Burns, I had the same experience with my ARR. Fortunately no harm done. I ended up lifting the choke connection internally. Apparently ARR has never heard of steering diodes.
My other issue was that the "waterproof" case filled up with water. You can imagine my face, and vocabulary, when I opened it on the work table. Easily fixed with RTV. Another reason I personally prefer the SSB units. Alan WA4SCA -----Original Message----- From: amsat-bb-boun...@amsat.org [mailto:amsat-bb-boun...@amsat.org] On Behalf Of Burns Fisher Sent: Wednesday, February 08, 2012 2:33 PM To: amsat-bb@amsat.org Subject: [amsat-bb] Re: AMSAT-BB Digest, Vol 7, Issue 65 Here are a couple things that were less than obvious to me about the ARR 70CM switched preamp. If you are going to power it with phantom power (i.e. up the feed line) you need to add a -C to the part number so they will add in the required choke from the feed line to the power input. But note that once you do this, you can't just use either phantom or external power. In my case, I got the choke ("I might need it someday") but used the external power. Oops...a nice short. It turns out that unless your transceiver has a high-pass filter (or just a cap!) you are probably going to be shorting out back through the feed line. When you do that, you may blow the choke and have to remove it anyway, depending on how much current got through it. (I'm not sure why they did not put a diode in, but hey...) The other thing is that I was going to get one of their phantom power injectors also. The problem there is that they only work with receive-only. So unless you can find one elsewhere, phantom power may be useful mainly if you transceiver supplies it (sigh, mine does not). And finally, another inobvious thing: The power connector has a third pin which, if you ground it, switches to transmit mode. So if you hook this up to the transciever, that's a way of getting around the "minimum power to switch" spec. (I think minimum power to switch is maybe 5W; my transceiver goes down to 5W, but with a 75' feed line, it's not gong to be 5W by the time it gets to the pre amp. The SSB preamp (or at least the 2M one that I have) comes with the choke, diode, etc and has a lower minimum switching power. It is more expensive, though. I hope this helps! Burns, W2BFJ _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
