Date   

Re: Loop Types

Tom Seeger
 

Hi Keith. It is a bit confusing isn't it. I've done a few experiments comparing a Moebius loop to a 2 turn coax loop, both from RG-8 cable using an LZ1AQ style amplifier. To be honest, I couldn't find much difference between them. However compared to a single turn, signals below 500 kHz were up a bit. But both the Moebius and 2 turn loops were down somewhat above 6 MHz. So its a trade off. I have also tried single turn 1 mm wire vs 8 mm wire. I think I see a very slight improvement above about 15-20 MHz but its hard to say with changing conditions and a time delay for the change over from one 1 to 8 mm wire. Also played with shielded vs unshielded. I build a setup using RG-8 cable and toggle switches to rapidly change over from one to the other. Again the differences were subtle and in my location, with my type of local noise, I just couldn't tell much difference. So I'd say inconclusive. All of my experiments were with a 1.2 m diameter circular loop. Presently I've settled on a 1 m unshielded loop made from RG-8 using just the shield. All within PVC electrical conduit. Seems to be easy and effective. Hopefully others will chime in with their findings.
Regards Tom


Re: LAA+ FM broadcast interference using SDRplay Bias-T but goes away using 12v Bias-T power inserter?

Simon
 

Hi

No exactly the opposite..Ie more volts the better..( up to a point!)
No more than 13.8v though as more than that and I suspect goodbye transistor..

The gain may increase alittle from 5v to 12v BUT the strong signal handling capability goes up much more in relation to gain.

Do not use ccw 5v amplified tee though ( but at 12v.) a standard tee is all that’s needed.

I run mine at 13.8v from the psu ( fused and common mode choked.)

Simon


Re: LAA+ FM broadcast interference using SDRplay Bias-T but goes away using 12v Bias-T power inserter?

Eric Inloes
 

Hi Simon,

Ah, I figured more voltage would make IMD worse as it would result in higher gain. I guess that's not the case here.

Thanks clarifying that. 


Re: LAA+ FM broadcast interference using SDRplay Bias-T but goes away using 12v Bias-T power inserter?

Simon
 

Eric

Chris answered your question.

To help stop intermod from strong stations the amp likes 12v rather than 5v.

As you have noticed it goes away when using 12v..so may i suggest you use the 12v tee rather than the 5v from your sdr.

This is not a fault with the ccw amp but is down to how the amp works..it is the same with many high end loop amps..they need full working voltage to “ reject” interference from unwanted signals..all my loop amps run at 12v..

Some people can get away with using 5v. Some can not..

Regards Simon g0zen


Re: LAA+ FM broadcast interference using SDRplay Bias-T but goes away using 12v Bias-T power inserter?

Eric Inloes
 
Edited

Hi Chris,

Hum... 
In this case it's just 5V form the SDRplay Bias-T and it's not anything else. Is there perhaps something more going on here? 

I am using a 1m diameter loop of 15.8mm OD copper pipe.

Thanks! 


Web sdr for me till new year..

Simon
 

Some complete @&@8 has put up some ( i hope.) dodgy xmas lights..s9+ all across the bands.makes the existing smpsu noise look silly!

making yet another phaser..To phase this out??

i already hated xmas..anyone got some land they will allow a remote  sdr rx to be sited??

simon g0zen 


Re: How to make a cardioid loop with a Loop Antenna Amplifier +

paul newland
 

Thanks for the input Simon
I'm one step nearer now.
My present iteration of the loop is an inverted delta, which works very well for me, is pretty sturdy and non-conductive, so may the way for me to go.
Best Wishes 
Paul


Re: How to make a cardioid loop with a Loop Antenna Amplifier +

Simon
 

Oh i forgot to add..if buying resistors from ebay or wherever make sure they are NOT Wirewound type..


Re: How to make a cardioid loop with a Loop Antenna Amplifier +

Simon
 

Ideally solder it on..but to try it out an electrical choc block thingy will do .( typically white or black small block with little screws in, used to join cables together in house wiring junction box etc..)

