Date   

Re: Covid..and making phased loop antenna array..

paul newland
 

On Mon, Jan 4, 2021 at 04:25 PM, Chris Moulding wrote:
At present I'm looking at designing a very high performance loop antenna amplifier. The original Loop Antenna Amplifier was originally meant to be a better low cost alternative to the MLA-30 but due to customer pressure I improved it to become comparable in performance to the Wellbrook and Bonito antenna amplifiers.

With the new design I'm starting from scratch using the best amplifier devices, filtering, weatherproofing and Cat5 interconnecting cable. The first prototype is running with the expected performance improvements. I expect to have the first batch ready in a month or two.







G'day Chris
If you get to see this, what might be the benefits of this new design over the LAA+ used outside?
The LAA+ works very well, but I must assume that there are advantages to be had with the new version, or you probably wouldn't make it.
Best Wishes
Paul


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

Simon
 

Hi Chris and everyone.

hope you are all well?

my initial evaluation of this loop gave me poor results..ie very little signal output..but I am not one to give up.I expect was hoping for a miracle antenna!! ( was only 1m dia single loop.)

After finding the original papers on this it suggests ( but gives no values.) of using inductance and not resistance in the loop ( directly above feed point.)

I ask please for more info..as why 110r used? Does this value need to be altered if loop has higher or lower inductance/ size etc..( i wish to try to use my quad 1m square loop.( total area 4m)

why a resistor and not an inductor?( as per original paper)

I ask as still on a quest to make the best  rx loop array I can here..  ie possibly phasing cardioid loops ( if i can get them to work to my satisfaction..)

My delay line 2 quad loop array is working well, i can get a good f/b ratio, but still struggle to hear USA on 160m ssb.. looking for better!! ( though it trounces the single quad loop!) 

please excuse my questions..all my rf knowledge is home learnt.. (did mechanical and electrical at uni..) so always on a learning curve re rf..( though been 40 yrs now since passed rae!  Getting old...)

regards..stay well Simon g0zen 


Re: New product...HF Antenna Isolator

Simon
 

That should tx well..you may well need a different rx antenna depending upon location and noise..Dont forget if using a fibreglass pole one can make it multiband..( 10-40m) very easily.

Ie a Chris made loop preamp etc..

Sure you have that in hand though..


Re: New product...HF Antenna Isolator

Andy.g4vcn@...
 

Thanks Chris


Re: New product...HF Antenna Isolator

Andy.g4vcn@...
 

Sorry, a quarter wave vertical :o)


Re: New product...HF Antenna Isolator

Andy.g4vcn@...
 

Hi Simon, Well just to test the loop counterpoise out I was going to try 40m,  My garden is too small for a proper radial system but a loop counterpoise would be easily achievable.
Cheers A

 


Re: New product...HF Antenna Isolator

Simon
 

Hi

What vertical you thinking of putting up?
For what bands I wonder?

Simon g0zen


Re: New product...HF Antenna Isolator

Chris Moulding
 

Hi Andy,

The link to a PDF of the article is:

www.crosscountrywireless.net/202010%20loop%20counterpoises.pdf

Regards,

Chris


Re: New product...HF Antenna Isolator

Andy.g4vcn@...
 

Hi Chris,  I have a limited space for a vertical with radials.
I have seen a YouTube video of a chap using your HF antenna Isolator (I think) to feed a Ground Loop Radial replacement system.
Said chap mentions that theres an article in Radcom on the subject but sadly I don't have it.... Do you have a PDF you could make available?
Many thanks in anticipation Andy..


Re: Covid..and making phased loop antenna array..

Simon
 

Hi again..

Updates..

Re coupling from mag loop to rx loop array..

Sorted!! ( for now.)

Was playing around on 40m..testing directional array vs full size inverted v vs 40m big mag loop vs other rx loop..

Interesting..and rather good! Hearing yb ja zl on directional loop array and not on others..ok not strong..s5.. but better than in noise.

What i noticed was no coupling from 40 mag loop..( again very h q antenna.) 40 mag loop is also real close to rx array..but not in line.


With this in mind i rotated 160-80m mag loop from nnw to w..so now not directly inline with closest rx loop..( was 1m away, now 2m.)

