Tag: w6lvp

Another Full Day Of Radio!

SPE Expert 1K-FA
Cabling is nearly complete

Installation of the SO2R RX Loop Antenna TX Relay

The SPE Expert 1K-FA amplifier allows connection of two transceivers, four antennas, and, an SO2R RX-ONLY antenna. When transmitting on Radio#1, Radio #2 is connected to the SO2R RX antenna. This enables the operator to listen on Radio #2, on any band, while working the latest DX on Radio #1, and vice versa. Automatically. The Expert amp does all the switching.

SPE Expert 1K-FA Linear Amplifier

SPE Expert 1K-FA
Business end of the 1K-FA. Two inputs, Four outputs, Internal Antenna Tuner, SO2R, and it’s FULLY AUTOMATIC.

SO2R operation also 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 etc.

W6LVP Loop Antenna

For an SO2R antenna it is suggested (and makes the most sense) to use a wideband RX antenna on this port. In my opinion the W6LVP Loop is the best antenna on the amateur market for this purpose. Perfect for use with my amplifier. I researched them all, and chose the LVP. The loop antenna is available in a version that includes a TX/RX Relay/Power Injector box. Wait, isn’t the SO2R port on the amplifier RX-ONLY? The answer is yes, but…and it’s a big but…only when the amp is turned on. Huh? When the 1K-FA amplifier is turned off, Radio #1 is connected to antenna #1 (which in this case is a resonant TX/RX antenna), and Radio #2 is connected to the SO2R antenna.

W6LVP RX Only Loop Antenna
The W6LVP Loop TX Relay has a dedicated PTT line from Radio #2

Found A Hitch!

Under the operating condition when the amp is turned off, Radio #2 will transmit into the RX-ONLY antenna. (!No Bueno!) And by doing so, would likely destroy the RX preamp in the loop antenna. Once I realized this I ordered the TX/RX Relay and put it place with a dedicated PTT line from Radio #2 to switch it. Even though the Relay Box can auto-sense RF, I felt a PTT line would better, perhaps even faster.  Some idiot-proofing by the operator, for the operator! I was sure it would only be a matter of time before I would make this mistake, so the relay was put into place.

Array Solutions - RXFEP
Array Solutions RXFEP – Receiver Front End Protector

During my research I found the Array Solutions RXFEP – Receiver Front End Protector. The RXFEP is a low cost solution and a must have ‘failsafe’ device to protect against overloading the RX in an SO2R configuration. After all, I’ll be transmitting with over 1KW output on an antenna in close proximity to the RX Loop antenna. The Flex 6000 series transceivers have RX front end protection built-in, the Flex 5000 does not, and one can never be too careful. Insertion loss? Not enough to bother me…

SPE Expert 1K-FA
The wiring is nearly complete. I know, I have to find a shorter 9 pin serial cable!

Next I will be adding the antenna connector breakout panels, an audio breakout, and the ground bar for the Single Point Station Ground.

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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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