Seafix v. Lokata and Logs

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Robert Connolly has sleepless nights, compares two vintage radio direction finding receivers

 

Robert Connolly has sleepless nights, compares two vintage radio direction finding receivers and supplies his list of NDB loggings for a somewhat quieter summer season.

 

 

Following the acquisition and restoration of the 1970’s Seafix handheld marine radio direction finder (RDF), I purchased some months ago, I have now acquired another marine handheld RDF receiver. This time it is a Lokata 7 handheld marine RDF, dating from around 1989/90.

Regular readers will be aware that I have owned one of these for a number of years. However, as I have previously indicated in this column, I had a problem with a small nylon cog in the tuning mechanism that prevented it from changing the frequency; of course, spares are not readily available.

When the opportunity arose to purchase a second-hand Lokata 7 at a sensible price, which came complete with its original headphones and user manual (Fig. 1), I could not resist, especially as the photographs of the item showed it on different frequencies, indicating that it was most probably working.

When it arrived, I found that it was in excellent condition and had not seen a lot of maritime use. At £25 plus postage, it was a little more expensive compared to the Seafix.

However, given its condition and the fact it was complete with working headphones and user manual, still made it a good bargain. I saw another Lokata 7 advertised recently for about £100, seriously overpriced!

The Seafix RDF uses an analogue tuning dial (Fig. 2) requiring some amount of guesswork when tuning; it has a frequency coverage from 200 to (approximately) 425kHz and is powered by 9V DC. It was originally equipped to contain six AA batteries but was later converted to use a 9V DC PP3 type battery.

The Lokata 7 has a digital frequency display (Fig. 3) with tuning in 100Hz steps. Tuning is done with your thumb, using the wheel below the display.

The Lokata 7 also features an internal timer facility, which would have been used in conjunction with the marine NDB beacon chains, operational prior to 1990. The timer is not needed when chasing today’s beacons.

The internal timer switches off the receiver after a certain period of time to conserve battery power. The Lokata user manual states that a set of batteries should last for a season.

Unlike the Seafix, the Lokata does not have a wideband broadcast station selection setting; it is not possible to use it for listening to the shipping forecast. However, the set does have a narrower band setting that may be used to obtain a precise bearing on the signal null.

The headphones are interesting, in that they are using a small speaker in the place where the separation for the earpieces is located. Audio continues from that speaker up through the two air spaced tubes to the earpieces; rather like a doctor’s stethoscope.

 

Comparing Seafix and Lokata

When we are used to high-performance receivers and antennas designed to pull in as much DX as possible, I find that it can always be interesting to back to more ‘basic’ equipment from time to time, as this throws up additional challenges and, sometimes, surprises.

With this in mind, I thought it would be a fascinating exercise to compare the performance of the Seafix and Lokata receivers to see if one or other was more sensitive.

To do this fairly, I decided that both receivers should be used during the same session to reduce any influences caused by propagation variations.

When using a receiver that has a built-in ferrite rod antenna for NDB searching – be it a dedicated RDF or a suitable portable general coverage radio – it is important to remember to ‘swing’ it slowly through 180 degrees on every frequency to eliminate the possibility of missing a beacon that is, possibly, in the receiver’s ‘null’ position. When using this type of equipment, it is always best to operate outdoors and away from as many potential local interference sources as possible.

The comparative listing in Table 1 shows the beacons received by each receiver within their tuning range. As can be seen from the table, the Lokata received several more beacons compared to the Seafix, both during daylight and in darkness. This indicated that it was the more sensitive receiver of the two.

Furthermore, it was easier to use because it has the more accurate digital frequency display. Daylight reception distance was, as expected, very similar on both receivers. Carrying out a similar session during darkness showed the Lokata receiving several additional UK NDBs, not heard on the Seafix unit.

Interestingly the DX signals from 351kHz OV Visby and 421kHz GE Madrid were of similar strength on both receivers. When the darker evenings return, I will wrap up warm and have another play with these receivers.

 

Seasonal Band Conditions

When I ran a daylight-check of the band around Midsummer’s Day, using my main equipment, I not only found the band quite noisy with static and the occasional closer thunder crash, but actual signal strength was also very variable, even for my ‘local’ beacons.