Coupling gone..result!! Now background noise floor on rx loop array s1-2..hearing many more stations..all well above noise floor here in london..ie ok lz la ea9 iz9 etc..( depends upon loop array direction.) no dx on 160m this eve.

Also preamps seem to be rf ok..as in tx 400w from loop no blown up sdr or preamp.

CHRIS please make a passive delay line..to go with your new preamp..or atleast make one to play with.quite stunning..make it 4 directional..

Mag loop simon ( happy except for m in law.) pls wish her well if you believe in the god thing..she does (very very Irish.)...( afraid i dont.)

Her name is Theresa..

Thank you.


Re: Covid..and making phased loop antenna array..

Simon
 

Hi

From researching alot on this..shielded vs unshielded...

From what I have found..shielded..but this is for LF work..not hf..all aimed at 160-40m max.

As Chris says ..OUTSIDE grade cable only..solid copper wires only..( one can buy cu platted ali..its cheaper..but a no no.)

If you have zero common made interference on your setup then i dont see the point in changing..

Here at my qth the is difference is alot!

Been comparing my “ old “ 4 square loop ( coax) with the new phased 2x 4 square loops..( cat5e.)

Noise on cat5e loops 10ish db down.thats with them switched to omnidirectional..( to try to be fair.) the noise i refer to is local man made crap..the coax feed loop has ALOT of ferrite on it..

I live in high noise urban area..maybe in a quiet out in the sticks area no difference???

Nothing is perfect..the cat5e takes more work to setup..espically if one has to mod existing equipment....its fragile and the stupid little wires like to break!

As stated by me..I DO not care about hf..max frequency i use loops for is 7mhz..all i care about is reducing the noise pickup on my loops and now making directional and low angle..so regards to unshielded shielded that maybe is a preference one has to make..note one does NOT connect shield to preamp, leave floating at that end..(if you go that route.)

Nice interesting thread..

Simon..


Re: Covid..and making phased loop antenna array..

Chris Moulding
 

Hi Tom,

The ethernet cable I used and used to supply with active loop antennas was an outdoor grade unshielded cable. Normal indoor ethernet cable will not last long with UV and rain water.

i often used it laid on the floor or buried just below the grass.

Attaching it to a metal support structure doesn't have any effect as it affects both pairs of the twisted pair equally so if the cable is correctly terminated in a 100 ohm impedance it cancels out any interference or noise coupled from from the metalwork.

Any excess cable can be coiled up. We used to buy the cable in 305m drums. For testing I fixed connectors on each end to measure the cable loss and isolation between the twisted pairs. From memory the loss at 30 MHz over a 305m drum was 10 dB.

Regards,

Chris


Re: Covid..and making phased loop antenna array..

Tom Seeger
 

I currently have 2 passive Lankford antennas and 2 active loop antennas. All are fed with quad shielded RG6 cable. I have the usual line chokes and ground rods etc. Due to their various locations I've buried 2 coax cables, 1 is hanging in the air from house to a tree, and another is tightly attached to my rain gutter and most of the way up a TV tower. I've never used ethernet cable for RF so I have some questions.
1/ Can it be buried directly under the grass top soil like RG6?
2/ Will attaching it to a metal rain gutter or tower affect its performance or induce noise?
3/ Chris Moulding's active dipole document recommends against shielded RJ45 cable. I'm mainly interested in NDB DX and lower HF reception, so would shielded ethernet cable be better in my case?
4/ If using a standard 30m pre-made cables do you just coil up the excess at the antenna or the shack?
Thanks in advance. Tom


Re: Covid..and making phased loop antenna array..

Simon
 

David

The -140 is with the powered preamps off, but with all the cables still connected..
This was done to see how much noise pick up the cable has..ie zero!

If i do the same but using coax it’s certainly not -140!!

With preamps on s1-3 noise ( last night.) This is east london qth.

Still defo getting coupling to main tx mag loop though..Not alot, but visable on sdr..

So looks like rx loops going to front of house..problem is one will be literally on side of house..not ideal..will test just one in front of house to check noise is ok..

All tests 160m..

Simon


Re: Covid..and making phased loop antenna array..

g13flat@gmail.com
 

Or just see if you can get some camo tape or scrim netting. 


