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Anybody mod a DB8E to good effect?

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Old 05-12-2018, 01:30 PM   #16  
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...It is a line of womens shoes sold at Nortstrom.
What size do you wear?
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Old 05-12-2018, 03:14 PM   #17  
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Yeah, I certainly agree with you regarding the need for compromise. I haven't run across any discussions of mods for the "e" version of the DB8e. If you see something regarding that idea, it would be neat to share.

My best guess is that, perhaps, one might squeeze up to an extra dB or so of forward gain out of a re-scale. Probably not worth the effort for a manufacturer.
I keep looking.
I did see a supposed DB16 build. The guy built 4 DB4's. Then made an x with phase lines so he only had to use 1 balun.
I'm not sure why he didnt build 2 DB8's instead and use a shorter harnesses.

If I can find the right sized aluminum rod. I am considering building 1 long DB16E.
It should be about 172 inches wide if I have figured it correctly.
It would be one big sail.
Just a ***t's and giggles project.
Def not practical.


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Old 03-29-2019, 09:02 AM   #18  
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Just thought I would revisit this thread.

Anybody try a Nist harness or one of Hol_lands HHH harnesses on a DB8E?

I picked up a couple of Winegard 8800's and have been looking at their phase line design.

On another note.

I have been discussing a mod with Calveras.

I am making plans on flying a diamond quad of DB4E panels.
Using twin lead soldered together to Belben RG6.
I will be using 4 ferrite beads slid over the coax as a non independence transforming balun.
Electrical shrink wrap will be used to make all connections water tight.

This should result in near zero loss.
5 locations where insertion loss occurs will be removed.
Additional loss created in the combiner and the PCB baluns will also be removed.

I have been considering replacing the independent reflectors and installing a single 1x1 square galvanized reflector.

I however am not sure that would change the optimum distance of the reflector from the elements.

Thoughts?
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Old 03-29-2019, 12:03 PM   #19  
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There is always signal loss in an antenna combiner circuit, unless it's amplified.

And standard heat shrink tubing will not make a connection water proof unless it's the stuff with heat activated inside liner, this type oozes around the connection and totally seals it off from the outside.

Four 14 dB antennas will get you 20 dB total gain if your lucky, some seem to think you can get more, in reality you cant.

And I would go with a quarter inch square sized hole on the reflector, it will work better.

Water proofing heat shrink.
https://www.amazon.com/OTC-4814-106-.../dp/B00BVL856I
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Old 03-29-2019, 01:53 PM   #20  
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Originally Posted by Sev View Post
I keep looking.
I did see a supposed DB16 build. The guy built 4 DB4's. Then made an x with phase lines so he only had to use 1 balun.
I'm not sure why he didnt build 2 DB8's instead and use a shorter harnesses.

If I can find the right sized aluminum rod. I am considering building 1 long DB16E.
It should be about 172 inches wide if I have figured it correctly.
It would be one big sail.
Just a ***t's and giggles project.
Def not practical.


The element lengths and bay spacing of the moneyrhythm antenna are too small for max gain. An 8-bay with proper dimensions would give more gain.

Fastening the elements to wood causes losses.

With the four antennas connected in parallel to the coax in that manner, there is no guarantee that it will match the 75 ohm impedance of the coax; it would depend upon the length of the feedlines and their conductor spacing.

Last edited by rabbit73; 03-29-2019 at 02:39 PM..
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Old 03-29-2019, 04:40 PM   #21  
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Originally Posted by Terryl3 View Post
There is always signal loss in an antenna combiner circuit, unless it's amplified.

And standard heat shrink tubing will not make a connection water proof unless it's the stuff with heat activated inside liner, this type oozes around the connection and totally seals it off from the outside.

Four 14 dB antennas will get you 20 dB total gain if your lucky, some seem to think you can get more, in reality you cant.

And I would go with a quarter inch square sized hole on the reflector, it will work better.