Received signals were quite weak, certainly well below average; however, quite suddenly, conditions picked up and signals became much stronger and clearer. Sadly, this occurred for a minute or so only, before signals were fading out again.

During the hours of darkness, this was no better, and my ears took a severe ‘bashing’ during my session. The handhelds were also affected by this but not to the extent of my main setup.

This left me thinking that I should, maybe, just use the handheld RDF receivers during the summer months.

Interestingly – not being able to sleep one night as I was preparing this column – I decided to have another listen to the band, to see if conditions were any better.

When I started my check around 02.45 UTC, the band was still quite noisy and fading in and out. However just after 03.15 UTC, about an hour before sunrise here, the static and fading suddenly died away, leaving a clear, workable, band. Static is, of course, caused mainly by lightning discharges in the atmosphere and is at a minimum around sunrise.

 

DGPS Correction Stations

Differential Global Positioning System (DGPS) correction stations are enhancements to the US Global Positioning System (GPS) and Russian GLONASS GPS network.

These provide improved location accuracy, from the 15m (nominal) GPS accuracy to about 10cm, in case of the best implementations. Accurate navigational position information is vital to shipping, especially in crowded sea areas close to ports in poor visibility.

The closure of the Decca navigation system in 2000 resulted in a move to GPS maritime navigation and entailed the requirement for greater position accuracy.

Therefore, it is no accident that many DGPS stations in Europe are located at lighthouses that were former marine radio NDBs, in the frequency band of 283 - 325kHz.

This is the main reason why I include these in this column from time to time. In the UK, the only exceptions to this are the stations located at Stirling and Wormleighton, both of which were former Decca navigation transmitter stations in a previous life.

Each DGPS signal employs a network of fixed, ground-based, reference stations to broadcast the difference between the positions indicated by the GPS satellite system and known fixed positions. Stations broadcast the difference between the measured satellite pseudo ranges and actual (internally-computed) pseudo-ranges. Receiving stations may correct their pseudo ranges by the same amount.

The digital correction signal is broadcast locally over ground-based transmitters, Fig. 2 shows a received example. To decode the signal, you need to have your receiver and PC sound card connected, preferably using the input socket of your sound card, although as some laptop sound cards only have the microphone input socket, this will suffice.

 

Decoding Software

You will require software to decode the audio signal. I use COAA’s DSC Decoder, downloadable from this website:

www.coaa.co.uk/software.htm

There is a 28-day free trial before this software needs to be registered or stops working. The other piece of software I use is MultiPSK, downloaded from this URL:

http://f6cte.free.fr

This excellent piece of software has its own DGPS decoder within the professional modes section. An unregistered version will run for about ten minutes of decoding DGPS signals. After this, you have to restart the programme if you wish to continue or register the software to achieve no such restriction.

DGPS transmissions use several different signal types, as follows:

Type 1 (or Russian Type 31) signals provide corrections for a full set of satellites.

Type 9 (or Russian Type 34) signals transmit sub-set differential corrections.

Type 7 (or Russian Type 35) messages contain Radio Beacon Almanacs.

Integrity monitoring within the header of Type 1 or Type 9 messages indicates the health status of the reference station; healthy, unhealthy or unmonitored. Reference stations and transmitters have assigned numbers for broadcast stations and reference stations.

Number blocks are allocated to all countries. In the case of the UK, station reference numbers (Station ID in the table) run from 440 to 449, and station transmitter numbers (BC in the table) from 680 to 699.

The transmitted signal always includes the reference station number.

The example in Fig. 3 is from Point Lynas, with a transmitter reference number of 682.

The purpose of the transmitter reference number is to indicate which transmitter the station is using, in those cases where stations have two transmitters available.

It is not known for certain whether Russian DGPS stations use the station ID or transmitter reference number or, perhaps, utilise the same number for both elements, as shown in the table.

There are two DGPS transmission speeds available. The most common one is 100bps; this is used by most European stations. A speed of 200bps is used in Norway, Portugal and the United States.

Software like MultiPSK will scan between the two speeds automatically if that option is selected, and manual selection is also available. You will often find a clue in the software waterfall display as the 200bps station transmission display looks wider compared to the 100bps.

DGPS signals are not confined to coastal areas. The system also covers some inland waterways such as the Danube. Table 2 has details of DGPS stations I received recently.

