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Old 12-Feb-2016, 4:57 AM   #1
Tristan
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DB4e vs DB4-PRO vs ClearStream 4V

Anyone have experience with these models listed in title from Antennas Direct?

In particular, I'm curious about:
1) differences between DB4e and DB4-PRO (other than stainless steel construction, and, ahem, price)
2) beam width of ClearStream 4V (vs 2V)? Both indicate "70 degrees" on the company website, but I can only find technical data on the website for the 2V.

Maybe ADTech can answer these questions?
Thanks!

--Tristan
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Old 12-Feb-2016, 11:26 AM   #2
ADTech
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1. The PRO is all stainless, that's it. It was extraordinarily expensive to manufacture compared to a stock DB4e and was a one-time only production item. There are no plans to make more as of this time. Its performance parameters are close enough to the stock DB4e that no separate technical data was produced. There is a formal technical data sheet for the DB4e, it's on the website. If you live by the ocean where salt air eats everything, get the PRO. Otherwise, stick with the standard version.

2. I don't see any beamwidth numbers for the C4 or C4V on the website but that thing can be a real potpourri of old and new stuff. Link where you saw it?

For the C4, the calculated UHF BW is ~43° at 470 MHz which narrows with increasing frequency to 31° at 698 MHz. There is no formal data sheet for the C4 (or C4V) although I do have calculated polar plots and a gain vs frequency chart somewhere on my computer at work. I'll see if I can dig them up. Performance of the VHF dipole will be considered to be the same as for the C2V, it's the same module.
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Last edited by ADTech; 12-Feb-2016 at 12:00 PM.
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Old 12-Feb-2016, 3:15 PM   #3
Tristan
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Quote:
Originally Posted by ADTech View Post
1. ...If you live by the ocean where salt air eats everything, get the PRO. Otherwise, stick with the standard version...
how close is "live by the ocean?" I assume within a few miles (in other words Seattle does not qualify)

Quote:
2. I don't see any beamwidth numbers for the C4 or C4V on the website but that thing can be a real potpourri of old and new stuff. Link where you saw it?
https://www.antennasdirect.com/store...V-antenna.html
From the overview:
"...The ClearStream™ 4V has a 70+ mile range and a generous beam width of 70 degrees..."
I thought this was a little suspicious, as the Clearstream 4 has no such description, and should be the same (other than the included VHF dipole). Also, there is this:
http://www.hdtvprimer.com/ANTENNAS/ClearStream4.html

Quote:
...although I do have calculated polar plots and a gain vs frequency chart somewhere on my computer at work. I'll see if I can dig them up...
That would be interesting, thank you for the offer, but I'm not sure I really need them as your answer about beam width will suffice. Also, my particular set-up needs the beam width of the C2 (70 degrees) but I won't get into that (I've posted in the Help With Reception forum about my particular needs).

What I would be curious about however is how exactly do you define 70 degrees? or 60 degrees? Is there some industry standard, or do you choose an "arbitrary" dBi cutoff to define this?

Thank you!
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Old 12-Feb-2016, 3:34 PM   #4
ADTech
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Quote:
how close is "live by the ocean?" I assume within a few miles (in other words Seattle does not qualify)
If your stuff corrodes from salt air, you're close enough.

Thanks for the link to the beamwidth, I overlooked that this morning. Silly me, I looked in the "Specifications" but didn't read the "Overview" carefully. I suspect someone used the verbiage from another model but didn't catch the different BW. I'll notify the marketing manager about it.

