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Author Topic: LW 150-500KHz Loop, need help...  (Read 1474 times)

Offline Looking-Glass

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LW 150-500KHz Loop, need help...
« on: April 27, 2018, 2347 UTC »
Last week I purchased from PK's Loop Antennas here in Australia a "HD Series Remote Tuned Amplified Long Wave Loop" to try and extend my NDB distances.  The said product covers 150-500KHz.

Assembled all OK and mounted outside on a temporary 11 foot length of pipe, coaxial run from base of loop to tuner box and tuner box via coax with PL-259 to Yaesu FT-2000D base radio.

One sheet of paper came with the product, brief intro to the antenna and assembly instruction, no hints or exercises in using the antenna though and a list of NZ, PNG and Australian NDB beacons... :(

I rang the fellow in Melbourne to advise him it arrived OK in the post undamaged, and mentioned politely his NDB list was way out of date and had errors, he got quite testy about that and had the gall to ask me to update the list for him! Hate to think his response should I have asked for a "exercise sheet" on operating the thing. ::)

Only real instruction on the sheet is: 

*  Tune your radio to desired frequency.
*  Slowly tune the Manual Tune control to the point of strongest reception.
*  Orientate the Loop Antenna to obtain clearest signal: edge-on towards the transmitter is best.

Over the past three days I have had a good fiddle about with it, during the day with local NDB's and at night/early morning when DX distance NDB's are in and the Loop is just not delivering a favourable result with me. I have found that in comparison, my existing 380 feet run of random wire in the trees (despite pulling in noise/crud/spurs etc) out performs the loop by far both local and DX wise.

Operating the Loop Examples:

Tuned to PKS on 242KHz (Parkes NSW) local beacon heard 24 hours for 200kms distance 559 report on wire. Switched to Loop, tuned tuner slowly around no result, went outside and slowly turned Loop in full rotation circle and not a hint of PKS, changed tuner setting, repeated rotation and zero, PKS still 559 on my wire, why nil on the Loop?

Tuned to NF on 260KHz (Norfolk Island) at 1130z a DX beacon for 1,755kms distance 549 report on wire.  Done the above tuning Tuner and rotating Loop slowly in full circle and back again and not a thing from NF, back to wire and NF has came up two spoints to 569 report.

Local beacons during the day:

347KHz  RIC (Richmond military) 74kms distance, wire plus 20dB over, Loop antenna 559 at best after rotation and tuning Tuner.

305KHz  GTH (Griffith NSW) 357kms distance, wire 569 report, Loop antenna, virtually zero.

398KHz  MDG (Mudgee NSW) 127kms distance, wire 429 report, Loop antenna, not found at all, zero result.

In conclusion: with the Loop I would have thought it would have at least dragged MDG Mudgee up a few points on the meter, very disappointed not hearing MDG on the Loop at all, despite careful rotating of the Loop and tuning of the Tuner.

Yes, happy that the Loop has rejected most of the spurs, harmonics, noise and crud across the band, but where is the DX? 

Very disappointed that 260KHz NF on Norfolk Island for 1,755kms distant and near 569 on the wire was not at all detected by the Loop, after all, that is what I bought the thing for was to enhance weak long distance signals.

Maybe I am missing something?  I will put it across to HFU's panel of LW Loop Antenna experts for their valued opinion... :)

« Last Edit: April 28, 2018, 0004 UTC by Looking-Glass »
Hermitage Flat, NSW.

Grid Square:  QF56dm.

Yaesu FT-1000D, Yaesu FT-2000D, ICOM IC-736 HF/50MHz, ICOM IC R75 & Tecsun S-2000 to 450 feet of wire, and a multi band vertical of dubious reliability.

Offline pinto vortando

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Re: LW 150-500KHz Loop, need help...
« Reply #1 on: April 28, 2018, 1426 UTC »
Not familiar with the specific loop antenna you mentioned so looked it up on the internet.  My first impression was that it looked well built but rather small for the LW DX use you desire.
Could find nothing like a schematic or detailed theory of operation or circuit description.  You didn't mention how long the length of the coax from tuner to loop.  Assuming that there is some tuning circuitry (varactors perhaps) at the loop base, a too long cable run to the loop could introduce excessive voltage drop or signal loss.  You also want to make sure that the 9 volt battery is fresh.  The description of the antenna on the manufacturer's site states that the output of the loop is low level and an in-line amplifier may be required.   It looks like the manufacturer does offer an optional control box that contains a LW amplifier for this loop. (Although, my thought is that maybe the best place for the amplifier would be at the loop.)  :-\    Not sure if you have this specific optional box which includes an amplifier or have available another LW amplifier but that could be the missing ingredient necessary to get the most out of the loop. 
Das Radiobunker somewhere in Michigan

Offline jFarley

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Re: LW 150-500KHz Loop, need help...
« Reply #2 on: April 28, 2018, 1508 UTC »
A couple of questions.