As in the case of NDB DXing, there are reception variations depending on propagation conditions, although many close European stations are received regularly during darkness, with some also present during daylight.

 

Summer Logging

While the summer months are not a great time for NDB chasing, they provide an opportunity to carry out routine maintenance on your antennas, feed lines, etc. This could save you potential damage caused by winter storms that may require you to get ladders out and climb up to roof level to prevent possible damage to your property. Trust me, when it is windy on the ground, the higher up you go, the windier it becomes, making the job dangerous.

Tony Stickells, who normally supplies an extensive log for this column, contacted me to advise that, since March, he has been plagued by local interference on a 24/7 basis that was totally wiping out the NDB band at his location.

When Andy Thomsett submitted his logs, he mentioned just how un-spectacular conditions were, concurring with my opinion regarding contemporary reception conditions.

However, the summer can throw up the occasional surprise, if conditions are suitable. For instance, I did find that some stations from Morocco made their existence known.

On a brighter note (as it were) by the time you read this the daylight hours will be shortening, and the winter season will be just around the corner. We can only hope that conditions will improve.

Table 3 details our loggings for the summer period. Until then, good hunting.

 

DXers for Table 3:

NDB reception this period during daylight (*).

A: Robert Connolly, Co. Down, Northern Ireland. NRD 525, Datong AD370 active antenna + Timewave DSP+9.

C: Andy Thomsett, Southwest England, ELAD FDM-DUOr and PA0RDT Mini-Whip.

 

Table 1 Seafix versus Lokata RDF receiver reception comparison

 

 

 

 

Freq

Ident

Location

Country

Seafix

Seafix

Lokata 7

Lokata 7

kHz

 

 

 

Daylight

Night

Daylight

Night

316.0

OE

Dublin

Ireland

ü

ü

ü

ü

319.0

VAR

Stavanger

Norway

ü

328.0

CL

Carlisle

England

ü

ü

ü

ü

328.5

EGT

Londonderry

N. Ireland

ü

ü

ü

ü

334.0

GMN

Gormanstown

Ireland

ü

ü

ü

ü

337.0

MY

Myggenaes

Faeroes

ü

337.0

WTN

Warton

England

 

 

ü

ü

340.0

HAW

Hawarden

Wales

ü

ü

ü

ü

347.0

NQY

Newquay

England

ü

ü

349.5

LPL

Liverpool

England

ü

ü

ü

351.0

OV

Visby

Sweden

ü

ü

352.0

NT

Newcastle

England

ü

355.0

PIK

Prestwick

Scotland

ü

ü

ü

ü

359.0

RWY

Ronaldsway

Isle of Man

ü

ü

ü

ü

361.0

CFN

Carickfinn

Ireland

ü

 

364.0

SLG

Sligo

Ireland

ü

ü

368.0

WTD

Waterford

Ireland

ü

ü

ü

378.0

KLY

Killiney

Ireland

ü

ü

ü

ü

382.0

LAR

Arruda

Portugal

ü

387.0

CML

Clonmel

Ireland

ü

ü

ü

ü

395.0

LAY

Islay

Scotland

ü

397.0

OP

Dublin

Ireland

ü

ü

ü

ü

399.0

NGY

New Galloway

Scotland

ü

ü

ü

ü

402.5

LBA

Leeds

England

ü

420.0

HB

Belfast City

N. Ireland

 

ü

ü

ü

421.0

GE

Madrid

Spain

 

ü

 

ü


Table 2: Recently received DGPS stations

 

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Freq

Stat ID

BC Ref

Bitrate

Station

Country

D/N

284.0

430

660

100

Mizen Head

Ireland

D

285.5

443

693

100

Stirling

Scotland

D

286.5

339

469

100

Porquerolles

France

N

286.5

513

793

200

Skomvær

Norway

N

287.5

454

715 / 716

100

Torshavn

Faeroes

N

288.5

435

670

100

Tory Island

Ireland

D

289.0

351

502

100

Cabo Mayor

Spain

N

289.5

451

700

100

Hammerodde Lt.

Denmark

N

290.0

452

705

100

Blavandshuk Lt.

Denmark

N

290.5

447

687

100

Flamborough Hd.

