[amsat-bb] Re: Feedback on downlink on VO-52
rnutter at networkref.com
Wed Apr 2 07:45:17 PST 2008
Desense may not be the correct word but I am hearing a distorted/fuzzy
version of my voice regardless of where I tune. I have tried one thing
- the coax I am using on the VHF antenna may not have been the best. It
was some old coax I had with BNC connectors on it (It was used on
network cards when thin-net was the way to go). I have found a heavier
piece of coax and have changed out the respective section. Will see how
John Kopala wrote:
> I have to throw in my 2 cents.
> I'm not sure why you would be getting any desense. I have virtually the
> same setup.
> I have not had any indications of desense with my installation.
> I'm using an IC-910H, separate feedlines, mast mounted preamps, and yagi
> Feedlines are 9913F7 ultraflex and are about 60' long plus connections from
> the preamps to the antennas.
> I have a 2 meter CP KLM (oldie), a 1.2 GHz looper, and a 435 KLM.
> Separation between the 2 meter and the 70 cm antennas is about 8 feet.
> I do use an elevation rotor and so the antennas can be aimed quite
> Normal power output is usually about 5 watts unless the satellites have a
> very low pass.
> Using more than 25 watts would be pretty unusual with most satellites.
> I live in Phoenix, AZ, and am surround by mountains, some within walking
> so in most directions I have an elevated, rugged horizon.
> The first question that I would ask is how much power are you running on the
> And then, how far apart are the antennas?
> I use the CI-V interface with SATPC32 to control the doppler. It works
> You just have to make sure the address in the radio matches what you have
> set in the software configuration files.
> For SSB I have the frequency updated whenever it gets off by 20 or more Hz.
> For FM I'm using 300 Hz.
> Maybe overkill on SSB, but it's better than having the tone jumping up and
> down all the time.
> As George said, do the CAT interface first, expecially if you plan to be
> doing SSB or CW.
> Once you have that set up, you can tweek your downlink on the CAT display
> when you first transmit.
> After that, your uplink and downlink should pretty well track with each
> The fun comes when you have to follow someone who has no doppler control.
> I don't think you are going to find any easy way to interface the Channel
> Master rotor to a computer interface.
> Generally the interfaces expect a voltage between 0 and 5 volts representing
> the azimuth of the antenna.
> A higher indicator voltage can be scaled down to the 0 to 5 range if you can
> find something suitable.
> Most ham rotors have separate wiring for the indicator potentiometer in the
> rotor and that can be easily scaled
> and used with computer interfaces.
> Hope this helps. I can set a picture of my antenna installation if that
> would help.
> Message: 13
> Date: Tue, 01 Apr 2008 10:12:03 -0500
> From: Ronald Nutter <rnutter at networkref.com>
> Subject: [amsat-bb] Re: Feedback on downlink on VO-52
> To: George Henry <ka3hsw at earthlink.net>, "amsat-bb at amsat.org >>
> AMSAT-BB" <amsat-bb at amsat.org>
> Message-ID: <47F250C3.7020801 at networkref.com>
> Content-Type: text/plain; charset=UTF-8; format=flowed
> I am using seperate antennas and feedlines. For the time being, I am
> using a Channel Master antenna to turn the antennas. I have a pvc pipe
> rig setup with the antennas at an angle of 25 degrees due to the clutter
> in the neighborhood I have to clear to see the sats. I hope to have a
> tower in the future but with being laid off from my job, cant really
> have any expenditures right now.
> I have the cat interface for the IC910H but havent looked into how to
> set it up yet.
> George Henry wrote:
>> -----Original Message-----
>>> From: Ronald Nutter <rnutter at networkref.com>
>>> Sent: Mar 31, 2008 10:40 PM
>>> To: AMSAT-BB <amsat-bb at amsat.org>
>>> Subject: [amsat-bb] Feedback on downlink on VO-52
>>> Thanks to the help of several on this listserv, I was able to get a
>>> contact on VO-52 until I lost coordination on keeping the rotor turned
>>> and the IC910H tweaked the right way on the VFO's. I had problems
>>> finding my downlink because of what I think is desensing on the 2M
>>> Can I resolve this by putting a filter on the 2M receive to stop the
>>> desensing like I would on the UHF receive on the FM birds ? If not, is
>>> there another way to fix the problem ?
>>> Thanks to W0EOZ for putting up with me while I was trying to figure
>>> things out. Hopefully my next contacts will last a bit longer <G>.
>> Are you using separate 2 meter and 70 cm antennas with separate feedlines,
>> or diplexing onto a single feedline to a single antenna? First thing to
>> do is reduce your uplink power as much as possible while still being
>> heard. If you are diplexing to a single feedline, you only have about
>> 60dB or so of isolation, so too much uplink power can exceed that. You
>> should be able to work VO-52 with 25 watts or less...
>> I have never experienced desense on 2 meters from my 70 cm uplink... only
>> the reverse, which can be cured with separate feedlines and antennas,
>> ample separation between the antennas, and the diplexer-as-filter trick
>> found at <http://www.amsat.org/amsat-new/articles/Mode-J/>
>> And I strongly recommend buying or building a CAT interface and letting
>> your tracking program take care of tuning the radio (and turning the
>> rotors, if you buy or build a rotor interface as well). The demo version
>> of SatPC32 is fully functional except for saving your station parameters,
>> and can be downloaded from <www.dk1tb.de/indexeng.htm>.
>> If you like it, register it: all proceeds go directly to AMSAT. A CAT
>> interface PC board with the harder-to-find chips included is available
>> from <www.farcircuits.net> and only costs about $20 to build. The
>> FOD-Track rotor control PC board is also available from Far Circuits, and
>> will cost $45 - $50 to build. The LVB Tracker is available thru the AMSAT
>> store, and has the advantage of being able to operate without a computer
>> attached... nice for mobile ops!
>> Go for the radio control first: that'll free you up to deal with the
>> rotors manually, and they demand far less attention than tuning does.
>> George, KA3HSW
> Sent via AMSAT-BB at 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
More information about the AMSAT-BB