Rotors Make The World Go Round…

My 14 year old Yaesu G-800DXA rotor has malfunctioned for the first time. It can be turned using the left/right switch, but there’s no movement of the azimuth indicator. This could be as simple as a bad connection, caused when I pulled the connector from the controller during the remodel. It’s possible, as I remember having trouble getting the connector out.

It could also be that the position potentiometer inside the rotor has failed. In which case I now have a “Plan B”. If the problem turns out to be inside the rotor I’ll replace the rotor, and consider repairing the old one for some future use.

I also have some rough spots in the G-800SDX rotor that I use for SAT azimuth. The rotor gives bad indication between 100 and 160 or so. This is surely an indication of impending failure. No worries, as the rotor was acquired secondhand for peanuts, and has been in operation for 6 years. It still works and will stay in operation until I replace the the HF rotor. The plan is to buy another G-800DXA for the HF antenna (since I already have a working computer interface card for it). FWIW the Idiom Press RotorCard from is highly recommended. It gives your rotor its own COM port number, and can be accessed by any software.

If possible I’ll change out the SAT and HF rotors the same day. I will most likely purchase both rotors (G-5500 and G-800DXA) new from wherever I find the lowest price. I’ve owned the Yaesu G-5500 AZ/EL Rotor, and there’s no doubt it’s the best. My cobbled together KENPRO/YAESU combo has been serving me well, it enabled me to get back on the satellites at a greatly reduced cost, and was a deciding factor to stay on with the SATS.

The existing satellite rotors will be replaced with a Yaesu G-5500 AZ/EL
Yaesu G-5500 AZ/EL from my previous installation.

I’ll use the leftover G-800SDX to turn the W6LVP Loop. We all know a rotor for the RX only Loop Antenna is a must have. The loop can be rotated to find the null or the peak, depending on the signal situation. Thus far I’ve only used the loop in a fixed position, so utilizing a rotor will open up some new possibilities.

For the replacement rotor I am considering the Green Heron G800/RT21 system. I’m waiting for a reply on the shipping cost before I order.

UPDATE: 030818 – Well, I got my answer from GHE. I’ll be shopping elsewhere…

SO2R RX Loop Antenna

Todays work included installation of the SO2R RX Loop Antenna and associated devices. The W6LVP relay will provide switching for the SO2R RX Loop Antenna. I’ll also install some front end protection.

Here are some of the items on the agenda:

SO2R RX Loop Antenna
The wiring is nearly complete.


The SPE Expert 1K-FA amplifier allows connection of two transceivers, four antennas, and, an SO2R RX antenna. When the OP is transmitting on radio#1, radio #2 is connected to the SO2R RX antenna. This enables the operator to listen on radio #2 while working the latest DX on radio #1, and vice versa.

SO2R RX Loop Antenna for low noise

Operating in SO2R mode presents the possibility of overloading or damaging the sensitive RX front ends of the two connected transceivers. The 1K-FA manual warns of this possibility and cautions the user about antenna separation and it is suggested (and makes the most sense) that receiver front end protection devices be considered.

The Flex transceivers have built-in RX protection, but adding an RX front end protection circuit offers one more level of protection.

From the May 2014 QST article:

The RXFEP uses multiple devices to soft limit input signals starting at –1 dBm and outputting a specified maximum signal level of +10 dBm to the re-ceiver input.While manufacturers do not generally specify the maximum safe input levels for their equipment, it is worth noting that ARRL Lab re-ceiver dynamic range tests include input signals as high as +10 dBm, and we haven’t lost one yet.

An obvious place to install this device is at the RECEIVE ONLY ANTENNA port of a receiver. By having it as close to the receiver as possible, any pickup on the cable between the device and the receiver is minimized. There is another potential application in some installations, however. Some receive-only antennas include a remote preamplifier at the antenna termination. A protector at the remote preamp input would also be appropriate, although consideration should be given to the preamp input impedance, with a transformation to 50 W, if needed. If there is a long coax run from the remote preamp to the receiver, a second protector could be used at the receiver in case of loose coax connectors or other shield impairments. It should be obvious, but I’ll say it anyway. This unit cannot be used on any antenna feed that is also used for transmitting. Damage to both the unit and the transmitter would be likely consequences.

The low noise RX Loop Antenna is hereby considered a major station improvement!

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EA4TX AS2X2 Antenna Switch

One Step Beyond SO2R

For all intents and purposes, my SO2R operation is self-contained. I use a Flex 6700 dedicated to SO2R operation. I’m operating through an SPE Expert 1K-FA amplifier. This allows using two TX antennas and a wideband RX Magnetic Loop antenna. I enjoy fully automatic operation utilizing one Flex SCU (Spectral Capture Unit) per TX antenna. Really a perfect setup! This configuration has now been thoroughly tested and fine tuned to my operating preferences. Battle tested in contest with more multi band contacts than was ever possible for me while working manually. (the M word). In comes the EA4TX AS2x2 switch to enhance station operation.

I can now freely operate on any band at any frequency, and always have the lowest SWR and the appropriate drive level set automatically. We all know nobody has time to wait around for you to tune up during a contest! You’ve got to be there or be square!

Flex 6500: Dedicated To Digital

Now that I have the SO2R contest station squared away, I’ve turned my attention to the Flex 6500. I have MMSSTV running on 14230, EasyPal on 14233, and two instances of WSJT-X running on any two of any of the other bands that may be open, 24/7. I can work digital modes back and forth between any two bands with a click of the mouse.

For that matter I can also TX from any of the running programs with a single click thanks to the Flex DAX TX feature that switches the TX slice automatically. Combine that with a multiband antenna, and the possibilities are endless!

Watch That Front End!

So now that the digital station is setup and running what’s the problem? Well it’s not a problem yet, but very well could be.

The Flex radios have some built-in protection for the front end of the radio, but it would not be wise to count solely on that feature for complete RX front end protection. In the SO2R setup I added an Array Solutions RXFEP on the RX only antenna to protect the RX when the amplifier is not in operation to switch the RX only antenna automatically. When the amp is off, I have an extra level of protection.

With the 6500 running 24/7 digital modes it would not be hard for me to imagine accidentally TX ‘ing at 1,000+ watts while forgetting the other radio is nearby in RX mode (aka an ‘Inband Radio’). It would just be a matter of time before this type of accident would take place. I could easily make this mistake, so I must add a level of protection against it. In a multi-transmitter environment this is a requirement.

EA4TX AS2X2 Antenna Switch

EA4TX 2X2 Antenna Switch

I researched several antenna switches for the purpose of disconnecting the Flex 6500 antenna when the SO2R contest station is transmitting. Keep in mind I need to be able to transmit 100 watts through the switch. I quickly learned that the the first two “RX Antenna Switches” were not intended for use where the second radio is also a transmitter. Instead they were designed to switch out a receiver only. You cannot transmit back through the second RX port. So the first two switches were eliminated.

I came across the EA4TX AS2X2 and found it could handle 200 watts. It is not an RX only switch, it is a two port switch designed for switching (or exchanging) two antennas (TX and/or RX) between two radios. I’ll only need one side of this switch as I only need to disconnect the Comet CHA-250B antenna, not necessarily switch it with another.

I purchased the EA4TX ARS-USB rotor controller and have been very happy with its quality and performance, so another EA4TX product is welcome. Yes, I saw the single star review. I’m not worried because I know DX Engineering stands behind what they sell, as pointed out in the review.

UPDATE: The AS2x2 arrived today and is now installed at the antenna input of the Flex 6500. Whenever the Flex 6700 is in TX, the antenna to the 6500 is disconnected. Better to be safe than sorry.

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