RFVenue Diversity Fin vs. Two 'Sharkfins'

[bmfsnd]

Is there any disadvantage to using the 2-in-1 nature of the Diversity Fin, compared to two individual fins?

I'm building a very low footprint bagmobile and an antenna like that could cut down on space and loading time.

Thanks

[syncsound]

Go here:

 

http://www.trewaudio.com/audioflow/dipole-vs-sharkfin-vs-polarized-diversity-diversity-fin/

 

Scroll down and read David Waelder's comments. He posted a link to an extensive comparative test.

[pkautzsch]

I remember reading a post by Jan just a few days ago, don't know the thread.

IIRC she wrote that they got slightly better results with a pair of standard fins over the RFVenue.

Remember that the RFVenue is one fin and one dipole.

[Philip Perkins]

I had them both on jobs (feeding two sets of RX) and didn't notice any diffs in practice.  One advantage to the 2-fin deal is that you can dismount one of them and move it elsewhere (than a setup with the 2 of them mounted together) to get more coverage in some situations--this helped me in the past.  The Venue dipole fin is very convenient and compact.  In practice I've been using them interchangeably.

[James Arnold]

Interesting that the above review on Trewaudio suggests they might not be the best idea combined with Lectro receivers. I kind of fancied one, but I use Lectro SR.

[glenn]

For Zaxcom wireless 2 fins are the better solution. A "fin" has multiple elements so there is more consistant RF levels vs a dipole that has sharper peaks and nulls as the transmitter is moved. Never in my opinion use a dipole over a fin unless you need omni directional coverage. The fin will also do a better job getting rid of interfering signals that are not in the intended direction of your wireless transmitters.

 

Glenn

[bmfsnd]

Thanks for the feedback everyone

[Philip Perkins]

I use only Lectro with my various fins, and they have all worked great, for decades, over several models of Lectro, in many many sorts fo locations and situations.

[Jeff Wexler]

  On 2/18/2015 at 9:50 PM, James Arnold said:

Interesting that the above review on Trewaudio suggests they might not be the best idea combined with Lectro receivers. I kind of fancied one, but I use Lectro SR.

Let's not forget that what we're talking about is not really comparing the use of 2 antennas vs. 1 antenna. Using 2 shark fin-style antennas is the norm for all wireless sets that have diversity receivers. Some people use Yagi-style antennas and a few have been known to use helical antennas. The RF Venue antenna IS 2 antennas --- 1 shark fin and 1 dipole. The obvious advantage for many of us is the simplicity of having a ONE-piece antenna vs. 2 pieces. The RF Venue represents that not so common practice of employing 2 TYPES of antennas feeding a diversity receiver. It is possible that the performance will be different when using Lectrosonics receivers compared to Zaxcom or Audio, Ltd. receivers because they each use a different type of diversity reception. Lectrosonics use what is referred to as antenna diversity and Zaxcom uses receiver diversity. I do not like the way some people refer to receiver diversity as TRUE diversity --- both methods work, obviously, and neither is truer than the other, just different. That said, I prefer receiver diversity, having had the longest experience with Audio, Ltd. and Zaxcom wireless. Someone with a lot more knowledge than I have can weigh in the relative advantages or disadvantages in terms of performance, but it is safe to say that there can be differences in the way in which the 2 methods interact with the receiving antenna.

[Philip Perkins]

And in the very old days some of us used "manual diversity"…..2 antennas on a  (Swintek etc) combiner into a single non diversity VHF receiver, or thru a homemade switch box that would switch antennas on log walk and talks etc (find a place between words to hit the switch).

[Jeff Wexler]

Right you are, Philip --- Manual Diversity! I had forgotten about that.

[bmfsnd]

  On 2/19/2015 at 5:53 PM, Jeff Wexler said:

Lectrosonics use what is referred to as antenna diversity and Zaxcom uses receiver diversity. I do not like the way some people refer to receiver diversity as TRUE diversity --- both methods work, obviously, and neither is truer than the other, just different. 

 

In that case, what if multiple receivers of different diversity types are being coupled together into something like an RF Multi? Will this favor a certain antennae setup? 

[John Blankenship]

  On 2/20/2015 at 8:02 PM, Matt Brodnick said:

In that case, what if multiple receivers of different diversity types are being coupled together into something like an RF Multi? Will this favor a certain antennae setup?

No. A good RF signal is a good RF signal. The antenna differences that have been outlined here, and in other threads, still apply.

[bmfsnd]

Thanks John 

 

  On 2/20/2015 at 9:20 PM, John Blankenship said:

No. A good RF signal is a good RF signal. The antenna differences that have been outlined here, and in other threads, still apply.

[Dave Pullmer]

Revisiting this thread - I’ve been using a diversity fin and it has been fine. I’m curious if anyone has moved to 2 LPDA antennae from the d-fin and noticed an improvement in range/stability.

[humbuk]

It is only my theoretical reasoning. I have tested many antennas, unfortunately not this one, but my combination of shark and dipole. I have the impression that it is impossible to say what is always better, in my opinion it depends on the conditions in which it is used - how many reflections, what is the interference...

[Philip Perkins]

My gear package is now much smaller than it was, and for one gig recently I needed to get more radios onto my antenna set up than I had "holes" for (only 4).  I used my back up antenna rig, with one set of 4 being on the Venue and the other being on my old Ramsey dual LPDA fins.  Noticed no diff in range at all.

[OB1]

Can't beat the diversity fin. Literally. I heard folks say two LPDAs will get you better range but in practice I have not experienced this advantage at all. Now maybe in a more complex environment with more challenging line-of-site, but I've been in some pretty obstacle filled shoots.

