Helical Antennas

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Andrew Broughton

Andrew Broughton

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Has anyone done a comparison of the PWS Helical vs. the Sennheiser?
Professional Wireless Systems-all-products-helical-rhcp
Sennheiser A 5000-CP - - Passive antenna

I think the Shure Helical is the same product as the PSW...
Shure Asia | HA-8241 PWS Helical Antenna

The Sennheiser is much more compact, but specs show it has 8db gain vs the 10db gain of the PWS. How much of a difference would that make? I'm mostly interested in comparisons for use in an IEM system, with distances < 100ft between antenna and receiver. I've used both, but never A/B'd them to see if there's a big advantage to the PWS antenna...
 
Re: Helical Antennas

The PWS one is better. But whether that matters depends on your application.

If you measure the A5000CP, you'll find its gain varies quite dramatically with frequency. the PWS one is more consistent over a wide range.

That said, both tend to be more than adequate for typical theatre/arena stage work. You might start to see differences once you get to covering stadium infields etc...
 
Re: Helical Antennas

Andrew Broughton said:
Has anyone done a comparison of the PWS Helical vs. the Sennheiser?
Professional Wireless Systems-all-products-helical-rhcp
Sennheiser A 5000-CP - - Passive antenna

I think the Shure Helical is the same product as the PSW...
Shure Asia | HA-8241 PWS Helical Antenna

The Sennheiser is much more compact, but specs show it has 8db gain vs the 10db gain of the PWS. How much of a difference would that make? I'm mostly interested in comparisons for use in an IEM system, with distances < 100ft between antenna and receiver. I've used both, but never A/B'd them to see if there's a big advantage to the PWS antenna...
Click to expand...

Hi Andy,

Both are very good antennas, especially if you know their secrets. Here are some specific differences to consider.

Below 500MHz, the A5000CP has unacceptably low return loss, large impedance mismatch, and high SWR, making it unsuitable for use with the low end of their own EM3732 A range or any of Shure's G band products. The rest of the Sennheiser bands are all above 506MHz, so it's a good match for them. It offers a wider radiation pattern with 80 degree -3dB beamwidth compared to the HA-8089's 60 degree pattern. As far as gain, the HA-8089 specs are a little misleading, since it achieves its peak gain well above the center of its 470MHz-950MHz range and outside our usable frequency ranges. In the UHF TV broadcast band, its gain ranges from around 7.5dB to 10dB (the graphic below is a calculated model, omitting dielectric losses from its structural materials). The A5000CP has gain around 8dB across its useful range, but suffers from wide variations in return loss, impedance, and SWR.

Mechanically, the A5000CP is a sealed system, with a very robust N-type connector, and is appropriate for outdoor deployment in all weather. Its radome and internal element support structure are made from acrylic, which can be brittle, especially at low temperatures. The HA-8089 has exposed elements, impedance matching section, and conductors, so it's more susceptible to degradation and damage from humid or corrosive environments. However, it is mainly constructed from polycarbonate, which has excellent impact resistance and can survive very rough handling. My biggest gripe is with the connector, which can be easily damaged due to its type, location, and protrusion.

I have posted supporting graphics below. The A5000CP data is from actual measurements and is typical of all that I have analyzed. The HA-8089 data is generated from a model constructed and analyzed with 4NEC2. I'm sorry that I don't have direct 1:1 comparisons to show, since a lot of my data is imprisoned in an old, dead laptop. :(~:-(~:sad:

A5000CP Impedance Analysis.jpgHA-8089 NEC2 Model.jpg
 
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Re: Helical Antennas

Andrew Broughton said:
I think the Shure Helical is the same product as the PSW...
Shure Asia | HA-8241 PWS Helical Antenna
Click to expand...

Correct. We manufacture and tune the antennas for Shure to resell. Shure sells both ranges, the HA-8089(470-698MHz) and the HA-8241(950MHz). The HA-8089 was redesigned to better cover the 470-698MHz range since the loss of the 700MHz band here is the US, and now there is no functional overlap of the two ranges.

