The Station At AA8V
Signal Flow

Click anywhere on the diagram below or use the table below to learn about that part of the station.

Click anywhere on the diagram above use the table below to learn about that part of the station.

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Introduction:
If your station involves more than a single transceiver and antenna it is a good idea to sketch out a signal flow diagram so you know how your station is connected. It is also a good idea to label all of the cables so that you can tell where each goes. There is nothing worse than trying to figure out where an unlabeled cable is supposed to go or what it is supposed be connected to! I originally sketched this diagram because many times I wanted to change something and I couldn't remember how things were connected. Now I keep the diagram handy in a recipe note box (along with other handy note cards) and consult it when needed.

The station is set up so that different antennas, transceivers, receivers, and transmitters can be selected, (as much as possible), without having to plug or unplug any cables. In the end I was able to pretty much achieve that goal, but in a couple cases it was easier to rely on plugging or unplugging a cable than to use another switch.

Antennas, Antenna Matching Network, and Antenna Monitoring:
One thing that is easy to see from the signal flow diagram is that it all begins and ends with the antenna. I use several different antennas and all but one of them needs a matching network (antenna tuner) to operate properly. An SWR/Wattmeter is needed to determine when a proper match is obtained and to measure power output. Though the Palstar antenna tuner I use contains a fine peak reading wattmeter, I find a digital sampling wattmeter like the MeterBuilder MB-1 to be much more useful. Such a meter can be used as a modulation meter for AM and SSB in addition to its the usual function as a wattmeter. It is very important that the coupler ("pickup") for the MB-1 wattmeter to be placed at the input of the antenna tuner, not the output. If placed on the output of the tuner the wattmeter cannot be used for adjusting the antenna tuner and it will not operate correctly.

Because the MB-1 coupler is separate from the meter itself, it can be easily be placed anywhere in the signal chain. An example of when this would be done is in adjusting the input circuit to the Ameritron AL-572 amplifier. If placed at the input of the amplifier, the input circuit to the amplifier can then be adjusted for the lowest SWR at the frequency most used by the operator. This provides the best match/load for the transmitter driving the amplifier. In fact, the MeterBuilder can accomodate up to four couplers and these can be selected from the front panel. For example, a separate couple could be left in-line at the input to the AL-572 amplifier to measure the power driving the amplifier. The MeterBuilder can even be configured to simultaneously read both couplers and display the input and output of the amplifier at the same time.

High Powered Amplifiers:
High powered amplifiers should be the last thing in the signal chain before the antenna and monitoring systems. Many stations will not have an amplifier. Those that do will usually only have a single amplifier. However, here at AA8V, there are two.

Whether two amplifiers can be "daisy chained" like this depends on the amplifiers. As it turns out, when in bypass mode, the AL-572 amplifier can easily handle the 250W output of the 813 amplifier. However, when in bypass mode, the 813 amplifier cannot handle the full 1300W output of the AL-572. Thus, the signal first goes into the 813 amplifier, and then the AL-572. The AL-572 is always bypassed unless placed in the transmit mode by the TenTec Jupiter. The Wingfoot 813 amplifier is always bypassed unless placed in transmit mode by the Wingfoot VFO exciter.

Wingfoot T/R Relay And Wingfoot VFO Exciter:
The Wingfoot T/R relay only goes into transmit mode when activated by the Wingfoot VFO Exciter.Whenever the Wingfoot Exciter is placed in spot or operate mode this relay is activated, switching the antenna to the output of the Wingfoot VFO Exciter. At all other times the relay simply passes the signal coming in through the receive ("R") port to the antenna ("A") or output port.

Manual T/R Switch:
The manual T/R switch does a lot more than switch from receive to transmit when using certain receivers and transmitters. It also reroutes the signal from one bank of equipment to another. For instance, if the Jupiter Transceiver or Drake Twins are used by themselves, it is left in the receive ("R") position. However, if the 6146B system or Viking Ranger is used with either the 6x2 receiver or the Hallicrafters SX-96, the manual T/R switch is left in the transmit ("T") position, and the second T/R relay takes care of switching from receive to transmit.

