Topics

HF Active Antenna placement


Chris Morrison
 

Hello Group, 
I moved back to Scotland at the end of last year and I'm just getting round to sorting out all my Amateur radio equipment. What the groups opinion on the best place to locate my CCW HF Active Antenna; my options are:
1) Attached to the outside my house, about 6meters above ground;
or
2) Attached to the garage about 3 meters above ground. 

The drawback to option 1 is that its close to the house and can bring in all the noise that comes with it, but it is higher than option 2. The option 2 is about 14 meters away from the house, but will be really close to the transmitting antenna (an Inv-L) when I get that installed. 

Currently I have the antenna mounted in my attic and I'm using it with my SDR-4 to monitor the WSPR frequencies, band hopping from 160m - 15m. I'm not getting many decoded stations, I'm thinking that the WSPR beacons are getting lost in the noise being picked up with the antenna being indoors.

73, 
Chris 
MM1PTT

 


Chris Moulding
 

Hi Chris,

Using any antenna in the roof space is not very effective these days due to the amount of RF noise on the mains wiring.

The test you have run has probably also shown that the noise may be high if it's mounted on the house outside. Being outside will increase the level of wanted signal and reduce the noise from the wiring but the noise may still may be too high.
I suggest you make some measurements of background noise and reference signals say the RWM time signals on 4.996, 9.996 and 14.996 MHz using the antenna mounted in the loft and then try the antenna on your garage at the same time of day and compare the results. The levels don't have to be calibrated precisely, you are just looking at the difference between the locations.

Running a test like this will give you some real results to base your decision on.

By the way talking about roof space antennas back in the 1970s I used to have four 6 element quads fed in phase for 144 MHz mounted in my parent's roof space. I remember one station operating portable 120 miles away saying I was so strong that he disconnected his antenna and could still read me using his car keys pressed into the antenna socket! Happy days...

Regards,

Chris


leslie norton
 

Chris I have had a similar situation to you and it really depends what the noise is, I initially had a wellbrook loop and could not rotate it out of the noise, so then you tend to blame the product. I had tried mounting it high, mounting it low etc. I bought a CCF antenna and im afraid its just the same, however the advantage is that it covers more frequency. My problem is VDSL and wherever i rotate it, its just the same. Im in a square of houses and several poles have several wires coming from all directions. If its on the market ive tried it, noise filters, timewave anc-4 rf noise canceller etc etc
Talking to others in my area, there are some who have given up the hobby and nothing will get rid of it, the only thing that will get rid is fibre to the house and that does not exist in my area.
I had moved from the Isle of Lewis to the NE England, the Isle of Lewis was very quiet for noise.
I have now gone mainly digital below 20m and noise is negligible 20m above.
Have been working on this over a year now but have stopped trying to find a solution.
If however the noise is due to other interference, led lights, internal wiring then mounting high and outside will work.


Bob G3REP
 

I am in much the same position as Leslie, but yet to make a concerted effort using a Common Mode filter on the coax which seems to work for some.
As my primary (&secondry) school teachers used to say, must try harder !

73s
Bob
G3REP


leslie norton
 

Unfortunately common mode filters didn't work for me for VDSL but it may help other interference.


bobsayers2000 <bobsayers2000@...>
 

And you're trying to tell me that the Instructors and Lecturers at the CoE didn't use to say that to you too, Bob? 

:-) 


Bob, G8IYK


On Fri, 1 Mar 2019 at 17:35, Bob G3REP via Groups.Io
<rparkes197@...> wrote:
I am in much the same position as Leslie, but yet to make a concerted effort using a Common Mode filter on the coax which seems to work for some.
As my primary (&secondry) school teachers used to say, must try harder !

73s
Bob
G3REP



Chris Morrison
 

I haven’t had a chance to move the CCW HF Active Antenna yet, but I’ve done some testing and comparisons with my other radio and antenna that is set-up at the moment to try and pin point where the lack of WSPR decode performance is coming from. As I had a little doubt wither the issue was the antenna or the radio/software setup. The testing isn’t scientific, more subjective looking at the noise floor on the pan adapters and WSPR decode performance.

 

My two radios are the Flex 6300 and the CCW SDR-4. Using the two outputs from the Active Antenna I can feed SDR-4 and the Flex 6300 Transverter/RX antenna port at the same time. The SDR-4 uses its internal soundcard and is driven by HDSDR, the output is then feed into WSJT-X 2.0.1 using Virtual Audio Cable (VB Audio). The Flex is driven by another computer using SmartSDR 2.4.9. Doing this side by side comparison of the two radios of WSPR decodes using the same antenna, results in the same number of decodes by both radios/computers with the Flex 6300 reporting 2-3db stronger decodes. I swapped ports on the antenna port on the Active Antenna to makes sure one output didn’t differ from the other, it didn’t make any difference the Flex still had the stronger decodes. This could be down to the performance of SDR-4 internal soundcard or just that the Flex is better receiver. I do have a Creative E-MU202 soundcard that supports 192 kHz sampling that I can try if I can dig out the Windows 7/10 beta drivers. But I’m not really concerned about that as I know that the SDR-4 is working in a consistent manner compared to my Flex 6300. What is concerning is the lack of decodes when using the Active Antenna and the signal strength of decoded signals. It’s rare to see a decode better than -20db when using the Active Antenna.

