Jump to content
Diego Sanchez

External antenna for Sennheiser G2

Recommended Posts

1 hour ago, astro said:

Any hints on where I can get isolated memory steel wire to build my own sma antennas?

Gesendet von meinem D5803 mit Tapatalk

Hi Astro. I ordered mine from eBay - http://www.ebay.com.au/itm/120476274177?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Just be aware that it won't tin if you try to solder it directly. I found that crimp connections worked ok, but ended up filling the little SMA centre pin receptacle with solder and then inserting the wire. So while it's not a properly soldered joint it was a reasonably strong mechanical connection (perhaps as the solder cools it contracts around the wire a little?), and you can also give the pin an extra bit of a crimp for good measure.

It also pays to be aware of the difference between super-elastic wire (which is the one you want) and memory wire, which will bend quite easily but only springs back to it's original shape if heated to above a certain temperature.

Cheers!

Dave.

Share this post


Link to post
Share on other sites
astro   
2 hours ago, Dave Williams said:

Hi Astro. I ordered mine from eBay - http://www.ebay.com.au/itm/120476274177?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Just be aware that it won't tin if you try to solder it directly. I found that crimp connections worked ok, but ended up filling the little SMA centre pin receptacle with solder and then inserting the wire. So while it's not a properly soldered joint it was a reasonably strong mechanical connection (perhaps as the solder cools it contracts around the wire a little?), and you can also give the pin an extra bit of a crimp for good measure.

It also pays to be aware of the difference between super-elastic wire (which is the one you want) and memory wire, which will bend quite easily but only springs back to it's original shape if heated to above a certain temperature.

Cheers!

Dave.

Hi Dave,

thanks for the hint! This wire isn't insulated. Did you cover it with shrink tubing?

Share this post


Link to post
Share on other sites
Mingo   

Hi all,

'I've been following this topic for a while. Just to make sure that where to ground the second antenna? On to the case?

and since grounding the antenna is a requirement, is there any possibility to make these puppies a dipole antenna?

Share this post


Link to post
Share on other sites
59 minutes ago, Rick Reineke said:

Where on the board does the secondary antenna get connected

there are solder blobs to the left of the horseshoe looking things, that is where each of the antennas connect to (one low near the screw, the other up next to the 1/8" connector)

Screen Shot 2016-03-31 at 2.20.02 PM.png

Share this post


Link to post
Share on other sites
On 3/31/2016 at 1:18 AM, astro said:

Hi Dave,

thanks for the hint! This wire isn't insulated. Did you cover it with shrink tubing?

Yep I used heat shrink tubing, which actually ended up slipping off the wire, so I ended up using a cigarette lighter flame and some hot-glue sticks to pre-coat the wire in a thin layer of hot glue so that when the heat-shrink shrunk it also bonded onto the wire really well. You can get commercial glue lined heat shrink but it's considerably more expensive.

 

On 3/31/2016 at 2:11 AM, Mingo said:

Hi all,

'I've been following this topic for a while. Just to make sure that where to ground the second antenna? On to the case?

and since grounding the antenna is a requirement, is there any possibility to make these puppies a dipole antenna?

Yes! By grounding the shield / sleeve of the second SMA to the case (any piece of copper or similar wire should do) you do allow the possibility of a remote dipole antenna. A whip is (kind of) the top half a dipole anyway with the metal enclosure being the other half. (Sort of anyway, haha... 'ground plane' or 'counterpoise' are probably more appropriate terms to use).

It's super easy to make a simple (albeit missing a balun) dipole from just coax cable. There's various examples on this forum and out in youtube land.

I also have made up a prototype that adapts a regular whip into a sleeve balun dipole design over on the DIY part of the forum if you wanna check it out. I haven't really had a chance to do many tests with it yet though...

Share this post


Link to post
Share on other sites
Mingo   
On 2016年4月4日 at 7:30 PM, Dave Williams said:

Yep I used heat shrink tubing, which actually ended up slipping off the wire, so I ended up using a cigarette lighter flame and some hot-glue sticks to pre-coat the wire in a thin layer of hot glue so that when the heat-shrink shrunk it also bonded onto the wire really well. You can get commercial glue lined heat shrink but it's considerably more expensive.

 

Yes! By grounding the shield / sleeve of the second SMA to the case (any piece of copper or similar wire should do) you do allow the possibility of a remote dipole antenna. A whip is (kind of) the top half a dipole anyway with the metal enclosure being the other half. (Sort of anyway, haha... 'ground plane' or 'counterpoise' are probably more appropriate terms to use).

It's super easy to make a simple (albeit missing a balun) dipole from just coax cable. There's various examples on this forum and out in youtube land.

I also have made up a prototype that adapts a regular whip into a sleeve balun dipole design over on the DIY part of the forum if you wanna check it out. I haven't really had a chance to do many tests with it yet though...

Thanks Dave. 

I've tried the external antenna. It works on the RX but not the TX. 

With the same setting and self made antenna, the TX just drop from -35dbm to -70dbm comparing with the original one in 1 meter range. 

And also, I didn't see any circuit that allows G3 using dipole antenna, is it really possible?

