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Broadband Active Antenna (experience, test, comparison)?


Ondřej Povalač
 

Hi, first of all, let me say hello to the group, I am new here, this is my first post.

 I live in Europe, Czech Republic. The bandplan here is a bit different so that there is no interesting communication above 470MHz. So basicaly, I am interested in:

- UHF (400-470MHz)

- some UHF AIR Satcom (230-380MHz), 

- VHF (137-174 MHz),

- VHF AIR (118-137MHz) and 

- HF (25-87MHz).



I would like to get some user experience with the Broadband Active Antenna made by CrossCountryWireless for the above frequencies.
Until now, I am using Diamond X300 for VHF/UHF listening. Not the best, but it works. I have 5 receivers, IC-R8500, Uniden BCD536HP, Uniden SDS200, AirSpy r2 and AirSpy r0 (for web access). I just purchased the CrossCountryCommunicatons HF/VHF/UHF multicoupler for the signal distribution to the receivers. Had to use a coax switch until now, which allowed me to use only one receiver at a time. So looking forward to the multicoupler.

Now for the antenna - can anybody share any experience with the VHF/UHF performance especially when compared to discones or one of the Diamond's "white stcks" (the X series). I would like to increase the signal quality on the VHF/UHF bands, but not too sure it will be better than X300, especialy when th X300 is over 3m tall, while this antenna is only 0.8m tall.

Any experince is welcome.

Thank you,
73 de Ondrej OK2TOP


WA8LMF
 

On 1/5/2020 4:12 PM, Ondřej Povalač wrote:
Hi, first of all, let me say hello to the group, I am new here, this is my first post.

 I live in Europe, Czech Republic. The bandplan here is a bit different so that there is no interesting communication above 470MHz. So basicaly, I am interested in:

- UHF (400-470MHz)

- some UHF AIR Satcom (230-380MHz), 

- VHF (137-174 MHz),

- VHF AIR (118-137MHz) and 

- HF (25-87MHz).



 Until now, I am using Diamond X300 for VHF/UHF listening. Not the best, but it works. I have 5 receivers, IC-R8500, Uniden BCD536HP, Uniden SDS200, AirSpy r2 and AirSpy r0 (for web access). I just purchased the CrossCountryCommunicatons HF/VHF/UHF multicoupler for the signal distribution to the receivers. Had to use a coax switch until now, which allowed me to use only one receiver at a time. So looking forward to the multicoupler.

Now for the antenna - can anybody share any experience with the VHF/UHF performance especially when compared to discones or one of the Diamond's "white stcks" (the X series). I would like to increase the signal quality on the VHF/UHF bands, but not too sure it will be better than X300, especialy when th X300 is over 3m tall, while this antenna is only 0.8m tall.

The X300 and other similar antennas in the Diamond and Comet families are intended specifically for amateur radio operation in the 144-148 Mhz "two-meter" VHF ham band, and 430-450 MHz "70 cm" UHF ham band.  These antennas consist of multiple relatively-sharply-tuned 1/2- or 5/8-wave antenna elements stacked above each other inside the fiberglass cover. At the design frequencies, the vertical radiation pattern of the antenna is focused towards the horizon.    As you move away from these center frequencies, the pattern starts skewing upwards from the horizon and suffers reduced signal pickup "straight out" toward the horizon.  The performance in the VHF air band and the UHF tactical air band (225-400 MHz) will be poor, since the antenna will be far far away from it's design frequencies.    Oddly, though, the skewed radiation pattern (i.e. up in the air instead of at the horizon) may actually help when you are trying to pick up aircraft rather than land vehicles.

On what you call "HF" the performance will be very poor to non-existent. [Technically "HF" ends at 30 MHz, while "VHF" is 30-300 MHz).  In the US at least, the span of 30-50 Mhz is used for two-way land mobile radio, and is often referred to as "VHF low band", by contrast with the 136-174  MHz "VHF high band".  The 30-70 MHz frequency span is sometimes referred to as "NATO band", since nearly all NATO member army field radios and tank radios operate in this span.]   In any case, the VHF/UHF X300 antenna will be so far away from it's design frequencies that it will barely work at all in the VHF low band.    