1) Is the tuning control a SINGLE turn pot or a MULTIPLE turn pot?

2) How sharply does the loop tune?  Is the tuning extremely sharp (as it should be for a loop of this size) or is it relatively broad?

3) Does the tuning extend beyond the 150-500 kHz range?

Will be thinking about this thru the day.
Joe Farley, Near Chicago
SDR-IQ / R8 / R7
Remote Resonant Loops for HF and LF / ALA 1530
Active 60" Whip / PA0RDT
QSLS appreciated to:    jfarley44@att.net

Offline Looking-Glass

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Re: LW 150-500KHz Loop, need help...
« Reply #3 on: April 28, 2018, 2242 UTC »
Thank you gentlemen for your responses, firstly:

Pinto Vortando: 

Yes, the Tuner unit is an tunable receive amplifier and sits on top of the radio, there is no 9 volt battery, instead it runs through an AC mains adapter, similar to a mobile phone charger, it has one tuning knob only.

The AC powered tuning unit was an optional extra which I purchased in lieu of the 9 volt battery powered unit. 

Coaxial run from the base of the Loop to the FT-2000D via the Tuner amplifier is 10 metres.

jFarley: 


The Tuner unit is a single full rotational turn (to stop point either side) with one tune knob only on face of amplifier tuner box, no meter.

Seems to tune very sharp.

Loop is made for 150-500KHz only and has no variant of that frequency block.

Have it mounted outside (as it's the outdoors model) well away from my garage metal roof on around 10 or so feet of pipe as temp measure.

The Tuner/Amplifier seems to work fine, when you turn the AC power off signals vanish, so it's a key to the Loops full operational requirement.

Last night it pulled in ESL on 349KHz in Victoria for 576kms a strength 569 report, however, on my trusty old wire ESL was 599 plus 10dB over! Very frustrating so far, going to try and find my old ARRL 1990 Handbook and see what it says, if anything, about LW Loop antennas... ;)
Hermitage Flat, NSW.

Grid Square:  QF56dm.

Yaesu FT-1000D, Yaesu FT-2000D, ICOM IC-736 HF/50MHz, ICOM IC R75 & Tecsun S-2000 to 450 feet of wire, and a multi band vertical of dubious reliability.

Offline Josh

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Re: LW 150-500KHz Loop, need help...
« Reply #4 on: April 29, 2018, 1752 UTC »
Can you take the output of the wire antenna and make a few turns near the loop and use both? Then try the loop again and see what's what.
Conveniently located near Vincennes Indiana.

Offline Looking-Glass

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Re: LW 150-500KHz Loop, need help...
« Reply #5 on: April 29, 2018, 2223 UTC »
Josh:  Could do but that would defeat the reason for investing in that Loop as a stand alone LW antenna with supposed greater performance over the wire... ;)
Hermitage Flat, NSW.

Grid Square:  QF56dm.

Yaesu FT-1000D, Yaesu FT-2000D, ICOM IC-736 HF/50MHz, ICOM IC R75 & Tecsun S-2000 to 450 feet of wire, and a multi band vertical of dubious reliability.

Offline pinto vortando

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Re: LW 150-500KHz Loop, need help...
« Reply #6 on: April 30, 2018, 0126 UTC »
IMHO, that 380' wire (especially if coupled to the receiver with a matching transformer or tuner) would be a superior LW DX antenna compared to that small loop.  However, the small size of the loop can be compensated by a properly designed amplifier.  A good choice would be a matched pair of FETs in a balanced configuration placed at the loop itself.  As mentioned in my previous post, was unable to find any info on the specifics of the tuner although you say that your tuner does contain an amplifier.   So, hard for me to comment as to why the loop is performing so poorly.
Das Radiobunker somewhere in Michigan

Offline Josh

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Re: LW 150-500KHz Loop, need help...
« Reply #7 on: April 30, 2018, 1701 UTC »
Josh:  Could do but that would defeat the reason for investing in that Loop as a stand alone LW antenna with supposed greater performance over the wire... ;)

True, but it then becomes a variometer and you can do some interesting tricks with one. You have them, give it a shot and see what turns up.
Conveniently located near Vincennes Indiana.

Offline pinto vortando

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Re: LW 150-500KHz Loop, need help...
« Reply #8 on: May 01, 2018, 1910 UTC »
Very frustrating so far, going to try and find my old ARRL 1990 Handbook and see what it says, if anything, about LW Loop antennas... ;)

Joe Carr's "Loop Antenna Handbook" is a good source.
Das Radiobunker somewhere in Michigan

Offline Looking-Glass

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Re: LW 150-500KHz Loop, need help...
« Reply #9 on: May 02, 2018, 0739 UTC »
Thank you all for your hints and suggestions. I rang the manufacturer yesterday and discussed the issues concerning the Loop and he told me to return it for a full refund.

