On Wed, 17 Sep 1997 10:20:05 -0400 "Healy, Rus" <RHealy@mdsroc.com>
writes:
>The A03 isn't a FET. It's a MMIC--a Mini-Circuits MAR-3, or an HP
>MSA-0385. (They're one in the same--all are made by HP [formerly
>Avantek].) It's quite an inexpensive device--about $1.50 and is 50
>ohms
>in and out. See Al (WB5LUA) Ward's two-part 1987 QST series on these
>babies.
>
>MMICs are avaliable from Down East Microwave at 908-996-3584. I
>suggest
>that the MAV-11 is a better device for this service than the MAR-3.
>It's
>more destruction-proof. It needs a 150-ohm, 1/2-watt bias resistor to
>operate from 13.8 V, rather than the 220- or 330-ohm resistor used for
>the MAR-3 at the same supply voltage.
>
>--73, Rus, NJ2L
Hi Russ;
I agree except the MAV-11 is no more destruction proof than the MAR-3. It
does have better IMD and NF specs but both are rated at the same +20dBm
maximum input level. The MAV-11 is used in the DEM 6M xvtr as a mixer
post-amp.
It is this very low tolerance to high RF levels that makes them a poor
choice in the ZJ box without some sure fire means of protection.
Another potential weak link is the MCL T9-1 transformer...its
subminiature size makes it a good candidate for getting zapped.
While the ZJ box is a good lab concept, it just may not be the proper
choice for those in somewhat hostile enviroments. Replacing pilot light
fuses every few minutes during a blizzard is not my idea of protection
especially if the box is 700' away. Why on earth anyone would want a
remote preamp on 160/80 is also questioned.
Another concern is an apparent difference in what is shipped. The ZJ box
I have here for evaluation here uses a MAR-6 and a 6V supply. Although it
is biased properly the MAR-6 has much lower performance specs than even
the MAR-3 and its 20+ dB of gain is way too much for a decent beverage.
Others may wish to check the device in their unit. The AO3 is the MAR-3
(orange dot) and the MAR-6 is marked AO6 with a white dot.
There are certainly other ways to build a mousetrap.
73 Carl KM1H
>
>>----------
>>From: philk5pc@connect.net[SMTP:philk5pc@connect.net]
>>Sent: Monday, September 15, 1997 9:10 PM
>>To: Jay E Ostrem
>>Cc: topband@contesting.com
>>Subject: Re: TopBand: Followup Beverage Box
>>
>>At 11:33 PM 9/15/97 +0100, you wrote:
>>>I had a few inquiries on what the FET looked like. It is a 4 radial
>lead
>>>flat package with AO3 printed on it.
>>> 73
>>>
>>> Jay W7CW in Gillette, Wyoming
>>
>>I would like a diagram of the ZJ stuff myself. They replaced my FET
>when it
>>burned out for nothing, but it takes a long time (about a month) for
>the
>>turn-around. I protect the input of all my ZJ boxes now with small
>pilot
>>lamps installed between the antenna input and the board. This has
>solved
>>all RFI and lightning problems so far.
>>
>>ZJ has good products, but furnish no technical info with it!
>>
>>(((73)))
>>Phil, K5PC
>>
>
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