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Frode L Hvatum

Lectronics antennae for Zaxcom QRX200

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Hi folks. New to the board here.

Looking forward to alle I can learn here.

I live in Oslo in Norway. I use exclusively Zaxcom for lavs, and the Nomad or a 633 for recorder.

 

We have a couple of Lectronics antennas for a Zaxcom QRX200, and after comparing them to the standard antennas we get 1 pixel(!) better reception. I have to say I´m seriously underwhelmed. Are we doing something wrong, or is that as expected?

 

The standard antennas give pretty good coverage, by all means, but sometimes you just wish for a few meters more when an actor is moving a away on a wide shot. 

(I know we can set the trxs to record, but this thread is about wireless range...)

Anybody have a tip on what is wrong?

 

...edited electronics to Lectronics (Safari autocorrected it)...

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Frode,  In your description you mention "electronics".  I'm pretty sure you meant Lectrosonics.  I'm an all Zaxcom  guy,  but aren't Lectro antennas BNC connectors? If they are,  How did you plug them into a Zaxcom? What length were both antennas cut to?

Thank you, Martin

 

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Any whip antenna is wire cut to a specific length. The difference of a pixel either way can be the difference of only 1 dB and can happen just based on relative antenna position at any given moment.

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Sorry for the late reply.

 

Martin: I got two cables BNC to SMA. Seems to be working fine.

 

Karl: I am talking about the SNA600 which has BNC

 

Glenn: The antennas have adjustable length and we tuned/adjusted the length to the area of frequencies we are using. 

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Hi Frode, well,  I think Glenn nailed it when he said pixel could be a db.  Where you're sitting or standing could make a db difference.  If you were right here in front of me, I would want to see what you're looking at, yes. 

 I'm just not sure at this point if there's much to see.

 

Thank you, Martin 

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Thanks for your reply!.

Ok. I understand that the placement of the receiver and transmitter will affect the signal level.

 

But this does not tell me what I´m doing wrong with the Lectronics antennas.

Or if they simply work as intended, and I misunderstood what I was getting.

I thought for sure they would boost the coverage compared to the antennas that come with the QRX200.

If they don´t then I don´t really understand the point of these antennas. Becuase they sure make the bag more unwieldy.

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I my experience dipoles make a significant (ymmv) improvement in range compared to a whip, but they should be up in the air a bit. I wouldn't think much improvement would be seen if they are still at bag level

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The dipoles are very slightly more effective than the whips (2dbi I think i read somewhere), but the real benefit comes from your ability to put them on the outside of the bag (minimizes the effect of anything spraying RF in your bag) and farther from each other (helps the diversity receivers work effectively). I use the SNAs and I don't notice a huge improvement in signal strength on the meters, but I do experience better signal stability on the outside edge of the range.

 

Practically that sounds like solid audio where the whips would be having intermittent dropouts.

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Thank you all who helped me understand this better!

Seems like I should have researched more before I got them... As always. ;-)

 

John: I see your point, but in my defense I did point out that I got a couple of metres more in range in the first post.

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A 1/4 wave whip and dipole have almost exactly the same antenna gain for a 50 Ohm input, if and this is a big if, the whip has the proper ground plane and both types are matched to 50 Ohms. A narrow wire whip above an infinite ground plane is about 35 Ohms and a fat dipole is 70 some odd Ohms. The reason the SNA 600 is generally more effective than a simple whip is that the whip's in bag  lousy and lossy ground plane, consists of the irregular shape of the metal receiver case and/or the wires, battery pack, recorder and anything else that is conductive within a 1/4 wavelength of the whip, while the SNA-600 needs no ground plane, as it is a complete antenna by itself. This assumes the SNA-600 is somewhat separated from those selfsame conductive objects in the bag and the big bag of salt water that owns and operates the antennas.

 

The SNA-600 also has a built in microstrip matching circuit that matches the dipole to 50 Ohms. In free space, the SNA-600 measures as an almost a perfectly performing dipole. The poor whip antenna is not matched and usually does not have the proper ground plane. So the dipole up in the air is much better than a whip stuck in the bag. If the whip were put up in the air, you would have to add a counterpoise (ground plane) and it would have no advantage in portability over the dipole.

 

Finally, a dipole (SNA-600) stuck on the side of a bag is not in free space and may not perform well unless it is a 1/4 wavelength or more away from conductive objects and bags of salt water. Whip antennas are used because they are compact, cheap, and work well enough for most situations. Further, in a bag, all antennas are compromised anyway. 

Best Regards,

Larry Fisher

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Thanks for the great explanation Larry!  I do know that I get much better reception with my two SNA-600s on the outside of the bag than I ever got with whips or even my home-brew coaxial dipoles.

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5 hours ago, Frode L Hvatum said:

...

John: I see your point, but in my defense I did point out that I got a couple of metres more in range in the first post.

 

Actually, you did not.  The only comparison you offered was of pixels.  You then said you wished for more range:

 

"The standard antennas give pretty good coverage, by all means, but sometimes you just wish for a few meters more when an actor is moving a away on a wide shot."

 

The improvements one can get from a better antenna include range and/or less dropout within range (as others have pointed out).  Yet the only comparison you've offered is of a pixel. 

 

A slight difference in signal strength will not give you the information you need about either range or dropout characteristics.  We've seen no comparisons of either. 

 

You asked for advice, so my advice is to locate the Lectro dipoles away from the bag, and do both range and dropout comparisons under a variety of conditions (one quick test will not give worthwhile comprehensive results). 

 

 

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2 hours ago, berniebeaudry said:

Thanks for the great explanation Larry!  I do know that I get much better reception with my two SNA-600s on the outside of the bag than I ever got with whips or even my home-brew coaxial dipoles.

Hi Bernie,

Absolutely. The big advantage of the dipoles is they can be located away from the bag, unlike a whip.

One thing I forgot to mention is that the SNA-600 is a fat dipole which extends the bandwidth over a thin rod dipole antenna. In fact, the size of the arms on the SNA-600 is at the maximum for best performance. A whip could be made "fat" also and gain wider bandwidth but would obviate one of the whip's big  advantages of being compact and flexible.

 

Trivia: SNA stands for Swiss Navy Antenna. SAA would have gotten us in trouble with Victorinox. And you know how we despise lawsuits.

Best Regards,

Larry Fisher

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John. Sorry, I see now that was unclear. I actuallly could go about two metres further before the TRXs dropping out with the Lectronics antennas.

 

Larry: Fantastic answer! Some of it is a bit over my head, since I do not have any theoretical knowledge of how radio transmission/reception works but I think I get the gist of it. Thanks!

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