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MEGA TEST -- HIGH-PERFORMANCE LNBS

 

INTRO

One of the simplest ways to improve the performance of your satellite system is to upgrade the dish electronics. We've been looking at four LNBs, for tweaking Astra and multi-satellite systems

 

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Low noise block converters or LNBs have a hard life; they operate around the clock, in extremes of temperature and humidity, and although they generally have a very low failure rate they do not last forever. Some fail as they get older, others suffer a drop in performance, resulting in poor picture quality. Some were of questionable quality to begin with, and swapping the original LNB for a newer type can have a significant effect; older, less efficient receivers also work better with a less noisy signal. Those living in borderline signal areas may benefit by fitting a high-performance LNB, rather than increasing the size of their dish, and anyone considering adapting their system for twin satellite operation will need an extra LNB, preferably a high quality one as it's a demanding application.

 

One word of caution; if you are troubled by an increase in sparklies, and your picture is getting steadily worse, don't rush out and buy a new LNB just yet, it could be that the dish needs re-aligning, or moisture has penetrated the connectors or the cable, it could even be a fault in the receiver, so check all of these things first.

 

We've been comparing four single-band, voltage-switched LNBs typically selling for between 50 and 100. They're all suitable for upgrading small (60-80cm) fixed dish systems; they can also be used on motorised or multi satellite systems but for maximum coverage and flexibility many users prefer dual or triple-band models. They all have noise figures, between 0.7 and 1.2dB. Don't be put off by the techno-jargon, the noise figure is simply a way of expressing how much noise has been added to the signal after it has passed through the LNB, so the lower the number the better. The noise figure has a direct bearing on the quality of the picture and in particular the amount of impulse noise, or sparklies.

 

The majority of LNBs supplied with budget and mid-market Astra systems have noise figures between 1.5 and 2.0dB, though they're getting better all the time, and 2.2 to 2.5dB was considered good not so long ago. To give us some kind of benchmark to work with we've compared our sample LNBs with a Marconi 'Blue Cap', with known performance. All of the LNBs were tested using a modified 60cm offset metal dish, connected to a Pace IRD and viewed on a Hitachi 'Opus' TV. Here's what we found.

 

MASPRO SCE-1

Definitely the odd one out, the Japanese-made SCE-1 is short black cylinder 100mm long with a diameter of 63mm; this is an unusual size and is not seen very often on small fixed dishes. However, undaunted by the challenge we managed to locate a suitable bracket and yes, it was worth the additional time and effort required to align the unit.  The quoted noise figure of 1.2dB is born out by the better than average performance which was clear to see. Checked against our reference blue cap, on a deliberately mis-aligned test-rig the SCE-1 managed to reduce the number of sparklies on UK Gold, one of the chosen Astra test channels, by well over 50%, the noise present in highly saturated colours was also improved significantly. Overall a very good result but in view of the unusual mounting requirements it probably wouldn't be suitable for a dual-LNB installation as none of the extension arms we've seen have a large enough mounting bracket.

 

Address:   MASPRO UK Unit 6, Drury Way Industrial Estate, Laxcon Close,

Neasden, London NW10 OTG

 

Tel: 081-451 6766

 

Verdict: (out of 5)

Performance ****

Ease of installation ***

Buying Satellite Rating  XX%

 

Throat dia: 63mm

Quoted noise figure: 1.2dB

 

 

MARCONI SOLO 1

The Solo is now Marconi's mainstay LNB for Astra and other FSS (fixed satellite services) systems, since the famous 'blue cap' went out of production a few months ago. Incidentally, the first blue caps rolled off the UK production line back in 1989, last year Marconi received a coveted Queens Award for Industry for manufacturing LNBs. Solo 1 has a 40mm throat and a conventionally shaped feedhorn, so it will directly replace the commonest types of LNB, including, or course, the blue cap.  The quoted noise figure for the Solo 1 is 'less than 1dB', a figure that was born out in our tests where it emerged as the joint winner, along with the Protel (Continental) model. Against our standard reference LNB the difference was clear to see, especially on UK Gold, which on our mis-aligned antenna, was almost unwatchable, with a significant number of  sparklies; when replaced by the Solo the sparkly count dropped to almost zero, with a noticeable improvement in colour reproduction, especially in areas of high saturation.

