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@mark_aok

So an update to my post earlier this summer asking if anyone had real world results switching directly from a DB4e to a DB8e. I've now gone through that process and have results at least for my location.

In brief, with the DB8e I experienced a roughly 3-5% increase in signal "strength" as displayed on the integrated TV firmware, and in exchange lost a significant number of channels. In my case probably 6 out of my available 17. The significant directionality of the DB8e in my case is a penalty since I have transmitters through a wide azimuth.

The DB4e on the other hand, picks up all those desired channels with a great azimuth range, but forfeits that small signal gain. It was an easy choice in my situation, to switch back to the DB4e.

I did rapid testing, switching the antennas several times within a space of few minutes, and re-scanning, so avoid atmospheric changes during the day which could skew the results.

I can see how the DB8e could be useful in some circumstances though. Where you have all your transmitters in a very tight angle at great range, you need maximum gain and don't care if it only captures what is directly in front of the arrays.

I did try the DB8e in a variety of other configurations, trying to angle each array to "see" the equivalent angles as the DB4e, but it was no contest. In my location I lost net gain when the arrays weren't totally parallel, and I also lost many of the same channels in that scenario.

I have a variety of people I know using DB8e's with great success where they are also 'in between' two primary transmitter azimuths, but they are also much close to the transmitters, not fringe, so that loss of gain with the arrays not parallel is less of an issue.

The construction of the DB8e was very nice. My only suggestion is that the collector assembly and U-bolt have an extra set of bolts which fasten down the collector and keep the U-bolt square to the collector bar. And a re-design to potentially take the load off the plastic collector case and keep the entire assembly presented to the pole in a more user-friendly way.

That being said, I didn't have any problems with it, I just thought about that during installs.

So that's the results.
 

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Great report. If you do need the additional gain and want to maintain the similar beam width, try stacking vertically another DB4e with the existing one.
 

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Stacking two identical antennas raises the total gain by about ~3dB, but it narrows the horizontal beam pattern considerably so it isn't a good option for him.

Horizontally ganging two identical antennas will also raise the total gain by about ~3dB, but it will make the beam pattern narrower vertically while maintaining the horizontal beam pattern, which is what the DB8e essentially does from the factory. Theoretically It sounds like that's what he would benefit from, but...

His testing shows that a single DB4e is better for certain situations than stacking or horizontally ganging two of them. I think this is very valuable information for people thinking about whether to make the same antenna change. :)
 

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I thought that vertical stacking of 2 identical antennas narrows the vertical beam width but that the horizontal beam width is not affected?
From AVS Forum said:
Side by side (Horizontal Stacked) with the screens touching (bound together) will give you a narrow beam on UHF and some limited VHF-hi reception.

One on top of the other (Vertical Stacked) end up with the same beam as a single 4221 but with the vertical beam squeezed some. Space them so that the top v elements of 1 antenna and the bottom v elements of the other are spaced the same distance as the rest of the elements, I think around 8".
The UHF gain either way will be very close to the same, be sure to feed them with equal lengths of feed line and if using baluns they should be exactly the same too.
 

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Ooooops!

I had a brain malfunction! :D I will leave my post up but add a note to it that I completely mixed up the two. Jorgek, sorry about that.

Aging sucks...
 

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AD 4 Bay is Tops

I would pick the AD 4 bay over the 8 bay.

I have tried both antennas, and settled for the 4 bay. It has slightly less gain, but the beam width is the big advantage.
The 8-bay can be tricky to aim, it's much heavier and bigger.

I paired my 4 bay with the AD VHF kit and it's been a rock solid performer for years - much more durable/reliable than several other antennas I have tried.
 

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Horizontally ganging two identical antennas will also raise the total gain by about ~3dB, but it will make the beam pattern narrower vertically while maintaining the horizontal beam pattern, which is what the DB8e essentially does from the factory.
It can be confusing when stacking and ganging are used synonymously.

