I posted the following message once before when simulcast transmitters were
being discussed but I don't think it made it to the list:
I've taken cell-site-surplus rubidium oscillators with 10 MHz outputs and
used them as the reference for GE Delta-S synthesized radios. If memory
serves the stock reference oscillator in the Delta-S VHF and UHF is 13.2
MHz. I made some firmware changes so that I could just program the radio
normally after hooking up the 10 MHz reference in its place.
The UHSO oscillators out of Micor/Purc stations are OK, but require more
frequent adjustment as they age, and of course, you need test equipment that
is high-stability as well. I have one of the rubidium oscillators on my
bench that all of my test equipment is locked to, and I verify the frequency
periodically with a GPS timebase just to make sure the rubidium hasn't
drifted. Although I don't know what the specs are for the rubidiums I have
(all of which are made by Ball/Efratom), carrier frequencies (as measured at
UHF) have never differed by more than 0.1 Hz. If you're at a site with
GPS-disciplined equipment already there (modern simulcast paging
transmitters, HD/IBOC FM transmitters, etc.), you might be able to convince
the owners to give you a split off their 10 MHz reference to save on the
cost of having to come up with your own.
I have three repeater transmitters running with the rubidium/Delta
combination, but I haven't tackled the audio delay issue yet. The
rubidium/Delta marriage and on-air testing has been more or less just a
proof-of-concept excercise up to this point. When I have more time I'll get
back to the project.
--- Jeff
--------------------------------------------
Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant
> -----Original Message-----
> From: [email protected]
> [mailto:[EMAIL PROTECTED] On Behalf Of JOHN MACKEY
> Sent: Sunday, June 05, 2005 7:37 PM
> To: [email protected]
> Subject: RE: [Repeater-Builder] Simulcast: Anyone done this
> for ham repeaters
>
>
> That's just it, resources!! I would love to put up a
> simulcast system. But
> the time, money, & other resources make it basically
> impossible. To do it
> right, you need to have it syn'ch to GPS. The OLDER systems
> that used high
> accuracy crystals in ovens needed regular attention. I make it to my
> repeaters about twice a year.
>
> ------ Original Message ------
> Received: Sun, 05 Jun 2005 05:24:31 PM CDT
> From: "Steve Bosshard \(NU5D\)" <[EMAIL PROTECTED]>
> SNIP
> > Most ham clubs do not have the resources for a simulcast
> system, but it
> > would be nice. Also a trunked 2 or 3 channel system could
> be viable.
>
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
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