[amsat-bb] Re: Feedback on downlink on VO-52

[Ronald Nutter]

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 
that works.

Ron

John Kopala wrote:
> Ron,
> 
> 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 
> antennas.
> 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 
> precisely.
> 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 
> distance,
> 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 
> uplink?
> And then, how far apart are the antennas?
> 
> I use the CI-V interface with SATPC32 to control the doppler.  It works 
> great.
> 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 
> other.
> 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.
> 
> John
> N7JK
> 
> 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.
> 
> Ron
> KA4KYI
> 
> 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 
>>> downlink.
>>>
>>> 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>.
>>>
>>> Ron
>>> KA4KYI
>> 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.
>>
>> 73,
>> George, KA3HSW
>>
>>
>>
>>
> 
> 
> 
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