[The Documentary Sound Guy]

I would think there's an advantage if you can spread the LDPAs apart a bit because physically separating the two diversity sources can compensate for the situation where an obstacle blocks line of sight.  Having multiple pickup patterns is useful, but if both antennae are in the same dead zone, the diversity fin isn't going to help.  This might come into play where a subject walks behind a car, for example, and one of the LDPAs has a better angle than the other.  I once ran into an issue where I unknowingly had a bunch of wires directly in front of the diversity fin (they were in a wall), which knocked out reception quite effectively.  This wouldn't have happened in a split setup where the antenna were physically distant from each other.

Strictly speaking, this isn't about range as much as it is about reliability ... and it's also fiendishly hard to actually test, so this is mostly theory; I haven't compared the two in practice enough to judge reliably.

Also, bear in mind that LDPA and Dipole antennas have different strengths under different circumstances.  LDPA have better "reach" in clear air, whereas a dipole may do better indoors because it can collect reflected signals from all directions and get a stronger signal in aggregate.  The theory behind the diversity fin is that having both pickup patterns in a single unit makes for a better "all around performance" in a wider set of circumstances, so you don't have to think so carefully about which antenna you are using.  I don't think it's necessarily about range ... I would think that if you have the time and equipment available, you could usually pick a more specialized antenna setup with longer range for a particular setup.  But, the diversity fin could be a better choice in a wider range of circumstances even if it doesn't win for any particular setup.

[Dave Pullmer]

Nice to hear your perspectives. I’ve been combing through my set up, thinking of what I could improve, and that was one area I was thinking about. Was curious if using 2 passive fins would buy me any gains, but it seems like that would be negligible or minimal at best.

 

I love the simplicity of the d-fin, though I have been thinking it could be nice to have 1 active antenna in case I need to go longer than my maximum 50ft run.

 

One other thing I have been thinking of is filters - I have read a few diversity fin users say they’ve benefited greatly from adding passive filters to their set up (RF Venue, or PWS). The mixers I’ve talked to have added 470-608 filters and said it has improved their range noticeably. Would this potentially be because the filters have a steeper cut off on both ends of the spectrum than the antenna? I’m always a bit surprised to hear of these gains when the filters people are implementing are quite wideband already (470-608).

[The Documentary Sound Guy]

I recently started playing with filters, and I would agree that they are probably more effective than playing with antenna design.  This was particularly true for helping separate my IFB transmitter (in my bag) from my receivers, but it has also been useful for avoiding heavy UHF traffic.  My filters are pretty narrow though ... I haven't used the wideband ones that you are looking at (though, I've heard the same anecdotal experiences that you have).

[borjam]

  On 2/10/2024 at 12:23 AM, The Documentary Sound Guy said:

I once ran into an issue where I unknowingly had a bunch of wires directly in front of the diversity fin (they were in a wall), which knocked out reception quite effectively.  This wouldn't have happened in a split setup where the antenna were physically distant from each other.

 

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Metallic objects within the antenna near field and they will disturb the antenna radiation pattern and/or detune it. Bear in mind that some directional antennas (Yagi-Uda for example) are created by adding additional elements which are not electrically connected to the dipole. Of course their lengths and distances are important. 

 

The simple rule of thumb is, avoid stuff at a distance of one wavelength. 

  On 2/10/2024 at 12:24 AM, Dave Pullmer said:

Nice to hear your perspectives. I’ve been combing through my set up, thinking of what I could improve, and that was one area I was thinking about. Was curious if using 2 passive fins would buy me any gains, but it seems like that would be negligible or minimal at best.

 

I love the simplicity of the d-fin, though I have been thinking it could be nice to have 1 active antenna in case I need to go longer than my maximum 50ft run.

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But be careful with the bandwidth of the active antenna amplifier. An antenna is rather poor as a band pass filter and LPDA antennas have a huge bandwidth, that is their most interesting property!

 

  On 2/10/2024 at 12:24 AM, Dave Pullmer said:

One other thing I have been thinking of is filters - I have read a few diversity fin users say they’ve benefited greatly from adding passive filters to their set up (RF Venue, or PWS). The mixers I’ve talked to have added 470-608 filters and said it has improved their range noticeably. Would this potentially be because the filters have a steeper cut off on both ends of the spectrum than the antenna? I’m always a bit surprised to hear of these gains when the filters people are implementing are quite wideband already (470-608).

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As I said, an antenna is not a filter  .

 

And wide band filters are more prone to interference. A strong signal outside your frequencies of interest can make the amplifier distort or even get into blocking.

 

Also, avoid excess gain. If you want to compensate for losses in your distribution system, say, a passive antenna distributor, adjust if possible the active antenna gain to compensate for that loss. No more. If the amplifier is not adjustable you can try an attenuator at the amplifier input.  

 

 

[OB1]

While on the subject of LPDA antennas, specifically the Diversity Fin. Can two D-fins be used as LPDA if only the LPDA BNC is connected on each? 

[Jim Rillie]

  On 2/11/2024 at 5:07 PM, OB1 said:

While on the subject of LPDA antennas, specifically the Diversity Fin. Can two D-fins be used as LPDA if only the LPDA BNC is connected on each? 

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I would think. yes, but they are solid and not as handy for exterior  use as the usual suspects LPDAs which are a bit open and less susceptible to wind shear.Also Why? 2 are probably more expensive than 2 regular shark fins...

[OB1]

  On 2/11/2024 at 6:04 PM, Jim Rillie said:

I would think. yes, but they are solid and not as handy for exterior  use as the usual suspects LPDAs which are a bit open and less susceptible to wind shear.Also Why? 2 are probably more expensive than 2 regular shark fins...

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We have 2 units, both use Dfins but not both are deployed at the same time sometimes. One unit is equipped with 620s and were thinking buying PSC batwings for the other, but if 2 Dfins work then that should fill that need at least for the short term.