Sharkfin Setup

[orionflood]

So this has been discussed at length on here about using sharkfins, but most of the forums sort of end in controversy/open ended, I think mostly because of its lengthy technical considerations, but is there a pamphlet out there by Larry F or someone that discusses this topic in general terms and then proceeds to its more technical side. What I generally gather from wanting to start a setup with sharkfins is that:

1)I need the proper 50ohm cable.

2) Although the pole doesn't make that much of a difference it's better if it isn't grounded/metal

3) Confusion abounds with me as to why people use more than two antenna(i?), wouldn't this increase phase cancellation?

4)I need to go from my receivers to an amplifier and then to the sharkfins? Does going from one receiver to another...are there any cabling rules with this? I tend to see with bag setups the crisscross look, which I can't explain why yet.

Please understand that I am generally not talking about a 98 meter to 100 meter change. I am talking about upgrading from the antenna that come from Lectrosonics/Zaxcom that are physically on the receiver to going to a sharkfin setup...meaning although it can reduce reception if I get it wrong I am not at this point concerned about a minor difference in reception among different manufacturers. I would consider a few dB reception a win. Thank you guys in advance for making fun and helping ha.

[studiomprd]

" is there a pamphlet out there "

yes, you could start at the Lectro site...

and google would be your friend.

" Confusion abounds with me as to why people use more than two antenna(i?), wouldn't this increase phase cancellation? "

what confusion ?? how many antenna inputs does your RX have ?? is the answer 2 ?? ...or more ??

" I need to go from my receivers to an amplifier and then to the sharkfins? "

no, you have that incorrect...

" Does going from one receiver to another...are there any cabling rules with this? "

guidelines, and they are not specific to a "sharkfin" type antenna...

" I am not at this point concerned about a minor difference in reception among different manufacturers. "

" consider a few dB reception a win. "

increase = a win ??

you really need to read some of the helpful information available on appropriate websites.

[LarryF]

So this has been discussed at length on here about using sharkfins, but most of the forums sort of end in controversy/open ended, I think mostly because of its lengthy technical considerations, but is there a pamphlet out there by Larry F or someone that discusses this topic in general terms and then proceeds to its more technical side. What I generally gather from wanting to start a setup with sharkfins is that:

1)I need the proper 50ohm cable.

2) Although the pole doesn't make that much of a difference it's better if it isn't grounded/metal

3) Confusion abounds with me as to why people use more than two antenna(i?), wouldn't this increase phase cancellation?

4)I need to go from my receivers to an amplifier and then to the sharkfins? Does going from one receiver to another...are there any cabling rules with this? I tend to see with bag setups the crisscross look, which I can't explain why yet.

Please understand that I am generally not talking about a 98 meter to 100 meter change. I am talking about upgrading from the antenna that come from Lectrosonics/Zaxcom that are physically on the receiver to going to a sharkfin setup...meaning although it can reduce reception if I get it wrong I am not at this point concerned about a minor difference in reception among different manufacturers. I would consider a few dB reception a win. Thank you guys in advance for making fun and helping ha.

Hi,

Here's some FAQ's on antennas in general that will give you some general knowledge of wireless mics and antennas:

http://www.lectrosonics.com/faqdb/index.php/component/mtree/wireless/antenna?Itemid=

Here's your questions in order:

1. Yes. 50 Ohms. The type cable depends on the length that you are running. See the above FAQ's.

2. Keep the metal pole behind the antenna by 6" or more or more than 12" away in any other direction.

3. Yes. I'm not sure why anyone would use more than two antennas except in weird studio arrangements involving multiple rooms. Generally those setups have major compromises.

4. You don't need or want an amplifier for short antenna runs. See the FAQ's above for more info about this. The criss cross look is just the usual cabling setup. Each receiver needs to have two different antennas to the two different antenna inputs., i.e., each receiver must hookup to antenna A and antenna B. The criss cross is incidental.

Best Regards,

Larry Fisher

Lectrosonics

[jrd456]

Try not to use an RF amp unless absolutely necessary.

J.D.

[pvanstry]

Here is my setup and i am very pleased.

- Two Lectrosonics ALP620 LPDA antenna

- two Times Microwave LMR240 ultra flex 12 feet cables ( very flexible and yet very little loss )

- PSC RF MULTI SMA splitter ( unity gain, no added gain simply compensate for it's own loss in splitting the signal to the different receivers ).

- Eight RG174 SMA to SMA 2 feet jumper ( from PSC to Lectrosonics SRa receivers ).

The ALP620 give me added gain on reception and also rejection of some of the signal coming from the side ( my own transmitter reflection and the outside world interference ). I would say probably around 4-5db of gain but minus the LMR240 loss of probably 0.5db. Net gain of 3.5-4.5db here.

The PSC simply give me the option of using different antenna and remote them. THIS IS THE CRUCIAL FACTOR HERE. By having the antenna 9 feet in the air, so clearing most of the obstacle in bethween the receiver and the transmitter, this is where i gain the most. The receivers almost never leave full deviation and i get 300% more range, i actually way more than needed in range. If i bring the antenna down to my level ( 4 feet off the ground with everyone in bethween the antenna and the transmitter ), range is not the same, actually quite a lot less.

Frequency coordination: Huge difference here, please use software, scan and use your head in selecting frequencies for your systems.

