[amsat-bb] Re: beginner question re: uplink power
corner5 at comcast.net
Sun Oct 19 13:22:07 PDT 2008
Thanks for replys (Re: beginner question re: uplink power)
In response to two points contained in replys from helpful others...
> Ed - KL7UW: I wonder if the Ramsey preamps allow for "hard" switching. That is
by separate control line that the radio PTT controls. Then You have
no issue with RF power and would run the units with the RF sense
disabled. I should state that "many" (dare I say most) experienced
VHFers that run high power (>100w) use hard-wired switching. I know
of NO eme stations that use RF sense control lines.
A: Ed, yes this is a good suggestion. In fact these preamps are very simple units. No, they do not have any switching that would
allow for external PPT communication from the TS2000 (0-100w at 2m, 0-50w at 70cm). That said, I certainly could add my own mast mount external relay
to do the switching. I also could simply install a DPDT or TPDT switch at the shack end and manually do the switching. This last
approach could lead to smoking the preamp the one time I forget to toggle it out of line. So, in the end I chose to
go with the RF sense remote switch. I hope the need to contain my uplink RF withing a chosen range (0-10 or
10-30 or 30-100 watts) will not be too limiting.
> Tim - N3TL: I would be curious to hear from anyone currently using verticals with preamps as their primary receive antennas.
A: Tim, I think technically you would not call my antennas vertical, but here is what I will start using:
I have now completed the 2m / 70cm pair of double moxon (co-phased) fixed omnis. Each antenna has two moxons that
are 90 deg to each other. I used the plans as published in
QST, August 2001, author = L.B. Cebik. I chose these antennas do to wishing to avoid the expense and tracking logistics of
a beam (for my first setup). I suspect I will go to this upgrade later as I learn more. Some prefer the more
conventional turn-style design, Lindenblad, Quadrafillar Helix but I thought I would try this out and see.
> Roger,WA1KAT: I think I would contact Ramsey and see what the resistor selection
limitations are, unless you have a schematic and can determine it from the
A: In fact I already have both the schematic as well as the resistor values that achieve the specific power windows.
I verified with Ramsey that if I wanted I could replace the resistor with a pot for a full range. Unfortunately
this does not really address the fact that I will still be restricted to a given range (although with the pot I
would have more flexibility as to choosing my range). Also a more wacky thought I had was to have the resistors
(or pots) located in the shack and toggle them as needed.
> Roger,WA1KAT: Hard wiring, as has been suggested, is your safest choice. As the switch has
the relay in it, maybe Ramsey can tell you where to tap in to directly
switch the sensor.
A: This is a very interesting approach. If I understand your idea here, you suggest to use the relay that is
on the RF switch board and toggle this relay with a PPT signal from the TS2000 (and not make use of the RF sense at all. Yes?
I do not know about the details of using the PPT signal in this way. I guess I need to hope that the PPT signal
is compatible with the relay (voltage). And then if I need to abandon the RF switch all together, are there suggestions
as to what is a good (not too expensive) remote relay design?
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