[NLRS] MGA-86576 - eBay Replacement ??

Mon Dec 9 01:57:27 EST 2013

Hello All !! Before I would jump to throwing in any replacement MMIC or Gaasfet device, I would really give Steve at DEMI a call / email and see what he would recommend for any device replacements (dont need to "reinvent the wheel" if you dont have to  ).....This is because I have noticed that some of the newer MMIC 's that have decent gain up in the microwaves MAY only be 'conditionally' stable in specific circuits (my experience shows that the 86576 falls into this category )...... I personally have been using the PGA-103 as 'second stages' up through 1296 , but the gain starts to fall off there. I like the PGA103's because they are very stable , predictable and have very low Noise Figures up through 1296 ..... Considering Jon's application , I would do some online researching IF Steve at DEMI did not have any thing to go with in the transverter .....   If this were my 2304 xvrtr and I needed a new preamp stage and could NOT find a suitable STABLE
 replacement MMIC device , I would put a bypass in the xvrtr and use an external ATF54143 Gasfet preamp ( I can get a complete preamp down to the size of a postage stamp for 1296 that has less than 0.70db Noise Figure and over 16db Gain ) on the outside or adapt the xvrtr board for that device ..... The reason I wanted to throw in my 2cents worth is to mention the issues that could arise with CONDITIONAL or UNCONDITIONAL stability of the specific devices ... I have been using some of 'old - school' preamp designs but they only work to a certain extent with a limited amount of devices out there today - ( i.e - the ATF 54143 is only CONDITIONALLY stable from around 200 mhz and down , above that the '54143 pretty much is an UNCONDITIONALLY stable device )......   Thanks for reading my rant - just dont want anyone to think that just any MMIC could work in place of a MGA-86576 - this instability issue could really be a problem if a different MMIC that had
 somewhat different S11 / S22 specs was installed . 73s !!! Ron KA0RYT  
--------------------------------------------
On Sun, 12/8/13, Zack Widup <w9sz.zack at gmail.com> wrote:

 Subject: Re: [NLRS] MGA-86576 - eBay?
 To: "NLRS List" <nlrs at mailman.qth.net>
 Date: Sunday, December 8, 2013, 1:36 PM

 Also, the ERA-2 is spec'd to 6 GHz but its
 s-parameters are listed through
 16 GHz. It
 has useful gain at 10 GHz. I've used them there.
 However, the
 noise figure isn't so
 great.

 73, Zack W9SZ

 On Sun, Dec
 8, 2013 at 11:53 AM, Dr. Gerald N. Johnson
 <geraldj at netins.net>wrote:

 >
 >
 > There is that risk. Its not a part most of
 us can test without installing
 > it in a
 circuit, and its stretched beyond ratings in the 10 GHz DEMI
 preamp
 > and transverter. It works quite
 well there. That would be the toughest test
 > for fakes.
 >
 > The MGA-86563 is the same chip in a
 different package that they are still
 >
 making. Trouble is the package parasitics limit its rated
 range to 6 GHz,
 > and its falling off
 rapidly there. I think the package can be twisted to
 > fit the footprint of the MGA-86576 for
 lower frequency applications than 10
 >
 GHz.
 >
 > The MGA-30989
 is in a larger package but that limits its rated
 performance
 > to 6 GHz and the S
 parameters show 0.67 dB gain at 10 GHz. A suitable
 > substitute at 5760 and down, a dud at 10
 GHz. And it its rated range the P1
 > is
 about +23 dBm, a power device with decent NF.
 >
 > The VMMK-3803 is a
 better part for 10 GHz operation for NF and gain over
 > the MGA-86976, but it is inconveniently
 tiny. Its in an 0402 package with
 > the
 ground pad in the middle and requires input bias to turn it
 on. That
 > package I'm sure won't
 stretch to the traces made for the 76 package (in
 > that HP/Agilent numbering scheme the last
 two digits of the part number are
 >
 package) and it doesn't appear to expose the pads for
 easy hand soldering.
 > It might work with
 tiny strips of copper foil added in dead bug position.
 >
 > Mouser has 490 of the
 MGA-86563 in stock at $2.60 each in small quantity
 > bulk and 3000 on order to be sold as cut
 tape for the same price.
 >
 > Mouser has 200 of the VMMK-3803 on order
 asking $7.60 each. They expect
 > delivery
 next March 19 and factory lead time is 26 weeks.
 >
 > Mouser has 794 of the
 MGA-30989 in stock at $2.68 each.
 >
 > Digi-Key has 448 MGA-86563 in bulk and
 7296 in cut tape for $2.91 and
 > $2.99
 each in single lots.
 >
 > DK has 925 VMMK-3803 in blk for $8.03 each
 and 9125 in cut tape for $8.28.
 >
 > DK has 233 MGA-30989 in bulk for $3
 each.
 >
 > Pictures of
 the adaptations of these parts to existing DEMI boards
 would
 > be worth showing at Aurora and
 the rest of the season's VHF and microwave
 > conferences.
 >
 > The RFMD NBB-400T1 that DK has 13,516 in
 stock at $8.60 is in the same
 > package
 as the MGA-86576. It has a 4 dB NF vs the original 2.5 dB
 NF
 > rating. Rated to the same 8 GHz.
 >
 > The RFMD NBB-300T1 is
 rated to 12 GHz, but the NF is 5 dB. DK has a pile
 > in stock.
 >
 > I believe DEMI has been using the NBB 310
 or NLB 310 (plastic package vs
 > ceramic)
 in transverters where NF isn't critical for a few years
 now in
 > place of the original collection
 of ERA parts. Rated past 10 GHz with 5 dB
 > NF and a bit more power out than the ERA
 used formerly.
 >
 > The
 RFMD SBW 5089Z is in a larger case rated to 8 GHz but with
 some
 > performance data to 10 GHz, not a
 super NF of 4 dB at 6 GHz. DK has in
 >
 stock.
 >
 > DK has some
 Hittite and Micro Tech parts to cover the 1 to 18 GHz
 range
 > all in QFN packages not
 interchangeable with the original part in question
 > and all just under $100 each. Except for
 the packaged Hittite part with
 >
 connectors for a mere $1601.28. They have only one of those
 in stock.
 >
 > There
 may be other suitable parts available from our most
 friendly
 > distributors Mouser and DK,
 I've searched enough for this morning.
 >
 > Some substitutions
 may need attention to input and output impedance
 > matching for optimum performance as well
 as changes in bias.
 >
 > 73, Jerry, K0CQ
 >
 >
 >
 >
 > On 12/8/2013 8:11 AM,
 John (JK) Kalenowsky, K9JK wrote:
 >
 >>
 >>
 >> I see a Chinese seller with 5
 for<$18 (not sure if there's a risk of
 >> the parts being fakes) and a US seller
 with 2 for $17.
 >>
 >> Your mileage/eBay experience may vary.
 Some assembly required.
 >> Batteries
 not included. I have no relations with any of these eBay
 >> sellers. (Other disclaimers ad
 infinitum.) --JK
 >>
 >>
 >>
 >>
 >>
 >
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