Share this post


Link to post
Share on other sites
AlexB   
On 3/2/2016 at 6:38 AM, Dave Williams said:

I had a look and that seems pretty handy to have something that will work with all Sennheiser systems, but I get the impression it will be pretty pricey. However I'm pretty sold on the Zaxcoms, especially as I already have a Nomad 12, so will be able to take full advantage of the various extra functions :) Oh and the wideband won't hurt either!

I got a whole bunch of connectors and RF cable (RG316) fairly cheaply off ebay. Also got some nitinol super-elastic wire to make whips with. For example - http://www.ebay.com.au/itm/191686834380?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I got those particular connectors to make my dipole adapter (details coming to DIY section soon), but the other bulkhead ones I got for the G3s were too long so I modified these other ones by cutting off the sleeve part, grinding the hex down to fit and using hot glue to hold the coax cable core which was crimped and soldered to the centre pin. Note the gap / void where I put the second SMA. I reckon that's probably where the IEM volume control would go if this receiver had been born an IEM.

 

When making new antennas, where do you start measuring to get the correct length for your frequency?

I got a few 1/4 Wave Whip Antennas from eBay that I cut down myself, but I suspect I've done it wrong. The seller told me to include everything except the connector (silver part) in my measurements. After doing so they are still about an inch longer then the external portion of the original G3 antenna.

Share this post


Link to post
Share on other sites

Hey ALex,

I think you will find that your measurment is correct and that you will get a better range with the longer antenna over the original Sennheiser antenna. I used the guide that Lectrosonics published using the" middle block" for the length. If you trim the antenna boot of the original Sennheiser antenna and grind off the bronze connecctor off of the antenna, you can make a backup antenna. All you will need is a SMA male connector that is made for RG174 Coax, solder and heat shrink tubing.

Also, slide the old Sennheiser boot over the crimped sleeve of the SMA connector to make it look better.

Good Luck.

Share this post


Link to post
Share on other sites
AlexB   

Mark, that's reassuring. I found the antenna length by using this frequency wavelength calculator. I read somewhere that you should measure the antenna length from where it's connected to the circuit board. But this is a while ago and I don't know if the information is correct.

My plan is to replace the original G3 antennas with a SMA connectors, and also adding a second one for the receiver like Dave has shown earlier in this thread. 

Share this post


Link to post
Share on other sites
sisal   
23 hours ago, AlexB said:

When making new antennas, where do you start measuring to get the correct length for your frequency?

You start to measure where the antenna exits the shielding:
20160408_224032.jpg

 

The original Sennheiser whips are not cut to the optimal length. They include the same antenna regardless of what block that device operates on. That may be why it works better with replacement whips..

Share this post


Link to post
Share on other sites
efksound   
On 7/4/2016 at 4:41 PM, mark kirchner said:

Hey ALex,

I think you will find that your measurment is correct and that you will get a better range with the longer antenna over the original Sennheiser antenna. I used the guide that Lectrosonics published using the" middle block" for the length. If you trim the antenna boot of the original Sennheiser antenna and grind off the bronze connecctor off of the antenna, you can make a backup antenna. All you will need is a SMA male connector that is made for RG174 Coax, solder and heat shrink tubing.

Also, slide the old Sennheiser boot over the crimped sleeve of the SMA connector to make it look better.

Good Luck.

Very good idea of using and modding the original whips and adding them an SMA connector, looks to me as a very cost effective alternative ! 

Share this post


Link to post
Share on other sites
42 minutes ago, efksound said:

Very good idea of using and modding the original whips and adding them an SMA connector, looks to me as a very cost effective alternative ! 

It is important that the bronze connection "connector" is carefully removed from the Sennheiser G3 antenna. The connection is very robust and I found the only way of removing the antenna wire intact, was by grinding/filing the connector down. Then the complete antenna "wire rope" can be utilized in the new SMA connector/antenna. They work fine for close range TX antennas or as backups.

Share this post


Link to post
Share on other sites
1 hour ago, efksound said:

Mark
by bronze connector you mean this ? :

1productsennheiser-091084.jpg

 

My photographs show the finished antenna, with length guide and the original Sennheiser rubber boot. Note the end of the crimp sleeve is where I started the measurement from. I first cut the boot were it meets the rectangular rubber block, then slide the antenna boot off the antenna for use on the new SMA antenna. Cut into the rectangular rubber block and you will find the bronze connector (that is also connected to the tab that your arrow points too). I hope this helps.

Whip1.jpg

Boot1.jpg

Share this post


Link to post
Share on other sites
On 4/6/2016 at 1:51 AM, Mingo said:

Thanks Dave. 

I've tried the external antenna. It works on the RX but not the TX. 

With the same setting and self made antenna, the TX just drop from -35dbm to -70dbm comparing with the original one in 1 meter range. 

And also, I didn't see any circuit that allows G3 using dipole antenna, is it really possible?

