In 2006, I got an 8 watt amplifier. This required several changes: (1) the addition of a sequencer (2) new connections between the transverter, amplifier, transfer relay and horn. At the same time, I switched from a WR-90 waveguide transition with a homemade horn to a modified DSS horn.
My previous 2W configuration had the transfer relay horizontal
in front of the transverter, with two straight pieces of UT-141 connecting
the TX and RX ports.
The UT-141 to the horn had a (approx) 120-degree bend to point it forward
and up to the horn.
After spending a lot of time trying to find a new place to locate the transfer relay, I ended up back where I started: straight out in front of the transverter. But due to the connections to the amplifier, I rotated the relay to be vertical, thus leaving space for connections from the TX port to the amplifier. For a 2W configuration, I bent an "S" shaped piece of UT-141 to connect from the TX port to the transfer relay I found that I needed 2 inches to make the two 90° bends work, so the relay was moved out further.
Since these pictures, I've put a small bar between the aluminum angles, directly under the relay. This is to support the relay in case of an extreme shock.
My feed horn is a commercial feed horn modified to work on 10ghz
by Donn Baker, WA2VOI.
In the past, I used a home-made horn on a WR-90 Waveguide Transition.
More about that in the History section.
In the 8W configuration, the transverter output goes to the input port of the amp, which points towards the front [power switch side] of the transverter.
My first contact with the 8W amp was with KM0T on the evening of 6/26/2006 when we had some nice rain cells between us. This path is about 185 miles, so the difference was noticeable. I worked Mike first at 2W then changed the plumbing and we worked again at 8W. Mike runs an SDR-1000 so he had a nice spectrum display was able to see that I had a stronger signal!
I got a really great idea from Dave, N0KP, to use copper wire to make bending
forms.
Copper is a LOT cheaper, and can be easily unbent and redone.
That allowed me to experiment with bending before committing to the
expensive UT-141.
I still had some measuring problems, as can be seen by the fact that the
RF relay is tilted to the side, because the line from the TX port is just
a little bit too long.
I made a simple bending jig out of two 5/8" dowells glued in to a block of
wood. If I build a new one, I'll use a larger piece of wood so I have more
flat surface to work on.
I'll also likely to put a third dowell to hold the wire when bending.
There have been many discussions locally about whether or not sequencing is
required at this power level. I decided not to take any chances and to
sequence my amplifier.
After many discussions about what sequence to do thing,
I settled on this sequence:
I got many different opinions about what sequence to use. One significant variation from above is to switch the transverter from RX to TX at the same time as the amplifier. I decided against that for several reasons: (1) I wanted the IF relay to be switched as soon as possible after PTT from the radio. (2) The opinion of somone I trust was that putting 2W into the amplifier when the amp is off was not a problem.
With the way I chose, I do not have to modify the DEMI transverter
control board. The entire sequencer is external to both the transverter
and the amplifier.
The design for this sequencer is largely lifted from a design by Paul Wade, W1GHZ he calls A simple, yet fool resistant, sequencer for transverters.
The 2N3904 is held on by the pull-up, and is turned off by PTT-L. This should require very little current, thus acting as a buffer for newer radios that have very little current carrying capacity on PTT (e.g. IC706MKIIG, FT-817).
When the transverter side of the circuit is on, it charges a capacitor that is bled off by the 10K-ohm resistor through a diode. This will hold the PTT to the transverter on for a short time after PTT is released. This gives the amplifier time to switch off before the RF T/R relay is switched from transmit back to receive.
Early on, the 20uf capacitor was originally a 10uf capacitor, but I decided that I would rather hold the transverter in transmit longer and lower the risk of transmit RF coming in the receiver.
The amplifier side of the circuit has a capacitor that is charged thru the 22K-ohm reisistor. This will hold the gate of the MOSFET below it's turn-on voltage for several tens of milliseconds, giving the RF T/R relay time to switch to transmit before the amplifier is sending 8W of RF power into it. The capacitor is discharged through the reverse diode immediately when PTT turns off.
The Dish
My current dish is a DISH Network dish.
This is the second dish I've had on 10ghz, see the
History section for what happened to the first dish.
After the spill, we re-bent the dish back to look straight, and even measured
it on a short range with good gain. However, in real world contacts I was
having trouble hearing and being heard. In the meantime I acquired a
DISH network dish which has now replaced it.
After roving the Red River Valley north of Fargo, ND in a very windy
September, 2004 (30mph+ average wind speed both days), I decided that I
needed to reduce the wind load by moving the radios up behind the dish.
That also put the dish down lower on the tripod.
I used the same mounting bracket, but only attached the lower U-Bolt to the
dish.
This was strong enough to carry everything by the upper support bar, but I was
never comfortable doing that.
My first horn was bent from brass sheet soldered to a homemade brass flange
that was then bolted to a WR-90 Waveguide Transition. I was happy with the
horn, except that the conector was an "N" connector and I had to use an
"N" to "SMA" adapter of unknown quality at this frequency.
My current configuration uses a single oak bar to support equipment,
on the 45-degree mounting pipe that is attached to the dish.
This moved the equipment closer to the dish, and makes the entire setup
take an inch or two less space.
To fit in the trunk of my Honda Civic, I need the equipment to take as
little space as possible.
History
Dish & Radios
My first dish was a DirectTV dish. This dish took an unfortunate spill
near the start of the 2004 ARRL 10GHZ-And-Up Cumulative Contest. The dish
was bent back (mostly) in to shape, but in the 2005 contest it became apparent
that it was out of shape enough to make a big difference in hearing and being
heard. I replaced it with a DISH network dish.
My first radio mounting can be seen here. It is a wood "H" bracket, with
two horizontal boards bolted to the vertical pipe. The radio is below
the dish, for the most part.
This sure looks simple and clutter-free compared to what I have today!
The first horn mounting was a board (trimmed to fit inside the dish arm) with
threaded rod holding the horn. It always looked like the horn was held at an
angle.
To get on the air, I left the relay dangerously hanging below the transverter.
I eventually changed that to have the relay out straight as it is today.
Horn
I first supported the horn using a pair of #10 threaded rods attached to a
board that fit in the dish arm, and to a pair of bent angle brackets that
supported the horn.
This horn never seemed to be quite straight, so I took an idea from W0ZQ and
used a square bottom U-Bolt to hold the horn.
I'm happy with this design, and keep it as a backup.
Ham Radio Equipment
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Home Page
$Id: 10ghz.html,v 1.3 2006/06/14 05:13:15 glen Exp glen $
2004-07.2/100_0174 - first config
2004-07.2/100_0176 - kinda can see the horn mounting
2005-06.1/100_0623 - v 1.1 (raised up)