If the Jupiter or Drake R4A is to be used to receive with either the 6AG7/6146B system or the Ranger transmitter, the transmitter of choice is plugged into position 2 of MFJ switch B, which is then set to position two. The manual T/R switch is then used to manually switch from receive to transmit.

MFJ-1700B Dual Switch::
The MFJ-1700B consists of two 6 position switches with SO-239 inputs and outputs mounted in a single case. The switch permits any of six different devices to be connected to either the receiver ("R") or transmit ("T") ports of the manual T/R switch without plugging or unplugging cables. Switch A is used to switch between either the Jupiter transceiver or the Drake Twins transceive system. Switch B currently has only one permanent connection to it, the second T/R relay, which is connected to port one. If the Jupiter or Drake R4A is to be used to receive with either the 6AG7/6146B system or the Ranger transmitter, the transmitter of choice is plugged into position 2 of switch B, which is then set to position two. The manual T/R switch is then used to manually switch from receive to transmit.

Second T/R Relay:
The second T/R relay allows a receiver and transmitter connected to its transmit and receive ports to be used as a complete station-within-a-station with automatic receive/transmit or PTT capability. The relay is controlled by either the automatic T/R system or the Push-To-Talk Relay system.

When used with the automatic T/R system, either the 6x2 or SX-96 receiver can be connected to the receive ("R") port and either the 6AG7/6146B or Ranger transmitter can be connected to the transmit ("T") port. When the manual T/R switch is set to the transmit port and MFJ switch B is set to port one, the receiver and transmitter will function as a complete station that automatically goes into transmit mode whenever the key is pressed.

When used with the Push-To-Talk Relay system, the Hallicrafters SX-96 receiver is connected to the receive port, and the Johnson Viking Ranger is connected to the transmit port. With the manual T/R switch set to the transmit port and MFJ switch B set to port one, the receiver and transmitter will function as a complete push-to-talk (PTT) AM station. Pressing the PTT bar on the D-104A microphone then places the system in transmit mode.

Transceivers:
There are two transceivers here at AA8V. One is a modern transceiver with digital signal processing, the TenTec Jupiter. The other transceiver is a 1965 system consisting of the Drake R4A receiver and the Drake T-4X .

I often use the TenTec Jupiter as a receiver, with the transmitter unused. I typically use it with the Wingfoot VFO system, the 6AG7/6146B system, or the Ranger transmitter.

The Drake transmitter and receiver are interconnected as a transceiver, but they can also be used independently. However, I usually use them together as a transceiver, since they work so well together.

Tube Transmitters:
I love vintage and tube gear more than I like modern gear, particularly transmitters. You just can't beat that glow when operating late at night. In addition to the Drake Twins and Wingfoot VFO/Amplifier system I have two other tube transmitters. One of these is a classic CW/AM transmitter from the mid-late 50s, the Johnson Viking Ranger. The other transmitter is a homebrew system consisting of a small VFO amplifier followed by a 6146B linear amplifier. Both of these are controlled by a digital VFO to give them modern frequency stability and precision. Either of these transmitters can be used with any of the receivers elsewhere in the station.

Tube Receivers:
Of the four receivers in the AA8V station, three of these are vacuum tube designs. One of these, the Drake R4A, is part of a transceiving system. The other two, the homebrew 6x2 and the Hallicrafters SX-96 are stand-alone receivers. One of these stand-alone receivers at a time is normally connected to the receive port of the second T/R relay. With the manual T/R switch set to the transmit port, they can then be used with either the Johnson Viking Ranger or the 6AG7 VFO amplifier/ 6146B linear amplifier system.

When the Hallicrafters SX-96 receiver is paired with the Johnson Viking Ranger, the result is a classic 1955 CW/AM station with automatic or PTT T/R control and modern frequency control and precision. In particular, it is a real pleasure running these two together on 40m AM.

When the 6x2 receiver and Timewave audio filter are paired with the 6AG7 VFO amplifier, 6146B linear amplifier, and the digital VFO, the result is a hybrid station that is almost as easy to use as a modern transceiver. The receiver and transmitter are all tube, and the audio filter, VFO, and auto T/R relay are solid state. There is absolutely no reason why vacuum tube and solid state technologies cannot be combined in the same station.

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If you have any questions or comments, you can send E-Mail to Dr. Greg Latta at glatta@frostburg.edu