 

With the Flex 6300 I can zoom out on the pan-adapter to show 7 MHz of spectrum. There is no obvious VDSL2+ interference, as no raised noise floor can be seen at the transitions from the Uplink and Downlink in the UK VDSL2+ band plans. There is also no drop in noise floor at the VDSL2+ guard bands. There is evidence of PLT outside the Ham bands, the noise floor is slightly raised outside the Ham bands, right up to 35MHz. So one of my neighbours must be using a PLT device but luckily for me it’s one of the better devices that notches out the ham bands. Looking just at the 40m band this morning, HDSDR with the SDR4 had a noise floor around -100dB in a quiet part of the band. The Flex had the noise floor averaging around -110dB. So the problem is isn’t a high noise floor.

 

The next test was to compare with another antenna. The antenna is a 80m/40m loaded dipole. Its installed in an inverted-v configuration going over the roof of the house with the apex being about 1m higher that Active Antenna which is located inside the attic. I have no way of feeding the dipole into the two radios at once so the test doesn’t compared the radio performance it’s a comparison between antennas taking into account that Flex has ~3dB better decode performance. With the dipole there are is a lot more decodes per cycle. The stations that where decoded by both antennas have  10-15db improvement with the dipole. Which suggests to me that problem is not noise, it’s just not receiving very well.  I checked the LED at both ends of the antenna, the green LED’s are clearly on. The red LED at the radio end is only noticeable when it’s dark, in a well lit room the red LED isn’t bright enough to tell that is on.

 

If the weather is favourable when I have time next weekend I’ll move the antenna outside, which will get it away from the house in fresh air and the CAT5 cable will unrolled, currently is its lying in a bit of a mess not too far away from the antenna.


Chris
MM1PTT


leslie norton
 

Excellent posting Chris.

Looks like you have ruled out VDSL issues as if its receiving decoded on other antennas then it should be doing the same on the CCW. Don’t forget the CCW has nulls so you may have to experiment with rotating it.
I haven’t tried mine fully yet on WSPR or FT8 as the noise floor doesn’t worry me on there, i don’t listen to the sounds.
SSB is another matter however.

The set up i use is either the CCW in to my FT990 (receive socket) or with the FT991A and via an MFJ-1708SDR using the ptt socket for switching but sometimes i use my SDRplay
I will experiment with FT8 and WSPR with the sdrplay (receive only) and the CCW and see what happens compared to my usual long wire.

Would be interested in your findings.

Les 
G4JNW


On 6 Mar 2019, at 11:22, Chris Morrison <chris.mm1ptt@...> wrote:

I haven’t had a chance to move the CCW HF Active Antenna yet, but I’ve done some testing and comparisons with my other radio and antenna that is set-up at the moment to try and pin point where the lack of WSPR decode performance is coming from. As I had a little doubt wither the issue was the antenna or the radio/software setup. The testing isn’t scientific, more subjective looking at the noise floor on the pan adapters and WSPR decode performance.

 

My two radios are the Flex 6300 and the CCW SDR-4. Using the two outputs from the Active Antenna I can feed SDR-4 and the Flex 6300 Transverter/RX antenna port at the same time. The SDR-4 uses its internal soundcard and is driven by HDSDR, the output is then feed into WSJT-X 2.0.1 using Virtual Audio Cable (VB Audio). The Flex is driven by another computer using SmartSDR 2.4.9. Doing this side by side comparison of the two radios of WSPR decodes using the same antenna, results in the same number of decodes by both radios/computers with the Flex 6300 reporting 2-3db stronger decodes. I swapped ports on the antenna port on the Active Antenna to makes sure one output didn’t differ from the other, it didn’t make any difference the Flex still had the stronger decodes. This could be down to the performance of SDR-4 internal soundcard or just that the Flex is better receiver. I do have a Creative E-MU202 soundcard that supports 192 kHz sampling that I can try if I can dig out the Windows 7/10 beta drivers. But I’m not really concerned about that as I know that the SDR-4 is working in a consistent manner compared to my Flex 6300. What is concerning is the lack of decodes when using the Active Antenna and the signal strength of decoded signals. It’s rare to see a decode better than -20db when using the Active Antenna.

