I have been playing with a new Triquint ULNA device (TQP3M9036). It
Shows a lot of promise. It is like a MAR or MSA device in that it is
50ohm in and out. and has a claimed NF about .4db nf ( their numbers).
I have built several pramps to test them and have gotten even better
than they claim and they cover 50-1296 with ease and NF is .4ish or
below. The S11 and S22 are both great and the OIP3 is +35db also
...very nice device. It has great promise as a good terrestrial LNA.
Preamps are foolproof to build and would cost under $50 if all the best
quality parts are used.
Just for information only ...
Pete WA2ODO
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Sri I made, at least a mistake, I send it again.
Hi all,
Very interesting answers. I come from Sats world, where the Doppler
is a serious issue and it is so quick that it is impossible to work
JT65.
I will speak thinking in one carrier. Sats need to receive in only
one fix frequency (it is an active RX with a wideband), if the Sat
receives a carrier in this frequency then it will be repeated. The
signal TX from the Sat will be in one fix frequency. So people who
work Sats must correct its TX frequency (according with actual
Doppler) to reach the sat in its fix frequency, in the same way
because of the Sats will repeat this signal in a fix frequency, people
must correct its RX frequency (according with actual Doppler).
This way of dealing with Doppler is very interesting because NOBODY
KNOWS the Doppler of the other stations and nobody needs to know it,
we only need to know our own Doppler.
If we would use this agreement to EME communications we will always
speak about the frequency we hit the Moon, in other words the
frequency which the Moon hear us and repeat our signal.
The actual EME software shows us the Doppler as the sum of the Doppler
effects to reach the Moon and to receive the bounce signal, so Moon
will receive us at ½ Doppler announced, the other ½ effect will appear
after de bounce.
I will try to set a couple of examples.
1.- We will agree to hit the Moon in 1296.070. This is the frequency I
will announce in the log. In our software the dates will be:
*Self Doppler
+3KHz
*DX Doppler
-2KHz
The sign that the software shows will aplly to RX frequency and the
opposite to the TX frequency, and always ½ magnitude on each one.
Both of us must deal with Doppler, each one must do their task to hit
the moon in the agreed frequency and to receive the bounce according
our Doppler. Then we must set on our transceivers:
*Me
TX: 1296.070 -1.5KHz = 1296.0685MHz
RX: 1296.070 +1.5KHz= 1296.0715MHz
*DX
TX: 1296.070 +1.0KHz = 1299.071MHz
RX: 1296.070 -1.0KHz= 1296.069MHz
Each station who sees the post will act only according its own
Doppler. Don´t mind where is the DX station.
2.- In this case I see a signal in my receiver in 1296.070. What
kind of pair of frequencies I must set (I know nothing about the DX
station I have still decode nothing), I only know me own Doppler, and
it is +2KHz. I must hit the moon in the same frequency that my
partner:
TX: 1296.070 -1.0KHz = 1296.069MHz
RX: 1296.070 = 1296.070MHz
WE WILL NOT NEED TO KNOW NO MORE THAN OUR DATES.
I haven´t spoken about what frequencies will be the echoes (both
echoes), to make the understanding easy.
As a drawback we should change our habits, we should always use the
RIT as follow:
TX: The frequency we choose plus the opposite sign of Doppler and ½
Doppler magnitude.
RIT: the sign of our Doppler and ½ Doppler magnitude.
Although at first glance it seems not to be interesting in 144MHz but
we will always hit the target in whatever band, even in 144MHz.
Somebody can tell that they need a computer, to do JT65 of course, if
you do CW surely have a smart phone with the proper software to know
your own Doppler or you can print it before.
If I made some mistakes let me know.
It is my 2 cents.
Juan Antonio
EA4CYQ
Hello moonlovers,
We do have some complete build and tested OE5JFL standalone antenna
trackers left after our Heelweg meeting.
More info about this design see the site from Johannes:
http://www.qsl.net/oe5jfl/EMEcontr_jfl.pdf
If you are interested please contact me off list.
In case you want to reduce the shippingcosts: we can take them to Hamradio
in Friedrichshafen end june and to the EME conference in august in Venice.
All boards are build and tested. No MAB25 encoders enclosed but can be
ordered if you need them.
In case there are more demands then available boards we will prepare 10 new
kits.
Jurgen PE1LWT and Johan PA3FPQ
Hello!
A quick update on the next EME conference.
The conference, as announced, will be held at the BHR Hotel near Treviso.
http://www.bhrtrevisohotel.com/it/bhr-treviso-hotel/home
The dates are confirmed: from 19th to 21th of august.
We reserved the whole hotel and conference center, that should be able to
accomodate the large part of the attendance, the others will be hosted in
other hotels nearby if necessary, at the same rates and with shuttles
between them (we will deal with the bookings).
The hotel is not far from Treviso airport, with free shuttles from it. This
choice was made because on Treviso airport land the majority of the low
cost airliners.
We have a good number of sponsors, that will help us to ensure an
unforgettable stay, from I0JXX, that many of you already know, to the fine
CW paddles maker Mr. Begali (which has in store a mindblowing EME limited
edition paddle for you to see), along with Messi e Paoloni Cables, CSY &
Son (Yaesu) and others.
One thing is for sure, the final raffle will be something!
While we are still working on the website (we had a shortage of webmasters
lately...), we did manage to prepare a neat collateral program for the
ladies, that will be available for the audience as soon as the site will be
online.
The good thing is, if you don't want to bother with looking for air
tickets, transfers and extensions for your trip (yes, there are some
proposals for those too), we will be able to deal with your necessities
directly. Since I own a Tour operator chances are that we will be able to
shave your ordinary travel costs.
