to replace it with a single element. Without modeling the change, who knows what the length and spacing of the new reflector will be.
Calaveras is offline  
post #17 of 73 Old 04-15-2020, 02:17 PM - Thread Starter
Member
 
ChiwaukeeOTA's Avatar
 
Join Date: May 2016
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 2
Modeling antenna

Quote:
Originally Posted by Calaveras View Post
I'm not trying to discourage you, but it's not something you'll do in a few days. There's a reason there are so few people doing modeling.

If you remove the reflector, you'll need to replace it with a single element. Without modeling the change, who knows what the length and spacing of the new reflector will be.
It's mind boggling for sure. I've heard that even if you have a great virtual design it may not fly in the field.

Sounds like I should contact Hollands, I thought I read somewhere he is retired, maybe he has some time and would like a challenge. I will reach out to him. I hope he'll help.

Thanks, Bob
ChiwaukeeOTA is offline  
post #18 of 73 Old 04-16-2020, 12:39 PM
AVS Forum Special Member
 
rabbit73's Avatar
 
Join Date: Apr 2008
Location: S.E. VA
Posts: 3,642
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 1091 Post(s)
Liked: 482
Quote:
Originally Posted by ChiwaukeeOTA View Post
So basically the reflector does nothing? Does it help to remove it?

Since this antenna was (probably) designed and built in China, maybe they didn't get the message?

I may do some testing with the reflector removed, but right now I need to figure out the directors.
Multi element reflectors go back even further, like to 1926 with the invention of the Yagi-Uda antenna.



Attached Thumbnails
Click image for larger version

Name:	Yagi-Uda Elements in Patent 69115_1.jpg
Views:	481
Size:	54.4 KB
ID:	2710906   Click image for larger version

Name:	Yagi-Uda Elements Patent 69115_2.jpg
Views:	478
Size:	166.2 KB
ID:	2710908  
dr1394 likes this.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html

Last edited by rabbit73; 04-16-2020 at 12:42 PM.
rabbit73 is offline  
post #19 of 73 Old 04-16-2020, 01:31 PM
AVS Forum Special Member
 
Calaveras's Avatar
 
Join Date: Jan 2007
Location: Hereford, AZ
Posts: 6,290
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 1966 Post(s)
Liked: 486
Quote:
Originally Posted by rabbit73 View Post
Multi element reflectors go back even further, like to 1926 with the invention of the Yagi-Uda antenna.

In the ARRL Antenna Book, I read over the sections on collinear arrays (DB8 type antenna) and corner reflectors. Although they didn't specifically mention multi element reflectors on a yagi in a vertical plane, they did say that when you bend the reflector of a collinear array to 90 degrees or less and you are using a single driven element, you can increase the gain. We see this all the time in UHF TV yagis. The reflectors shown in the Japanese patent are bent. The bent reflector elements need to be at least 1/4 wave longer on each side to work. Reflector elements of standard length as used in the 30-2476 don't produce more gain. The reflector would need to be much larger if it is bent.
Calaveras is offline  
post #20 of 73 Old 04-16-2020, 02:53 PM
AVS Forum Special Member
 
rabbit73's Avatar
 
Join Date: Apr 2008
Location: S.E. VA
Posts: 3,642
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 1091 Post(s)
Liked: 482
The reflector elements in the Yagi patent are not bent, they are straight tubing. The top view of the antenna is looking down at the top of straight vertical elements indicated as small circles. The dotted lines merely indicate the intended arrangement. Uda's original experiments that he did for Dr. Yagi were vertical parasitic arrays.

Please read:
Projector of the Sharpest Beam of Electric Waves
By Hidetsugu Yagi and Shintaro Uda
http://www.wa5vjb.com/references/Yagi1926.pdf

It is true that having more than one reflector behind the DE isn't going to give much more gain, which is probably why they dropped that approach in later designs after the patent.

