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Re: [Amps] VHF all-mode and DC-to-daylight rigs

To: manfred@ludens.cl, amps@contesting.com
Subject: Re: [Amps] VHF all-mode and DC-to-daylight rigs
From: Scott via Amps <amps@contesting.com>
Reply-to: Ka9p@aol.com
Date: Fri, 6 Jan 2017 11:02:24 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>
I've really enjoyed this thread, and having 3 old Yaesu dc to daylight  
radios (817/897/847) have to say they are all still imminently useable subject  
to the strong nearby transmitter issue, which I've encountered only once, 
with  the 817.
 
But where does the notion of no useable satellites come from?  There  are 
at least 5 (+) reliable LEO linear transponder satellites, and I've yet to  
listen to an orbit where there isn't activity.  And the old Yaesus have  been 
fine for accessing them with half way decent antennas, without  preamps.
 
Granted it's not AO-13, but plenty of fun to be had - we had more interest  
from younger, newer hams in our Field Day satellite station than just about 
any  other thing.
 
And of course there still is a lot of ISS activity with schools etc,
 
OK, satellite cheerleading over.
 
73 Scott ka9p
 
 
In a message dated 1/6/2017 9:30:53 A.M. Central Standard Time,  
manfred@ludens.cl writes:

Cathy,

> For weak-signal usage, you want low noise figure  and high
> sensitivity, but you really don't care about dynamic  range.  You are
> unlikely to have a strong signal next door to  desense your rig.
> There is plenty of bandwidth and few  signals.

The problem is just when you have nearby high power  transmitters, on 
frequencies close enough to the ham bands to get through  the front-end 
filters. Such as low UHF TV stations, and certain kinds of  radar 
stations. Or perhaps a ham neighbor using significant power on the  same 
band.

In my case none of that applies, so indeed I don't need  much dynamic range.

> I do hope that with the launch of Phase 4 and  geostationary
> communication on 5/10 GHz, we'll see a new era of ham  satellite
> usage.  I know several local hams who are interested in  building the
> 5/10 GHz ground station.

I would join in too. But  I don't think that Phase 4 sats will be here 
very soon. Or at all. They  are complex to build and expensive to launch. 
We have ever fewer  technically capable people among us, and most of them 
are too engaged in  the dollar hunt to devote lots of time to ham 
projects. So there is a  severe shortage of committed, technically 
capable hams, to develop and  build advanced satellites. And even when 
they build one, rising several  million dollars for a launch of such a 
sat isn't easy either!

In  the 1990s I was involved in building what we intended to be the first  
Chilean sat, CESAR-1. It would have been a Microsat with 9600 baud GMSK  
uplinks on 2m and downlinks on 70cm, and several added features and  
experiments. My own hands-on involvement ended when it was financially  
impossible to procure some essential test equipment, and I delivered the  
transmitters and one receiver without having been fully tested. Several  
other volunteers also had such trouble, or simply couldn't devote enough  
time to the sat. The project leader, CE2MH, ended up hiring people do to  
the remaining work, but those people had neither enough motivation nor  
expertise, and failed. The project was delayed ad infinitum, until CE2MH  
got ill and finally died, and that was it. Nobody stepped in to take his  
place. CESAR-1 will never fly.

And that was just a low orbit  Microsat, largely based on a proven design 
by AMSAT-US. We just had to  copy that, and add our own customizations. 
It's a far larger task to  develop a new satellite from scratch, and a 
Phase 4 sat is enormously more  complex than a low orbit Microsat.

>> Since there are no really  usable sats, there is no demand for
>> VHF/UHF SSB operation
>  
> Your club doesn't do weak-signal tropo VHF?  That's too  bad.

No, neither my club, nor anyone within my possible coverage. I'm  not 
aware of anyone on South America regularly doing it! Maybe there are  
some, but I don't know about them. When I have tried casually listening,  
on those days when there are strong meteor showers, I haven't heard  
anything.

The closest we come to weak signal work on VHF in this  part of the world 
is chasing distant repeaters, when there is some tropo  ducting, mostly 
in summer. Oversea propagation between central Chile and  Peru are fairly 
common, covering distances of 2500km or so. But that's of  course all 
done in  FM.

Manfred

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