Re making the loop..Chris used am imaginative idea of a “hula hoop”. Just tape wire to it..(frame for loop needs to be non conductive.) so no good tapping wire and resistor to say an ali bike rim.


Re: LAA+ FM broadcast interference using SDRplay Bias-T but goes away using 12v Bias-T power inserter?

Chris Moulding
 

Hi Eric,

For the best dynamic range from the head amplifier it is best to feed the amplifier with 12V via an unamplified Bias T. The base unit running off 5 V USB also has an additional amplifier so this may be over-driving your receiver.

If you are using a 1m diameter loop it will be resonant as a full wave quad loop in the VHF FM band. Make the loop larger or smaller to move the resonant frequency.

Regards,

Chris


Re: How to make a cardioid loop with a Loop Antenna Amplifier +

paul newland
 

Greetings
As the performance offered by this cardioide loop design is so attractive, I am pretty keen to have a go at constructing one.
However, I have a couple of issues that are holding me back. Firstly, I am electronically "challenged" (know nothing) and have never, to my knowledge even seen  a resistor.
Never mind the hands full of thumbs, how would one actually connect the resistor(s) to the wire?
Would an electrical block connector work, or do they have to be soldered together and if so, how does one avoid putting the connection under stress?
Any guidance would be much appreciated.
Best Wishes
Paul


Re: Noise antenna..

Simon
 

Hi Tom

This is not xmas lights but their outside lights..”up lights” on their exterior walls making their house look nice..

Been there for years, but getting worse as time goes by.

Will post a pic of them later..


LAA+ FM broadcast interference using SDRplay Bias-T but goes away using 12v Bias-T power inserter?

Eric Inloes
 

So it seems that there is FM broadcast interference using the SDRplay Bias-T throughout the HF band but it goes away when i use the 12V Bias-T power inserter you include as an option. 

Any ideas as to what's going on here? 


Re: Tips to improve LAA+ Performance?

Eric Inloes
 

Hi all,

RG-58 is finally here and it appears that all the tweaks have improved HF somewhat.

HF conditions are poor now so i'll have to do some more testing.


Re: Noise antenna..

Tom Crosbie G6PZZ
 

Simon,

Local noise has got worse here too in the last couple of weeks due to the proliferation of exterior festive lighting. It’s probably made worse by interior lights adding to the fray.

I don’t know how you approach these neighbours without coming across like a misery guts. I doubt you’ll persuade anyone to turn them off. Not until January anyway.

Perhaps a leaflet could be created that explains just how much interference is being generated by these devices and dropped off at the offending households, with an offer to help reduce the problem.

 

You could also stretch and twist the power leads at dead of night  and break the power connections. Eventually you’ll hit the worst offender….

 

Tom G6PZZ

 

From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of Simon
Sent: 09 December 2020 20:20
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Noise antenna..

 

Nothing then???

ok update..have found source of noise..well almost..its either house A or B. Both directly opposite each other, Both have led up lights on side of house..about 70m sw of me..
will work out which house it is tomorrow..

so need a directional antenna with lots of “gain” compared to say cardioid loop and importantly with no real dx potential..( which also rules out cardioid loop,) to use as noise antenna.

need something that will not receive any dx as once passed though phaser will also null out dx!

any ideas?????

also, which maybe better..how to approach said offender and get them to replace led bulbs..or light sensor ( Which seems more appropriate as noise always there 24hrs a day.noise gets worse as lamps switch on..) 
I thinking tell them the truth, but also suggest interference slowing down their wifi?? I dont mind replacing bulbs etc myself, but I suspect that could be iffy..( legally.)

anyone been here before?? Advice..

thanks Simon 


Re: Noise antenna..