Horizontal beamwidth is technically defined as the "Half-Power Beam Width (HPBW)". This is the arc that covers the peak lobe and defines where the reception is 1/2 the peak on either side of maximum, also known as the -3 dB points. A good tutorial is available at http://www.antenna-theory.com/basics/radPatDefs.php

Should you need the wide BW of a C4 but desire a bit more gain, you can stack two C2s vertically on the same mast and combine them with a reversed splitter and two equal length coax segments. This will compress the radiation pattern vertically and will provide a 2-3 dB increase in forward gain while maintaining horizontal HPBW. This is the same as what happens when we go from our C1 to the C2 UHF loops or from a DB2e to a DB4e.
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Last edited by ADTech; 12-Feb-2016 at 3:37 PM.
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Old 12-Feb-2016, 5:46 PM   #5
Tristan
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Quote:
Originally Posted by ADTech View Post
Thanks for the link to the beamwidth, I overlooked that this morning...
Yes, I had to go back and search to be sure I really saw it there.

Quote:
Horizontal beamwidth is technically defined as the "Half-Power Beam Width (HPBW)". This is the arc that covers the peak lobe and defines where the reception is 1/2 the peak on either side of maximum, also known as the -3 dB points. A good tutorial is available at http://www.antenna-theory.com/basics/radPatDefs.php
Thank you that is helpful

Quote:
Should you need the wide BW of a C4 but desire a bit more gain, you can stack two C2s vertically on the same mast and combine them with a reversed splitter and two equal length coax segments...
Interesting... just to be clear you mean "...the wide BW of a C2 (not C4)..." correct? In any event I think I would do better just going with a DB4e which is >similar< (by my understanding) to a pair of C2s stacked.

Thanks again, your input is always helpful
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Old 29-Feb-2016, 1:49 PM   #6
shoman94
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Quote:
Originally Posted by ADTech View Post
If your stuff corrodes from salt air, you're close enough.

Thanks for the link to the beamwidth, I overlooked that this morning. Silly me, I looked in the "Specifications" but didn't read the "Overview" carefully. I suspect someone used the verbiage from another model but didn't catch the different BW. I'll notify the marketing manager about it.

Horizontal beamwidth is technically defined as the "Half-Power Beam Width (HPBW)". This is the arc that covers the peak lobe and defines where the reception is 1/2 the peak on either side of maximum, also known as the -3 dB points. A good tutorial is available at http://www.antenna-theory.com/basics/radPatDefs.php

Should you need the wide BW of a C4 but desire a bit more gain, you can stack two C2s vertically on the same mast and combine them with a reversed splitter and two equal length coax segments. This will compress the radiation pattern vertically and will provide a 2-3 dB increase in forward gain while maintaining horizontal HPBW. This is the same as what happens when we go from our C1 to the C2 UHF loops or from a DB2e to a DB4e.
I tried combining it that way (stacking them) and it lost some power. Probably because using the splitter creates a loss or 3db. I think I would have needed a combiner similar to what included with the C4 to make that work. Just like the "old" vs "new" DB8 that introduced the PCB combiner. I'd be interested in trying it that way(PCB method) but basically using the splitter made it have the same reception as the C2.

This is the C4 spec sheet I had found thanks to Google. I'm thinking the 70 degree width is from the to bubbles on the higher UHF channels.

C4 spec sheet
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Old 29-Feb-2016, 7:13 PM   #7
rabbit73
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Quote:
Probably because using the splitter creates a loss or 3db.
Not true.

When you use a splitter in reverse as a combiner, the loss is about 0.5 dB, which means that the most gain you can get when combining two identical antennas aimed in the same direction is 2.5 dB. When a splitter is used as a splitter, the loss about 3.5 dB because you are dividing the power in half.

It is possible to make a lower-loss combiner by connecting the coax lines from each antenna in parallel, which gives 37.5 ohms. This can be converted to 75 ohms by using a quarter wave matching section of 50 ohm coax.

It is also possible to make a half-wave coaxial balun that has less loss than a conventional ferrite core balun.

Any losses between the antenna and the input of the preamp subtract directly from the antenna gain.

Calaveras at AVS Forum used the parallel combiner and half-wave coaxial baluns for the lowest losses when combining his two 91XG UHF antennas.
http://www.aa6g.org/DTV/index.html
http://www.aa6g.org/DTV/ABD/Antenna_Block_Diagram.html

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Last edited by rabbit73; 29-Feb-2016 at 7:56 PM.
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Old 29-Feb-2016, 7:32 PM   #8
shoman94
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Quote:
Originally Posted by rabbit73 View Post
Not true.