England

D

291.0

439

691

100

Wormleighton

England

D

291.5

445

685

100

Sumburgh Head

Scotland

N

292.0

460

720

100

Holmsjö

Sweden

N

293.0

432

665

100

Loop Head

Ireland

D

293.5

494

764

100

Iffezheim

Germany

N

294.0

428

428

200

Vlieland Lt.

Netherlands

N

295.0

850

850

200

Obříství

Czech Rep

N

295.5

444

684

100

Butt of Lewis

Scotland

D

296.0

453

710

100

Skagen West

Denmark

N

296.0

354

508

100

Cabo Finisterre

Spain

N

297.0

446

686

100

Girdle Ness

Scotland

N

297.5

442

682

100

Point Lynas

Wales

D

298.0

468

734

100

Nynäshamn

Sweden

N

298.5

492

762

100

Dune Helgoland

Germany

D

299.0

330

460

100

Héauville

France

D

299.5

448

688

100

North Foreland

England

D

299.5

463

726

100

Skutskär

Sweden

N

301.0

510

820 / 790

200

Halten

Norway

N

301.5

404

604

100

Turku

Finland

N

302.0

426

652 / 653

200

Gilze Rijen

Netherlands

N

302.0

359

518

100

Cabo de Palos

Spain

N

302.5

490

760

100

Koblenz

Germany

N

303.5

493

763

100

Zeven

Germany

D

304.0

503

783 / 813

200

Lista

Norway

D

304.5

388

468

100

Cap Bear

France

N

304.5

535

535

200

Klaipeda Rear Lt.

Lithuania

N

305.5

341

482

200

Sagres

Portugal

N

306.0

441

681

100

Lizard

England

D

307.0

334

464

100

Les Sables-d'Olonne

France

N

307.5

440

680

100

St Catherine's Pt. Lt

England

D

308.0

491

761

100

Groβ Moordorf

Germany

D

308.5

332

462

100

Point de Buis

France

D

309.0

333

463

100

Pen Men

France

N

309.5

449

689

100

Nash Point

Wales

D

310.0

336

466

100

Cap Ferret

France

D

310.5

500

780 / 810

200

Færder

Norway

N

311.5

340

480

200

Cabo Carvoeiro

Portugal

N

312.0

420

640 / 641

200

Oostende

Belgium

D

312.5

425

650 / 651

200

Hoek Van Holland

Netherlands

D

313.0

505

785 / 815

200

Utsira Lt.

Norway

N

313.5

496

766

100

Mauken

Germany

N

313.5

366

532

100

Cabo San Sebastián

Spain

N

314.0

507

787 / 817

200

Utvær Lt.

Norway

N

314.5

495

765

100

Bad Abbach

Germany

N

 

Table 3: Summer 2018 NDB DXing Logs

 

