Re: [amsat-bb] Transverters with *70cm* IF's

[Luis Martins <luis.martins@xxxxxxxxxxxxxxx>]

hi dave,
i've been folowing your thread with interest and now i have a question.
with a telescope tripod (which i was already thinking of buying) how do you ajust
azimut and elevation ?? by hand or do you mount a rotor on top of it ?

luis

Dave Metz wrote:

>  > From:          tlang@freeway.apana.org.au (Tony Langdon)
>  > Date:          02 Feb 00 20:44:01 +1000
>  > Subject:       Re: [amsat-bb] Transverters with *70cm* IF's
>  > Organization:  Fidonet: Freeway Usenet <=> FTN gateway
>  > To:            amsat-bb@AMSAT.Org
>
>  >
>  > Hello Dave.
>  >
>
>  >
>  >  DM> Now comes the tricky part, how to get on 1.2Ghz for the uplink.
>  >  DM> I could use a converter to mix my 70cm signal up to 1.2Ghz.  However,
>  >  DM> I am told that there will be "problems with the third harmonic of
>  >  DM> 70cm." That is, the possible third harmonic of my 70cm radio will mix
>  >  DM> with the output of the upconverter mixer producing spurs.  How serious
>  >  DM> this potential problem would be I do not know.  It would take some
>  >  DM> experimenting to find out.
>  >
>  > I think it's worth attempting though.  I have a 2m to 70cm transverter, which
>  > should have the same potential problem.  This is a 20 year old commercial
>  > model, which performs quite well.  However, it is worth noting that the Tx side
>  > of the unit uses double conversion (2m -> 28 MHz -> 70cm).  Perhaps this is to
>  > minimise the possibility of harmonic bleedthrough.
>
> I think you are correct.  Otherwise why do the extra conversion stage?
> Maybe someone else reading this message can shead some light on the
> problem.  Anyone out there???
>  >
>  >  DM> Another consideration is the problem of generating a useful amount of
>  >  DM> power on 1.2Ghz.   The only route I have found is to use ERA MMIC amps
>  >  DM> to produce 7mw of drive.  Then use M57787 hybrid amp (7mw in gives
>  >  DM> 1.5W out) to drive a M57763 (1W in gives 18 watts out).  Cost for the
>  >
>  > We have a locally available set of kits which will provide a total of 10W SSB
>  > on 1.2 GHz.  Just a matter of when to purchase the kit and start building.
>
> Is there more information available on this kit?
>  >
>  >  DM> two amp is $170!   The current plan is too have the converters LO and
>  >  DM> mixer in the shack.  Pipe the RF up to the antenna at low level and
>  >  DM> have a ERA-x buffer stage overcome the loss of the feedline.  The PA
>  >  DM> stage would be at the antenna to reduce loss of the those expensive
>  >  DM> watts at 1.2Ghz.
>  >
>  > My converters will be at the antennas too.  The antennas themselves will be
>  > portable affairs.  I hope to procure a tripod or similar to stand them on.
>  >
> If you do, consider the stability of the tripod carefully.  A conventional
> camera tripod is not designed for holding a large load like a radio and
> an antenna array.  They blow over in the wind!   You might want to consider
> something like the portable telescope mounts that I have seen.
> They are a 4" OD post about 4-5' high.  At the base are four legs that
> extend about 2' each.   The legs can be folded up against the post by
> loosening a bolt.  At the end of each leg is a foot on a leveling screw for
> fine adjustment of the leveling.  They are not all that large to carry,
> and are very robust.  No reason that any decent metal worker could
> not build one in short order.
>  >
>  > I'm following the thread with interest... for obvious reasons. :-)
>  >
>  >  DM> I suspect that it will take me a good two years to build all of the
>  >  DM> stuff I need.  Till then, see you on mode U/V!
>  >
>  > I'm hoping to be operational within 18 months.  As for Mode U/V, it'll depend
>  > on if I can get enough antenna gain out of a portable station for these bands.
>  > :-)  Also need another transverter (10-2m or 10m-70cm) so I can tune the two
>  > bands independently.
>
>  >
>  > Tony
>  >
>  > .. otted lab rat!
>  > --
>  > |Fidonet:  Tony Langdon 3:633/284.18
>  > |Internet: tlang@freeway.apana.org.au
>
> --73-- David WA0AUQ
>
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