Block spacing: Having everything in the same block is not a good idea. I have only two channel per block and i space every block with an empty unused one ( 470-22-24-26 ). Keeps my spectrum space open.

Transmitting power: When dealing with multiple transmitters in an interior environment, especially if close packed, reduce power on the transmitters. It will reduce reflection and really help the receivers in clearly "receiving" the signal from the transmitters.

Body shadow: Reduce to amount of body mass in bethween the receivers and the transmitter. This includes people sitting in front of you but also where you position the transmitter on the actual person. I look at what will be shot and how but i doubt i go for a side ( hip, thigh, ankle ). When doing a bag gig, i usually end up putting my SMV ( without a clip ) in the front pocket of a person pants or shorts.

But the single most important thing in Antenna system is to not confused Gain that you have using a better ( position and type ) of antenna and Amplified gain, the later causing more problem if not used properly. Amplifed gain should be only applied to compensate for a necessary piece of gear ( splitters, Cables or excessive connectors ) inserting a loss. You want Unity NO MORE in amplified gain. You are compensating NOT adding signal for a better reception which will result in other issues. Antenna gain ( better antenna, best antenna for a situation and especially clearer antenna position ) is really what you want. THere is a big difference in bethween a pair of "Shark fin" mounted on a bag VS a pair of "Shark fin" on a mast with a clear view of the Transmitter.

My two cents.

Pascal

[studiomprd]

"By having the antenna 9 feet in the air, so clearing most of the obstacle in bethween the receiver and the transmitter, this is where i gain the most.... Reduce to amount of body mass in bethween the receivers and the transmitter. This includes people sitting in front of you but also where you position the transmitter on the actual person.... not confused Gain that you have using a better ( position and type ) of antenna and Amplified gain, the later causing more problem if not used properly. ...My two cents. "

that was at least a dollar's worth!!

[pvanstry]

I'm stunned.....

[dominiquegreffard]

Pascal is the man. I had the privilege to have him over the phone recently to discuss about my antenna plans. There is a lot of simple aspects of using wireless that are underestimated and pascal explained it gracefully again. There s his bag old bag antenna setup somewhere on jw. It s a beauty.

[Cloud Wang]

3. Yes. I'm not sure why anyone would use more than two antennas except in weird studio arrangements involving multiple rooms. Generally those setups have major compromises.

、

hi Larry

i did run into some weird situations this year for some reality show, that contestants will run into couple different locations,so i need to throw more than one pair antenna out. I'm wondering if Lectro makes any antenna signal combiner ? do you have a product ID i can check ?

best

Cloud

[Solid Goldberger]

Cloud,

Thanks for bringing this up, this is something I've wondered about for years, ever since touring the SNL stage at 30 Rock as a teenager. They had the whole place wired up with antennas, presumably for those famous walk-and-talk monologues during the host intros.

Wondered what kind of equipment one might need to effectively recieve RF signals from a single point, but covering beyond the reach of a single pair of antennas? I know PSC makes a combiner that operates with up to 4, but I don't really understand how it works, could anyone explain? Also, what if you needed to blanket an even larger area? Is this possible using a single set of receivers?

Larry, you mentioned there were significant tradeoffs to using more then 2 antenna, could you elaborate when you have the time?

E.

[LarryF]

Cloud,

Thanks for bringing this up, this is something I've wondered about for years, ever since touring the SNL stage at 30 Rock as a teenager. They had the whole place wired up with antennas, presumably for those famous walk-and-talk monologues during the host intros.

Wondered what kind of equipment one might need to effectively recieve RF signals from a single point, but covering beyond the reach of a single pair of antennas? I know PSC makes a combiner that operates with up to 4, but I don't really understand how it works, could anyone explain? Also, what if you needed to blanket an even larger area? Is this possible using a single set of receivers?

Larry, you mentioned there were significant tradeoffs to using more then 2 antenna, could you elaborate when you have the time?

E.

I'll make up an FAQ on the Lectro site this afternoon (or so) and provide a link here in a new thread. That way it will be available more easily to searches. It is a complex problem, not easily solved and with a whole series of compromises.

Best Regards,

Larry F

[studiomprd]

" It is a complex problem, not easily solved and with a whole series of compromises. "

amen...

I have designed large area, complex receiving situations, similar to SNL, Leno, Letterman, etc. and it takes a lot of planning, and a bunch of $$$

sometimes you will find multiple antennae (sic) when a lot of different equipment is involved (like individual antennae (sic) for each RX, or different bands or blocks, or even directions.... there can get to be a lot of physics, and of course a bit of voodoo...

[johnpaul215]

If you are setting up at a location, could you have multiple receivers tuned to the same freqs and run XLRs/snake back to your cart (or long coax antenna lines)? For example, a set of RXs for the west half of a location and another set on the east half, all tuned to the same transmitters. Set it up so coverage overlaps and you just mix based on which RX they are closer to. Some jobs just need more than you can fit in a bag.

[studiomprd]

" could you have multiple receivers... "

of course.

(BTW, that would be Receiver Diversity)

[LarryF]

I'll make up an FAQ on the Lectro site this afternoon (or so) and provide a link here in a new thread. That way it will be available more easily to searches. It is a complex problem, not easily solved and with a whole series of compromises.

Best Regards,

Larry F

The new thread is "Combining antennas from multiple studio locations" Tags are combiner splitter antenna.

Best,

Larry F

Lectro