At 08:05 AM 3/12/2007, Alan P. Biddle wrote:
From the instructions which come with the units:
===== Connection of the preamplifier into the system is quite straightforward. The coaxial cable from the antenna is connected to the preamplifier input terminal (labelled ANT). Preamplifier output (labelled XCVR) feeds the coaxial cable that connects to the station transceiver or amplifier. Control cable used with the MSPXXXVDG should be shielded. Non-shielded cable acts much like an antenna. Nearby lightning strikes are capable of inducing sufficient voltage on this "antenna" to damage the preamplifier. Shielded cable effectively eliminates this problem. Always mount the MSPXXXVDG with the connectors facing down to avoid water accumulation around the connectors.
Wiring of the power connector is illustrated on the schematic diagram. For rf keyed operation only the VDC and GND connections are necessary. The preamplifier will sense the presence ofrfand automatically switch the preamplifier out of circuit. Hard keying of the preamplifier for transmit/receive changeover can also be accomplished. The C terrminal of the power connector places the preamplifier in transmit when grounded. Also, transmit/receive changeover can be controlled with only the +VDC connection. Apply +12VDC for receive and remove for transmit. The dropout delay function should be defeated for hard keying operation. For hard keying operation transmit/receive relay sequencing is mandatory if preamplifier failure is to be avoided. A circuit such as the ARR TRS04VD will provide sequentially keyed outputs that accurately control the timing of all system transmit/receive changeovers. Review the TRS04VD instruction sheet for more detailed information. =====
I OCRed this, so the formatting is not great. My understanding is that "hard keying" they mean something like QSK where you will beat the relays to death. Certainly CW, and perhaps SSB. However, there is a "relay delay dropout capacitor" which as shipped will protect the unit, and of course preclude QSK. So I suspect the answer to your question is no. In my satellite operations, I have always been tranmitting on a different band than receiving, so I just left the pre-amp on the TX side off. No harm if you forget, of course, unless you do it all the time.
Hope this helps,
Alan WA4SCA
Alan,
Hard keying is NOT QSK like. It is like PTT: You key your radio for transmit and it stays in Tx until you un key. Using the C terminal allows a sequencer to switch the unit into Tx-mode without the unit needing to sense RF on the coax line. This is much preferred. RF sensing T/R is more like QSK that you mention (especially when using CW/SSB). The relays in the ARR preamp will chatter back-n-forth with each RF peak. There is a RC time constant to smooth this our somewhat, but they cannot hold the relay too long or it will not switch fast enough from receive using RF sensing (I've probably confused a few of you by now). The ARR switching preamp apparently works just like many brick transmitting amps: you can use auto RF sensing or hard keying to control T/R.
Short answer: best method is using hard keying of the C-terminal which is controlled by a sequencer.
The bigger question is how you key the sequencer? You can run the PTT line from your microphone to the sequencer. Then the sequencer will have a keying line to your radio's PTT circuit. For CW it is probably easiest to have manual switch T/R controlling the sequencer. If you are running digital you can run a line from the computer (usually the software provides this on a RTS line at the serial port) to control the sequencer. I do all three on my station.
73, Ed - KL7UW ====================================== BP40IQ 50-MHz - 10-GHz www.kl7uw.com 144-EME: FT-847, mgf-1801, 4x-xpol-20, 185w DUBUS Magazine USA Rep dubususa@hotmail.com ======================================