 

Address:  MARCONI  ELECTRONICS LTD Elstree Way, Borehamwood

Herts WD6 1RX

 

Tel: 081-953 2030

 

Verdict: (out of 5)

Performance *****

Ease of installation *****

Buying Satellite Rating  95%

 

Throat dia:   40mm

Quoted noise figure: <1dB

 

 

 

PHILIPS

This LNB is manufactured by Philips in their Crayfeld factory, it is also supplied to other companies, including Channel Master and appears under a number of other guises. This particular model is supplied as standard with Philip's RAST-256 package, which includes the STU-802 tuner. Although operationally similar to most other FSS LNBs, it is a slightly unusual design in that it uses a 'polyrod' lens, instead of a conventional feedhorn. The polyrod lens, which was developed by Marconi,  increases the efficiency of  the antenna by ensuring that more of the signal ends up inside the LNB. Another consequence of this design is a significantly narrower throat, around 25mm, so it will not fit the majority of dishes without a new or modified feed bracket, unless it's replacing a similar-sized LNB. On some dishes this type of LNB may require a little more effort during alignment, to get the best from it. The quoted noise figure for this LNB is 1.2dB, which is not the lowest figure in this survey, but still appreciably better than most standard LNBs. In our tests it performed well with a marked reduction in sparklies, compared with the blue cap reference. Not, perhaps such a dramatic improvement as the other models but still a worthwhile increase in picture quality over most standard LNBs.

 

Address: PHILIPS CONSUMER ELECTRONICS, City House,

420-430 London Road,  Croydon CR9 3QR.  

 

Tel: 081-689 4444

 

Verdict: (out of 5)

Performance ***

Ease of installation ***

Buying Satellite Rating  85%

 

Throat dia:   25mm

Quoted noise figure: 1.2dB

 

 

PROTEL

A popular and widely-used LNB, badged Protel but manufactured by Continental who also supply the LNBs used in a number of packaged systems. Physically this is the smallest of the four LNBs we've looked at, though the front-end is a familiar shape with a conventional circular feedhorn that has a 40mm throat, so it will fit the majority of dishes without any problems, as a direct replacement. The cast alloy box containing the electronics is less than half the size of the Philips unit, and only two-thirds as large as the Marconi Solo. In common with most other LNBs it has electronic, dual probe, polarity switching, controlled by the receiver via the LNB cable. In our evaluation tests this came out as the joint winner, with the Marconi Solo, compared with the reference blue cap there was a substantial reduction in sparklies on UK Gold, and a considerable improvement in colour reproduction, particularly in highly saturated areas where noise and sparklies are most prevalent.

 

Address: Protel Distribution Ltd., Communication House, 879 High Road Finchley, London N12 8QA.

Tel:  081-445 4441

Verdict: (out of 5)

Performance *****

Ease of installation *****

Buying Satellite Rating  95%

 

Throat dia:  40mm

Quoted noise figure: 0.7dB

 

VERDICT

All other things being equal the Protel and Marconi LNBs would be our first choice on a fixed dish, dual-LNB system, where low noise figures are essential in order to get the best from weaker signals, from the satellites either side of Astra. If our results are anything to go by both LNBs would do well as performance-boosters on 60cm dishes, in the Midlands and Northern England, say, where it's normally  preferable to use an 80cm dish. The Philips and Maspro LNBs are both worthwhile upgrades, especially on older systems, where the existing LNB is not giving its best, or the receiver is struggling, however, be warned that neither of them use the most popular 40mm diameter fitting so depending on the type of dish you have, the mounting bracket may need to be changed or modified.

 

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R.Maybury 1993 1908

 

 


 

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