The US patent is even more confusing and it only has Yagi's name on it.
US Patent 1,860,123
https://patents.google.com/patent/US1860123A/en
Attached Thumbnails
Click image for larger version

Name:	Yagi Antenna-Uda Setup3.jpg
Views:	422
Size:	120.7 KB
ID:	2711048  
Attached Files
File Type: pdf Yagi Origin 1926.pdf (249.4 KB, 1 views)

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html

Last edited by rabbit73; 04-16-2020 at 03:50 PM.
rabbit73 is offline  
post #21 of 73 Old 04-16-2020, 03:06 PM - Thread Starter
Member
 
ChiwaukeeOTA's Avatar
 
Join Date: May 2016
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 2
Quote:
Originally Posted by rabbit73 View Post
The reflector elements in the Yagi patent are not bent, they are straight tubing. The top view of the antenna is looking down at the top of straight vertical elements indicated as small circles. The dotted lines merely indicate the intended arrangement. Uda's original experiments that he did for Dr. Yagi were vertical parasitic arrays.


Please read:
Projector of the Sharpest Beam of Electric Waves
By Hidetsugu Yagi and Shintaro Uda

http://www.wa5vjb.com/references/Yagi1926.pdf
Hi Rabbit,

It's amazing they developed the antenna before TV was invented. Did Udi/Yagi know what they were inventing this antenna for?

Bob
ChiwaukeeOTA is offline  
post #22 of 73 Old 04-16-2020, 03:56 PM
AVS Forum Special Member
 
Calaveras's Avatar
 
Join Date: Jan 2007
Location: Hereford, AZ
Posts: 6,290
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 1966 Post(s)
Liked: 486
Quote:
Originally Posted by rabbit73 View Post
The reflector elements in the Yagi patent are not bent, they are straight tubing. The top view of the antenna is looking down at the top of straight vertical elements indicated as small circles. The dotted lines merely indicate the intended arrangement. Uda's original experiments that he did for Dr. Yagi were vertical parasitic arrays.

My bad. I didn't mean that the elements were bent. I meant the reflector assembly was bent into a 90 degree assembly or a parabolic assembly with straight elements as shown in your illustrations.
Calaveras is offline  
post #23 of 73 Old 04-16-2020, 04:04 PM
AVS Forum Special Member
 
rabbit73's Avatar
 
Join Date: Apr 2008
Location: S.E. VA
Posts: 3,642
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 1091 Post(s)
Liked: 482
Oh, OK. I think they were just trying to cover all possibilities in the patent. Later, Kraus got the patent for the corner reflector in 1938.

Trigonal reflector thread:
https://www.eham.net/forum/view?id=topic=70697.0

Viezbicke's trigonal reflector has the upper and lower reflector elements to the rear of the centered reflector element. He claims 0.75 dB added gain.
Yagi Antenna Design
NBS Technical Note 688
https://tf.nist.gov/general/pdf/451.pdf

Attached Thumbnails
Click image for larger version

Name:	NBS Trigonal Reflector2.jpg
Views:	434
Size:	54.1 KB
ID:	2711084  

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html

Last edited by rabbit73; 04-16-2020 at 05:52 PM.
rabbit73 is offline  
post #24 of 73 Old 04-16-2020, 04:12 PM
AVS Forum Special Member
 
rabbit73's Avatar
 
Join Date: Apr 2008
Location: S.E. VA
Posts: 3,642
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 1091 Post(s)
Liked: 482
Quote:
Originally Posted by ChiwaukeeOTA View Post
Hi Rabbit,

It's amazing they developed the antenna before TV was invented. Did Udi/Yagi know what they were inventing this antenna for?

Bob
I doubt that they knew it would be used for radar or TV, but they did understand that their antenna would be more directional and have more gain.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html
rabbit73 is offline  
post #25 of 73 Old 04-16-2020, 04:21 PM - Thread Starter
Member
 
ChiwaukeeOTA's Avatar
 
Join Date: May 2016
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 2
Rabbit

Quote:
Originally Posted by rabbit73 View Post
I doubt that they knew it would be used for radar or TV, but they did understand that their antenna would be more directional and have more gain.
Thanks, As always, thanks for your insight. You have a huge library of info.