When you use a splitter in reverse as a combiner, the loss is about 0.5 dB, which means that the most gain you can get when combining two identical antennas aimed in the same direction is 2.5 dB. When a splitter is used as a splitter, the loss about 3.5 dB because you are dividing the power in half.

It is possible to make a lower-loss combiner by connecting the coax lines from each antenna in parallel, which gives 37.5 ohms. This can be converted to 75 ohms by using a quarter wave matching section of 50 ohm coax.

It is also possible to make a half-wave coaxial balun that has less loss than a conventional ferrite core balun.

Any losses between the antenna and the input of the preamp subtract directly from the antenna gain.
Interesting. I've been reading that this afternoon as well. Basically I took my C4V that is stacked horizontally and stacked them vertically. Used 2 300-75ohm converters to 12" equal length coax to a splitter used as a combiner. My result was a loss in signal to my FOX tower which is the hardest for me to get. I expected it to be as strong as horizontally stacked but I was wrong. The only problem I could think of was all these connections added up to a signal loss.
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Old 29-Feb-2016, 8:14 PM   #9
rabbit73
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Quote:
I expected it to be as strong as horizontally stacked but I was wrong. The only problem I could think of was all these connections added up to a signal loss.
That is one possibility. Did you use 300 to 75 ohm baluns from another source? The loss of baluns is not constant for all frequencies. If you used different baluns than used by the manufacturer, there could be losses from a SWR mismatch.

When I combined two 4-bay antennas to give more gain for channel 15, I tried about 20 different baluns. I found that the loss on that channel varied about 5 dB between the best and worst baluns.

OTA signals constantly vary in strength, sometimes as much as 10 dB in a half hour. The only valid test would be with a constant strength test signal and a signal level meter which gives a reading in dB.

These are the signal level meters (SLMs) that I use for measurements:

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Last edited by rabbit73; 29-Feb-2016 at 8:25 PM.
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Old 29-Feb-2016, 11:30 PM   #10
ADTech
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Quote:
Basically I took my C4V that is stacked horizontally and stacked them vertically. Used 2 300-75ohm converters to 12" equal length coax to a splitter used as a combiner. My result was a loss in signal to my FOX tower which is the hardest for me to get. I expected it to be as strong as horizontally stacked but I was wrong. The only problem I could think of was all these connections added up to a signal loss.
You need to flip one of the baluns. Most likely, you're feeding the combiner/splitter with one loop 180° out of phase which will cause a big, giant dead spot straight ahead with major lobes skewed high and low.

Quote:
This is the C4 spec sheet I had found thanks to Google. I'm thinking the 70 degree width is from the to bubbles on the higher UHF channels.
No. The HPBW is explicitly stated as 43° which is it's calculated value at the low end of UHF, it narrows to almost 30° at 698 MHz. Only the major lobe is considered when the HPBW is specified.
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Last edited by ADTech; 29-Feb-2016 at 11:33 PM.
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Old 1-Mar-2016, 12:53 AM   #11
shoman94
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Originally Posted by ADTech View Post
You need to flip one of the baluns. Most likely, you're feeding the combiner/splitter with one loop 180° out of phase which will cause a big, giant dead spot straight ahead with major lobes skewed high and low.



No. The HPBW is explicitly stated as 43° which is it's calculated value at the low end of UHF, it narrows to almost 30° at 698 MHz. Only the major lobe is considered when the HPBW is specified.
Son of a gun! The baluns can be installed out of phase! =(

Is there a way to test the balun prior to installing?

Never mind. I was going to try it but the parts are almost 35 bucks so I ordered a DB4e to try instead.

Last edited by shoman94; 2-Mar-2016 at 12:01 PM.
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