Hi Mingo, that sounds like a connection issue to me, I had some similar problems when the pin of the SMA connector on one of my homemade whips wasn't protruding enough (but if it works on the RX, then the antenna is probably fine). Also carefully check that there are no loose connections or shorts in the TX; I accidentally created a tiny solder bridge to the little horseshoe shaped pad when I was modifying mine and this killed the RF entirely. I haven't modified my TXs as the stock antenna is softer than my 'memory wire' ones, and I didn't want to risk it being uncomfortable for talent.

Yep, so long as the sleeve of the SMA connector has a connection to the case (ground) you can run an extension of any length (subject to cable losses of a couple of dB per metre) to a dipole or LPDA, or helical etc... You could also incorporate it into a RF management / amplification system.

 

If anyone is interested in how to calculate the various lengths for antennas themselves, it uses my favourite formula that is also used in acoustics calculations: ƒ=v÷λ 

Where ƒ is frequency in Hz, v is velocity (speed of light in particular medium) in m/s, and λ is wavelength in metres. Rearranged as λ=v÷ƒ we can calculate a single wavelength, and from that 1/2 or 1/4 wave whips and dipoles etc...

If you want to get super finicky the velocity factor (speed of light for) of copper is something like 0.95 so this will change the dimensions slightly - Speed of light in a vacuum is 299,792,458 m/s. So the speed that waves propagate in copper is 299792458 x 0.95 = 284,802,835 m/s.

So for example, my G3s sit in the 'B' range 626 - 668MHz so to create an antenna that is most resonant in the centre of that band (647MHz) the calculation is a follows: λ = 284,802,835 ÷ 647,000,000 = 0.44m

So a 1/4 wave whip antenna is 0.44 ÷ 4 = 0.11m or 11cm so a 1/2 wave dipole is just two elements that are each 11cm long.

However! It's important to note the relative weighting of this information. Yes these are technically the 'correct' values, but will there be a noticeable or even measurable impact if you're a few mm out? Very unlikely. There are way too many other variables at work in a real-world situation.

Share this post


Link to post
Share on other sites

Just made a few whip antennas (block 19) using the super-elastic wire the Dave Williams recommended. The heat shrink tubing that I used is the 3/64th diameter size. I also filed small notches in the wire to help with the mechanical connection at the solder point.

WhipAntenna19web.jpg

Share this post


Link to post
Share on other sites
50 minutes ago, mark kirchner said:

Just made a few whip antennas (block 19) using the super-elastic wire the Dave Williams recommended. The heat shrink tubing that I used is the 3/64th diameter size. I also filed small notches in the wire to help with the mechanical connection at the solder point.

WhipAntenna19web.jpg

do tell what that magic wire is

Share this post


Link to post
Share on other sites

Hello Jack,

This is an Ebay link for the super-elastic wire that Dave Williams wrote about. It is slightly thinner than the stock that Remote Audio uses. If you want want me to put a small sample in the mail to you just PM me.

http://www.ebay.com.au/itm/120476274177?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Share this post


Link to post
Share on other sites
Mingo   
On April 11, 2016 at 0:14 PM, Dave Williams said:

Hi Mingo, that sounds like a connection issue to me, I had some similar problems when the pin of the SMA connector on one of my homemade whips wasn't protruding enough (but if it works on the RX, then the antenna is probably fine). Also carefully check that there are no loose connections or shorts in the TX; I accidentally created a tiny solder bridge to the little horseshoe shaped pad when I was modifying mine and this killed the RF entirely. I haven't modified my TXs as the stock antenna is softer than my 'memory wire' ones, and I didn't want to risk it being uncomfortable for talent.

Yep, so long as the sleeve of the SMA connector has a connection to the case (ground) you can run an extension of any length (subject to cable losses of a couple of dB per metre) to a dipole or LPDA, or helical etc... You could also incorporate it into a RF management / amplification system.

 

If anyone is interested in how to calculate the various lengths for antennas themselves, it uses my favourite formula that is also used in acoustics calculations: ƒ=v÷λ 

Where ƒ is frequency in Hz, v is velocity (speed of light in particular medium) in m/s, and λ is wavelength in metres. Rearranged as λ=v÷ƒ we can calculate a single wavelength, and from that 1/2 or 1/4 wave whips and dipoles etc...

If you want to get super finicky the velocity factor (speed of light for) of copper is something like 0.95 so this will change the dimensions slightly - Speed of light in a vacuum is 299,792,458 m/s. So the speed that waves propagate in copper is 299792458 x 0.95 = 284,802,835 m/s.

So for example, my G3s sit in the 'B' range 626 - 668MHz so to create an antenna that is most resonant in the centre of that band (647MHz) the calculation is a follows: λ = 284,802,835 ÷ 647,000,000 = 0.44m

So a 1/4 wave whip antenna is 0.44 ÷ 4 = 0.11m or 11cm so a 1/2 wave dipole is just two elements that are each 11cm long.

However! It's important to note the relative weighting of this information. Yes these are technically the 'correct' values, but will there be a noticeable or even measurable impact if you're a few mm out? Very unlikely. There are way too many other variables at work in a real-world situation.

Dear Dave,

Jese, It was the connection issue.

The pin inside was too long so that I snapped the connection point.

It works now!

Thanks!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


×