Water proofing heat shrink.
https://www.amazon.com/OTC-4814-106-.../dp/B00BVL856I
True.
However the loss will be far less than what occurs with 13 points of insertion, 2 PCB baluns, 6 lengths length of RG6 and the inefficiency of 3 combiners if I just stacked 2 DB8E's in the normal manner.

Even getting rid of the PCB baluns and adding solid phase lines similar to a Nist or a Hol_lands HHH would improve the over all efficiency of a DB8E. Especially if one were going to stack them.
The stack would only have 5 points of insertion and only 1 combiner.
Of course a third set of phase lines could be run to eliminate the combiner and just have a balun and 1 point of insertion.

Right now I am looking at linking 2 sets of Winegard 8800's horizontally in that manner.

As far as the waterproof shrink wrap is concerned.
I use it every time I install a well pump.
Or any other type of electrical splice that will be subject to moisture.
Thank you for specifying, as most people are unaware of shrink wrap. Much less there being a specific waterproofing product.

20 dB is perfectly fine.
It will have a Kitztec KT200 Coax hooked to it. According to some testing by Calveras it has a noise figure of .6 for VHF and 1.2 for UHF.

Appreciate the advice on the 1/4 inch. I had considered it. However. I get some fairly substantial winds on a regular basis. The Wind load produced with the 1/4 in mesh might be pushing my luck a bit.
I'll also be sailing a sizable 2-13 VHF below it.
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Old 03-29-2019, 05:15 PM   #22  
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Originally Posted by rabbit73 View Post
The element lengths and bay spacing of the moneyrhythm antenna are too small for max gain. An 8-bay with proper dimensions would give more gain.

Fastening the elements to wood causes losses.

With the four antennas connected in parallel to the coax in that manner, there is no guarantee that it will match the 75 ohm impedance of the coax; it would depend upon the length of the feedlines and their conductor spacing.
All true.
Here is a nice 8 bay build.
The balun is in the center.
It was based on the Big Birtha on Instructables.
The guy is on a DX'ing site.

I would like to do a quad build of it.




Last edited by Sev; 03-29-2019 at 05:19 PM..
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Old 03-29-2019, 07:42 PM   #23  
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Quote:
Originally Posted by Sev View Post
All true.
Here is a nice 8 bay build.
The balun is in the center.
It was based on the Big Birtha on Instructables.
The guy is on a DX'ing site.

I would like to do a quad build of it.
The Big Bertha dimensions are correct for the 14 to 51 UHF band. They are based on mclapp's diagrams. The new 14 to 36 UHF band will require the dimensions rescaled a little larger for best performance.

Retired Jr. High science teacher deceiver uses two baluns and a splitter in reverse as a combiner. Unless I missed it, he doesn't mention that the baluns must be connected so that the two 4-bay sections are in phase.



If the two sections are not connected in phase, the main lobe will split in two with a null in the center of aim.



Your antenna uses a harness to connect the two 4-bay sections.

What is the yellow at the ends of your whiskers?

Last edited by rabbit73; 03-29-2019 at 08:07 PM..
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Old 03-30-2019, 05:13 AM   #24  
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Originally Posted by rabbit73 View Post
The Big Bertha dimensions are correct for the 14 to 51 UHF band. They are based on mclapp's diagrams. The new 14 to 36 UHF band will require the dimensions rescaled a little larger for best performance.

Retired Jr. High science teacher deceiver uses two baluns and a splitter in reverse as a combiner. Unless I missed it, he doesn't mention that the baluns must be connected so that the two 4-bay sections are in phase.



If the two sections are not connected in phase, the main lobe will split in two with a null in the center of aim.



Your antenna uses a harness to connect the two 4-bay sections.

What is the yellow at the ends of your whiskers?
Sorry for the confusion. It is not my build.

I came across it a while back.
I was wondering the very same thing. Perhaps he got the idea from the DB8E. As they cover the ends of the elements with a plastic sleeve.
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