Note that there are variants of the Diamond  & Comet antennas that are "tri-band" and cover the amateur radio 50-54 MHz "six meter" ham band in addition to the two higher frequency bands.   This antenna would have far more (though satill not ideal) pickup throughout the VHF low band. 


By contrast, the common discone antennas like the Icom AH-7000 will cover continuously from 30-1200 MHz. But the gain is actually NEGATIVE compared to a simple vertical half-wave dipole scaled to any given frequency; i.e. -2 dB relative to a dipole.   The discone is often referred to as being "equally bad at all frequencies", but it does have the advantage of operating with uniform performance and pattern over a far wider range of frequencies than just about any other kind of antenna.  It is quite usable for monitoring strong relatively nearby signals on any frequency. It is NOT very good for weak distant signals grazing the horizon.    It would be an ideal mate for the HF/VHF/UHF multicoupler. 

Like the white fibreglass collinear whips, the discone is vertically polarized and non-directional.  This makes it work well for mobile radio services that universally use vertical whip antennas on vehicles.   It is a poor performer for TV and FM radio broadcast services that are usually horizontally polarized.  (Some EU countries use a mix of horizontal and vertical polarization for TV broadcasting.)    I normally leave an AH-7000 connected to my communications service monitor when I have no specific requirements for higher performance or more specialized antennas.

Assuming you use a 1 meter diameter (3.1 meter circumference) loop on the CCW antenna, the results at VHF & UHF will vary wildly.   At VHF-low, where the length (circumference) of the loop conductor is short compared to the wavelength of the incoming signal, it should act like a compact magnetic loop antenna, exhibiting a pickup pattern similar to a horizontal dipole, but with the maximum pickup off the edges (not the broadside) of the loop.   At 100 Mhz (center of FM broadcast band), the wavelength is 3 meters. I.e. the antenna is now a full-wavelength loop, and will act more strongly like a standard half-wave horizontal dipole.      As you move above 100 MHz, the loop will now become multiple wavelengths long, causing the simple dipole pattern to breakup into multiple lobes at various angles with deep pickup nulls in between.   I.e. the pickup of a a given signal from a given direction will require carefully rotating the loop for best pickup.   


Stephen H. Smith    wa8lmf (at) aol.com
Skype:        WA8LMF
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Home Page:          http://wa8lmf.net

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Martin - G8JNJ
 

Hi,

For general VHF / UHF monitoring the smaller white stick dual band co-linear antennas work OK. They provide a bit of gain on the UHF bands and work as a 1/4 wave on the Low VHF bands and are less conspicuous than a discone. However the out of band performance does vary somewhat depending upon the exact configuration of the internal matching network, so it's difficult to predict exactly how one type would perform on the bands you are interested in. Most types I have tried do work in the VHF and UHF aircraft bands, and you can hear Satcom downlinks with them, which is usually a good guide to performance.

One other type of antenna that has given me good results in the past, especially if you can combine it with a good mast head pre-amplifier is the 'double discone' type similar to this.

https://sigmaeurocomm.co.uk/product/double-discone-scanner-base-station-antenna-aerial/  

However they are a bit large, and may not go unnoticed once installed.

Regards,

Martin - G8JNJ


leslie norton
 

I know its a bit off CCW topic but i had to reply Martin (sorry Chris)
The Satcom your referring to is what range of frequencies.
I listen to aircraft on VHF on my white stick but monitor L band Satcom on a satellite dish.
in the range of 1537 but as you know satellite dishes are very narrow.
Are you receiving L band on a vertical?

On 6 Jan 2020, at 13:47, Martin - G8JNJ via Groups.Io <martin_ehrenfried@...> wrote:

Hi,

For general VHF / UHF monitoring the smaller white stick dual band co-linear antennas work OK. They provide a bit of gain on the UHF bands and work as a 1/4 wave on the Low VHF bands and are less conspicuous than a discone. However the out of band performance does vary somewhat depending upon the exact configuration of the internal matching network, so it's difficult to predict exactly how one type would perform on the bands you are interested in. Most types I have tried do work in the VHF and UHF aircraft bands, and you can hear Satcom downlinks with them, which is usually a good guide to performance.

