Topics

Loop height above gnd and 2 loops


Simon
 

Now I am on a quest to get better performance on 160m.

To get more received signal strength from usa etc..

There is not much more I can do with my current loop..its big, switchable directions made of 4 loops in each direction..( although one direction n/s is totally unusable on 1846-1850..ssb dx.. due to an unidentifiable smpsu somewhere.)

Done some internet research on this and height seems not to matter..atleast unless one can get 20m plus up..I can do 5..just above house gutter height, and that would have to be a single small loop.

so maybe 2 loops..feed together? No way I can space them far apart, so no real chance of correctly phasing them unless digital delay lines etc made..

worth the effort?? Not sure..

my current loop is not bad..very comparable to hack green websdr, sometimes worse sometimes better..
most of the time it beats derby websdr..talking dx here not lnter uk..

I am struggling to hear weaker usa ssb 160m stations..last night I was being called by a k4 etc ( who was obviously hearing me calling cq,) but he was in and out of the noise ..( same on hack green though..)

any thoughts please??

Mag loop Simon g0zen 


Simon
 

Oh, location urban east london..no sea to put antenna above!! 


Chris Moulding
 

Hi Simon.

There are two ways you could improve your loop antenna system.

The first would be to elevate the loop above the local clutter (houses, trees,etc). This will increase the signal levels but also tend to reduce local interference as the height of the antenna is increased.

Some years back I ran a WebSDR station with four SDR-4+ receivers and used one of our HF Active Loop antennas at 9m above ground.

As it was above all the local clutter this gave an excellent performance on all bands including 160m. I had one of the receivers monitoring the SSB section of the 20m amateur band. At that time there had been an earthquake in Nepal and apparently my WebSDR station was the only one that could hear the one radio amateur still transmitting requests for assistance from Nepal. I found out after a phone call from a relief organisation who had been listening to the traffic when the WebSDR server crashed due to the number of listeners on the system!

The second way to improve your antenna system would to give it some directivity to minimise signals and noise coming from the rear of the antenna as it is points to the US.

One of my long term projects is looking an manufacturing a cardioid loop based on the original design by C&S Antennas in the 1970s. According to their original articles and the tests I ran on a prototype it has a 12 dB front to back ratio that in your case would give a good useful reduction in unwanted signals and noise.

Mounting a cardioid loop as high as you can would probably be your best option.

Regards,

Chris


Martin - G8JNJ
 

As Chris has already suggested it's probably not about absolute gain but improving the directivity.

Maybe two loops with an adjustable phasing network like a noise canceller, or something like the SDR Play Duo which has two coherent receivers that can be used with two antennas to steer the direction.

https://www.sdrplay.com/wp-content/uploads/2018/05/RSPduoDatasheetV0.6.pdf

Alternatively this simple phaser can work surprisingly well, especially on the LF bands (see attached).

Regards,

Martin











Simon
 

Thank you both for your replies

Chris any more info on c and s loops?? Google fighting me on this!

Is 6-7 m high enough? Can not go much higher with out local council/ wife issues..will be mounted on side of house..will be set in one direction..the one that nulls out the smpsu noise on 1845-1850..fortunately thats not towards usa..( will add a bird nesting box to pole....illegal to disturb once in use..keeps council people away..)



Perhaps on an antenna rotator if work’s well with phaser and second loop..would be nice to hear South Africa zs better than am now..(160m.)...would need to be able to remove smpsu noise if facing zs..( very frustrating yesterday at about 5pm..zs there..would have heard me, but i had bloody smpsu noise on his frequency..just too much noise for qso, so did not call.1852khz ssb.)

Thanks Martin ..that looks easy to make..junk box time!!


Ps been working the stronger usa/ canada etc stations on ssb 160 this werk. using the mag loop..but really want to work the weaker stations..last night could hear circa 3-4 local nets..but not quite good enough to give a call too..)

Thanks for your help


Simon

On 8 Nov 2020, at 15:11, Chris Moulding <chrism@crosscountrywireless.net> wrote:

cardioid


Chris Moulding
 

I'll do some more work on it this week to measure the optimum values for the cardioid loop using a Loop Antenna Amplifier +.

Once I've done that I'll post the loop design on this forum and make a YouTube video explaining how it works.

Regards,

Chris


Simon
 

Thanks

But could you send me some details via email..may have one made before you..