We are working hard to host the opening of the conference in Venice, but
logistics is a true nightmare, and politics adds to the equation rendering
this part of the organization a total mess to deal with, but we don't give
up easily!
If you have any questions, or you want to make a leap of faith and book
your flights well in advance, or you want to submit a paper for the
conference, drop me an email to iw3hvb(at)eme2016.org
I'll come back soon.
Enjoy the rest of the holiday season!
Giulio IW3HVB
With unusual December WX and temps around 60F / 16C Frank NC1I and I decided
to spend a few hours driving around Rhode Island this past weekend to check
out sites we have had on the short list for a future RI EME DXpedition.
We're pretty excited about one of them: good moon horizon, away from homes
and businesses, etc. We met with the property owners and discussed what we
are looking to do and they seem supportive.
Over the coming weeks I'll continue to work on the logistics for this
operation. As I've mentioned in the past - in the USA the Amateur Radio
service has secondary status on 70cm with the military being the primary
user. In eastern Massachusetts (near RI) there is a large radar
installation that we can't cause interference to (we're normally limited to
QRPP). While we have a special high power permit for 70cm we want to make
sure we inform the radar facility in advance of our planned operation.
Our thoughts would be to run the same station we had in Vermont: 4 yagis on
70cm and the 2.4m dish on 23cm with QRO on both bands. We'd likely setup
the station during the weekend prior to our operation and then return for an
extended weekend on 70cm - and then back the following weekend for 23cm.
Looking at DL7APV's moon calendar we are thinking these dates: 70cm on Apr
08/09/10 and 23cm on Apr 16/17. Because of the difficulty of QRO on 70cm
from Rhode Island we want to make sure we can work as many people as
possible.
Happy Holidays and best wishes for the New Year 2016!
Bob W1QA
Far from conclusion.....
Take a "typical" well engineered pallet designed for 1kW output. We are
lucky, assume efficiency is 80% biased in AB1.
Following the load line we see efficiency would drop to ~63% at ~50%
power output, we must design the cooling system for this factor,
hams have a habit of either running things flat out or 1/2 power....
DC input power is 1250W at max output but dissipation is worse at lower
power, assume max dissipation is 320W.
Typical device has a RthetaJC of ~0.15K/W, that means the case
temperature due to purely conduction should be 320*0.15=48C below
the junction temperature if we do our job right.
This is where things get complicated. As a design aim for "long life"
which can be interpreted as operating 24/7 at full power, the junction
temperature should be kept below 175C. This is an arguable point but a
figure adopted by most commercial (non ham) manufacturers.
Taking 175C in our example means the maximum case temperature to aim for
will be typically 175-48=127C.
The purpose of a spreader plate is just that. It is not immediately
obvious as to the behavior of the spreader and to get a true answer requires
thermodynamic tools, However I will make it easy. 0.2% tungsten doped
copper (to make it easy to machine) has a conductivity close to 400W/m/K,
so how big does it need to be ?
Well, there is an upper bound, once past this it is diminishing returns.
As it happens that value is close to the spreader size specified by many
semiconductor manufacturers for this type of device, you can assume they
have done their homework correctly.
So for our example a spreader 125x75x15 mm has an effective RthetaSC=
~0.18K/W, if we doubled the area RthetaSC would drop to ~0.15K/W,
if we made it 1mx1m it would only be ~0.13K/W. This is following the
general behavior of a point source in contact with an infinite heatsink.
To improve this dramatically we need a material with a much higher
conductivity...e.g. diamond.
So following our observations we need to keep the spreader at
127-(320*0.18)= ~70C.
Taking a typical bonded-fin heatsink with a effective conductivity of
1000W/m^2/K we would need an airflow of ~0.025m^3/s in an ambient of 25C
to keep the exhaust temperature below 60C. That equates roughly to a
pair of 80x80x30 high efficiency fans shifting at 6.5m/s giving an
effective
RthetaSH of ~0.03K/W for the heatsink. We are already approaching an
engineering limit for an air cooled heatsink.
We can now introduce some changes and see where this leads.....
Substitute the spreader with aluminium, conductivity is around 60% of
copper but the effective RthetaSC for the same size spreader rises to
0.23K/W at best, given the same heatsink the exhaust temperature would
have to be below 43C.
Turns out our build is not quite so efficient and we get 75%, oh and the
antenna VSWR is 1.15:1. Our dissipation figure has risen to 420W.
Given our simplification on the spreader we rework the effective
RthetaSC, it arises that the exhaust temperature needs to be BELOW
ambient.....
so junction temp suffers and goes thru the roof = BANG.
You can see how we quickly get into trouble.
One can draw your own conclusions as to why most commercial ham amps
actually turn out to be quite unreliable.
If the device is bolted down, rather than soldered, and ALL flatness
considerations are taken into account, the variability ought to be less
than 5%.
Remember, heatsink compounds should only be used to fill microscopic
voids, heatsink compounds like Arctic Silver 5 have quite a high thermal
resistance compared to the numbers I have shown here, but of course,
needless to say this remains far far better than air.....
Most compounds use silver and a number of ceramic oxides, electrical
conductivity is unpredictable and you need upwards of 250 hours operation
at expected temperature before it does its work correctly.......not
just slap it on and hope for the best.
So,
When buying/building your 1kW amp, ask yourself the following:
How big is the spreader compared to the device manufacturers
recommendations and what is it made of ?
What is the specification of the heatsink and cooling fans used ?
How efficient is the final pallett ?
What VSWR, overcurrent protection is used, what are the trip points (deg
C, Amps).
Where is the temperature sensor ? (if its anywhere BUT the spreader walk
away).
Demonstrate this all by pulling the coax off the TX port say 1/2 dozen
times at full power.
73'
Keith G4FUF/XV4F