On Tue, 5 Jan 2021 at 12:43, David Cutter via groups.io <d.cutter=ntlworld.com@groups.io> wrote:
Simon

I'm staggered by your results and you must have some local magic going on to get a noise floor of -140dBm, don't change a thing, you're in a sweet spot.

BTW if you can't hide your loops you could try some simple camouflage, eg light grey mat car paint primer with the odd splash of mat pale green or brown to break up the straight lines. If you can raise and lower it so it's not always visible, your neighbours can have little to complain about.

Good luck, I'm looking forward to the next episode on this channel.

David G3UNA


> On 05 January 2021 at 11:47 Simon <ohhellnotagain@...> wrote:
>
>
> Ahhhh so it does..
>
> Since i only interested in 160-40( max.) I have not seen this ..ie no losses noticable here.( cable  runs are shortish.)
>
> I shall carry on using the screen..zero common mode interference..dont want to upset that..
>
> Simon






Re: Covid..and making phased loop antenna array..

David Cutter
 

Simon

I'm staggered by your results and you must have some local magic going on to get a noise floor of -140dBm, don't change a thing, you're in a sweet spot.

BTW if you can't hide your loops you could try some simple camouflage, eg light grey mat car paint primer with the odd splash of mat pale green or brown to break up the straight lines. If you can raise and lower it so it's not always visible, your neighbours can have little to complain about.

Good luck, I'm looking forward to the next episode on this channel.

David G3UNA

On 05 January 2021 at 11:47 Simon <ohhellnotagain@gmail.com> wrote:


Ahhhh so it does..

Since i only interested in 160-40( max.) I have not seen this ..ie no losses noticable here.( cable runs are shortish.)

I shall carry on using the screen..zero common mode interference..dont want to upset that..

Simon


Re: Covid..and making phased loop antenna array..

Simon
 

Ahhhh so it does..

Since i only interested in 160-40( max.) I have not seen this ..ie no losses noticable here.( cable runs are shortish.)

I shall carry on using the screen..zero common mode interference..dont want to upset that..

Simon


Re: Covid..and making phased loop antenna array..

Ian Pawson G0FCT
 

Simon,
Your question is answered in the manual Chris has provided. The manual states:

"Following tests with different types of cable we don't recommend the use of shielded cable as the extra capacitance caused extra losses at higher frequencies."

73,
Ian G0FCT


Re: Covid..and making phased loop antenna array..

Simon
 

Hi Chris

Question

Why do you not recommend using of the screen in cat5e?

I am using..its screened at rx delay line controller/ psu / rx out to rig——- screen connects to passive delay line—— follows out to the preamps..BUT IS NOT connected at preamps..ie left floating..

I here at my qth in london have a genuine -140 dbm plus noise floor with preamps off..( measured on elad duo trx..sdr console software.) ie noise floor of rx..so no common mode interference induced.thats with circa 50m of cat5e running around garden and front room( much to Mary’s annoyance!)


I cannot see it getting any better with no screening..only worse..

Please explain why you recommend this..genuinely interested!!( every db helps!!)..i am not using rj45’s but hard wired in via screwterminals..( no rj 45 crimper to hand and no way of getting out to but one ..bloody covid self isolation!)


I am using very high quality german made cat5e..( ebay bargain.£20 for 300m!!..result!)

Also my preamps are grounded to rf gnd via copper stake..this is via diode protection and 100k resistor.( mainly for qro tx protection.) ( at input to loop on preamp.)
See diagram in email..

Stay well Simon


Re: Covid..and making phased loop antenna array..

Karl Thompson
 




On Mon, 4 Jan 2021 at 18:55, Craig
<topnut1@...> wrote:

Thank you Chris

On 1/4/2021 12:39 PM, Chris Moulding wrote:
Here is the Operating Manual for the HF Active Antennap i designed back in 2015 for the RSGB Noise Measurement program.

It has some information on the Cat5 cable wiring and the RJ45 connectors. Note in the manual the original connectors needed rounding slightly with a file. I later sourced a better cable gland that would allow a unmodified RJ45 connector through and still compress to make a watertight seal on the rubber sleeve on the cable.

The link to the Operating Manual is: http://www.crosscountrywireless.net/CCW_HF_Active_Antenna_Operating_Manual.pdf

Regards,

Chris

241 - 260 of 7736