Simon


Chris Moulding
 

I did some work with the 4NEC2 antenna modelling tool to optimise the values for a cardioid loop using a Loop Antenna Amplifier +.

This afternoon I built a prototype and mounted it on the 4.5m carbon fibre windsurfing mast I use for quick testing at the workshop.

This confirmed the antenna modelling results. The antenna pattern is a good cardioid pattern up to around 8 MHz above which it becomes circular.

Two off-air measurements today, one on a medium wave station on 909 kHz gave a front to back ratio of 28 dB and another on 5 MHz gave 23 dB.

There was a very noticeable increase in signal to noise ratio when the antenna was pointed at the required station.

I'll write all this up over the next few days and post it on a new web page with photos, loop arrangements and layout diagrams. It's quicker to do this than try and explain over the forum or email.

Regards,

Chris


Simon
 

Hi

Thank you..

Can u post a pic if you took one?

To give me an idea

Thanks..( i ask as Wife working till late all week, and i can play making loops without getting in trouble this week.)

Simon


Chris Moulding
 

OK, here's a photo of the prototype...


Simon
 

Ok

U naughty man..not much help..

Hmmm..looking at a circa 1m dia loop.open at bottom.with a vertical wire running down from one side of input to amp..

I can not get any more info from the pic..

Naughty naughty man..now i am going to have to practice my morse..( last used 30 yrs ago.) as have not alot to be going on..dont want to waste my copper tube on something that i may have got completely wrong..

Simon


Simon
 

Actually loop may not be open..there could be a coupling wire ran along the loop that the amp connects too..depending upon how long i look at pic..hmmm..


Chris Moulding
 

OK a bit of detail for you,

I'll leave the detailed description of how it works for the web page, in very basic terms its a loop antenna and sense antenna in one.

It's using a purple hulahoop to hold a wire loop. At the top of the wire loop is a break bridged with a 110 ohm resistor (2 x 220 ohm resistors in parallel).

Due to the resistance it doesn't need thick copper to make the loop, I used 1mm wire.

The loop ends feed to the terminals on the Loop Antenna Amplifier +. From one of the terminals run a wire down to an earth or ground rod at the base of the mast.

Do not connect the earth or ground wire to the BNC socket as it will bypass the common mode choke and isolation transformer in the amplifier.

Regards,

Chris


Simon
 

Thank you!

Sorry ..the earth wire..does length mater..? Can some be horizontal..i ask as need to figure out mounting on house..out front is paved..( car parking.)
Side is paved but only a walk way..BUt side holds dipole up..

Out back is toooo close to tx Aerials.



Simon..


Simon
 

Does it still retain the side nulls, or are they lost at the expense of forward directivity?...without the side nulls i may be in trouble here ( re smpsu noise north south direction on 1846-1850.)

( sorry..) Simon

On 9 Nov 2020, at 20:14, Simon via groups.io <ohhellnotagain=gmail.com@groups.io> wrote:

Thank you!

Sorry ..the earth wire..does length mater..? Can some be horizontal..i ask as need to figure out mounting on house..out front is paved..( car parking.)
Side is paved but only a walk way..BUt side holds dipole up..

Out back is toooo close to tx Aerials.



Simon..







Chris Moulding
 

I only made front to back measurements today.

I'll measure the polar diagram on a local medium wave station tomorrow.

Regards,

Chris


Simon
 

Hi

Thank you..

See below for really poor drawing of plan of house..end of terrace..
As you can see not much room..
160-80 loop and 40m loop are the tx mag loops.
The 10-40m dipole is inverted v at 8m apex..it is trx for 10-40m, but only 100w not full qro..

Currently the active loop is in corner of land next to house..small land, not actually ours..but owners happy..road runs next to front of house and this land..

So only options of a high( ish ) loop are at A B or C..shack is on gnd level.
Chimney is out of the question due to no way of getting to it without ££ spent ..

Option A and B both have mounts attached to house..point C would need me to make one..(easy.)

If it turns out your cardioid antenna has no significant nulls on side then I will not be able to null out local smpsu noise..so then would try 2 loops and phaser to try to get some more gain/ better snr..

But each loop soo close to each other..( max 7m.) would it work??

Noise appears to be n/s direction..

Could try a loop in loft..but that is bound to fail..

Note current active loop is not high..can not be in its location( hiding behind tall hedge.)
Loops on house would be circa 6m to base of loops

Simon




Photo below is old..but gives idea of where to place higher loops..


