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Antennas and sma connections


osa

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I am having a series of troubles with sma antennas and zaxcom sma female jacks. 1st problem i am experincing is seemingly 1 by 1 my antennas are coming apart. Currently they are a mix of zaxcom supplied and remote audio. I applied heatshrink and super glue at connector bases and it worked for a while but the pin inside still works out of the connector over time. I recall lectro transmitters having seemingly indestructible sma antennas. Anyone know if those are still a current product available? Or any other suggestions thst might work?

2nd problem is i swap between above antennas and sharkfins and lectro sna antennas on my micplexer, qrx's and camera link as well depending on the needs of the job. I noticed i started losing range on the right side of my mic plexer.  After troubleshooting I deduced the SMA jack on the micplexer to be bad. Zaxcom was very cool about selling me a set of 2 to replace myself. After replacing, my camera link transmission range was dropping by about 50 to 75 percent. Full on antenna crisis mode at this point. After serious troubleshooting and using a magnifyer lense with my bad eyes i finally solved the problem hopefully shown in photos below. Inside the small sma jacks is a metal female sleeve the antwnna pin slides into. That sleeve is surrounded by some sort of wax like ring separating the tube from outter shell. Somehow pins from various antennas insterted themselves outside the female tube and smashing it flat - like when kids would bite the metal rings on pencil erasers etc. Holy cow my bad eyes would have never found that otherwise!

 

I have no idea how to avoid this completely in the future. I need to be able to swap antennas.  I think for starters I need to be more delicate when switching antennas. I also need to leave antennas attached at all times until switching versus removing at the end of each job and re attaching at the beginning of each job. But I know even that won't guarantee quality over time. Ultimately just wanted to share  Even if just to help others avoid or prolong these types of problems from happening.

 

Meanwhile i fixed camera link temporarely with a small pin but it needs sent in for repair to be back 100%. 

 

 

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SMA connectors do have a 500 “connection cycle” rating. I have made SMA antennas and can say from experience the soldering the SMA connector pin on to steel cable can be challenging. Also the wax like material that forms the dielectric insulator is made of polytetrafluoroethylene. I had to look that name for you, it is not on the top of my mind.

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26 minutes ago, mark kirchner said:

SMA connectors do have a 500 “connection cycle” rating. I have made SMA antennas and can say from experience the soldering the SMA connector pin on to steel cable can be challenging. Also the wax like material that forms the dielectric insulator is made of polytetrafluoroethylene. I had to look that name for you, it is not on the top of my mind.

Very good info. Leaving connected is a great idea then. However the strain on the antennas causing them to pull out - chances are greater. What also concerns me about the nova coming out soon is the all in one box factor. Backup qrx's and my 2nd cam link on order is one thing... maybe the jacks are similar like qrx's and can be user replaced?

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On 7/13/2019 at 7:32 PM, Johnny Karlsson said:

I would recommend these. They fold so you could keep them on the receiver most of the time unless switching to fins etc.

 

 

95CBA252-BC9E-4B39-B230-EB8D0D269CD8.jpeg

 Does anyone possibly have any feedback on these and their integrity versus the classic whips? 

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The AMJ have been improved several times as we have gotten feedback from the field. Though they are pretty tough now, they will never be as rugged as our simple steel wire whip. They are the easiest way to get a vertical orientation from a horizontal receiver or a receiver that is going to be used in a variety of positions. IMHO, buy the AMJ with a spare; good advice on any critical but low cost part of your kit.

Best Regards,

Larry F

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16 minutes ago, LarryF said:

The AMJ have been improved several times as we have gotten feedback from the field. Though they are pretty tough now, they will never be as rugged as our simple steel wire whip. They are the easiest way to get a vertical orientation from a horizontal receiver or a receiver that is going to be used in a variety of positions. IMHO, buy the AMJ with a spare; good advice on any critical but low cost part of your kit.

Best Regards,

Larry F

I dig it! Thx larry

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14 hours ago, Johnny Karlsson said:

FWIW, I have been using the AMJ antennas for at least 5 years. So far none have broken.

 

Same here, yet so many people complain that they break easily— even the updated versions. I leave some on at the end of each day, I take some off.... and I travel extensively so they see their fair share of movement. It’s all voodoo. 

