I am nervous as well, Tom...hi Hi
I'm really thinking of employing a separate relay that I control with a simple
switch, vice depending on the rig to switch "correctly"
using a simple switch is antiquated and slow but....for certain I can control
the switch over mo betta AND prevent damage to the low noise amplifier...
> From: w8ji@w8ji.com
> To: rodenkirch_llc@msn.com; topband@contesting.com
> Date: Mon, 13 Jan 2014 11:37:50 -0500
> Subject: Re: Topband: Single antenna port xcvr but want to employ
> separatereceive antenna
>
> > Anyone have an RTR-1 or 1A that is excess to their needs and willing to
> > sell OR have another idea of how I can employ a separate receive antenna
> > when I have one antenna port?
> > Thank you, in advance, for any replies....off line replies work for me.
> > 72/73, Jim Rodenkirch K9JWV
>
>
>
> Be REAL careful how you do this, Jim!!!! What works for one radio or system
> will not always work for another. This is highly radio (and even amplifier)
> dependent. I can say that based on some very good field experience in how
> things interface. (I'm actually looking at newer radios today to check their
> control systems.)
>
>
> Many radios only have a few milliseconds between the low signal and the RF
> output, some don't have any time between the TX signal and the RF output.
> You have to get any relay completely transferred and all of the bounce gone
> before RF appears. Normally the "back to receive" end of the sequence is
> not a worry.
>
> Many radios do not have the best timing for the external amplifier relay
> control ports. Some amplifiers do not like other stuff hanging on the TX
> control line.
>
> If you pull a relay low to go TX and you ever lose power to the relay, lose
> the relay, or lose the relay path, the system defaults with the transmitter
> running into the receiver antenna. You have to decide if that can damage RX
> antenna stuff. This requires a fast relay pull in time, and a slow release
> time..
>
> The solution seems to be to release a relay to go from RX antenna to the TX
> antenna, but this system requires a very fast release time and sometimes a
> slower actuation time. This means we cannot use a backpulse diode because it
> will slow the relay too much, and it will go into TX mode after the RF
> appears.
>
> In all cases the relay has to be pretty fast compared to the radio's window
> between pulling the TX line low and outputting RF. If the relay is ever
> mid-way in transfer, still bouncing, or in the wrong position when RF
> appears, the least that happens is broadband transfer clicks. The most is
> usually damage to the RX antenna.
>
> If there is a reasonable way to do it, it is better to add a RX port in the
> radio and avoid all this. :)
>
> 73 Tom
>
>
> _________________
> Topband Reflector Archives - http://www.contesting.com/_topband
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
|