FREQ

C/S

LOCATION

COUNTRY

DXer

267.0

CNU

Marrakech

Morocco

A

274.0

SAL

Ilha Do Sal

Cape Verde

A

277.0

CHT

Chiltern

England

A

316.0

OE

Dublin

Rep. of Ireland

A* B

318.0

BPL

Blackpool

England

A*

319.0

VAR

Varhaug

Norway

A

321.0

STM

Scilly Isles

England

A B

322.0

TLN

Hyères

France

A

322.0

RL

La Rochelle

France

A

323.0

WPL

Welshpool

Wales

B

325.0

AST

Asturias

Spain

A

328.0

CL

Carlisle

England

A*

328.0

HAV

Haverfordwest

Wales

B

328.5

EGT

Londonderry

N. Ireland

A*

329.0

JW

Jersey

England

B

331.0

GLW

Glasgow

Scotland

A*

331.0

GST

Gloucester

England

B

332.0

OY

Aldergrove

N. Ireland

A*

334.0

GMN

Gormanstown

Rep. of Ireland

A* B

335.0

WCO

Westcott

England

B

337.0

EX

Exeter

England

B

337.0

MY

Myggenaes

Faeroes

A

337.0

WTN

Warton

England

A* B

338.0

FNY

Doncaster

England

A*

338.0

GU

Brest - Guipavas

France

B

339.0

BIA

Bournemouth

England

B

340.0

HAW

Hawarden

Wales

A*

341.0

EDN

Edinburgh

Scotland

A

342.0

LL

Leirn

Norway

A

342.0

VLD

Valladolid

Spain

A

342.5

NWI

Norwich

England

B

343.0

YVL

Yeovil

England

B

345.0

CSD

Daouarat

Morocco

A

345.0

LN

Lannion

France

B

345.5

CF

Čáslav

Czech Republic

A

346.0

LHO

Le Havre

France

B

347.0

NQY

Newquay

England

A* B

347.5

TD

Teesside

England

A

348.0

CL

Cahors - Lalbenque

France

A

349.5

LPL

Liverpool

England

A*

350.5

ROT

Rotterdam

Holland

A

351.0

DSA

Dieppe

France

B

351.0

OV

Visby

Sweden

A

351.5

PLA

Pula

Croatia

A

352.0

ENS

Ennis

Rep. of Ireland

A

352.0

NT

Newcastle

England

A

352.0

WOD

Woodley

England

B

353.0

SB

St. Brieuc

France

A B

354.0

MTZ

Metz

France

A B

355.0

PIK

Prestwick

Scotland

A* B

356.0

WBA

Wolverhampton

England

A*

357.0

LP

Cholet

France

A B

358.0

BRS

Biscarosse

France

B

358.0

LT

Le Touquet

France

A B

359.0

LOR

Lorient 

France

B

359.0

RWY

Ronaldsway

Isle of Man

A* B

361.0

CFN

Carickfinn

Rep. of Ireland

A

361.0

NB

Bordeaux 

France

B

363.0

PI

Poitiers

France

B

364.0

KNK

Connaught

Rep. of Ireland

A*

366.0

UTH

Uthaug

Norway

A

368.0

WTD

Waterford

Ireland

A* B

368.5

WHI

Whitegate

England

A* B

370.0

CUL

Culdrose

England

B

371.0

STR

Sintra

Portugal

A

372.0

ODR

Odderøya

Norway

A

374.5

ANC

Ancona 

Italy

A

376.0

BJA

Beja

Portugal

A B

378.0

KLY

Killiney

Rep. of Ireland

A* B

380.0

CBL

Campbelltown

Scotland

A* B

380.0

FIL

Horta

Azores

A B

382.0

LAR

Arruda

Portugal

A

382.0

SBG

Salzburg

Austria

B

384.0

SLG

Sligo

Rep. of Ireland

A* B

385.0

WL

Walney Island

England

A*

387.0

CML

Clonmel

Rep. of Ireland

A* B

388.5

CDF

Cardiff

Wales

B

389.0

CP

Lisbon

Portugal

A B

390.0

DR

Dinard

France

B

391.0

BV

Beauvais - Tillé

France

B

393.0

BD

Bordeaux

France

A

394.0

DND

Dundee

Scotland

A*

395.0

FOY

Foynes

Rep. of Ireland

A* B

395.0

LAY

Islay

Scotland

A*

397.0

OP

Dublin

Rep. of Ireland

A* B

398.0

MT

St-Nazaire / Montoir

France

B

398.0

OK

Connaught

Rep. of Ireland

A*

399.0

NGY

New Galloway

Scotland

A* B

400.0

AG

Agen

France

B

401.0

COA

La Coruña

Spain

A

401.0

LA

Laval

France

B

402.5

LBA

Leeds

England

B

404.0

LRD

Lleida

Spain

A

404.0

MRV

Merveille

France

A B

406.0

TW

Toulouse

France

A

406.5

BOT

Bottrop

Germany

B

410.0

C

La Coruña

Spain

A

414.0

BRI

Bristol

England

A* B

415.0

TOE

Toulouse

France

A

417.0

AX

Auxerre

France

B

417.0

SNO

Santiago

Spain

A

418.0

MK

Calais

France

A B

419.0

EMT

Épinal

France

A

420.0

HB

Belfast City

N. Ireland

A* B

421.0

BUR

Burnham

England

B

421.0

GE

Madrid

Spain

A B

424.0

PHG

Phalsbourg - Bourcheid

France

B

425.0

EVR

Évora

Portugal

A B

426.0

CTS

Castets

France

B

427.0

RY

Royan

France

B

428.0

BST

Lanvéoc 

France

B

428.0

CTX

Châteauroux

France

A B

432.0

PRD

Peyrehorade

France

B

433.5

HEN

Henton

England

B

444.0

NRD

Inowrocław

Poland

A

 

 

This article was featured in the September 2018 issue of Radio User