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-   -   Removing DB4e reflector (http://forum.tvfool.com/showthread.php?t=16731)

shoman94 13-Mar-2020 3:34 PM

Removing DB4e reflector
 
How would removing the reflector change the gain? How would it look compared to the reception graph of the DB4e?

Tim 13-Mar-2020 5:13 PM

Quote:

Originally Posted by shoman94 (Post 62699)
How would removing the reflector change the gain? How would it look compared to the reception graph of the DB4e?

Hollands posted the gain figures and pattern for the Antennas Direct DB4 with no reflector a few years ago. The DB4e should be similar.

Basically, removing the reflector decreases the gain somewhat and makes the antenna bi-directional.

https://imageevent.com/holl_ands/mul...tienoreflector

shoman94 13-Mar-2020 5:36 PM

Quote:

Originally Posted by Tim (Post 62700)
Hollands posted the gain figures and pattern for the Antennas Direct DB4 with no reflector a few years ago. The DB4e should be similar.

Basically, removing the reflector decreases the gain somewhat and makes the antenna bi-directional.

https://imageevent.com/holl_ands/mul...tienoreflector

Thanks for that....

Ouch what a huge hit below 530mhz.

I don't think that would work for me.

https://www.rabbitears.info/searchma...study_id=69426

I aimed at 331 TRUE and only have some issues with 26-1.

Tim 14-Mar-2020 1:01 AM

Quote:

Originally Posted by shoman94 (Post 62701)
Thanks for that....

Ouch what a huge hit below 530mhz.

I don't think that would work for me.

https://www.rabbitears.info/searchma...study_id=69426

I aimed at 331 TRUE and only have some issues with 26-1.

I think the gain figures for the DB4e are much better at the lower end of the band than they were for the DB4.

Tower Guy 14-Mar-2020 2:51 AM

Do you get WMTW on RF channel 8 or RF channel 26?

Can you receive PBS on WENH (RF channel 11)?

ADTech 14-Mar-2020 10:22 PM

Quote:

Ouch what a huge hit below 530mhz.
As noted by Tim, that was for the old DB4 which was discontinued many years ago.


Get the tech data sheet for the DB4e off the website, print out the horizontal polar pattern, draw a new curve 2-3 dB inside the existing curve (on the "hot" side), then mirror that to the other side. You'll be right in the ballpark as to what would be expected.

shoman94 15-Mar-2020 3:08 AM

Quote:

Originally Posted by Tower Guy (Post 62704)
Do you get WMTW on RF channel 8 or RF channel 26?

Can you receive PBS on WENH (RF channel 11)?

I get it with RF channel 8. I have a di-pole kit for it.

I do not get channel 11 or 10 PBS's.

shoman94 15-Mar-2020 3:11 AM

Quote:

Originally Posted by ADTech (Post 62706)
As noted by Tim, that was for the old DB4 which was discontinued many years ago.


Get the tech data sheet for the DB4e off the website, print out the horizontal polar pattern, draw a new curve 2-3 dB inside the existing curve (on the "hot" side), then mirror that to the other side. You'll be right in the ballpark as to what would be expected.

So I will likely lose maybe 2-3 db on the front end on each of the 4 patterns?

Also what do you think would happen if only one reflector was removed?

shoman94 15-Mar-2020 4:26 PM

Quote:

Originally Posted by ADTech (Post 62706)
?

I could try adjusting the backside lobe to line up with 246 degrees and the front side would end up at 16 degrees. Or do you think removing the reflector and adjusting the front side to 331 or 357?

https://www.rabbitears.info/searchma...study_id=69987

shoman94 15-Mar-2020 6:07 PM

So currently if I aim directly or near directly to the Fox/CBS tower (they are on the same tower) I get all kids of errors and glitches. CBS is glitch free. The height I changed by about 2ft and it doesn't change anything.

I'm gonna try without a preamp and see if the signal are just too strong now.

shoman94 15-Mar-2020 9:03 PM

I took off the juice preamp and everything is coming in better now. Even PBS is watchable now but it does have a 12ish% error rate with the sun out so I'll see what happened tonight.


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