[amsat-bb] Re: Almost There
kq6ea at verizon.net
Sat Jan 4 17:55:11 PST 2014
Getting rid of the diplexer will reduce the loss, but not improve the
gain. The gain is dependent on the design of the antenna.
73, Jim KQ6EA
Adding a preamp at the antenna is always a good idea for satellite use.
On 01/05/2014 12:42 AM, Joel Black wrote:
> After a rocky start to my Christmas Vacation (I fell off a ladder
> while pruning limbs from a tree - nothing broken, just banged up and
> bruised), I almost have my satellite station back on the air.
> After doing some selling and horse-trading, I am back in possession of
> my FT-847 that I sold to my dad.
> After cleaning out my storage building, I found a couple of fairly
> long runs of LMR400UF. I need to measure them, but I think it is more
> than enough to get me outside and up the mast.
> I also have a U-100 control box thanks to someone on the list.
> I operate an iMac with Mac OS X 10.9.1 so, for now, I am using SatPC32
> on my virtual machine. I have played around with MacDopplerPro, but it
> locks up on my computer continuously. I don't know if it has something
> to do with the USB-to-serial converter (I *do* have a null modem cable
> between the USB-to-serial converter and the FT-847), or if MDP is just
> limited in the unregistered version. The USB adapter works fine with
> my K3.
> Let me ask a question about the Arrow Antenna. Someone mentioned Elk
> Antennas and, while I'm sure it's a fine product, I am already in
> possession of the Arrow. I've done a lot of reading and without
> getting into the arguments about Arrow vs. Elk and length of elements,
> etc., element isolation, and published vs. unpublished gain amounts
> let me tell you what I'm thinking:
> First, I'm going to eliminate the diplexer. I will not need it for one
> thing. For another, it's limited to 10 W max input. From what I have
> read, my gain will be increased quite a bit. I don't remember the
> exact amount, but it's quite dramatic.
> Second, the feed on the Arrow is a gamma match. From my reading, and
> I'm no engineer, for a gamma match to work properly the element(s) (at
> least the driven element) needs to be grounded. That's fine and,
> again, I don't want to get into the "why's" I just want to make sure
> I'm correct. Therefore, my question is:
> Is there any reason I cannot turn the driven element 90 degrees to
> allow for a better connection to the BNC connector? Maybe not even 90
> degrees, but enough to get to the BNC connector without the male
> connector on the cable touching the boom. I want to weatherproof those
> connections. What I'd like to do after I turn the gamma match is feed
> it with a very short length of LMR240 and then into a preamp. After
> the preamp, I'll have the LMR400UF to run to the FT-847. Most gamma
> matches I see on commercial antennas are on the side of the antenna -
> if horizontal, they're below (or above) the boom; if vertical, it's
> off to one side. The Arrow is the only antenna I've seen with a gamma
> match on which the gamma match is not to one side or the other of the
> boom. I hope I'm making sense.
> Anyway, I wanted to let those folks who helped out know that I
> appreciate it and that I'm much closer to being back on the birds than
> I was a few weeks ago.
> Joel - W4JBB
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