Rabbit, What do you think about this antenna design, I mean should I just go with trial and error because I'm no whiz with antenna modeling software? Or, are there any "rules of thumb" for director spacing? And width of course.

Dealing with the reflector should not be so bad I might think.
ChiwaukeeOTA is offline  
post #26 of 73 Old 04-16-2020, 05:12 PM
AVS Forum Special Member
 
rabbit73's Avatar
 
Join Date: Apr 2008
Location: S.E. VA
Posts: 3,642
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 1091 Post(s)
Liked: 482
Quote:
Originally Posted by ChiwaukeeOTA View Post
Rabbit, What do you think about this antenna design, I mean should I just go with trial and error because I'm no whiz with antenna modeling software? Or, are there any "rules of thumb" for director spacing? And width of course.
I think it is an interesting project. Normally, you would think of a design, do a computer model, and finally build a prototype antenna for proof of performance.

Computer modeling doesn't appeal to me, it seems too tedious. I would rather make antenna measurements and leave the modeling to guys that love to do it. I'm 86, so I don't want to spend my time doing something I don't love.

After 10 or 12 directors, you get diminishing returns. Then you stack two of them. Only you can decide what your goal is and how much effort you are willing to put into it. You will be able to get more gain, but your antenna will be much larger and more difficult to aim.

When it stops being fun, find something else to do.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html

Last edited by rabbit73; 04-16-2020 at 05:15 PM.
rabbit73 is offline  
post #27 of 73 Old 04-17-2020, 06:09 AM - Thread Starter
Member
 
ChiwaukeeOTA's Avatar
 
Join Date: May 2016
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 2
Rabbit, thank you. I always like your perspective.. so far this project is still fun. So I'll give it some more effort. I was hoping somebody would chime in with some director spacing info.

There's a lot of great people here. Calaveras has offered his help, he gave me some guidance on my quarter wave low loss combiner, which I spent some time building last night.

I'm surprised others haven't joined in. Do you think there's something in the way I posted it,it's not a attracting some enthusiasts? Should I try another forum?

BTW, Calaveras, I started on my 1/4 wave combiner. what do you recommend for a filler to keep the weather out of it?

I was thinking Epoxy since it is NEVER coming back apart, I hope.

Attached Thumbnails
Click image for larger version

Name:	20200416_230719_1587128817254.jpg
Views:	666
Size:	5.20 MB
ID:	2711294   Click image for larger version

Name:	94038624_3127755277243234_1064960243672285184_n (2).jpg
Views:	25
Size:	14.5 KB
ID:	2711362  

Last edited by ChiwaukeeOTA; 04-17-2020 at 08:47 AM.
ChiwaukeeOTA is offline  
post #28 of 73 Old 04-17-2020, 07:30 AM
Member
 
MSev's Avatar
 
Join Date: Oct 2005
Posts: 107
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 31 Post(s)
Liked: 12
Quote:
Originally Posted by keeper View Post
This is great work. I have two of these antennas just laying in my garage. I use the old antenna craft antenna. I will be following these results closely.
I have 2 of the y10-7-13's.
I was planning on attaching the nose and the reflector on from 30-2476 units to them. As I recall that hack worked well.

I need to find another Y10-2-6 so I can create a stacked set of plural antennas. Otherwise I will have to build one.
MSev is offline  
post #29 of 73 Old 04-17-2020, 08:47 AM
AVS Forum Special Member
 
rabbit73's Avatar
 
Join Date: Apr 2008
Location: S.E. VA
Posts: 3,642
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 1091 Post(s)
Liked: 482
Quote:
Originally Posted by ChiwaukeeOTA View Post
I'm surprised others haven't joined in. Do you think there's something in the way I posted it,it's not a attracting some enthusiasts? Should I try another forum?
I think you have done a good job of presenting your case: you want to hack the 30-2476 for light DXing. You have shown us good photos and test results. You have learned that one antenna mounted up high can be as good as two mounted lower. You have shown us that a preamp with a low noise figure can improve reception. And now, you are willing to try a low-loss combiner for two antennas.