 

Cheers,

Evan

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Thanks guys for all the great input. I am placing an order now thru a dealer so i can get all brand new amj's current versions for all of my antenna ports. I think i am up to 16 total. Perosnally a worthy investment i feel. I am also gonna get bnc to sma adapters for larget antenna rig cabling. Here is what i have determined and seems obvious in hindsight. The right angle sma's on the low loss cables - and even the straight ones - have a wobble. If you dont apply the correct pressure and even backthread a bit to make sure you are perfectly straight, the tip of the pin catches the outside of the female sleeve inside the jack and the threading down of the connector smashes the outside of the receving sleeve flat like a half moon.

 

For me personally trying to do this in the field with precision is next to impossible. I found an adapter solution i am going to employ moving forward that eliminates this wobble and should always keep the pin going straight down.

 

 I am going to go out on a limb and say it is quite possible others out there may be experiencing this problem and might not know it because the metals inside the connector are still making contact.  For me it was my mic plexer that brought it to my attention because the right channel stopped working altogether due to the pin smashing it down completely inside. It really is hard to see if you have bad eyes like i do.

 

 Again thanks everybody for helping me figure out a good solution!

 

-Ken

 

 

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To reduce  wear and tear on the connectors of expensive instruments in the lab we use "connector savers".

Leave these adapters on the receiver, replace as needed.

 

https://www.minicircuits.com/pdfs/SF-MQK50+.pdf

or

https://www.americanradiosupply.com/sma-male-to-sma-female-coaxial-adapter-connector-saver/

 

etc.

 

Mark

 

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  • 2 weeks later...
On 7/13/2019 at 6:29 PM, John Blankenship said:

I haven't had the SMA issues you have -- over the years a couple of SSMA pins broken, but that's it.

 

One recommendation would be short pigtails, or adapters -- such as male SMA to female BNC.  Then your frequent insertions and removals would be via the more robust BNC connections.

 

 

This might be a question for LarryF - would adding adapters require modifying antennas for the added length? My guess is this might be more appropriate regarding transmitters vs receivers. I will do some tests in the field to compare. I also have some classic lectro branded bnc antennas to throw into the mix to see what works 

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2 hours ago, osa said:

This might be a question for LarryF - would adding adapters require modifying antennas for the added length? My guess is this might be more appropriate regarding transmitters vs receivers. I will do some tests in the field to compare. I also have some classic lectro branded bnc antennas to throw into the mix to see what works 

Quality adapters look like 50 Ohm transmission lines (cable) and won't affect the antenna tuning (length). What will affect the antennas is moving them the adapters length away from the ground plane represented by the transmitter or receiver case. This effect will be small in the scheme of things because you already have a large bag of water (talent) detuning the antenna or you have surrounding gear like mixers and recorders in the bag. My opinion is that it is more theoretical than real. We determine the length of various antennas by mounting them on the case of a dummy device and trimming the antenna for best match to 50 Ohms. This is in free air and is rarely how the device is used but it is the best we can do. Calculating the antenna length in an EM program would take 10 times as long and be 1/10 as accurate.

Best Regards,

Larry Fisher 

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Copy thx really appreciate the input. Testing on a job right now and if there is a degrading in signal it is super minimal with adapters in place. John THANK YOU this suggestion you had was one i had not thought of. Much faster swaps and much safer for the female jacks

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  • 1 year later...
On 7/15/2019 at 11:18 AM, osa said:

 Does anyone possibly have any feedback on these and their integrity versus the classic whips? 

Just wanted to report back on these antennas - i switched over to these replacing all my antennas and i love them. However sure enough i managed to figure out how to break them. Indeed like mentioned prior they are highly durable but not indestructible. Twice i have had some sort of impact on these antennas. although they dont show visual damage, the pin inside cracks and give the illusion the antenna is still functioning.  Then one day you suddenly lose transmission/reception range and may think the device itself is failing. The way to verify is 1) the pin falls out (obvious) or 2) the pin is loose by checking with tweezers etc. the loose pin is the killer because it looks ok to the eye but causes rando drop outs. 
 

-Ken

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