One other type of antenna that has given me good results in the past, especially if you can combine it with a good mast head pre-amplifier is the 'double discone' type similar to this.

https://sigmaeurocomm.co.uk/product/double-discone-scanner-base-station-antenna-aerial/  

However they are a bit large, and may not go unnoticed once installed.

Regards,

Martin - G8JNJ


Martin - G8JNJ
 

Hi Leslie,

UHF Satcom, typically 225-300MHz and weather sats around 138MHz. 

https://uhf-satcom.com/satellite-reception/uhf

You need a dish or something with a bit more gain for L-Band.

Regards,

Martin - G8JNJ


Ondřej Povalač
 

Hi everyone,
Thank you very much for all your comments.
I wil try to bring some more info regarding my past experience with receive antennas. I tested quite a lot on my QTH with various results. Also, I live in an area with very low traffic on VHF/UHF, no  local services  so I need to work with very weak and distant signals. I can't use a directional (yagi) antenna as this would require a rotor, which I don't have a supply and control cable for (on the roof). So looking for a decent omnidirectional antenna.
I tested these models:

Discones:
- W32DD (Watson double discone)
- D130NJ (Diamond discone) 
- SD1300N (Sirio discone)
- DA3200 (AOR discone)
All the the discones perform equaly -  quite good on VHF Low, not very good on VHF high and aoor on Satcom, milair and UHF. Did not notice any specific advantage with double discone

White sticks:
X50 (Diamond X50 white stick)
X300 (Diamond X300 white stick)
D777 (Diamond D777 airband and milair white stick)
All the white stick perform similar, but the longer = the better, especialy on VHF. I was very disappointed with D777 which actualy received airband worse than X300. The X300 picks satcom well (about 5-10 satelites normally), even though the signal is weak, but readable. The white sticks are poor on VHF low.

Other special antennas
Sirio GP 160 LB-N (Sirio broadband antenna, 145-175 MHz)
Sirio GP 430 LB-N (Sirio broadband antenna 380-480 MHz)
These two were connected by duplexer into one cable. I was expecting a lot from this combination, but the UHF could not outperform the X300.

You can see that I made lot of trials on VHF and UHF in search for a perfest antenna setup. Almost all antennas were tested with and without low noise preamplifier (build on ePHEMT transistors - noise figure circa 0.7)

As I have the best experience with X300 from the above, I am thinking about buying the X7000 which has even more gain on the VHF and UHF. I perfectly understand, that these antennas are tuned sharply for the 145 and 430 bands, but for some reason, they perform good also outside these bands.
Space is is  a problem in my case, I can put almost anything on my roof (it will look tiny anyway compared to my 6x6 meters square Cobweb :-)

Before trying the longer X7000 white stick, I was interested in the Broadband Active Antenna by Cross Country Wireless (works from 200kHz to 1400 MHz) ... Here is the link http://www.crosscountrywireless.net/broadband_active_antenna.htm
The question is whether it will outperform the X300 or the other above mentioned antennas especialy on VHF and UHF.

What do you think?

Thanks, 
73, Ondrej OK2TOP


Ondřej Povalač
 

On Sun, Jan 5, 2020 at 06:42 PM, WA8LMF wrote:

Assuming you use a 1 meter diameter (3.1 meter circumference) loop on the CCW antenna...

Sorry, I was not very specific... I am thinking about this model, not the CCW loop antenna - http://www.crosscountrywireless.net/broadband_active_antenna.htm
My apologies.
73, Ondrej


Chris Moulding
 

Hi Ondrej,

The Broadband Active Antenna has two wideband antenna elements with a very low noise amplifier directly at the antenna feed point so there is no feeder loss before the amplifier. This gives a good performance on VHF air band, military UHF air band band and ADS-B, typically better than non-active antennas depending on the extra feeder loss. The antenna also acts as an electric field antenna at HF so gives a fairly good performance on HF if mounted away from any electrical equipment.

