|Q102 FT301 RF amplifier of the RF
board. The board plugs in to the
transceiver and (on this particular
circuit board ..both Q102 and Q103
are dual gate mosfets in sockets.
|Dual Gate MOSFET..SHOOTOUT NUMBER 2 dated 9 December 2013.
This time..I have taken better resolution pictures and I test a few more
different DG mosfets.
In my testing done so far..the SFE1612 has always been a bit better. Here
with the signals strong it is a clear winner. I was sent about 20 SFE1612s
by a USA distributor. He said they did not have much data on this device
but he thinks they were used in Sonobuoy radios. Either thats military or
perhaps aviation or ships.
Anyway you look at it. The SFE1612 is a winner compared to the other dual
gate mosfets I have tested.
When doing the dual gate mosfet testing AND when using my FT301..I use
the SFE1612 in the mixer stage of the RF board FT301 as the mixer Q103.
If you are thinking of asking to buy some SFE1612s from me..SORRY..I only
have about 20 and (at least for now)..I plan to hold onto them. I plan to try
them in my HW7 and Ten Tec Argonaut 509s and 515.
I am going to be trying to do a buy for some of these devices.
Here I am putting some leads on a BF981 to "create" a radial lead
device to plug into transistor socket. These devices seem to do almost
as well as the MOTOROLA branded 3N211 above pictured.
IF I were to choose between the modified BF981 and the T.I. Malaysia
3n211 I would choose my BF981 modded. It is a tad bit better in my test
and Iam a little susplicious now of the T.I. 3N211s I have in stock.
The 3N204 did surprisingly well in this test. MIND YOU..BEAR IN MIND...THIS is a
test using relatively simple equipment. The dummy load putting out the 28.060
mhz energy (about 1 watt) from the IC718 ..the dummy load is in the same room
and is only about 8 ft away from the receiver.
--So..the signals are strong! -- I would rather have a real weak signal to try the
test with..but the S meter readings might not be that easy to discern.
--- For each device..I rock the tune controls and preselector for maximum signal
strength for each device. -- This is a relative test..but unbiased. I just want to
find out how the devices I have in my collection perform.
The NTE 222 did not do as well as I might have thought this test.
This is the second time I have tested these 3N211s (Texas Instrument Branded) and
Malaysia as well. They dont seem to be quite as good as the MOTOROLA branded 3N211s.
Im suspicous of these TI branded devices and I m not going to buy any more of them.
THIS IS the second time I have tested the 40673 and each time..I find it does not do as
well..(in the RF amplifier application) as say most of the others I test. I still keep these and
I sell them most reasonable ($5.50 each)..but I (myself) wont be using them.
Motorola brand 81-128 (some sort of house number I susplect). It has
been tested in both DG mosfet shootouts and so far has given a good
I bought a whack of these 40823s and 40820s from ebay at a real good price.
I didnt want to buy too many..in case they were duds!! Anyways ..they seem
to be quite good parts with the 40823 being slightly higher gain perhaps.
I am SOLD OUT of 40823s and I have only a few left of the 40820s. I was
selling them at $3 each..which is cheap for dg mosfets.
I have two different parts that are formed leads comming from a plastic body. The entire part nr cannot be printed on the part. I think I bought these
parts from some ham on the QRP-L list. In order to test them and get them to fit into the 4 lead transistor socket..I had to do some creative lead
bending to get them to fit. -- It can be done though! The test results below pictured. Both are about the same performance wise.
The RF generator in this test is my
IC718. The frequency is 28.060 Mhz
and the RF power is dialed down
to 1 watt and the test mode is AM
with the mic audio gain at zero.
What I do to generate the test
signal is I jam the microphone
button to ON position between two
The dummy load is attached to the
radio with a short coax jumper.
The FT301 has plug in circuit boards. I work on
FT301 radios. Sometimes..people send me
boards in the mail to diagnose and repair. I have
all the parts for these radios. They are still fairly
popular even though they are roughly 35 years
old. Some of the parts such as the final PA
transistors are a bit pricey to buy. I dont have
any spare PA transistors in stock.
|Homebrew dummy load pictured on a bench with my FT757GX..(which is sort of
retired right now).
Below pictures of some BF981s that I built up recently. I
can sell these "modded" BF981s for $5 each and to ship
them in the mail.. costs about $1.50 in Canada, $3 to USA
and $5.20 to Europe.
I just made up a couple for a fellow in Germany. I plan to try
potting my recent BF981/radial leads in epoxy to make them
more rugged. I will post pictures of this creation in the next
I plan to make them RUGGED..and if I can make them look
good..that would be great! Might take a bit of work to do
BF 981 dual gate mosfet. YOu can buy them for about $1.80 or so. I take some cheap 1N914 small signal diodes and clip the leads off them. Then I bend the little
crook at one end. Taking a razor blade..I roughen up the surfaces to allow better (more surface area) for the solder to stick to. -- The whole process can be
done by hand without any jigs or anything. I use a piece of tape on the bench. I also ground myself periodically to a grounded piece of gear nearby. These
devices are diode protected but you dont want to zap them with static.
You can do a PULL test on the leads to make sure the connections are solid. The hardest
part of the whole process is keeping the hand pressure steady as a solder joint cools. If
too much hand vibration..then the solder joint will be a loose joint that is likely to break
during handling (and sometimes does).
With all these dual gate mosfets..the pinout pattern is the same layout..which allows direct drop in..plug in ..compatibility. I always bring out this
sketch to allow me to line up the pins ..when I am making up these BF981s with radial leads.
LINK BACK TO MY HOME PAGE
www.earlandrews.com (these are mirror sites).
|I sell all kinds of parts for ham radio
experimenters, tinkerers, builders, QRPers
and electronics hobbyists.
I sell from my basement shop up here in
Elliot Lake, ON. Canada (north of Michigan
State across Lake Huron).
To see my big SUPERLIST of parts
Any small amounts of money I make selling
parts or doing the odd repair..helps pay for
this and my other web sites and helps to buy
shop supplies and parts for experiments ect.
IT IS A HOBBY NOT A BUSINESS .. (I am a
retired Canadian Federal Public Servant who
took an early retirement option)...
to send an email to me..
CLICK HERE THIS LINK..73 EARL VE3AB
This "31-11" (on the part itself) is really part number MEM631-11 (the -11 suffix
stands for leads cut and bent option)
|I'M SOLD OUT OF 40823s and
40820s.. I'd like to buy more if
anyone has some for sale 73 ve3ab