When is a MAR-6 not a MAR-6?

[G3GJA]

The answer is when you buy them on eBay from Mainline Electronics!

Beware! the item http://www.ebay.co.uk/itm/MAR-6-Mimic-a ... 5ad7717503 are not the Minicircuits MAR-6; they are in fact Avago (was HP) MSA-0686

Although related to the 'Power from Digilite on 23cm' thread I thought this problem needs its own in case other DigiLite buiders have bought what they thought were MAR-6 from Mainline and have been caught by the same misrepresentation.

I've not been able to get as clean an output as others seem to be getting on my 23cm Digilite or as much power. A bit of research into datasheets showed that the markings on my MMICs were wrong for for the MAR-6. The MSA-0686 uses similar biasing but is only specified to 800MHz (-3dB) and has a much lower 1dB compression point.

I had a MSA-0886 to hand and fitted that using a 150R to 12v to bias it similar to Brian G4EWJ's arrangement. The reduction in the spectral regrowth was amazing compared with the MSA-0686. The main lobes are still -25dB down from the crest but other lobes that were -35dB down and -42dB have gone completely and there's just a little crud at -60dB . Power output is now +2dBm without modulation and with the crest is about -8dBm.

This really does reinforce the need for good linearity in amplifiers following the DigiLite! (and to be wary of what you buy on eBay )

[g4bbh]

This may account for a dodgy batch of MAR-6 that I purchased 6 months ago from Mainline (eBay item 390161593603). Those in a W1GHn 1152MHz LO and 1296MHZ transverter did not work as expected with low gain. Thinking I had zapped them I replaced them (from the same batch) and still no joy. Purchased another batch from a different supplier and fitted them instead then everything worked as it should. The markings on good and bad MAR-6s were near identical.
Who said 'Buyer Beware'?
Dick G4BBH

[G3GJA]

Hi Dick

Long time no see, hope you are well.

From my tests the MSA-0686 is pretty poor at 23cms. I'm building my 70cm version of the Digilite now so it will be interesting to see if these Mainline ones are any good there. The spec at 500MHz looks OK although the 1dB compression is only +2dBm. Certainly no good for a 1152MHz LO!

73 Clive G8EQZ / G3GJA

[g4bbh]

Hi Clive. I am also looking at a 70cm version but will need to get 23cm going first. I did take the precaution of ordering enough of most parts for two DigiLite boards. I am a bit slow on SMD these days, even with a binocular microscope and find it rather difficult to keep a steady hand but can manage a few 0603 components - I need to employ a little Japanese (female) helper but the XYL won't let me!
I now buy direct from Minicircuits - hang the postage costs, at least I can trust them! I still have one of the so-called MAR-6 that came from Mainline and they are marked with an Agilent logo followed by '06'. This looks almost the same as the markings on the real McCoy. The Mainline ones are certainly rubbish anywhere above 1GHz. Even the 1152MHz local oscillator amplifier on my transverter was several dB down.
Dick G4BBH

[M0ATV]

I actually ordered a batch many weeks ago from the same seller in the link above, as a result of using them I have to keep the I/Q trimmer levels at 40%-50% or the side shoulders on waveform increase too much, also resulted in very low output of around 1mw from digilite board.

[G4EWJ]

That explains why I had the same problem Tony.

I don't have a MAR-6, but looking at the data sheets, the MAR-6 is marked 06 and has straight legs and the MSA-0686 is marked A06 and has bent legs. Just to confuse the issue, there is also a MAR-6SM which is marked 06 and has bent legs.

Brian

[G4EWJ]

I was given a 'MAR-6' yesterday. It's marked A06L. Has anyone seen that marking before?

Brian

[G3GJA]

Like Brian, I've found the MSA-0886 (from RS Components) a good device to use for U5 at 23cms. Getting about 10dB more out than the Mainline 'MAR-6' and no re-growth. I don't have 10v regs to hand so I've paralled a 220R & 330R for R26 & R42 giving 130R and then connected that to 12v via a 10µH choke after cutting the track between C20 and R26.

I've also completed my 70cm version and applied the same changes; got 20mW out with no mod! To get it linear I increased the post modulator / pre MMIC attenuator from -2.6db to -12dB. Now getting a very clean 1mW output so the MSA-0886 is good for 70cm too. I did try the Mainline device at 70cm and it was atrocious. Low output and wide as barn door.

Now not sure what I can use the rest of Mainline devices for.... if anything!

Not come across any references to the A06L marking. I'd be interested to hear how that device performs.

Clive G3GJA

[G4OHV]

I got stung with this one also, I think Mainline will be receiving a rude phone call.....not a bad little earner at over £9 a go!, 60 odd sold!

I wonder if anyone knows another dealer who sells the real MAR-6's, without excessive postage or high minimal orders?, noticed JAB do them but unsure their pedigree!

regards

Col

[M0ATV]

Blimey, a lot of pseudo MAR-6 devices are out there, Ive just ordered a batch from mini-circuits, so will let you know what they are like when arrive & fitted.