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SMA modded Sennheiser G3 Drop Out Issues


DaFlo

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Hi everyone,

 

Hope you’re all doing well.

 

A junior soundie here. I’ve run into an issue with my recently modified G3’s. 

 

The units are suffering terrible drop outs when the line of sight between transmitter-reciever antennae is broken. 

Unfortunately that includes the talent whose back the transmitter sits on. 
 

I can’t help but think that this isn’t supposed to happen, and I’ve somehow made a mistake along the way. 

I follow Steve Oakley’s youtube tutorial, got my connectors from ebay and am using remote audio sma whip antennas.


Are the sma units supposed to be this directional? 
If so, what is used to overcome the problem? Is there a more omnidirectional antenna to consider, should I consider something like a Betso Bowtie to catch more of the frequencies there, or is the best solution to save faster for Lectro/Zaxcom?

 

Thanks for reading!

 

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I would guess the connection from the sma connector to the board. Have you checked the connection is solid? Another possibility is that you damaged a part of the RF board while trying to solder the wire to the sma connector. I did this to one of my old G3s.

 

the whips are omnidirectional and so is the bow tie. Other than the fact that the bow tie is a 1/2 wave antenna and the whip is 1/4 wave you most likely wont see much difference in performance between them.

 

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Check the solder connections and make sure the center pin on your SMA antennas are intact.

 

That being said, there's no reason this mod will give you "better" range unless you use it to attach an external antenna that you can raise up above any away from sources of interference (humans) Anecdotally, people claim to be getting 10% better performance, but that's tough to prove in the world of RF.

 

1. You should be looking for the cleanest frequency available.

2. Get the Tx antenna away from sweaty skin.

3. Get the Rx antenna away from sources of interference.

4. Retain Line of Sight as much as possible, especially at the far end of your range.

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38 minutes ago, jason porter said:

[snip] That being said, there's no reason this mod will give you "better" range unless you use it to attach an external antenna that you can raise up above any away from sources of interference (humans) Anecdotally, people claim to be getting 10% better performance, but that's tough to prove in the world of RF. [snip]

Absolutely correct. Even with the best RF measuring equipment, it would be hard to distingwish a  "10%"  improvement. Making a radiated power comparison between a wire soldered to a PC board and an SMA antenna is difficult and the 1 dB difference that represents 10% of range, would be in the noise. Walking around and making a seat of the pants judgement about small differences in range is almost laughable.

Best Regards,

Larry Fisher

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Going off topic. - I was wondering about that Larry. I've done comparisons of signal strength with an Anritsu spectrum analyzer and when I've wanted to report signal strength  comparisons from a test I did on this forum, I struggle to state a db level as the signal bounces around so much, even using a marker's readout. 

 

When doing this, what's the correct way to read and report a signal strength? Do you have any suggestions?

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I do SMA mods as a service, and I occasionally get units in to repair/redo the mod that was attempted by someone else.

 

The 3 most likely causes I would guess for your issue are (from most likely to least):

  1. Broken connection between SMA pin and RF board (thus no signal getting to antenna)
  2. Short between RF out and case (all RF power getting dumped to ground)
  3. Damage to components/PCB while mod was performed

 

If you can post a picture here we can possibly help you diagnose the issue.

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Thank you everyone for getting back to me so quickly! Really appreciate the help. 

 

I overlooked something quite significant, actually. As I don't have soldering tools myself yet, I did the modification over at a friend's shop, who works with motherboards and computers. 

He made a suggestion - an additional step - which I believe is very likely the culprit to this problem. 

 

The sma connector was grounded to case. Sounds to me like that is ruining the whole RF output. 

A valuable lesson in following tried-and-tested instructions to a tee... Won't be making that mistake again!

 

For curiousity's sake, I grabbed a photo of one of the units anyway - looks as if the wiring to the SMA was loose and came off on disassembly. I'll be going back in to fix them all from here, without any unnecessary additional steps this time.

 

Thanks again for all your help, everyone.

277312795_324563766241580_7177676668422361183_n.jpg

277545015_341382864630076_4183114020500180384_n.jpg

277688242_2595659070568202_6511664842378871394_n.jpg

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as you say, the ground wire to the case isnt necessary. but it would still be sensible to connect the thread of the SMA to the case.

just file away a little of the case where the threads will make contact with it, and at the top of the case where the bolt will tighten up. as long as when you test with a continuity checker there is no connection between the centre of the SMA and the shell, you should be ok.

i would also suggest a higher wattage soldering iron, as it doesnt look like youve properly melted the solder, but have held the iron on too long, and melted the insulation of the yellow jumper cable. and it may also be, that if the wire came away from the pin of the SMA, and wasnt ripped off (you can still see the tinned end) that it may not have been properly soldered to the SMA which could have affected your signal.

good luck for attempt 2. im sure you'll nail it.

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