The manufacturer is building a special tuner unit to be coupled to my 380 feet of wire, which, as he has said, will reduce the crud/noise and harmonics across the band.

This is what Pinto Vortando suggested so the maker is going in that direction, hope it works.

The Tuner Unit is now in the post as advice was received today, thanks again to all who offered comments and support, case now closed... :D

Hermitage Flat, NSW.

Grid Square:  QF56dm.

Yaesu FT-1000D, Yaesu FT-2000D, ICOM IC-736 HF/50MHz, ICOM IC R75 & Tecsun S-2000 to 450 feet of wire, and a multi band vertical of dubious reliability.

Offline pinto vortando

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Re: LW 150-500KHz Loop, need help...
« Reply #10 on: May 03, 2018, 2129 UTC »
Hope your special tuner unit works out...  let us know.
Das Radiobunker somewhere in Michigan

Offline Looking-Glass

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Re: LW 150-500KHz Loop, need help...
« Reply #11 on: May 05, 2018, 0024 UTC »
Pinto Vortando:  The filter arrived in Parcel Post yesterday, managed to quickly hook it up early this morning around 0300hrs local when I got home from work.

380 foot wire plugs into filter. small steel box, PL-259 from wire in, and then filter to FT-2000D, no tuning capabilities on unit.

Seems to have reduced the crud and harmonics from the MW band quite a bit making the NDB's much clearer reception wise.

Have a feeling it may have knocked an 'S' point off the signals, but the band was poor so maybe I am incorrect.

The important test will be performed this evening when the MW harmonics are all over the band just after Grey Line and up until around 1100z when they are at their worst.

He said the cut off for the filter is around 550KHz I think, cannot remember as half a sleep from shift work when he rang. ;D
« Last Edit: May 05, 2018, 0026 UTC by Looking-Glass »
Hermitage Flat, NSW.

Grid Square:  QF56dm.

Yaesu FT-1000D, Yaesu FT-2000D, ICOM IC-736 HF/50MHz, ICOM IC R75 & Tecsun S-2000 to 450 feet of wire, and a multi band vertical of dubious reliability.

Offline pinto vortando

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Re: LW 150-500KHz Loop, need help...
« Reply #12 on: May 05, 2018, 0845 UTC »
Sounds like a low pass filter unit.  Keep the connection from the filter to the receiver as short as possible.
Ideally, use a PL-259 double male adapter to connect the SO-239 on the filter directly to the SO-239 on the receiver.   ;)
« Last Edit: May 05, 2018, 0848 UTC by pinto vortando »
Das Radiobunker somewhere in Michigan

Offline Josh

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Re: LW 150-500KHz Loop, need help...
« Reply #13 on: May 05, 2018, 1726 UTC »
It's tempting to roll your own loops for vlf work.
This paper on loops is very interesting;
http://www.vlf.it/feletti2/idealloop.html
Conveniently located near Vincennes Indiana.

Offline Looking-Glass

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Re: LW 150-500KHz Loop, need help...
« Reply #14 on: May 06, 2018, 2351 UTC »
Josh:  Thanks for that link, interesting Loop antenna, will read it all in its full form when I have time, working permanent night shift has its drawbacks.  Will look at it proper when I get my five days off soon.

Pinto Vortando:  The filter he sent up works well in getting rid of the AM band carriers and assorted harmonics, certainly cleared up the LW band, however, the spurs and buzzing from modern devices such as flat screen TV's and gamer consoles plus computer HD and monitors still comes through.  Not a great deal can be done about that.  The mains lead from the FT-2000D has ferrite beats wrapped around it too,l and is properly earthed.

I ran a series of comparison tests with the filter in and filter out (during the day) and found that it takes one 'S' point off the local beacons when in line with the FT-2000D to the 380 feet of wire. I guess a single 'S' unit in not a huge issue but when dealing with a border line signal it could prove whether one positively idents the signal or not for a claim.

Had a go at it around 0300 local when I came home from work this morning but LW coniditions were very poor with few, if any beacons audible above 1,500kms.  At 2 degrees in the shack I didn't hang around long and went to bed by 0315hrs local.

Incidentally, I found the HF bands 4MHz through to 9MHz near dead with very few signals, no sunspots and the solar season low is certainly affecting DX... :-\
Hermitage Flat, NSW.

Grid Square:  QF56dm.

Yaesu FT-1000D, Yaesu FT-2000D, ICOM IC-736 HF/50MHz, ICOM IC R75 & Tecsun S-2000 to 450 feet of wire, and a multi band vertical of dubious reliability.