And there's not much left to say that Jason hasn't said already. What a great post! To add, the PWS helical has a few dB more rear rejection than the A5000, but nothing significant. And, consider the PWS Domed Helical. It was made in response to requests for a smaller form factor. Instead of fitting the Helical in a large tomtom case, the Domed Helical can fit inside any 14" snare case. If you've used both and like the improvements of circular polarization (which cannot be understated for IEMs) there isn't a world of difference between the three CP antennas made by PWS, Sennheiser, or RFVenue when compared to a LPDA. There are three different form factors, each having their own benefit over the others.

Cameron Stuckey
Professional Wireless
 
Re: Helical Antennas

Jason Glass said:
The RF Venue CP Beam is an option. http://www.rfvenue.com/rf-venue-cp-beam-antenna

While I have not personally tested one in depth, I have friends who have used them with great success. It's a truly brilliant design that can pack into a two-space rack drawer. A quick look at their patent art supports their specs and indicates that they should have similar performance to the HA-8089. Adjustable spiral antenna for portable use - Patent application
Click to expand...
That is great packaging! Thanks for that link.
 
Re: Helical Antennas

Cameron Stuckey said:
If you've used both and like the improvements of circular polarization (which cannot be understated for IEMs) there isn't a world of difference between the three CP antennas made by PWS, Sennheiser, or RFVenue when compared to a LPDA. There are three different form factors, each having their own benefit over the others.

Cameron Stuckey
Professional Wireless
Click to expand...
Great info. Thanks, Cameron!
 
Re: Helical Antennas

Jens Bacher said:
Whatever you do stay away from this one, horrible: circular polarization antenna
Click to expand...

I use some simple omni DVB antenna's. These work in the same frequency band.
Biggest problem was the power supply, 5V instead of 12V.
Also the gain is quite high, so I have to be carefull with overmodulation. (Keep antenna's at least 4 meter away from transmitters)
But it does work FOR ME and it doesn't cost a thing. :)
 
Re: Helical Antennas

Steve Payne said:
Would you care to elaborate? These may not be nearly as good as the others being discussed here - I don't know. I use the kaltmans in place of paddles and they work great in my admittedly not so demanding situations.
Click to expand...

I would also appreciate that. I have "heard things" about that antenna, but nothing concrete.

If any of you would like to send me one for analysis with my instruments, please PM me. I would be happy to share the results.
 
Re: Helical Antennas

The CPantenna is really a OEM RFID antenna, meaning it is tuned to work in the 900 Mhz ISM band. It does not perform very good below 700Mhz. The local Sennheiser office here actually sold a very similar antenna, but it was clearly labeled to only work above 780Mhz, where WL mics in Denmark used to reside.

This is an comparision of an Sennheiser 2003 (standard lpda) and CP antenna used as a transmitter, they are both picked up by a Sennheiser wideband omni (1031). The receive antenna is on-axis to the transmit antenna and is vertical polarized. Measurements are done outdoors, you can see a few strong carriers.
2003, horizontal and vertical: https://dl.dropboxusercontent.com/u/18154497/2003hor-ver.jpg
CP antenna, horizontal, vertical and at 45 degree: https://dl.dropboxusercontent.com/u/18154497/cpantennahor-ver-45.jpg

As you can see the CP does not give nearly the same signal at any orientation. It is 10-12dB down over much of the spectrum.

This is how it looks on a directional coupler (lower is better): https://dl.dropboxusercontent.com/u/18154497/cpantenna.jpg This clearly shows how it is tuned to work best around 900Mhz.
This a Sennheiser 5000 in comparison: https://dl.dropboxusercontent.com/u/18154497/cp5000.jpg
 
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Re: Helical Antennas

Thanks, Jen! I added the images inline so they'll still be here when dropbox goes away.

Jens Bacher said:
The CPantenna is really a OEM RFID antenna, meaning it is tuned to work in the 900 Mhz ISM band. It does not perform very good below 700Mhz. The local Sennheiser office here actually sold a very similar antenna, but it was clearly labeled to only work above 780Mhz, where WL mics in Denmark used to reside.

