RA60 module drive and bias recomendations

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g0nzo
Posts: 43
Joined: Tue Oct 20, 2009 6:30 pm

RA60 module drive and bias recomendations

Post by g0nzo » Tue Feb 19, 2019 4:14 pm

I'm mounting up some RA60 Mitsubishi modules for DATV.
Can anyone recommend starting drive levels and bias settings, for clean DVB-S?

Ta
Jules

g0mjw
Posts: 2327
Joined: Sat Sep 20, 2014 9:15 am

Re: RA60 module drive and bias recomendations

Post by g0mjw » Tue Feb 19, 2019 5:25 pm

Did you file it flat on the back? It needs about 4.5V say 3-5A (adjust for best shoulders) and just a few mW of drive. You get 5W out.

Mike

g8vpg
Posts: 381
Joined: Fri Oct 11, 2013 9:35 am

Re: RA60 module drive and bias recomendations

Post by g8vpg » Tue Feb 19, 2019 5:59 pm

Jules,
I usually set mine up for 3-4A quiescent current. I recommend you download a copy of GM3SEK's paper AN4 from g4ddk.com, which contains much very good practical information about using these modules.
73 Shaun.

radiogareth
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Joined: Wed Jan 06, 2016 9:46 am

Re: RA60 module drive and bias recomendations

Post by radiogareth » Tue Feb 19, 2019 7:22 pm

Filing or sanding the back takes a while but is hugely recommended. I used a belt sander, conveniently supplied (by Lidl) with upside down clamping brackets. Even so it took a surprising amount of time to get it down to less than 1 thou gap in the middle (measured with feeler gauges over a flat edge), whiles taking care to avoid heat buildup.
Gareth

g0nzo
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Joined: Tue Oct 20, 2009 6:30 pm

Re: RA60 module drive and bias recomendations

Post by g0nzo » Wed Feb 20, 2019 12:31 am

Thanks for the info.

I have an M1 module, and the gap/bow was measured at around a thou. Without filing.
Good enough, with a smear of grease?

Jules

radiogareth
Posts: 1215
Joined: Wed Jan 06, 2016 9:46 am

Re: RA60 module drive and bias recomendations

Post by radiogareth » Wed Feb 20, 2019 7:53 am

I believe so, for some odd reason some of the later modules (4M unit anyway) has the ends tabbed down so causing the middle to sit high. Data on the RA60 Mitsubishi module shows it as flat though.
Gareth

G4FRE
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Joined: Fri May 26, 2017 6:57 am

Re: RA60 module drive and bias recomendations

Post by G4FRE » Wed Feb 20, 2019 6:55 pm

You might also like to take a look at the Downeastmicrowave document on the amplifier modules at http://01895fa.netsolhost.com/PDF/MOSFET%20PA_pdf.PDF

Dave
g4fre

g0nzo
Posts: 43
Joined: Tue Oct 20, 2009 6:30 pm

Re: RA60 module drive and bias recomendations

Post by g0nzo » Tue Feb 26, 2019 12:55 pm

Cheers for the advice peoples.

Though I have the M1 modules (flat-ish flange) I did the sanding trick on the 70cm module. I didn't bother with the 2mtr one, as the bow was only a thou or so, and at those wavelengths, the close coupling to the sink/pcb is probably less critical. Just used grease to fill the gap. But I will keep an eye on the module temp.

With a 3dB pad on the input, I am seeing around 7watts for 4-5mW of drive. Both 2mtrs and 70cm look pretty similar. And a nice warm sink! All of which sounds about right.
I can start playing with some DATV drive, once I get the Portsdown boxed up.

Out of interest, has anyone seen Mitsubishi modules in this power range for 4mtrs? I can not find any listings for the RA60 or RA80 on the 0608 band.

g8vpg
Posts: 381
Joined: Fri Oct 11, 2013 9:35 am

Re: RA60 module drive and bias recomendations

Post by g8vpg » Tue Feb 26, 2019 1:23 pm

Yes, there is a 68-88MHz 60W module that works well at 71MHz. I bought mine from Anglia Live.
73 Shaun.

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