If long distance VHF air band work is your main interest we have also made versions tuned to cover the VHF air band for professional customers. These give excellent results especially if mounted at a good height. They are particularly good at receiving aircraft at the extreme line of sight range say 250 miles away.

At present we have two major orders on the go so we have restricted some of the items on the web site which are labour-intensive including the Broadband Active Antenna. I expect that we will have them on sale again by the end of February.

Regards,

Chris


Ondřej Povalač
 

Hi Chris,
thanks for your reply. As for the specific VHF AIR, this is not the only (although very important) band, which I would like to monitor. So the primary bands I am interested in are 118-174 MHz (AIR + VHF) and 400-470 MHz  (UHF) and the secondary bands are 25-87 MHz (VHF low) and 230-380 MHz (MilAIR). On the secondary bands, I don't need the tuned antenna as I realize, that all together the primary and secondary bands are in fact the whole VHF and UHF spectrum :-)

So for the primary bands, I would like to try active antenna to see if that performs well compared to X300. Also, I know that you make this antenna 0,8m long (to fit within accetable postage of Royal Mail), however, do you think that making "custom version" of this antenna with 2-3times the length would perform even better on these bands? (better gain?)
I am aware that the sale of Broadband Active Antenna is now suspended, but I don't need it soon as I can mount it on my roof only after winter, not now. So plenty of time from this point of view.

I am just trying to decide, whether this antenna is a way to go and whether "custom length" would make things even better. Also not sure about shipping price for such extended length.
Thanks again for your reply.
73, Ondrej OK2TOP


Martin - G8JNJ
 

Hi Ondrej,

You have tried pretty much every combination of VHF/UHF omni-directional antenna I can think of, and have already exceeded the point of diminishing returns.

Realistically I don't think you will be able to realise much further improvement regardless of whatever omni antenna you chose to use, unless you find a better location, such as a mountain top, that would give you a much more distant 'radio horizon', which is why most transmitter (and receiver) sites are located in such places.

To increase range you need more gain, but this has two implications. The first is that to increase gain you have to concentrate the antenna pattern to form a narrower, but a higher gain lobe. This has implications for non-terrestrial reception as the 'beam ' pattern becomes narrower to focus out towards the horizon, with the result that the 'overhead' gain is diminished. The second problem is that generally speaking the more gain you try to achieve the narrower the bandwidth of the antenna becomes, which affects the 'out of band' performance.

The only true broadband antennas with gain tend to be log-periodics, but these are directional so you would either have to rotate the antenna or use multiple fixed log-periods in a phase arrangement.

This is one type I have used in the past (and also the much bigger 50MHz version).

https://www.nevadaradio.co.uk/product/create-clp-5130-2n/

I also added two more elements to extend the frequency coverage down to 70MHz and also converted the rearmost element to a wire mesh bow-tie to extend the coverage even lower in frequency, but all it started to get a bit unwieldy, and in the end I took it down and just stuck with a dual band white stick, which didn't perform quite as well but was much less hassle to maintain.

Adding a pre-amp at the antenna can help improve the 'out of band performance by minimising mismatch losses, but this only works up to a certain point and even if you have a very low noise pre-amplifier, the noise figure is only valid when it 'sees' a matched feedpoint impedance.

What you are trying to achieve is almost impossible with a single antenna, so I think you will have to use multiple dedicated antennas and diplex the signals together.

Regards,

Martin - G8JNJ


Ondřej Povalač
 

Hi Martin,
i agree that increased performance based on single antenna is impossible. So the only advantage could be elimination of losses in the coax and connectors ... I have about 25m of Aircell 7, together with few connectors, I am around 5dB loss in the whole system. Might add ePHEMT LNA to compensate this loss, but this is all.
On my new QTH (I am building a cottage next year), I will have a tower where I want to install rotor and several directional antennas. So this will be better.

Right now, I will stick to the current antenna (have allready range over 100km) and try to add LNA to the antenna povered by Bias Tee.

Thanks,
73, Ondrej