[NLRS] MGA-86576 wrap up

[Dr. Gerald N. Johnson]

On 12/9/2013 9:09 AM, w0zq at aol.com wrote:
>
>
>
> To close out the story, having heard from several of you, yes the
> MGA-86576 is past its end-of-life.  I used my last one to resolve my
> "dead" 2304 DEMI transverter.  For some reason I seem to pop them.  I
> don't know if its because of my rover set-up with closely spaced
> antennas on 6m through 3456 running higher-ish power, or perhaps I
> need sequencing as the 2304 system runs about 30 watts.  I am
> thinking the latter as I am using an older SMA relay for T/R and I am
> unsure of its isolation as well as PTT race.

Usually a microwave rated SMA relay will have very good isolation at 2.3 
GHz. Lack of sequencing may have changed that from burning the contacts 
and isolation is never guaranteed while the relay parts are moving. I 
need to replace the TR relay on my 10 GHz station because its not 
sequenced well enough. I can simply add some delay to TXinh and that 
should solve the problem.

The closed spaced antennas can apply significant power to the 2.3 
receiver. Some put all transverters in transmit mode to protect their 
receiver RF stages.
>
> Several have pointed out the MSA-86563 is a possible replacement
> part.  Both devices are GaAs MMICs.  Our friends at DigiKey have
> stock on this part at just under $3.00 in eachs .... very reasonable.
> Bad news is that the package is a SOT-363 rather than the "standard"
> 76 package.  The SOT-363 package is about the size of coarsely ground
> pepper albeit you can grab the corners as RF-in is on pin 1 and
> RF-out is kiddie corner on pin 4 with pins 2, 3, 5 and 6 as ground.
> Both devices are biased by a 5 volt source.  At 2.3 GHz, the 86563
> has about the same noise figure (1.6 dB) but about 3 dB less gain (20
> dB vs 23.7).  I think that one could use one of these as a
> replacement part albeit you would need to figure out out to place it
> onto the PCB with a proper ground.  Also, the missing 3 dB may need
> to be made up further down the chain.

Its the same chip in a different package. The first three digits show 
that. In HP/Agilent/Avago part numbers the first three digits are the 
chip and the last two the package. The 63 package is small, but much 
larger than the VMMK-3803 that Avago offers as an alternative. It 
probably will need extensions on the traces on the board. A strip from 
ground to ground under it should be first, then the in and out traces 
may need extension with straps, straps of 5 or 10 mil copper about 25 
mils wide. A source of solderable copper appears in Hobby Lobby in long 
rolls where its sold for use with stained glass applications. I know at 
least one surface is solderable, I don't know about the side that goes 
to the glass, it might have an adhesive that might be a benefit or a 
curse. I have a roll but haven't yet tried it yet.

There is likely excess gain in the receive chain so the 3 dB lower loss 
will only mean 3 dB better strong signal handling and no change in MDS.
>
> For now I think I am going to try to figure out how to do some
> sequencing for that set-up.
>
> 73, Jon W0ZQ
>
73, Jerry, K0CQ