Jeff,
I appreciate the thoughts. Anytime I've looked at a scheme which allows simply
swapping the TX and RX to get back on the air, I arrive at the same
conclusions...
(1) If I took a lightning hit at the site, I'd want my spares to have been
stored somewhere else.
(2) Once I swap the TX and RX, I still can't bring either home for repair
without taking the machine off the air.
As far as the automated switchover, the 7K has three receiver and two
transmitter ports, so I wouldn't even need coax relays to provide remote swap
capabilities. I could just crystal each radio for simplex, wire both receivers
and both transmitters into the controller, issue a remote DTMF command to swap
them, and instantly implement a second repeater on the upside-down split.
I think my answer is going to end up being building a stash of spares, and
using two radios.
73,
Paul, AE4KR
----- Original Message -----
From: Jeff DePolo
To: Repeater-Builder@yahoogroups.com
Sent: Monday, April 26, 2010 12:11 PM
Subject: RE: [Repeater-Builder] Mitreks as UHF Repeaters?
Because of the internal desense issue, I'd build them the same, but operate
the two radios separately. That is, use one as a transmitter and the other
as the receiver by default. No duplex mods required. If the Tx dies on
one, swap the system cables around to make the formerly-transmitter radio
the receiver, and vice-versa. You could even automate the changeover via a
couple of coaxial relays and some simple homebrew transistor and/or relay
logic tied into your controller.
--- Jeff WN3A
> -----Original Message-----
> From: Repeater-Builder@yahoogroups.com
> [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Paul Plack
> Sent: Monday, April 26, 2010 1:49 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Mitreks as UHF Repeaters?
>
>
>
> ?
> Tim,
>
> My plan at this point is to convert them to full duplex, so I
> can use the second Mitrek to prepare a complete, plug-in,
> standby set of RF decks. The mods look very straightforward,
> but I was wondering if there were any gremlins people discovered.
>
> Your heatsink approach, however, is exactly what I was
> talking about. I have several very large heatsinks originally
> designed for use with big SCR switching circuits which look
> to be more than generous for a 30w PA at 100% duty cycle.
>
> My first repeater was built from a 2w Repco exciter board
> repurposed from RFID service. It was supposedly rated for
> continuous duty, but had to run very hot to dump the heat it
> produced through the little aluminum tab mounted to its own
> PC board within the case. I fashioned a new tab with a 90ยบ
> twist which allows sinking the little PA to the case itself,
> and it never got above "warm to the touch," even after hours key-down.
>
> Guys, I appreciate all the input.
>
> 73,
> Paul, AE4KR
>
>
> ----- Original Message -----
> From: w7...@comcast.net <mailto:w7...@comcast.net>
> To: Repeater-Builder@yahoogroups.com
> <mailto:Repeater-Builder@yahoogroups.com>
> Sent: Monday, April 26, 2010 10:16 AM
> Subject: Re: [Repeater-Builder] Mitreks as UHF Repeaters?
>
>
>
>
>
> Isn't the rpt. going to be built using (2) Mitrex, thus
> shielding should not be a problem. I have, in the past (with
> the help of a Bridgeport mill), fashioned "Larger Heatsinks",
> that bolt onto the orig. Mitrex heat sink....seems to
> dissipate heat well...
>
>
>
> No virus found in this incoming message.
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> Date: 04/26/10 02:31:00
>
>
>