Ttfn Simon


Simon
 
Edited

Hi Chris

did you have any time today to do measurements?

also..been thinking..( a bad thing maybe.)..if the directional  loop can not null out the smpsu noise here in the direction i want the antenna to face ( most of the time.) ie nw to usa, then a phasing unit with another standard loop picking up the noise..cancelling out.??? .though i can see this upsetting the radiation pattern abit..

also the earth on the new loop vertical sense wire..what type of earth? A rod in the gnd..or tied to existing radial system etc..
due to my location, the earth could be a long way from loop..( unless mounted on side of house.) even this if on side  I expect will cause issues..6 m vertical wire with 2 m horizontal at best..no way here of having the loop above gutter height and a direct gnd..
electical noise pickup from the earth..will it not make the loop “noisey”??

how about if vertical length at 6+2 is ok combining your neat recent isolated earth solution ( rad com.) 

is there a min or max length of sense wire?? Itching to try it..but to start with would be only 2-3m above gnd..( test.)

Sorry for the questions..simon

(of course all of above would be irrelevant if someone on here in the sticks would offer me use of their field to put up a beverage and use their wifi..happy to rent....lol.)


Chris Moulding
 

Hi Simon,

I plotted the antenna pattern today.

I used a strong medium wave station in ground wave range as a source and turned the antenna making signal measurements every 20 degrees.

Results on 160m will be similar only with slightly reduced levels in the nulls.

The unsymmetrical "lump" in the pattern was caused when the antenna was pointing directly at the reflection off the metal clad school building next door about 20m away.

The -3 dB beamwidth is 100 degrees.

On the attached chart the inner circle is the -20 dB ring.

In the design the resistor caused the loop to operate as it's own sense antenna but as the sense antenna works as a vertical it needs some form of earth or counterpoise. It doesn't need much as the earth rod I used was only pushed 6" into the soil so it's possible that say a 1 m length of wire hanging down will also act as a counterpoise. I'll test that tomorrow.

Regarding your comment on a Beverage antenna, I did some work on Beverage antennas a couple of years ago as I was commissioned to build antenna amplifiers for a major European contest group. I searched the internet for Beverage's original articles and found his original report to the A.I.R.E which details all his work after the patent was granted. A lot of the stuff written by amateurs about Beverage antennas is incorrect and they can be used at HF as long as the length is kept to a maximum of 2.5 wavelengths.

I did a demo at the Bolton Wireless Club where we ran 40m of wire out along the car park. It happened to be in direct line with Moscow and we spent the evening listening to radio amateurs on 80m around Moscow coming in like locals!

I've posted all the articles on a web page:

http://www.crosscountrywireless.net/beverage_antenna_amplifier.htm

Regards,

Chris


On 10/11/2020 18:11, Simon wrote:

[Edited Message Follows]

Hi Chris

did you have any time today to do measurements?

also..been thinking..( a bad thing maybe.)..if the directional  loop can not null out the smpsu noise here in the direction i want the antenna to face ( most of the time.) ie nw to usa, then a phasing unit with another standard loop picking up the noise..cancelling out.??? .though i can see this upsetting the radiation pattern abit..

also the earth on the new loop vertical sense wire..what type of earth? A rod in the gnd..or tied to existing radial system etc..
due to my location, the earth could be a long way from loop..( unless mounted on side of house.) even this if on side  I expect will cause issues..6 m vertical wire with 2 m horizontal at best..no way here of having the loop above gutter height and a direct gnd..
electical noise pickup from the earth..will it not make the loop “noisey”??

how about if vertical length at 6+2 is ok combining your neat recent isolated earth solution ( rad com.) 

is there a min or max length of sense wire?? Itching to try it..but to start with would be only 2-3m above gnd..( test.)

Sorry for the questions..simon

(of course all of above would be irrelevant if someone on here in the sticks would offer me use of their field to put up a beverage and use their wifi..happy to rent....lol.)
-- 
Chris Moulding
Cross Country Wireless
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Cell/Workshop: +44(0)7752 391908
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Chris Moulding
 

I hadn't spotted that that reply was going to the group.

Here's a tidier version of the cardioid loop polar diagram I measured today:

I'm working on a web page to show how to make a cardioid loop using a Loop Antenna Amplifier +.

Regards,

Chris