Simon
 

Nothing then???

ok update..have found source of noise..well almost..its either house A or B. Both directly opposite each other, Both have led up lights on side of house..about 70m sw of me..
will work out which house it is tomorrow..

so need a directional antenna with lots of “gain” compared to say cardioid loop and importantly with no real dx potential..( which also rules out cardioid loop,) to use as noise antenna.

need something that will not receive any dx as once passed though phaser will also null out dx!

any ideas?????

also, which maybe better..how to approach said offender and get them to replace led bulbs..or light sensor ( Which seems more appropriate as noise always there 24hrs a day.noise gets worse as lamps switch on..) 
I thinking tell them the truth, but also suggest interference slowing down their wifi?? I dont mind replacing bulbs etc myself, but I suspect that could be iffy..( legally.)

anyone been here before?? Advice..

thanks Simon 


Re: LAA+ Surprisingly good at VHF

paul newland
 

"Because I can I decided to see how the LAA+ performed at VHF when compared to a VHF/UHF discone."

We live around 156M above sea level and I have a good discone above our roofline with a CCW LAA+ mounted with centre about 1M above ground level, beside the house.
There is a local VOR at a distance of 11.5NM from here at 61M above sea level (and over the horizon from here there being hilly ground in between).
Nonetheless, I get a reasonable signal via the LAA+, but unsurpisingly a somewhat stronger one from the discone. (image of CCW reception attached).
However, comparing signal reception on airband when conditions permit, the LAA+ provides a markedly better cleaner signal compared to the discone, which is actually pretty good in it's own right.
So, given a fair shot, I reckon that you'll do pretty well with yours and even with the LAA+ at the bottom of the loop (obviously not ideal for it), I still get some local VHF Marine Band activity (with great clarity).
Best Wishes
Paul


Re: LAA+ Surprisingly good at VHF

Paul Sayer
 

I have a smaller loop at about 70" in circumference.  I can try that as well.


Re: LAA+ Surprisingly good at VHF

Paul Sayer
 

Thanks for your reply. Things to definitely try.

 One thing I have forgotten. The loop is connected via the uTune ports of my Yaesu FTDX1200. That introduces a bit more loss at VHF. Next weekend I will try a direct connection. 

Still very impressive considering the loop is on the ground and not in the air. Plus the cross polarisation loss.

Regards. 

Paul G0VKT 

On Sun, 6 Dec 2020, 17:02 Chris Moulding, <chrism@...> wrote:
Hi Paul,

Thanks for the feedback on your experiments at VHF with the Loop Antenna Amplifier +.

We specify the LAA+ to cover up to 150 MHz due to the low pass filter built into the head unit. In practice it will cover the marine band around 156 MHz with a few dB of loss.

There are two ways that you can improve reception of the VHF marine band with the LAA+.

The first is to check the polarisation of your loop. If the LAA+ is at the bottom of your loop then its horizontally polarised at VHF. For vertical polarisation you need to feed the loop from the side.

The second point is that at VHF the loop is acting as a full wave loop like a quad element. If you make the loop out of wire 1963 mm or 77 inches long it will be resonant on the VHF marine band.

If you try both these changes I'm sure that the loop antenna will out-perform your discone.

Regards,

Chris


Noise antenna..

Simon
 

Looking for ideas ( that i have not already tried,) for noise antenna to feed a phaser..in the attempt to null out a smpsu on 1845-1855khz..
this noise varies in amplitude and frequency depending upon time of day..it originates  from  atleast 100m away at about 210 degrees ( i think.)

I can not null it out enough on the BIG trx mag loop, but can on the active loop array.. Unfortunately until I build the extra loop and delay line the active loop is not suitable for working real  weak ssb on 160m from stateside. ( hence wanting to use the big loop.) The cardioid loop is no better..It has too low an output and also facing  nw will not null out the noise.

so to cancel out the noise on the big loop..

have tried different combinations of active loops..one was successful in that it received the noise same level as the big loop..( this ment did not have to reduce input ftom big loop into phaser, thus keeping sn ok.) BUT the loop in question was also hearing stuff I want to hear, so once feed though phaser cancelled it out!.. so no go..

so..miniwhip?? Short vertical.. OR out of the box thinking.
a.) use ( suitably connected) a street light very conveniently next to front garden hedge..?
B.) low iron railing/ fence around my front garden?
C.) 6m Ali pole holding up end of  dipole?

I like the street lamp  option..high impedance amp from street lamp against earth..

thoughts??

thanks Simon 

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