 

With the Flex 6300 I can zoom out on the pan-adapter to show 7 MHz of spectrum. There is no obvious VDSL2+ interference, as no raised noise floor can be seen at the transitions from the Uplink and Downlink in the UK VDSL2+ band plans. There is also no drop in noise floor at the VDSL2+ guard bands. There is evidence of PLT outside the Ham bands, the noise floor is slightly raised outside the Ham bands, right up to 35MHz. So one of my neighbours must be using a PLT device but luckily for me it’s one of the better devices that notches out the ham bands. Looking just at the 40m band this morning, HDSDR with the SDR4 had a noise floor around -100dB in a quiet part of the band. The Flex had the noise floor averaging around -110dB. So the problem is isn’t a high noise floor.

 

The next test was to compare with another antenna. The antenna is a 80m/40m loaded dipole. Its installed in an inverted-v configuration going over the roof of the house with the apex being about 1m higher that Active Antenna which is located inside the attic. I have no way of feeding the dipole into the two radios at once so the test doesn’t compared the radio performance it’s a comparison between antennas taking into account that Flex has ~3dB better decode performance. With the dipole there are is a lot more decodes per cycle. The stations that where decoded by both antennas have  10-15db improvement with the dipole. Which suggests to me that problem is not noise, it’s just not receiving very well.  I checked the LED at both ends of the antenna, the green LED’s are clearly on. The red LED at the radio end is only noticeable when it’s dark, in a well lit room the red LED isn’t bright enough to tell that is on.

 

If the weather is favourable when I have time next weekend I’ll move the antenna outside, which will get it away from the house in fresh air and the CAT5 cable will unrolled, currently is its lying in a bit of a mess not too far away from the antenna.

Chris
MM1PTT


Chris Morrison
 

Thanks for your reply Les, 
I mounted the Active Antenna vertically so not to have any nulls. I can easily change the orientation by reaching up into the loft hatch.  I can try that before the weekend, I'm guessing it wont make much difference. 
The trouble with mounting the antenna outside is getting the feeder into the attic, it requires a ladder. During the week it too dark by the time I get home and last weekend we had that storm warning.

Chris
MM1PTT 


leslie norton
 

Yep i know that feeling, im retired but do have ladders, even though im not keen on heights. I managed to get up 25ft and drill a hole into the wall and the loft space. The rest was inside work but im lucky because the loft is boarded out.


On 6 Mar 2019, at 14:21, Chris Morrison <chris.mm1ptt@...> wrote:

Thanks for your reply Les, 
I mounted the Active Antenna vertically so not to have any nulls. I can easily change the orientation by reaching up into the loft hatch.  I can try that before the weekend, I'm guessing it wont make much difference. 
The trouble with mounting the antenna outside is getting the feeder into the attic, it requires a ladder. During the week it too dark by the time I get home and last weekend we had that storm warning.

Chris
MM1PTT 


Chris Moulding
 

The HF Active Antenna is designed to work like a doublet antenna.

The antenna when used in it's normal position mounted so that the elements are horizontal is as close to perfectly balanced as I can design it and it should reject most of the very local noise sources in the near field of the antenna.

It can be mounted vertically but only if it is in the clear with no nearby metalwork or wiring to unbalance it and the feeder should run at right angles to the elements for some distance (at least 5 - 10 m).

Vertically mounted in the roof space as you describe it will have disturbed the balance of the antenna with the wiring, roof tiles or slates and odd feeder placement all having an effect.

If you really need  a vertically polarised HF antenna we do build the VLF/LF/HF Active Vertical Antenna where the design is based on an ITU design for a radio survey antenna. It makes a great HF antenna but again really has to be mounted up in the clear. I've run a few tests where I've used the prototype to measure signal levels at different heights and around various obstacles. Buildings, trees and other clutter can have a big effect on the signal level compared to the antenna mounted up high in the clear. One interesting measurement that needs further investigation was the 40 dB drop in VDSL noise at the back of the house compared to the front where the brick building was shielding the antenna from the RF noise.

By the way I'm happy to see that a transceiver costing £2000 more than the SDR-4+ receiver shows a small improvement in signal level!

I recently bought a Ten-Tec Omni VI transceiver which has a very low phase noise oscillator and I'm regularly reading and working FT8 stations at -24 dB reliably in the presence of some very strong stations. In the Omni VI the local oscillator is divided by 40 to reduce the phase noise by 32 dB. It certainly makes a difference and it's something I'll consider if I do any development of the Sentinel 4 SDR receiver.

Regards,

Chris


Mark Parker <mwtp2@...>
 

Hi all,

I have had my HF Active Antenna for about month or two now, I wanted to temporary try in attic space, one thing I never managed to do with a Wellbrook loop due to the hatch size.
Was very impressed by the amount of gain but like previous posts the household noise is just to much to do any serious work. My plan is to trial the antenna at  top of my garden some 25 meters away from houses and do some tests with my Perseus, my preference is weak signal work so will be trying WSPR spots as well on various bands. Hoping to set something up in coming weeks..

73s
Mark