What you want to do is very specific. There aren't many people that have the knowledge and experience to give you exactly what you want, which is computer modeling of the antenna with additional directors. The 30-2476 has been modeled by holl_ands; he is best qualified to model that antenna with the additional directors.
https://imageevent.com/holl_ands/yag...agistellarlabs

Without modeling, you are making good progress with your tests and measurements. You are using the empirical method (trial-and-error) that was used by assistant professor Shintaro Uda when he invented the Yagi-Uda antenna for Dr. Yagi, when Peter Viezbicke designed Yagi antennas for the NBS, and when Edison invented the incandescent light bulb.





I think this forum is your best choice; digitalhome.ca would be second choice, but there are too many guys there that think they know a lot about modeling, but don't.

So far, your thread has had 653 views; that's pretty good. Of those people that have viewed your thread, there are only a few that are qualified to give a useful answer.

The combiner should be OK for short-term testing with a little adhesive on the underside of the back cover and epoxy on the outside seam. But, the connectors that attach to the combiner housing are vulnerable to water ingress. I would prefer the combiner in a housing with the coax entering the bottom.
Attached Thumbnails
Click image for larger version

Name:	Shintaro Uda.jpg
Views:	403
Size:	59.3 KB
ID:	2711482  

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html

Last edited by rabbit73; 04-17-2020 at 10:17 AM.
rabbit73 is offline  
post #30 of 73 Old 04-17-2020, 09:02 AM - Thread Starter
Member
 
ChiwaukeeOTA's Avatar
 
Join Date: May 2016
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 2
Keep on trying...

Quote:
Originally Posted by rabbit73 View Post
I think you have done a good job of presenting your case: you want to hack the 30-2476 for light DXing. You have shown us good photos and test results. You have learned that one antenna mounted up high can be as good as two mounted lower. You have shown us that a preamp with a low noise figure can improve reception. And now, you are willing to try a low-loss combiner for two antennas.

What you want to do is very specific. There aren't many people that have the knowledge and experience to give you exactly what you want, which is computer modeling of the antenna with additional directors. The 30-2476 has been modeled by holl_ands; he is best qualified to model that antenna with the additional directors.
https://imageevent.com/holl_ands/yag...agistellarlabs

Without modeling, you are making good progress with your tests and measurements.

I think this forum is your best choice; digitalhome.ca would be second choice, but there are too many guys there that think they know a lot about modeling, but don't.

So far, your thread has had 653 views; that's pretty good. Of those people that have viewed your thread, there are only a few that are qualified to give a useful answer.

The combiner should be OK for short-term testing with a little adhesive on the underside of the back cover and epoxy on the outside seam. But, the connectors that attach to the combiner housing are vulnerable to water ingress. I would prefer the combiner in a housing with the coax entering the bottom.
Hello Rabbit, Wow, 653 views! Well I guess you are right, very few are able to help. So be it. I guess I made my case, I do my best. Your words are encouraging, trial and error may be my path to success.


BTW, without your guidance on these forums I would have never learned how to post photo. One good thing about AVS is you can drop and drag and it doesn't matter what the size is. But getting a photo to post in the body of the post takes a lot of playing around with: [IMG] & [/IMG] same as TV Fool. BTW, the HiDef Forum seems to be taken over or Hi jacked. I wanted to go back and read some stuff and it keeps taking me to a DVD page, WTF?

I have tried to contact Holl_ands through the PM system here. So far, he hasn't responded. I hope to contact him, he sounds like the one to talk to.

I followed your link and there it is the 30-2476. Wow, he is very thorough. I don't see and mods though but he seems to like this particular antenna.

Last edited by ChiwaukeeOTA; 04-17-2020 at 10:15 AM.
ChiwaukeeOTA is offline  
Sponsored Links
Advertisement
 
Reply HDTV Technical

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off