On another note, I see that Princess Auto has Al tubing on sale. Thinking I might build Nikimi's Y15FD yagi for my chum's cottage on Big Rideau lake to replace his 8-bay clone.

And I will get to use my new $60 NanoVNA to measure return loss!

 

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It is the other way around.
When stacking horizontally (side by side), the Horiz beam is narrowed, and the vert beam remains the same.
When stacking vertically (one above the other) , the Horizontal beam is roughly the same, but the vertical beam is narrowed (roughly by half). Thus when stacking vertically it's more critical to make sure ur mast is plumb and your antenna's vert beam is actually aimed at the horizon.
Else you might be undershooting the distant TXMTRs.

Also should point out when stacked like a db8 horizontally, not only is the horiz beam narrowed but two smaller side lobes appear on either side of the main lobe.
This can be used to your advantage depending on the spread of distant vs local transmitters. For instance where I live there is no reason to aim the main lobe at Grand Island and the CN tower, when one of two smaller lobes will suffice. So I normally aim the main lobe at the weaker difficult transmiiters in the direction of Hamilton (Font Hill and Hamilton). And the smaller sidelobe at GI and the CN Tower. That helps to keep the strong local signals of GI in check.

Code:
db4e

         --- Gain ---              -- Ratios -- -- Impedance --           
   Freq    Raw    Net   SWR [B]BeamW[/B]    F/R    F/B    Real    Imag  AGT  corr
==========================================================================
  467.0  11.97  11.21  2.34  [B]61.6[/B]  18.61  19.28  150.01  109.23 1.05  0.20
  473.0  11.97  11.19  2.37  [B]61.4[/B]  18.52  19.04  149.58  112.86 1.05  0.20
  479.0  11.98  11.18  2.38  [B]61.1 [/B] 18.44  18.86  149.82  116.47 1.05  0.20

db8e

         --- Gain ---              -- Ratios -- -- Impedance --           
   Freq    Raw    Net   SWR [B]BeamW[/B]    F/R    F/B    Real    Imag  AGT  corr
==========================================================================
  467.0  14.95  14.18  2.35  [B]24.7[/B]  18.34  18.34  164.38  140.91 0.96 -0.17
  473.0  14.96  14.17  2.38  [B]24.5[/B]  18.15  18.15  163.99  144.70 0.96 -0.17
  479.0  14.98  14.17  2.40  [B]24.2[/B]  18.01  18.01  164.39  148.51 0.96 -0.17
db4e

db8e
 

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I previously used the db8e and took advantage of the nulls to lessen the effect of CHCH (15) interfering on the previous allotment of WUTV on RF 14.

It worked - I finally could get WUTV on 14, and initially all the TO stations; but this was not the case long-term.
Most TOs came in, but the weaker ones (e.g., CITY) were inconsistent.
Granted, this was with the db8e in the fixed direction of GI, and if I turned the antenna to TO, the weaker TOs would come in.

Nonetheless, with the goal of having all TOs and BUFs come in with a fixed antenna direction, I tried the db4e again and initially, WUTV on RF14 was hit or miss..., until I got a new TV (2018 Samsumg), WUTV became rock solid;
I assume the newer tuner was the difference in handling the interference.

From this, I thought the new tuner would also help in the same fashion when WNYO switched to RF16, however, it rarely comes in with the db4e and new Samsung TV.

To be fair, I think the current signal on WNYO - RF16 is weaker than the signal WUTV had on RF 14.
Hopefully, when WNYO puts out their permanent signal (September 2020?), it will come in...

Overall the db8e is a very good antenna with tremendous gain from the main lobe, nulls that can knock down strong/local signals, and some decent reception from the side lobes;
a little tricky to aim/figure out and it may require a rotator.
Alternatively, you could change/separate the aiming of each of the 4-bays, which I have not done, but I'm thinking this might eliminate the nulls - allowing the stronger signals to wipe out the weaker ones that are adjacent.

The db4e is not tricky - good gain and very forgiving aim; good for most situation unless you have very strong/local signals interfering with weaker distant signals that have RFs right beside each other.
 
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