This is an comparision of an Sennheiser 2003 (standard lpda) and CP antenna used as a transmitter, they are both picked up by a Sennheiser wideband omni (1031). The receive antenna is on-axis to the transmit antenna and is vertical polarized. Measurements are done outdoors, you can see a few strong carriers.
2003, horizontal and vertical:
2003hor-ver.jpg

https://dl.dropboxusercontent.com/u/18154497/2003hor-ver.jpg



CP antenna, horizontal, vertical and at 45 degree:
cpantennahor-ver-45.jpg

https://dl.dropboxusercontent.com/u/18154497/cpantennahor-ver-45.jpg

As you can see the CP does not give nearly the same signal at any orientation. It is 10-12dB down over much of the spectrum.

This is how it looks on a directional coupler (lower is better):
cpantenna.jpg

https://dl.dropboxusercontent.com/u/18154497/cpantenna.jpg This clearly shows how it is tuned to work best around 900Mhz.

This a Sennheiser 5000 in comparison:
cp5000.jpg

https://dl.dropboxusercontent.com/u/18154497/cp5000.jpg
Click to expand...
 

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Re: Helical Antennas

Andrew Broughton said:
Thanks, Jen! I added the images inline so they'll still be here when dropbox goes away.
Click to expand...

I think the choice of antenna is not cut and dried. It ls clear that when the transmitter and receiver polarization match the LPDA has better performance, it is about 10dB hotter and has wider frequency response. This is not news, it is a known characteristic of circular polarized antennas of all types. When the transmitter and receiver antennas are 90º apart though the CP has better and flatter response down to its rolloff which is quite high at what looks to be a little under 575MHz. The right hand third of the chart is irrelevant in the US as we can't use anything above 698MHz, soon to be a much lower cutoff.

It would be interesting to see this same comparison with a Sennheiser A5000CP or PWS Helical, which also give up some forward gain for circular polarization, but which may make it back up with Higher gain (narrower coverage) designs. Gain vs coverage is a tradeoff that the user has to decide on for each use.

A look at off axis response would also be helpful, since the antennas are rarely directly on axis in real life.

Is the Kaltman CP antenna a similar design to the Clair CP?

Mac
 
Re: Helical Antennas

mackerr said:
Is the Kaltman CP antenna a similar design to the Clair CP?
Click to expand...

The Clair CF1090 was specifically designed for the application and is manufactured by Fractal Antenna Systems for Clair.

Fractal has numerous, very strong patents for the use of fractal geometry to reduce the physical size of elements, ground planes, counterpoises, and impedance matchers for a given frequency band.
 
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Re: Helical Antennas

mackerr said:
I think the choice of antenna is not cut and dried. It ls clear that when the transmitter and receiver polarization match the LPDA has better performance, it is about 10dB hotter and has wider frequency response. This is not news, it is a known characteristic of circular polarized antennas of all types. When the transmitter and receiver antennas are 90º apart though the CP has better and flatter response down to its rolloff which is quite high at what looks to be a little under 575MHz. The right hand third of the chart is irrelevant in the US as we can't use anything above 698MHz, soon to be a much lower cutoff.
Click to expand...
Notice how the CPantenna gives almost exactly the same performance as a LPDA at 850 Mhz, but drops of fast around 825Mhz. So the lower level is not primarily because of the circular polarization that "costs" 3dB, it must be other factors.

It would be interesting to see this same comparison with a Sennheiser A5000CP or PWS Helical, which also give up some forward gain for circular polarization, but which may make it back up with Higher gain (narrower coverage) designs. Gain vs coverage is a tradeoff that the user has to decide on for each use.

A look at off axis response would also be helpful, since the antennas are rarely directly on axis in real life.

Is the Kaltman CP antenna a similar design to the Clair CP?

Mac
Click to expand...
I'll try to make some comparisons when the weather here gets better..

Another interesting antenna is the Mipro AT-100, it measures quite good, but it is too expensive compared to the "real" CP5000.
 
Re: Helical Antennas

ive used the kaltman in several very non demanding situations with uhfr and slx, I never dropped a signal during the show but I rarely drop signal with even whip antennas and properly selected channels. interested to see how tests come out with for it for others and in more demanding situations.
 
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